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| Intellectual disability - microarray and sequencing v5.532 | DOCK4 |
Zornitza Stark gene: DOCK4 was added gene: DOCK4 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: DOCK4 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: DOCK4 were set to 38526744 Phenotypes for gene: DOCK4 were set to DOCK4-related neurodevelopmental disorder (MONDO:0060490) Review for gene: DOCK4 was set to GREEN Added comment: 7 unrelated individuals reported with heterozygous variants (missense or null variants) in DOCK4. The individuals either had ID or DD between mild and moderate with brain abnormalities. Two of the individuals are reportedly compound heterozygous. Functional assay neuro-2A Dock4 knockout cells by using the Alt-R CRISPR-Cas9 system utilizing two different guide RNAs (ko1 and ko2) and one nonspecific control guide RNA (C: control). The assay depicted the loss of function mechanism in the presence of either p.Arg853Leu and p.Asp946_Lys1966delinsValSer* (described as 945VS). Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.421 | HSD17B10 | Arina Puzriakova Added comment: Comment on mode of inheritance: Should be updated from 'XL, biallelic in females' to 'XL, monoallelic in females' as female patients harbouring heterozygous variants have been described. Some carrier females shown to have mild to moderate developmental delay or intellectual disability (PMIDs: 12112118; 16148061; 22127393; 34765396) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.409 | BAZ2B |
Dmitrijs Rots gene: BAZ2B was added gene: BAZ2B was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: BAZ2B was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: BAZ2B were set to PMID: 31999386 Phenotypes for gene: BAZ2B were set to developmental delay, intellectual disability and autism spectrum disorder Review for gene: BAZ2B was set to GREEN Added comment: BAZ2B gene is intolerant to LoF variants in population (pLI=1) and PMID: 31999386 described that de novo LoF variants are statistically enriched among NDD cases & summarize 10 cases. Enough evidence for the green rating. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.255 | CMIP |
Tord Jonson changed review comment from: CMIP (MANE Select NM_198390) loss of function-variants (deletions) have been reported in two studies that describes patients with syndromic ASD and co-morbid gastrointestinal issues. See Van der Aa et al., 2012, Haploinsufficiency of CMIP in a girl with autism spectrum disorder and developmental delay due to a de novo deletion on chromosome 16q23.2 (PMID: 22689534); and Luo et al., 2017, CMIP haploinsufficiency in two patients with autism spectrum disorder and co-occurring gastrointestinal issues (PMID: 28504353). In addition, we have observed a local case with a de novo deletion encompassing only the genes CMIP and GAN in a patient with gastrostomy, intellectual disability, autism, ADHD and seizures. Sources: Other; to: CMIP (MANE Select NM_198390) loss of function-variants (deletions) have been reported in two studies that describes patients with syndromic ASD and co-morbid gastrointestinal issues. See Van der Aa et al., 2012, Haploinsufficiency of CMIP in a girl with autism spectrum disorder and developmental delay due to a de novo deletion on chromosome 16q23.2 (PMID: 22689534); and Luo et al., 2017, CMIP haploinsufficiency in two patients with autism spectrum disorder and co-occurring gastrointestinal issues (PMID: 28504353). In addition, we have observed a local case with a de novo deletion encompassing only the genes CMIP and GAN in a patient with gastrostomy, intellectual disability, autism, ADHD and seizures. |
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| Intellectual disability - microarray and sequencing v5.255 | CMIP |
Tord Jonson gene: CMIP was added gene: CMIP was added to Intellectual disability - microarray and sequencing. Sources: Other Mode of inheritance for gene: CMIP was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CMIP were set to PMID: 22689534; 28504353 Phenotypes for gene: CMIP were set to HP:0012759; HP:0000717; HP:0007018; HP:0001250; HP:0011471 Penetrance for gene: CMIP were set to unknown Review for gene: CMIP was set to GREEN gene: CMIP was marked as current diagnostic Added comment: CMIP (MANE Select NM_198390) loss of function-variants (deletions) have been reported in two studies that describes patients with syndromic ASD and co-morbid gastrointestinal issues. See Van der Aa et al., 2012, Haploinsufficiency of CMIP in a girl with autism spectrum disorder and developmental delay due to a de novo deletion on chromosome 16q23.2 (PMID: 22689534); and Luo et al., 2017, CMIP haploinsufficiency in two patients with autism spectrum disorder and co-occurring gastrointestinal issues (PMID: 28504353). In addition, we have observed a local case with a de novo deletion encompassing only the genes CMIP and GAN in a patient with gastrostomy, intellectual disability, autism, ADHD and seizures. Sources: Other |
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| Intellectual disability - microarray and sequencing v5.170 | ATG4D |
Dmitrijs Rots gene: ATG4D was added gene: ATG4D was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: ATG4D was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ATG4D were set to 36765070 Phenotypes for gene: ATG4D were set to neurodevelopmental disorder characterized by speech and motor impairment Review for gene: ATG4D was set to GREEN Added comment: Morimoto et al., described 3 cases from 2 families with ATG4D biallelic variants and provided some functional evidence. No data about homozygous or compound heterozygous with two rare variants in ATG4D in gnomAD database. Sources: Literature |
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| Intellectual disability - microarray and sequencing v4.92 | NUP214 |
Eleanor Williams changed review comment from: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families one of Palestinian decent, the other Northern European (not Finnish descent). Each had two affected siblings in which neurological decline was seen after febrile events. The older son in family A, exhibited minor developmental delay from infancy. A homozygous missense variant was identified in NUP214 (p.Arg38Cys) in family A and segregated with the disease in available family members. In family B affected sisters were compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6). Functional studies with fibroblasts from one patient in family A showed a decrease in NUP214 and NUP88 levels compared to controls, PMID: 30758658 - Shamseldin et al 2019 - describe a multiplex consanguineous family in which four affected members presented with severe neonatal hypotonia, profound global developmental delay, progressive microcephaly and early death (<2 year old). Whole exome sequencing revealed the presence of a novel homozygous missense variant in NUP214, p.D154G. PMID: 29483668 - Egloff et al 2018 - report a 4-year-old girl presenting with developmental delay, growth retardation and facial dysmorphism. She was found to have a 9q deletion inherited from her healthy mother and a hemizygous one-base pair deletion in the NUP214 gene inherited from her father. From patient leukocytes it was found that the expression level of the NUP214 transcript was significantly decreased and close to zero in the patient compared to the controls. ; to: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families one of Palestinian decent, the other Northern European (not Finnish descent). Each had two affected family members in which neurological decline was seen after febrile events. The older son in family A, exhibited minor developmental delay from infancy. A homozygous missense variant was identified in NUP214 (p.Arg38Cys) in family A and segregated with the disease in available family members. In family B affected sisters were compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6). Functional studies with fibroblasts from one patient in family A showed a decrease in NUP214 and NUP88 levels compared to controls, PMID: 30758658 - Shamseldin et al 2019 - describe a multiplex consanguineous family in which four affected members presented with severe neonatal hypotonia, profound global developmental delay, progressive microcephaly and early death (<2 year old). Whole exome sequencing revealed the presence of a novel homozygous missense variant in NUP214, p.D154G. PMID: 29483668 - Egloff et al 2018 - report a 4-year-old girl presenting with developmental delay, growth retardation and facial dysmorphism. She was found to have a 9q deletion inherited from her healthy mother and a hemizygous one-base pair deletion in the NUP214 gene inherited from her father. From patient leukocytes it was found that the expression level of the NUP214 transcript was significantly decreased and close to zero in the patient compared to the controls. |
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| Intellectual disability - microarray and sequencing v4.65 | RAB39B | Achchuthan Shanmugasundram Added comment: Comment on publications: Additional cases diagnosed with intellectual disability, autism, macrocephaly and poor motor coordination reported in PMIDs 29152164, 32873259 & 34761259. There are also ample functional evidence including studies from animal models described in these and other publications. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1736 | DPH5 | Sarah Leigh edited their review of gene: DPH5: Added comment: Not associated with a phenotype in OMIM, but as moderate Gen2Phen gene for DPH5-related neurodevelopmental disorder. PMID: 35482014 reports four DPH5 variants in fives cases from three unrelated families. Biallelic NM_001077394.2:c.521dup (p.Asn174LysfsTer10) was identified in a consanguinous family (PMID: 35482014, family 3), the index case, an affected sibling and cousin all died in infancy. Affected members families 1 & 2 (PMID: 35482014) were seen in childhood, all had profound intellectual disability and seizures were seen in both families. A supportive mouse model was described, as were in vitro functonal studies (PMID: 35482014).; Changed rating: GREEN | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1736 | DPH5 | Sarah Leigh Added comment: Comment on phenotypes: As described by Gen2Phen (https://www.ebi.ac.uk/gene2phenotype/gfd?dbID=4902). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1720 | PTPA |
Konstantinos Varvagiannis gene: PTPA was added gene: PTPA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PTPA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PTPA were set to 36073231 Phenotypes for gene: PTPA were set to Intellectual disability; Parkinsonism Penetrance for gene: PTPA were set to Complete Review for gene: PTPA was set to AMBER Added comment: Biallelic PTPA pathogenic variants lead to a form of ID with later-onset parkinsonism based on 4 individuals from 2 families in the literature. Affected individuals were homozygous for missense variants demonstrated to result to reduced mRNA and protein levels as well as PP2A complex activation. Drosophila studies support an age-dependent locomotor dysfunction. Variants in other PP2A-complex-related genes also lead to NDDs. Summary provided below. There is currently no associated phenotype in OMIM, G2P, PanelApp Australia or SysNDD. Consider inclusion in relevant panels (ID, Parkinsonism/movement disorders, etc) with amber rating pending further reports. ------ Fevga, Tesson et al (2022 - PMID: 36073231) describe the features of 4 individuals, from 2 unrelated families, with biallelic pathogenic PTPA variants. These presented with normal or delayed early milestones, learning disability and ID (mild to moderate) followed by progressive signs of parkinsonism (at the age of 11 yrs in 2 sibs, 15 yrs in another individual). Motor symptoms were responsive to levodopa and later to deep brain stimulation. Linkage analysis in one consanguineous family followed by exome revealed homozygosity for a missense PTPA variant (NM_178001:c.893T>G/p.Met298Arg). Exome sequencing in affected subjects from the 2nd family revealed homozygosity for a further missense variant (c.512C>A/p.Ala171Asp). There were no other candidate variants for the phenotype following parental / segregation studies. Role of the gene: As the authors discuss, PTPA (or PPP2R4) is ubiquitously expressed in all tissues incl. brain and encodes a phosphotyrosyl phosphatase activator of the dimeric form of protein phosphatase-2A (PP2A). PP2A in turn, is the major Ser/Thr phosphatase in brain targeting a large number of proteins involved in diverse functions. Activation of PP2A is dependent on its methylation, which is negatively regulated by the PP2A-specific methylesterase (PME-1). By binding to PME-1, PTPA counteracts the negative influence of the former on PP2A. Pathogenic variants in genes encoding subunits/regulators of the PP2A complex (e.g. PPP2R1A or PPP2CA) are associated with neurodevelopmental disorders. Variant studies: Upon overexpression of wt and both variants in a HEK-293 cell line the authors demonstrated that both variants resulted in significantly reduced mRNA and protein levels (which for Ala171Asp were attributed to increased proteasomal degradation). Both variants were shown to result in impaired PP2A complex activation compared to wt. Drosophila / animal models: Pan-neuronal RNAi-mediated knockdown of ptpa in Drosophila resulted in an age-dependent locomotor dysfunction, reversible with L-DOPA treatment. Previous studies in mice suggest cognitive/electrophysiological impairments upon downregulation of PP2A activity in transgenic mice. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1701 | UBAP2L |
Konstantinos Varvagiannis gene: UBAP2L was added gene: UBAP2L was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: UBAP2L was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: UBAP2L were set to 35977029 Phenotypes for gene: UBAP2L were set to Delayed speech and language development; Motor delay; Intellectual disability; Autistic behavior; Seizures; Microcephaly; Abnormality of head or neck; Short stature; Abnormality of the skeletal system Penetrance for gene: UBAP2L were set to unknown Review for gene: UBAP2L was set to GREEN Added comment: Based on Jia et al (2022 - PMID: 35977029) speech, motor delay as well as ID are observed in individuals harboring de novo pLoF variants in UBAP2L. The gene encodes a regulator of the stress granule (SG) assembly. Extensive evidence is provided on the effect of variants as well as the role of UBAP2L and other genes for components and/or regulation of SG in pathogenesis of NDDs. Among others a Ubap2l htz deletion mouse model (behavioral and cognitive impairment, abnormal cortical development due to impaired SG assembly, etc). Data from 26 previous studies, aggregating 40,853 probands with NDDs (mostly DD/ID, also ASD) suggest enrichment for DNMs in UBAP2L or other genes previously known and further shown to be important for SG formation (incl. G3BP1/G3BP2, CAPRIN1). Details provided below. Not associated with any phenotype in OMIM, G2P or SysNDD. -------- Jia et al (2022 - PMID: 35977029) describe 12 affected individuals with heterozygous de novo pLoF variants in UBAP2L. Phenotype: Features included hypotonia, speech (11/11) and motor delay (8/12), ID (8/10 with formal evaluation), variable behavioral concerns (ADHD 5/11, ASD in 4/10, etc). Seizures were reported in 7/12 with 3/10 having a formal diagnosis of epilepsy. Few had microcephaly (3/10). Facial dysmorphisms were common (9/9) and included abnormal palpebral fissures, deep prominent concha, high broad forehead, hypertelorism, thin upper lip and mild synophrys (each in 4 or less individuals). Short stature or skeletal alterations were described in some (4/10 each). Role of the gene: UBAP2L encodes an essential regulator of stress granule assembly. Stress granules are membraneless cytoplasmic compartments in eukaryotic cells, induced upon a variety of stressors and playing a role in regulation of gene expression. Variants identified : 9 nonsense/frameshift UBAP2L variants and 3 splicing ones were reported, in all cases as de novo events, upon trio/quad exome sequencing. All were absent from gnomAD. There were no other causative variants. Variant effect/studies (NM_014847.4 / NP_055662.3) : - Minigene assays revealed that the 3 splice variants all resulted in out-of-frame exon skipping. - In patient fibroblasts one of these splice variants was demonstrated to result to reduced protein levels. - 8 of the 9 nonsense/frameshift variants were predicted to result to NMD. - 1 nonsense variant (c.88C>T/p.Q30*) was shown to result to decreased protein expression in patient fibroblasts, with detection of the protein using an antibody for the C terminus but not the N terminus. Protein N-terminal sequencing confirmed that the protein lacked the N terminus, with utilization of an alternative start site (11 codons downstream). - Generation of HeLa UBAP2L KO cell lines resulted in significant reduction of SG numbers which was also the case for 4 variants studied, under stress conditions. - The protein has a DUF domain (aa 495-526) known to mediate interaction of UBAP2L with G3BP1 (a stress granule marker) with deletions of this domain leading to shuttling of UBAP2L from the cytoplasm to the nucleus. Truncating variants upstream of the DUF domain were shown to result in nuclear localization. Mouse model : - The authors generated Ubap2l KO model with hmz deletion of Ubap2l resulting in a lethal phenotype (2.6% survived) and htz deletion leading to behavioral issues (low preference for social novelty, anxious-like behaviors) and cognitive impairment. - Ubap2l haploinsufficiency resulted in abnormal cortical development and lamination with reduction of neural progenitor proliferation. - Ubap2l deficiency was shown to impair SG assembly during cortical development both under physiological stress conditions or upon utilization of an oxidative stress inducer. Additional evidence of UBAP2L and SG overall in pathogenesis of NDDs: - Based on DNMs from 40,853 individuals with NDDs from 26 studies (9,228 with ASD, 31,625 with DD/ID) the authors demonstrate significant excess of DNM in 31 genes encoding SG components, regulators or both, the latter being the case for UBAP2L and 2 further genes (G3BP1 and G3BP2 - both with crucial roles in SG assembly). - Excess dn splice-site (N=3) and missense (N=5) variants in G3BP1 were observed in the above cohort [c.95+1G>A, c.353+1G>T, c.539+1G>A / p.S208C, R320C, V366M]. - Excess dn missense (N=7) variants in G3BP2 were observed in the above cohort [p.R13W, D151N, E158K, L209P, E399D, K408E, R438C]. - Generation of G3BP1 or G3BP2 KO HeLa cell lines and immunofluorescence upon use of oxidative stress inducer revealed significant reduction of stress granules. - Generation of HeLa cell lines for 5 G3BP1 mutants (R78C*, R132I*, S208C*, R320C*, V366M) and 7 G3BP2 mutants (p.R13W*, D151N*, E158K, L209P*, E399D, K408E, R438C) revealed that several (those in asterisk) resulted in significantly fewer SG formation under oxidative stress compared to WT while the subcellular distribution of the proteins under stress was identical to WT. - Among the identified genes for SG enriched for DNMs, CAPRIN1 was implicated in previous publications as a NDD risk gene with 3 dn missense SNVs reported (p.I373K, p.Q446H, p.L484P). CAPRIN1 binding to G3BP1/2 has been shown to promote SG formation. Significant reduction of SG was observed in CAPRIN1 KO HeLa lines. p.I373K abolished interaction with G3BP1/2 and disrupted SG formation. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1677 | ZMYND8 |
Konstantinos Varvagiannis gene: ZMYND8 was added gene: ZMYND8 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZMYND8 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZMYND8 were set to 35916866; 32530565 Phenotypes for gene: ZMYND8 were set to Delayed speech and language development; Motor delay; Intellectual disability; Abnormality of cardiovascular system morphology; Hearing abnormality; Abnormality of vision; Abnormality of the face; Seizures Penetrance for gene: ZMYND8 were set to unknown Review for gene: ZMYND8 was set to GREEN Added comment: Dias et al (2022 - PMID: 35916866) describe the phenotype of 11 unrelated individuals with monoallelic de novo (or suspected de novo) missense (N=9) or truncating (N=2) ZMYND8 variants. One of these subjects was previously reported by Suzuki et al (2020 - PMID: 32530565). Features included speech delay/language difficulties (9/11), motor delay (9/11), ID (in 10/11 - profound in 1, moderate in 2), CHD (7/11 - PDA, VSD, ASD, pulmonary stenosis, etc), hearing or vision impairment (7/11). Seizures were reported in few (in text 5/11, table 2/11). Variable non-familial facial features were present in (9/11). As the authors discuss, ZMYND8 encodes a multidomain protein playing a role in transcription regulation, chromatin remodeling, regulation of super enhancers, DNA damage response/tumor suppression. The protein is broadly expressed in brain and shows highest expression in early development. Molecular modeling and/or a yeast two-hybrid system were suggestive of disrupted interaction of ZMYND8 with Drebrin (missense variants in PWWP domain) or GATAD2A (variants in MYND domain). Neuronal Zmynd8 knockdown in Drosophila resulted in deficits in habituation learning. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1677 | ZMYND15 |
Konstantinos Varvagiannis gene: ZMYND15 was added gene: ZMYND15 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZMYND15 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZMYND15 were set to 35916866; 32530565 Phenotypes for gene: ZMYND15 were set to Delayed speech and language development; Motor delay; Intellectual disability; Abnormality of cardiovascular system morphology; Hearing abnormality; Abnormality of vision; Abnormality of the face; Seizures Penetrance for gene: ZMYND15 were set to unknown Review for gene: ZMYND15 was set to GREEN Added comment: Dias et al (2022 - PMID: 35916866) describe the phenotype of 11 unrelated individuals with monoallelic de novo (or suspected de novo) missense (N=9) or truncating (N=2) ZMYND8 variants. One of these subjects was previously reported by Suzuki et al (2020 - PMID: 32530565). Features included speech delay/language difficulties (9/11), motor delay (9/11), ID (in 10/11 - profound in 1, moderate in 2), CHD (7/11 - PDA, VSD, ASD, pulmonary stenosis, etc), hearing or vision impairment (7/11). Seizures were reported in few (in text 5/11, table 2/11). Variable non-familial facial features were present in (9/11). As the authors discuss, ZMYND8 encodes a multidomain protein playing a role in transcription regulation, chromatin remodeling, regulation of super enhancers, DNA damage response/tumor suppression. The protein is broadly expressed in brain and shows highest expression in early development. Molecular modeling and/or a yeast two-hybrid system were suggestive of disrupted interaction of ZMYND8 with Drebrin (missense variants in PWWP domain) or GATAD2A (variants in MYND domain). Neuronal Zmynd8 knockdown in Drosophila resulted in deficits in habituation learning. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1628 | PPFIBP1 |
Konstantinos Varvagiannis gene: PPFIBP1 was added gene: PPFIBP1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PPFIBP1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PPFIBP1 were set to 35830857; 30214071 Phenotypes for gene: PPFIBP1 were set to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Abnormality of brain morphology; Abnormality of the cerebral white matter; Cerebral calcification; Abnormal cortical gyration; Hypertonia; Spastic tetraplegia; Generalized hypotonia; Small for gestational age; Growth delay; Failure to thrive; Feeding difficulties; abnormal heart morphology; Hearing abnormality; Cryptorchidism; Abnormality of vision Penetrance for gene: PPFIBP1 were set to Complete Review for gene: PPFIBP1 was set to GREEN Added comment: Consider inclusion with green rating in the ID, epilepsy as well as other likely relevant gene panels (microcephaly, white matter disorders, corpus callosum abnormalities, intracerebral calficication disorders, malformations of cortical development, hereditary spastic paraplegia, growth failure in early childhood, etc) based on the summary below. ---- Rosenhahn et al (2022 - PMID: 35830857) describe the phenotype of 16 individuals - belonging to 12 unrelated families - with biallelic PPFIBP1 pathogenic variants. Most (14/16) were born to consanguineous parents. One of these families was previously reported by Shaheen et al (2019 - PMID: 30214071) who first identified PPFIBP1 as a candidate gene for congenital microcephaly. In the current study, Rosenhahn also identified a fetus homozygous for a missense variant and similar features. All individuals presented global DD/ID (16/16 - in 15 cases profound/severe) and epilepsy (16/16 - onset 1d-4y / median 2m - focal seizures in 11/16, epileptic spams in 7/16, generalized onset in 7/16, myoclonic in 6/16 - drug-resistant : 13/16). Almost all (15/16) had microcephaly, commonly congenital (9/16) and progressive (11/16). Other neurological findings included hypertonia (10/16), spastic tetraplegia (6/16), hypotonia (5/16), dystonic movements (3/16) or nystagmus (4/16). Brain abnormalities were identified in all investigated with MRI and included leukoencephalopathy (11/14) mostly periventricular, abnormal cortex morphology (7/14 - polymicrogyria 1, increased cortical thickness 4, pachygyria 3), cortical atrophy, corpus callosum hypoplasia (7/14). Intracranial calcifications were identified in all (9/9) investigated with CT scan. Abnormal growth was reported for several (SGA in 9/16, FTT 8/16, short stature 7/16) often associated with feeding difficulties (7/16). Other features incl. abnormal hearing (4/16), congenital heart defects (7/16), ophthalmologic findings (8/16), undescended testes (3/10). There were no overlapping facial features. The fetus displayed similar features incl. SGA, microcephaly, intracranial calcifications. Investigations incl. exome/genome sequencing (singleton or trio) with Sanger for confirmation/segregation of variants where necessary. Variable previous investigations incl. metabolic screening, TORCH screening, chromosomal studies (CMA) are mentioned in the supplement and were non-diagnostic. Additional candidate variants were identified in few cases although cases with plausible dual diagnoses (e.g. ind14) were not included in the overall phenotypic description. 9 pLoF variants (nonsense, frameshift, 1 splicing) predicted to lead to NMD were identified. There were no functional studies performed. The missense variant c.2177G>T / p.Gly726Val (NM_003622.4) was predicted deleterious by in silico tools while the AA change causing severe steric problems upon modelling. PPFIBP1 encodes PPFIA-binding protein 1 also known as liprin-β1. As the authors discuss: The liprin family of proteins comprises liprins α1 to 4 and liprin β1 and β2 in mammals. Liprin β1 is known to homodimerize and heterodimerize with α-liprins. In fibroblast cultures liprins β1 and α1 colocalize to cell membrane and periphery of focal adhesions. Members of the liprin-α fam. are scaffold proteins playing a role in synapse formation/signaling and axonal transport. A ko model of the PPFIBP1 ortholog in C.elegans displayed abnormal locomotion behavior. In Drosophila, null-allele mutants resulted in altered axon outgrowth and synapse formation of R7 photoreceptors and reduced neuromuscular junction size (Refs provided in article). Using a PPFIBP1/hlb-1 ko C.elegans model the authors demonstrated defects in spontaneous and light-induced behavior. Sensitivity of the worms to an acetylcholinesterase inhibitor (aldicarb) was suggestive of a presynaptic defect. ---- There is currently no PPFIBP1 - associated phenotype in OMIM / G2P. SysNDD lists PPFIBP1 among the ID genes (limited evidence based on the 3 sibs reported by Shaheen et al, 2019 - PMID: 30214071). In PanelApp Australia the gene is listed with green rating for ID, epilepsy, microcephaly based on the medRxiv pre-print. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1628 | SEMA3E |
Sarah Leigh gene: SEMA3E was added gene: SEMA3E was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SEMA3E was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: SEMA3E were set to 35628442 Phenotypes for gene: SEMA3E were set to Severe Intellectual Disability with Cognitive Regression Review for gene: SEMA3E was set to AMBER Added comment: Not associated with a phenotype in OMIM or Gen2Phen. One variant has been reported in a case of Severe Intellectual Disability with Cognitive Regression (PMID: 35628442). PMID: 35628442 also describes functional studies which show that this variant impairs protein secretion and hampers the binding to both embryonic mouse neuronal cells and tissues, furthermore, SEMA3E was revealed to be expressed during human brain development. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1593 | ALKBH8 |
Konstantinos Varvagiannis edited their review of gene: ALKBH8: Added comment: Please consider upgrade to green rating. 2 additional relevant families reported in literature, as summarized below. While affected individuals from 3 (of the 4 total) families with the disorder were homozygous for truncating variants in the last exon (potentially corresponding to hypomorphic / incomplete LoF rather than null alleles), a more recent publication describes 2 sibs homozygous for a missense SNV with demonstrated loss-of-function in the context of normal protein levels. ----- Saad et al (2020 - PMID: 33544954) report 2 sibs, born to consanguineous parents from Egypt homozygous for an ALKBH8 frameshift variant. Both exhibited global DD and ID (proband IQ of 51 / Stanford Binet test, sib: 42 using Weschler scale). There was no history of seizures. Family based exome sequencing of both sibs and parents revealed homozygosity for NM_001301010.1:c.1684delC [p.(Arg562Alafs*56))] within a region of AOH. As the authors note this variant also occurred in the last exon of the gene, likely escaping NMD and based on previous evidence from Monnies et al, hypothesize that truncating variants in the last exon represent hypomorphic alleles encoding for a partially functional protein, while protein truncating variants in earlier exons may be null alleles. Maddirevula et al (2021 - PMID: 34757492) describe the phenotype of 2 sibs, homozygous for a missense variant. Features included severe DD and ID, microcephaly, facial dysmorphism and epilepsy (the latter limited to the elder one). Exome with autozygome analysis identified homozygosity for a missense variant (NM_138775.2:c.1874G>A / p.Arg625His) with Sanger for confirmation / segregation studies.LC-MS/MS using tRNA isolated from LCLs from the affected individual, a carrier parent and controls revealed complete loss of ALKBH8-dependent tRNA posttranscriptional modifications, the results being suggestive of abrogation of the catalytic activities of both MT and Ox domains. The protein was detected at low levels in LCLs from control and patient samples, a finding that was also supported by immunoblot analysis suggesting that the observed loss-of-function is not mediated by loss of the protein.; Changed rating: GREEN; Changed publications to: 33544954, 34757492 |
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| Intellectual disability - microarray and sequencing v3.1593 | ACO2 |
Sarah Leigh commented on gene: ACO2: New paper (34056600) describing ACO2 as a cause of autosomal dominant optic atrophy - update of inheritance needed. Tom Cullup (Great Ormond Street Hospital), 17 Feb 2022 |
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| Intellectual disability - microarray and sequencing v3.1580 | DROSHA |
Konstantinos Varvagiannis gene: DROSHA was added gene: DROSHA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DROSHA was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: DROSHA were set to 35405010 Phenotypes for gene: DROSHA were set to Global developmental delay; Intellectual disability; Seizures; Cerebral white matter atrophy; Abnormality of the corpus callosum; Abnormality of movement; Stereotypic behavior; Abnormality of head or neck; Short foot Penetrance for gene: DROSHA were set to unknown Mode of pathogenicity for gene: DROSHA was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: DROSHA was set to AMBER Added comment: Profound DD, ID and seizures have been reported in 2 unrelated subjects with de novo missense variants. The gene has a role in miRNA biogenesis. Both variants described have been shown to have effect on DROSHA's function in Drosophila / C. elegans (partial loss-of-function vs possibility of antimorphic effect discussed || in gnomAD several individuals with LoF alleles / Z=3.98 – pLI : 0.09). There is currently no DROSHA-related phenotype in OMIM, G2P, SysNDD. In PanelApp Australia the gene has amber rating in genetic epilepsy and microcephaly panels (not currently included in the ID one). Consider inclusion in the current panel with amber rating. Also consider inclusion in other possibly relevant panels (given postnatal microcephaly, abn. corpus callosum, progressive white matter atrophy, etc) [ NOT added ] ----- Barish, Senturk, Schoch et al (2022 - PMID: 35405010) describe the phenotype of 2 unrelated individuals with de novo missense DROSHA variants. Features included generalized hypotonia, postnatal microcephaly (-2,6 and -6 SD), feeding difficulties, profound DD and ID, seizures, abnormal movements (choreoathetosis / stereotypic movements), variable respiratory symptoms (in one case episodes of hyperventilation/apnea), cardiovascular or skeletal findings. Brain MRI demonstrated white matter atrophy and thin corpus callosum in both. Brachycephaly with broad face as well as short feet were also among the shared features. Both were investigated by trio ES/GS which were otherwise non diagnostic and without other candidate variants. The 1st individual harbored a de novo htz missense DROSHA variant (c.3656A>G/p.Asp1219Gly) while the 2nd subject had another missense variant (c.4024C>T/p.Arg1342Trp) [NM_013235.4] confirmed by Sanger seq. DROSHA (on 5p13.3) encodes a ribonuclease, subunit of the microprocessor complex, involved in miRNA biogenesis. Specifically, miRNAs are transcribed as part of pri-miRNAs (primary-miRNAs) which are cleaved to pre-miRNAs (precursor-miRNAs) in the nucleus by DROSHA (and its partner DGCR8 or Pasha) and then exported to the cytoplasm for further processing. Cleavage of pre-miRNAs by DICER1 generates mature miRNAs subsequently loaded to the RISC (RNA-induced silencing) complex which uses miRNA as template for recognition and cleavage of complementary mRNA with RNAse. As the authors discuss, miRNA defects have a well-established role in development of model organisms e.g. (several Refs. provided): - in C. elegans miRNA mutants causing lethality, developmental arrest and heterochronicity - in Drosophila playing a role in the development of ovary, eye, nervous system etc. - in mice mRNAs play a role in BMP and TGF-beta signaling while neuronal loss of miRNA processing leads to neurodegeneration/anatomical defects. Feingold syndrome 2 is the single Mendelian disease associated to date with miRNAs, through deletion of a cluster containing 6 MIR genes. miRNA dysregulation is also observed in Rett syndrome - and DROSHA implicated in the pathogenesis of the syndrome - as MECP2 and FOXG1 are cofactors of the microprocessor complex regulating processing of miRNA. One of the individuals here reported had a clinical diagnosis of Rett spectrum while both had overlapping features with Rett s. Studies of DROSHA-dependent miRNAs in fibroblasts from one individual revealed significantly altered expression of mature miRNA (e.g. increased miR98, a miRNA with reduced expression in studies of somatic DROSHA variants) although this was not likely due to processing errors (given only a modest decrease of precursor miRNAs). Previous studies have demonstrated that drosha (the Drosophila ortholog) null mutants die during post-embryonic development with 100% lethality before adulthood (3rd instar larval stage/beginning of pupariation). Mosaic flies with mutant eyes are small-eyed, while viable hypomorphic alleles display synaptic transmission defects (several Refs provided). Here, homozygous flies for null alleles died at the end of 3rd instar larval stage/beginning of pupariation, while loss of drosha resulted in lack of imaginal disc tissue (which surrounds the larval brain) and severely reduced brain size, the latter similar to the microcephaly phenotype. [To the best of my understanding] introduction of a mutated genomic rescue construct (carrying similar substitutions as those observed in human subjects) in eye-specific drosha null (W1123X) flies was partially able to rescue eye/head size for wt or Asp1219Gly (human:Asp1084Gly) suggesting that the latter is a partial LoF allele. Arg1210Trp (corresponding to human Arg1342Trp) was able to rescue the eye phenotype and was not damaging to the function in the specific assay. Drosha expression levels were similar for genomic rescue flies either for wt or for the Asp-Gly variant suggesting that the effect was not due to expression levels (but rather function). Expression of mature miRNAs known to be regulated by Drosha were not affected when comparing wildtype larvae with genomic construct for wt or Asp1084Gly. Upon expression of human cDNA using GAL4/UAS system in drosha mutant (null) eye clones, the reference partially rescued the eye size defect, Asp-Gly behaved as partial loss-of-function allele (~50% function compared to ref), while the Arg-Trp variant was shown to behave as a weaker loss-of-function allele. The authors generated eye-specific drosha mutant clones to study the aging adult eye using ERG recordings. While null mutants display almost no response to light (7- and 20-day old flies), wt genomic rescue was shown to rescue ERG responses, Asp-Gly variant had significant defects (at both 7 and 20 days) and the Arg-Trp had defects approaching statistical significance only at the age of 20 days. Overall these data suggested that Arg-Trp had less severe effect compared to Asp-Gly (as above) while both variants led to progressive neuronal dysfunction. Using CRISPR/Cas9 the authors generated C.elegans knock-ins for a variant analogous to the Asp1219Gly human one. Homozygous animals were inviable at larval stages, displayed a heterochronic phenotype (heterochronicity : development of cells or tissues at an abnormal time relative to other unaffected events in an organism / miRNAs are known to be involved in the heterochronic gene pathway) while this variant was deleterious to the Drosha's ability to process miRNAs. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1580 | SOX11 | Sarah Leigh Added comment: Comment on phenotypes: Described as MENTAL RETARDATION, AUTOSOMAL DOMINANT, 27 by Gen2Phen (https://www.ebi.ac.uk/gene2phenotype/gfd?dbID=405). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1576 | PRPF8 |
Konstantinos Varvagiannis gene: PRPF8 was added gene: PRPF8 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PRPF8 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PRPF8 were set to 35543142 Phenotypes for gene: PRPF8 were set to Global developmental delay; Intellectual disability; Seizures; Autism; Retinitis pigmentosa 13, MIM # 600059 Penetrance for gene: PRPF8 were set to unknown Review for gene: PRPF8 was set to AMBER Added comment: A recent study suggests that heterozygous PRPF8 variants are associated with a syndromic form of DD/ID, in some cases epilepsy with heterogeneous other clinical findings. However the authors acknowledge that not all variants within their cohort may be pathogenic (5 VUSs using ACMG criteria) and that conclusive evidence may necessitate functional studies. Heterozygous variants (typically clustering in exon 42) have been reported to cause a non-syndromic form of RP with variable expressivity and incomplete penetrance (Retinitis pigmentosa 13, MIM # 600059) . Overall consider inclusion with amber rating. ------ O'Grady et al. (2022 - PMID: 35543142) describe the phenotype of 14 unrelated individuals with heterozygous, mostly de novo, missense and pLoF variants in PRPF8. Nearly all had some degree of global developmental delay or ID (13/14). 6/14 had a diagnosis of ASD. Seizures were reported in 4 or 5 subjects. Other features included short stature (6/14), abnormal gait, cardiac anomalies and somewhat overlapping facial features (11/14). Ages ranged from 4 - 19 years (median : 9y). PRPF8 encodes a component of the spliceosomes which in turn are involved in removal of introns from mRNA precursors. The gene is ubiquitously expressed with expression within brain being highest in cerebral cortex, basal ganglia and cerebellum (Refs. provided). Individuals were investigated with exome sequencing (12/14) or an autism/ID panel of >2500 genes (likely application of virtual panel on exome data). 13 individuals harbored a missense SNV and 1 further had a frameshift variant. In 12 individuals the variant had occurred de novo. 1 individual had inherited the variant from a possibly mosaic parent, while for 1 further a single parental sample was available. PRPF8 is intolerant to both missense (Z = 8.28) and pLoF variants (pLI : 1). Variants in 5 individuals were formally classified as VUS while 2 variants were present in gnomAD. Additional findings (CNVs/SNVs) were reported, in some cases possibly of relevance. As the authors discuss, heterozygous pathogenic missense SNVs cause (and account for ~2-3% of) non-syndromic AD retinitis pigmentosa with variable expressivity and incomplete penetrance. Variants for this phenotype are typically missense - although nonsense ones have also been reported - clustering within ex42 (of 43) encoding the MPN domain (aa 2103-2335 / NP_006436) and weakening interaction with 2 other spliceosomal proteins. Variants in the present study occurred throughout the gene. Although not universally assessed within the cohort, only one participant had RP (in this case variant within the MPN domain). There were no variant studies performed. Animal models: the authors cite a study by Graziotto et al (2011 - PMID: 20811066) where knock-in mice for a missense variant in ex42 displayed defects of the retinal pigment epithelium. A zebrafish ko model also cited (Keightley et al, 2013 - PMID: 23714367) displayed widespread apoptosis in brain and spinal cord. The authors cite a previous bioinformatic study identifying PRPF8 as a major hub connecting gene-interaction networks for NDDs (Casanova et al, 2018 - PMID: 30420816) as well as 2 studies demonstrating enrichment of variants in individuals with NDDs compared to controls (da Silva Montenegro et al, 2020 - PMID: 31696658, Karczewski et al, 2020 - PMID: 32461654). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1568 | PHF14 |
Dmitrijs Rots gene: PHF14 was added gene: PHF14 was added to Intellectual disability. Sources: Literature,Expert list Mode of inheritance for gene: PHF14 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: PHF14 were set to 35074918 Phenotypes for gene: PHF14 were set to Autism Review for gene: PHF14 was set to GREEN Added comment: Multiple individuals in the literature reported with NDD and de novo PHF14 variants + experimental findings (in 35074918). Additional info from AutDB:"De novo missense variants in the PHF14 gene have been identified in an ASD proband from the SPARK cohort (Feliciano et al., 2019) and the Autism Sequencing Consortium cohort (Satterstrom et al., 2020), while additional rare de novo non-coding variation in this gene has also been observed in ASD probands (Sanders et al., 2015; Yuen et al., 2017). Zhou et al., 2022 reported that PHF14 forms a complex with MECP2 and TCF20; in the same report, the authors described two individuals with de novo variants in PHF14 who presented with neurodevelopmental phenotypes, including a patient with a de novo PHF14 missense variant that abolished the MECP2-PHF14-TCF20 interaction." Sources: Literature, Expert list |
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| Intellectual disability - microarray and sequencing v3.1564 | ADD1 |
Konstantinos Varvagiannis gene: ADD1 was added gene: ADD1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ADD1 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: ADD1 were set to 34906466 Phenotypes for gene: ADD1 were set to Global developmental delay; Intellectual disability; Seizures; Ventriculomegaly; Abnormality of the corpus callosum Penetrance for gene: ADD1 were set to unknown Review for gene: ADD1 was set to AMBER Added comment: A recent study suggests an ADD1-related phenotype (3 subjects with monoallelic de novo variants/1 with biallelic variants) with DD/ID and ventriculomegaly or corpus callosum dysgenesis and possibly seizures among the features. There is currently no associated phenotype in other databases (OMIM, G2P, SysID, PanelApp Australia). Consider inclusion in the current panel with amber / green rating (3 subjects/variants/families, role of the gene and mouse models recapitulating ventriculomegaly/CC abnormalities, relevant expression, variant studies demonstrating abn. protein levels and/or disruption of adducin heterodimer formation || monoallelic vs bi-allelic variants). Please consider inclusion in other possibly relevant gene panels (e.g. for corpus callosum / ventriculomegaly) [ Not added ]. -------- Qi et al (2022 - PMID: 34906466) describe the phenotype of 3 unrelated individuals with monoallelic de novo ADD1 pathogenic variants as well as of a fourth homozygous for a missense SNV. Overall, the authors propose a common phenotype consisting of morphological brain abnormalities (incl. ventriculomegaly and corpus callosum dysgenesis) and neurological symptoms such as DD and/or ID and attention deficit. All individuals were investigated with singleton/trio ES. De novo variants - phenotype: One individual investigated for hypotonia, DD & ID, partial ACC, well controlled seizures (on ketogenic diet) and proportional short stature harbored a de novo stopgain variant (NM_014189.3:c.1418G>A / p.Trp473*) absent from gnomAD. Another affected subject with hypotonia, FTT/feeding difficulties, mild motor delays complete ACC, a seizure (2y11m), staring spells without EEG correlate, and fatigue (with low coenz. Q10, and complex I & IV deficiency in muscle biopsy) had a de novo fs variant (NM_001119:c.2029_2039del / p.Glu680Argfs*7 - gnomAD:0) and a VUS in a gene not associated with phenotype to date. A 3rd subject investigated for seizures (onset:1y), speech delay, mild ID, ADHD, without MRI abnormalities harbored a de novo missense SNV (NM_001119:c.670C>T / p.His224Tyr - gnomAD:0) and with cmp htz for 2 missense SPTBN2 SNV not fitting the phenotype (no ataxia). Biallelic variants - phenotype: One individual with ID, and ACC, abnormal sulcation, enlarged lateral and 3rd ventricles, abnormal of white matter and hypoplastic vermis upon MRI was reported to harbor in homozygosity a missense SNV (NM_001119:c.169A>T / p.Arg57Trp). There was an additional variant in a gene without associated phenotype to date and not expressed in brain. Role of the encoded protein: ADD1 encodes adducin 1/alpha (similar to ADD2, ADD3 encoding other adducins). As the authors note, adducins are cytoskeleton proteins critical for osmotic rigidity and cell shape. In neurons they have been reported to form membrane associated periodic ring-like structures with actin and β-spectrin. Deletion of Add1 in mice results in increased MPS ring diameter and axonal degeneration (several refs provided). ADD1/2/3 form heterodimers which in turn form heterotetramers. ADD1 is expressed in most tissues. Mouse model: Previous mouse models have demonstrated that Add1 null mice have also undetectable ADD2/3 (suggesting a role for stabilization of the latter) and exhibit growth delay, anemia and develop lethal hydrocephalus and ventriculomegaly with 50% penetrance (cited PMIDs: 27068466, 18723693). Here the authors demonstrated that surviving mice had ventriculomegaly and thinning of corpus callosum thus recapitulating the respective human phenotypes. Htz mice also presented thinner CC, though not to a statistically significant extent. ADD1 expression and isoforms: - Performing mRNA studies and W.Blot in (developing - GW15-17) human or mouse brain (E12.5-P40) the authors demonstrated dynamic expression of ADD1 with differentially expressed isoforms, notably alternative splicing of ex10 and ex15 with NM_176801 (extended ex10, inclusion of ex15) corresponding to a neuronal isoform and NM_001119 (shorter ex10, exclusion of ex15) corresponding to a neural progenitor cell (NPC) isoform. - Variants here reported appear to affect both isoforms with the exception of NM_001119:c.2029_2039del / p.Glu680Argfs*7 affecting only the longer NPC one. - PTBP1 is an RNA binding protein expressed in NPCs known to suppress neuronal exon insertion. The authors demonstrated in mouse Neuro2A cells, through shRNA targeting of Ptbp1, that the latter suppresses the neuronal Add1 isoform. Variant studies demonstrated that effect of variants was mediated by decreased protein levels and/or disruption of adducin complex formation (ADD1-ADD2 dimer formation known to be mediated by N- and C- terminal ADD1 domains): - Expression of Arg57Trp (found in hmz in one individual) NPC and neuronal isoforms in Neuro2a cells showed that while protein levels were not significantly affected, there were (also) truncated protein products for both isoforms suggesting that aberrant splicing or protein translation/cleavage may apply. - The authors generated HEK293FT cells for the truncating variants demonstrating decreased protein levels (using N-/C- terminal antibodies). - Reduced (HA-tagged)-ADD1-(V5-tagged)-ADD2 protein interaction was shown to apply for the Arg57Trp and Arg473* in HEK293FT cells. Similarly in Neuro2a cells, reduced ADD1-ADD2 interaction was shown for His224Tyr. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1564 | BUB1 |
Konstantinos Varvagiannis gene: BUB1 was added gene: BUB1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: BUB1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: BUB1 were set to 35044816 Phenotypes for gene: BUB1 were set to Congenital microcephaly; Global developmental delay; Intellectual disability; Abnormal heart morphology; Growth delay Penetrance for gene: BUB1 were set to Complete Review for gene: BUB1 was set to AMBER Added comment: A recent study provides evidence that this gene (biallelic variants) is relevant for inclusion in the DD/ID panel likely with amber / green rating (2 unrelated individuals with similar phenotype, 3 variants, role of this gene, extensive variant studies and demonstrated effects on cohesion and chromosome segregation, similarities with other disorders caused by mutations in mitosis-associated genes at the clinical and cellular level || number of affected subjects/families, different protein levels/kinase activity likely underlying few differences observed, role of monoallelic variants unclear). This gene could probably be included in other panels e.g. for microcephaly (not added). There is no BUB1-related phenotype in OMIM, G2P, SysID, PanelApp Australia. ------ Carvalhal, Bader et al (2022 - PMID: 35044816) describe the phenotype of 2 unrelated individuals with biallelic BUB1 pathogenic variants and provide evidence for the underlying mechanism for this condition. Common features comprised congenital microcephaly (2/2 | -2,8 and -2.9 SDs respectively / -7 and -4,9 SDs on last evaluation), DD/ID (2/2 - in one case with formal evaluation mild), some degree of growth retardation (2/2) and cardiovascular findings (2/2 - small ASD type II). Other findings limited to one subject included Pierre-Robin sequence, Axenfeld-Rieger anomaly, choanal stenosis, hypospadias, tracheal stenosis, etc. Initial genetic testing was normal (incl. CMA in both, metabolic testing and individual genes incl. PITX2, GREM1, FOXD3, FOXC1 for one proband). Exome sequencing revealed homozygosity for a start-lost variant (NM_004336.4:c.2T>G / p.?) in the first subject (P1). The variant lied within a 14-Mb region of homozygosity (no reported consanguinity). The second individual (P2) was compound htz for a splice-site and a frameshift variant (c.2625+1G>A and c.2197dupG) with Sanger sequencing used for confirmation and segregation studies. BUB1 encodes BUB1 Mitotic checkpoint serine/threonine kinase (/Budding uninhibited by benzimidazoles 1, s. cerevisiae, homolog of) a multifunctional component of the segregation machinery contributing to multiple mitotic processes. The protein has a kinetochore localization domain, multiple binding motifs and a C-terminal kinase domain (aa 784-1085) this structure allowing both kinase dependent/independent activities. cDNA sequencing revealed that the splice variant leads to skipping of ex21 and in-frame deletion of 54 residues in the kinase domain (c.2625+1G>A / p.Val822_Leu875del). Both individuals exhibited normal BUB1 mRNA levels (fibroblasts in both, tracheal tissue in one) but severely reduced protein levels (fibroblasts). A shorter protein product corresponding to the in-frame deletion variant was also detected. The authors performed additional experiments to confirm small amounts of full-length protein produced by the start-lost variant. This was shown in SV40-transformed fibroblasts from the corresponding individual (treatment with a proteasome inhibitor resulted also in higher levels). Upon generation RPE1 cells using CRISPR for the start-lost variant, again, small amounts of full length protein were detected, which was not the case for complete knockout HAP1 cells. No shorter versions could be detected in the patient cells or RPE1 cells, arguing against utilization of an alternative start codon. (Use of non-AUG start codons discussed based on literature). In line with small amounts of full-length protein the authors provided evidence for residual kinase activity for the start-loss variant (through proxy of phosphorylation of its substrate and use of a BUB1 kinase inhibitor). Cells from the individual with the frameshift variant and the splice variant had no residual kinase activity. The authors provide evidence for mitotic defects in cells from both individuals with prolonged mitosis duration and chromosome segregation defects. Some patient-specific findings were thought to be related with BUB1 protein levels (affecting BUB1-mediated kinetochore recruitment of BUBR1, important for chromosome alignment) and others due to residual kinase activity [->phosphorylation of H2A at Threonine 120-> affecting centromeric recruitment of Aurora B, SGO1 (role in protection of centromeric cohesion), TOP2A (a protein preventing DNA breakage during sister chromatid separation), these correlated with high anaphase bridges (in P2), aneuploidy observed in lymphoblasts and primary fibroblasts from P2 but not P2's lymphocytes or lymphocytes from P1) and defective sister chromatid cohesion defects (in primary fibroblasts from P2, milder effect for P1). Overall the authors provide evidence for overlapping clinical and cellular phenotype for this condition with primary microcephalies (MCPH - mutations in genes for mitotic regulators incl. kinetochore proteins or regulators of chromosome organization), mosaic variegated aneuploidy (biallelic variants in genes for kinetochore proteins, with random aneuploidies occurring in >5% cells of different tissues) and cohesinopathies (mostly Roberts or Warsaw breakage syndromes - characterized by cohesion loss and/or spontaneous railroad chromosomes). Mouse model: Hmz disruption in mice is lethal shortly after E3.5 (cited PMID: 19772675), while a hypomorphic mutant mouse (lacking exons 2-3, expressing <5% of wt protein levels) is viable but exhibits increased tumorigenesis with aging and aneuploidy (cited PMID: 19117986). Mutant mice that lack kinase activity though with preserved Bub1 protein abundance, did not display increased susceptibility, despite substantial segregation errors and aneuploidies (cited PMID: 23209306). The authors note that monoallelic germline BUB1 variants have been described in small number of individuals with CRC, exhibiting reduced expression levels and variegated aneuploidy in multiple tissues (cited PMID: 23747338) although the role of BUB1 is debated (cited PMIDs: 27713038, 29448935). Based on the discussion, complete loss of BUB1 activity is presumed to be embryonically lethal based on the mouse study (PMID: 19772675) and reduced BUB1 expression associated with spontaneous miscarriages (cited PMID: 20643875, to my understanding in this study mRNA levels remained relatively constant despite reduced Bub1 protein levels, mRNA RT-PCR followed by sequencing revealed only 2 synonymous BUB1 variants). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1562 | PABPC1 |
Konstantinos Varvagiannis gene: PABPC1 was added gene: PABPC1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PABPC1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PABPC1 were set to 35511136 Phenotypes for gene: PABPC1 were set to Global developmental delay; Expressive language delay; Intellectual disability; Behavioral abnormality; Seizures Penetrance for gene: PABPC1 were set to unknown Review for gene: PABPC1 was set to AMBER Added comment: Wegler et al (2022 - PMID: 35511136) describe the phenotype of 4 individuals with de novo variants in the PABP domain of PABPC1. Overlapping features included DD (4/4) with weak expressive language (4/4), learning disability/borderline intellectual functioning (in 2) to more severe ID (in 2 others), treatable/self-limiting seizures (in 3 for whom this information was available) as well as variable behavioral issues (impaired social skills, concentration/sleeping problems, ADHD, anxiety or autism). Other features involved feeding difficulties (3/4), hearing impairment (in 2/3) or variable other phenotypes. Contribution of de novo variants found in other genes was thought possible. All 4 were investigated by trio exome sequencing following negative previous routine diagnostic work-up. WES revealed heterozygous de novo PABPC1 variants, 3 of which were missense SNVs (c.1687G>A/p.Gly563Ser, c.1691A>C/p.Glu564Gly, c.1709T>C/p.Ile570Thr using NM_002568.3) and a fourth an in-frame deletion (c.1664_1666del/p.Pro555del). Additional de novo variants were reported in 3 cases (IGF2R missense SNV, htz KDM5B stopgain, RBBP4 - the latter not associated with any phenotype to date). PABPC1 encodes Polyadenylate-binding protein, cytoplasmic, 1 which as the authors summarize has an important role overall in regulation of gene expression (poly(A) tail length, mRNA formation, export of processed mRNAs to cytoplasm, translation initiation promotion and termination, mRNA stability, NMD). Translation is regulated by Polyadenylate-binding protein–interacting proteins (PAIPs) which control PABP activity. PAIP2 in particular, which is highly expressed in CNS, is known to inhibit translation via binding to the PABP domain of PABPC1 and is thought to play an important role through transcriptional regulation for synaptic plasticity and memory. To evaluate plausibility as a DD gene the authors performed analyses using publicly available data, with PABPC1 ranking high in terms of protein-protein interaction (PPI) and co-expression with known DD genes. Variants were absent from gnomAD with in silico predictions in favour of a deleterious effect. While PABPC1 is intolerant to both missense and LoF variants (z-score 4.49, pLI of 1), occurrence of these 4 dn variants and their clustering in the PABP domain appeared to be of statistical significance (p=0.002 and p=2.8x10-8) rather than being explained by random occurrence. Structural modeling of variants suggested that all were in close spatial vicinity within the PABP domain, likely influencing PAIP2 binding. In HeLa cells the variants were shown not to affect subcellular localization (to the cytoplasm) compared to wt. In addition, there were no significant differences upon stress conditions under which the protein localizes to stress granules. In HeLa cells, co-immunoprecipitation assays using C-terminal HA tagged PABPC1, revealed that 3 variants (Gly563Ser, Glu564Gly, Ile570Thr) significantly reduced physical PABPC1-PAIP2 interaction compared with wt, which was also observed though to a not significant extent for Pro555del. (Other variants from literature also studied as discussed below). Pabpc1 is highly expressed in all regions of the developing mouse brain with remarkable decrease after birth, suggesting a critical role in prenatal brain development. Through electroporation with Pabpc1-directed shRNA the authors provided evidence that Pabpc1 LoF results in abnormal neural progenitor cell proliferation with rescue experiments using human WT or missense variants (Gly563Ser, Glu564Gly, Ile570Thr) showing that only the WT could rescue the proliferation phenotype. Overall a model whereby weakened PABPC1-PAIP2 interaction, leading to dysregulation to gene expression homeostasis and interference with proliferation of neural progenitors and the later to the NDD phenotype is proposed. Given previous reports in the literature for de novo PABPC1 variants, namely Lys138Glu, Asp204Val, Arg481His, Pro456Leu the authors noted that the phenotypes reported in the respective individuals were rather explained by other variants (16p11.2 dup, ARID1A dn, TBL1XR1 dn variants). These PABPC1 variants do not lie in the PABP domain, have lower in silico pathogenicity scores (MPC/CADD), with structural modelling suggestive of no significant effect. Importantly, upon co-immunoprecipitation studies with PAIP2 which were here performed, these variants had no effect. Pathogenicity of these variants - not located within the PABP domain - through another mechanism cannot be however ruled out. (PMIDs cited, though not reviewed based on this discussion: De Rubeis et al, 2014 - PMID: 25363760, Guo et al, 2019 - PMID: 30504930, Kaplanis et al, 2020 - PMID: 33057194). Currently there is no PABPC1-related phenotype in other databases (incl. OMIM, G2P, SysID, PanelApp Australia). Consider inclusion in the gene panels for ID and epilepsy with amber / green rating (DD with or without ID in >= 3 individuals/families/variants – also the case for seizures, role of the gene, statistical evidence for the gene/occurrence and clustering of variants, functional studies with strong evidence for at least 3 variants || learning difficulties/borderline intellectual functioning in 2 affected individuals, phenotype in few might be "blended" due to additional de novo variants). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1562 | CTR9 |
Konstantinos Varvagiannis gene: CTR9 was added gene: CTR9 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CTR9 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CTR9 were set to 35499524; 2815719; 25363760; 27479843; 25099282; 29292210 Phenotypes for gene: CTR9 were set to Delayed speech and language development; Motor delay; Intellectual disability; Behavioral abnormality; Autistic behavior; Failure to thrive; Feeding difficulties; Abnormality of the cardiovascular system Penetrance for gene: CTR9 were set to unknown Mode of pathogenicity for gene: CTR9 was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: CTR9 was set to AMBER Added comment: Meuwissen, Verstraeten, Ranza et al (2022 - PMID: 35499524) describe the phenotype of 13 unrelated individuals harboring heterozygous - predominantly de novo - CTR9 missense variants. Overlapping features included delayed speech and/or motor development (each in 9 cases) with the latter complicated by hypotonia or hyperlaxity in some cases. Balance or coordination problems were also reported in some. Variable degrees of ID ranging from mild to severe were observed in all individuals of relevant age except for 3 who however experienced impairment in other domains and/or learning difficulties (8/11 - 2 individuals were too young for evaluation). Few had evidence of regression. Other features included behavioral abnormalities (incl. ASD in 4), FTT/feeding problems (in 5), cardiovascular findings (in 4 - incl. infantile thoracic aortic aneurysm, VSD, pulm. valve stenosis, SVAS). The authors reported variable/nonspecific dysmorphic features. WES revealed heterozygous CTR9 missense variants in all cases (NM_014633.5 as RefSeq). The variants occurred de novo in most (11/13) individuals with a one proband having inherited the variant from his affected parent. For one case, a single parental sample was available. Most SNVs were absent from gnomAD with the exception of c.1364A>G/p.Asn455Ser and c.2633G>A/p.Arg878Gln present once in the database (Z-score for CTR9: 4.3 / pLI : 1). The variants affected highly conserved residues with in silico predictions mostly in favor of a deleterious effect. CTR9 encodes a subunit of the PAF1 complex (PAF1C) with the other subunits encoded by PAF1, LEO1, CDC73, RTF1 and WDR61/SKI8. The complex acts as a transcriptional regulator with CTR9 binding RNA polymerase II. The complex influences gene expression by promoting H2BK123 ubiquitylation, H3K4 and H3K36 methylation. In yeast, Paf1 and Ctr9 appear to mediate involvement of Paf1C in induction of mitophagy (several Refs provided). In silico modeling: a group of N-terminal variants likely destabilize structure, another group possibly perturbs CTR9-PAF1 interactions and a 3rd class influences interactions with other subunits. p.Glu15Lys did not appear to influence protein stability. Functional studies: H3K4/H3K36 methylation analysis, mitochondrial quality assessment and RNA-seq studies in fibroblasts did not provide conclusive evidence for downstream consequences of the variants (albeit a brain-specific effect - as demonstrated for other disorders – cannot be excluded). Animal models: In zebrafish, the Paf1C complex has been shown to play a role in cardiac specification and heart morphogenesis with ctr9 mutants showing severe defects in morphogenesis of primitive heart tube (cited PMID: 21338598). This supports a role of the CTR9 variants in the cardiac abnormalities observed in 4 individuals. Although Paf1C zebrafish homologues are required for Notch-regulated transcription (cited PMID: 17721442), there was no supporting evidence from RNA-seq analyses performed by the authors. In Drosophila, Ctr9 has a key role at multiple stages of nervous system development in Drosophila (cited PMID: 27520958). In rat, Ctr9 is expressed in dopaminergic neurons, with its expression not restricted to the nucleus, regulating dopamine transporter activity (cited PMID: 26048990). As commented, de novo CTR9 variants have been identified in indivdiduals with developmental disorders in larger cohorts, though without phenotypic details (DDD study - PMID:2815719, De Rubeis et al, 2014 - PMID: 25363760, Lelieveld et al PMID: 27479843) [ https://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=CTR9 ] Two previous studies (Hanks et al, 2014 - PMID: 25099282, Martins et al 2018, PMID: 29292210) have identified individuals with pLoF variants [in almost all cases leading to skipping of ex9 e.g. NM_014633.4:c.958-9A>G or (RefSeq not provided) c.1194+2T>C, c.1194+3A>C, the single exception being c.106C>T/p.Q36*] in individuals and families with Wilms tumor after exclusion of other genetic causes. Analyses of tumor samples revealed in several of these cases either LOH (most commonly) or truncating variants as second hits. These individuals did not display neurodevelopmental phenotypes (despite detailed clinical information provided in the 2 studies). CTR9 is included in the gene panels for WT and Tumor predisposition - childhood onset with green rating. [In addition few individuals with hyperparathyroidism jaw tumor syndrome due to heterozygous variants in CDC73 - another subunit of the PAF1 complex - have been reported with WT]. Given these reports, commenting on the embryonic lethality of Ctr9 homozygous ko mice (MGI) and the observation of only missense variants in their cohort Meuwissen, Verstraeten, Ranza et al presume that a dominant-negative effect may apply for the variants they report. Consider inclusion in the current panel with amber (variant effect/underlying mechanism unknown) or green rating (>3 individuals/families/variants, multiple reports, some supporting evidence from animal models). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1561 | DNAH14 |
Konstantinos Varvagiannis gene: DNAH14 was added gene: DNAH14 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DNAH14 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DNAH14 were set to 35438214 Penetrance for gene: DNAH14 were set to unknown Review for gene: DNAH14 was set to RED Added comment: Li et al (2022 - PMID: 35438214) describe 3 individuals harboring biallelic DNAH14 variants. In addition the authors perform a review of cases previously published in the literature. The reported phenotype does not appear to be very consistent or specific (seizures with highly variable age of onset with or without DD / cognitive delay). Comparison with previously reported subjects (not further reviewed) - discussed in text and appearing mixed in table 1 - does not seem to support an overlapping phenotype. The authors comment that DNAH14 encodes a heavy chain of axonemal dyneins. Little evidence is provided to support the role of the gene in the pathogenesis of the disorder and pathogenicity of the variants (ultra-rare and predicted in silico to be deleterious). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1561 | DPH5 |
Konstantinos Varvagiannis gene: DPH5 was added gene: DPH5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DPH5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DPH5 were set to 35482014 Phenotypes for gene: DPH5 were set to Abnormality of prenatal development or birth; Neonatal hypotonia; Global developmental delay; Intellectual disability; Seizures; Abnormality of the cardiovascular system; Abnormality of the globe; Feeding difficulties; Short stature; Abnormality of head or neck Penetrance for gene: DPH5 were set to unknown Review for gene: DPH5 was set to AMBER Added comment: Shankar et al (2022 - PMID: 35482014) present evidence for a diphthamide-deficiency syndrome due to biallelic DPH5 pathogenic variants. As the authors summarize, DPH5 encodes a methyltransferase critical to the biosynthesis of diphthamide. Diphthamide is a post translationally modified histidine residue found in eukaryotic elongation factor 2 (eEF2). eEF2 is essential for mRNA translation and protein synthesis. The role of diphthamide is not clear, although it serves as a target for ADP-ribosylation, the latter resulting in inactivation of the eEF2 (inhibition of its translocation activity) and arrest of protein synthesis. Biosynthesis of diphthamide is complex involving multiple components (DPH1-DPH7) and the methylating co-factor S-adenosyl methionine, with 2 diphthamide-deficiency disorders due to biallelic DPH1 or DPH2 pathogenic variants and a NDD phenotype reported to date. The authors describe a phenotypic spectrum associated with biallelic DPH5 variants ranging from a prenatally lethal presentation to profound neurodevelopmental disorder. Details are provided on 5 individuals from 3 unrelated families. While one subject died at the age of few days due to multisystem complications, the phenotype appeared to be relatively consistent with prenatal findings (decreased fetal movements in 2 from 2 families, polyhydramnios in 2 from 2 families), hypotonia, global DD and ID (4/4 from 2 families - profound in 3), seizures (3/5 from 2 families - abnormal EEG in 4/4), cardiovascular findings (5/5, MVP and regurgitation in 2 from Fam1 || aortic dilatation in 2 sibs from Fam2 || VSD, ASD and hypopl. PA, pericardial effusion in 5th), GI issues (5/5, poor feeding in 4), short stature (4/4). Ocular findings were reported in 3/4 (gray sclerae in 2, ocular melanocytosis in 2). The authors describe some common craniofacial findings incl. broad/prominent forehead (5/5), sparse eyebrows (4/5), downturned corners of mouth or triangular chin (each in 3/5). WES/WGS revealed biallelic DPH5 variants in all affected individuals, namely: homozygosity for a missense variant in 2 sibs (NM_001077394.2:c.779A>G/p.His260Arg). Homozygosity for c.521dupA/p.Asn174LysTer10 for the individual deceased in the neonatal period (for this family there was significant history of spontaneous miscarriages/stillbirth/neonatal death). Two sibs born to non-consanguineous parents were compound htz for a stopgain and a missense SNV (c.619C>T/p.Arg207*, c.329A>G/p.Asn110Ser). In silico modeling revealed that the pLoF variants, not predicted to lead to NMD, likely remove the domain for interaction with eEF2 while the missense ones also affected interaction with eEF2. In recombinant MCF7 breast cancer cell line-derived DPH5-knockouts, transfected with recombinant expr. plasmids encoding wt or the 4 variants, the 2 truncating variants were shown to affect ADP-ribosylation of eEF2's diphthamide (total lack / minimal enzymatic activity for Arg207* and Asn174Lysfs respectively). Asn110Ser and His260Arg had residual activities which was thought to be explained by high expression levels compensating partial inactivation (given the multicopy plasmid-driven expression). ADP-ribosylation assays in S. cerevisiae demonstrated loss of function for the 2 truncating variants. Although the 2 missense variants retained sufficient activity to produce diphthamide (assayed through toxin induced ADP-ribosylation of eEF2), more sensitive assays indicated that diphthamide synthesis was also partially compromised for both variants. Generation of a knockin mouse model for His260Arg, appeared to recapitulate the human phenotypes with craniofacial, ophthalmologic, cardiac and visceral abnormalities and hmz mice being subviable. A single homozygous liveborn mouse had low birthweight, FTT, craniofacial dysmorphology, polydactyly, abnormal grooming behavior and early death. Few heterozygous embryos had craniofacial features, decreased body weight, reduced neuromuscular function without other abnormalities, either due to their inbred background or in the context of milder phenotype of heterozygosity in mice. DPH5 is ubiquitously expressed in all human tissues. The gene has a pLI of 0 and LOEUF score of 0.77 (0.48-1.27) in gnomAD. The authors refer to unpublished data, noting that complete absence of DPH5 is incompatible with life with embryonic lethality of a Dph5(ko/ko) line. The phenotype bears similarities to DPH1- and DPH2- related NDDs (both AR / green and amber respectively in ID panel) and appears to be more severe compared to the phenotype of de novo EEF2 variants (cited PMID: 33355653). Please consider inclusion in the ID panel with amber (4 individuals from 2 families with ID) / green rating (rather consistent phenotype in 3 families probably representing a continuous spectrum, variant studies, mouse model, similarities with diphthamide-deficiency syndromes). Also consider amber rating in the epilepsy panel (3 individuals from 2 families reported). The gene may be also relevant in other gene panels e.g. for congenital heart disease, short stature, etc (not added). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1561 | CCDC82 |
Konstantinos Varvagiannis gene: CCDC82 was added gene: CCDC82 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CCDC82 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CCDC82 were set to 27457812; 28397838; 35118659; 35373332 Phenotypes for gene: CCDC82 were set to Global developmental delay; Intellectual disability; Spastic paraparesis Penetrance for gene: CCDC82 were set to Complete Review for gene: CCDC82 was set to AMBER Added comment: The phenotype of individuals with biallelic CCDC82 variants has been reported - in most cases briefly - in the following reports (each summarizing the findings of previous ones): Riazzudin et al (2017 - PMID: 27457812) in a large consanguineous pedigree from Pakistan (PKMR206) identified 4 individuals homozygous for a fs variant [NM_024725.3:c.373delG / p.(Asp125Ilefs*6)] (V3,V4,V5,V10). There was no other variant segregating with the phenotype of ID (Delayed CMS, moderate ID and speech delay probably common to all, V3,4,5 had also mild hypotonia and motor weakness). There was one unaffected sib tested (homozygous for ref. alelle). 2 further affected males (V1, V2) with similar phenotype were not tested. Harripaul et al (2018 - PMID: 28397838) reported 2 sibs with nonsyndromic ID belonging to a consanguineous family (AS17) from the Middle-East. Both were homozygous for NM_024725.3:c.535C>T / p.Arg179*. The variant was confirmed with Sanger sequencing and parents were heterozygous carriers. Two additional affected sibs were probably not tested. Yahia et al (2022 - PMID: 35118659) described 2 sibs belonging to a consanguineous family from Sudan. These presented global DD (last evaluation at 4y and 9m) and spasticity. There was a common history of infantile spasms with the elder developing GTC convulsions with spontaneous resolution. Additionaly, both presented microcephaly (<-2 and <-3SD). Exome sequencing revealed homozygosity for c.535C>T / p.Arg179* (previously reported by Harripaul et al). Sanger sequencing was used for confirmation and demonstration of carrier state of parents. Two similarly affected sibs were not available for testing. Bauer et al (2022 - PMID: 35373332) reported a 21 y.o. male born to consanguineous parents from Pakistan. Features included short stature, ID, spastic paraparesis (at the age of 3y). Gelastic seizures were suspected but not confirmed (repeated normal EEGs). WES revealed homozygosity for a fs CCDC82 variant [NM_001318736.1:c.183del / p.(Phe61Leufs*27)] with Sanger confirmation in proband and heterozygous parents. There was another hmz variant, albeit classified as VUS and not thought to fit the clinical presentation. As proposed by Bauer et al. overlapping features include spastic paraparesis, DD and dysmorphic features. As commented, CCDC82 encodes coiled-coil domain protein 82, a protein with unknown function. Consider inclusion probably with amber rating (>3 individuals/families/variants, role of the gene not known, variant studies not performed to date, animal models not discussed). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1561 | CDK9 |
Konstantinos Varvagiannis changed review comment from: There are 4 studies reporting on the phenotype associated with biallelic CDK9 pathogenic variants. DD and ID are part of the phenotype which appears to be relatively consistent. CDK9 encodes Cyclin-dependent kinase 9. There are 4 missense variants reported to date - one of which recurrent (NM_001261.3:c.673C>T / p.Arg225Cys) - with studies for 3 variants suggesting a LoF effect (loss of kinase activity) [Ref4]. Animal models also provide some supporting evidence [discussed Ref4]. Consider inclusion in the current panel (probably with green rating) as well as other possibly relevant ones. Details provided below. [1]----- Shaheen et al (2016 - PMID: 26633546) studied patients with apparently novel phenotypes with positive family history consistent with AR inheritance mode due to consanguinity. After autozygome analysis the authors determined the shared autozygome (ROH >1 Mb / Axiom SNP Chip) in families with multiple affected individuals. This analysis was followed by whole exome/genome sequencing. Using this approach, they managed to map the phenotype of interest to a single novel locus in some families, which was also the case in a large consanguineous family with 2 similarly affected cousins (11DG0424, 11DG1630). Within a 20 Mb region of homozygosity, followed by WES in a single affected individual and Sanger confirmation with compatible segregation studies in parents and 10 unaffected sibs, the authors identified a homozygous CDK9 missense SNV (NM_001261.3:c.673C>T / p.Arg225Cys) responsible for this phenotype. In silico predictions were concordant in favor of a deleterious effect. Features (detailed in the suppl.) included global DD (2/2), severe ID (1/1), cerebral and (mild) cerebellar atrophy (2/2), microcephaly (2/2), ocular anomalies (2/2, coloboma in 2/2, congenital cataract 2/2, etc), heart defects (2/2, PDA in both, ASD), variable genitourinary anomalies (2/2 incl. hydronephrosis, VUR reflux/recurrent UTIs, kidney atrophy, abn. genitalia in 1), abnormalities of the limbs (2/2, bilateral talipes equinovarus : 2/2) or the skeleton (1/2 - butterfly vertebrae). One was reported to have some degree of growth delay (<10th centile for length, <5th for weight and OFC). There was no hearing defect reported (large ears in 1/2). Overall, the authors used the term CHARGE-like phenotype. [2]----- Maddirevula et al (2019 - PMID: 30237576) performed autozygome and exome analysis of individuals with suspected Mendelian disorders. They reported 3 individuals (18DG0161, 18DG0162, 18DG0165) born to 3 different consanguineous families (information in fig2) from Qatar, homozygous for CDK9 p.Arg225Cys. All presented a CHARGE-like phenotype with features ophtalmologic findings (3/3 - abnormal ERG in one, congenital cataracts the other, visual impairment in the 3rd, though NO evidence of coloboma in at least two), heart defect (2/3 had VSD), choanal atresia (3/3), retarded growth/FTT (1/3) or global DD (3/3 - in suppl. table 1), (genito)urinary anomalies (1/3 - dysplastic atrophic kidney) or ear anomalies (3/3 - preauricular tags 2/3, bilateral deafness 1/3, bilat.ossicular anomalies 1/3). Other features incl. epilepsy (2/3), brain MRI abnormalities (2/3), facial asymmetry in one, vertebral segmentation defect in 1/3. [3]----- Hu et al (2019 - PMID: 29302074) performed WES/WGS in 404 consanguineous families from Iran, having 2 or more offspring with ID. In this context they reported 2 females and a male (III:1,4,3 belonging to fam. M9100018 - details in suppl. text) born to first cousin parents from Iran. Features included DD (3/3 - walking at 3y, words at 4y), moderate ID (3/3 - WAIS-IV IQ of 40-43), short stature (3/3 below 3rd %le). Vision and hearing were normal. All three were homozygous for a missense SNV (NM_001261:c.280C>T, p.Arg94Cys) which was ultrarare in ExAC, with severa in silico tools in favor of a deleterious effect. The authors commented that CDK9 is the catalytic core of transcription elongation factor p-TEFb essential for transcription elongation of numerous genes, Cdk9/Cyclin T1 complex may participate in neuronal differentiation, CDK9-cyclinK in maintenance of genomic integrity, with the protein encoded also interacted with AF4/FMR2. In addition the gene was commented to have ubiquitous expression with high protein expression in glial and neuronal cells of the cortex (based on Uniprot and Human Protein Atlas). [4]----- Nishina et al (2021 - PMID: 33640901) described an 8 y.o. male with facial asymmetry, ear/hearing anomalies (microtia, preauricular tags, bilateral hearing loss), ocular/vision anomalies (blepharophimosis, lacrimal obstruction, eyelid dermoids, duane-like anomaly, congenital cataracts, retinal dystrophy), cleft lip and palate, abnormalities of the limbs (finger contractures with associated absence of creases, cutaneous syndactyly, etc). Other features included cardiac dysrhythmia and undescended testes. Development was delayed with associated ID (walking 3y, words 7y, at 10y: could count to 20, 4 word sentences). There was no evidence of coloboma or choanal atresia. Trio exome sequencing revealed that the child was compound htz for 2 missense SNVs (NM_001261.3:c.862G>A / p.Ala288Thr and c.907C>T /p.Arg303Cys) with Sanger confirmation. These were ultrarare/not present in gnomAD. Both lied in the protein kinase catalytic domain of CDK9, with high conservation across different species and in silico predictions in favor of deleterious effect. In vitro studies in HEK293 cells demonstrated that the kinase activity for both variants was significantly reduced compared to wt. Kinase activity was also reduced for the Arg225Cys variant (reported in Refs 1 & 2). The authors briefly discuss evidence from zebrafish (regulates larval morphogenesis incl. brain, heart, eye, blood vessels) and mouse models. In the latter complete LoF is lethal while heterozygous LoF is associated with abnormal morphology of heart, skin and epididymis (PMIDs cited by the authors : 27715402, 30100824). Sources: Literature; to: There are 4 studies reporting on the phenotype associated with biallelic CDK9 pathogenic variants. DD and ID are part of the phenotype which appears to be relatively consistent. CDK9 encodes Cyclin-dependent kinase 9. There are 4 missense variants reported to date - one of which recurrent (NM_001261.3:c.673C>T / p.Arg225Cys) - with studies for 3 variants suggesting a LoF effect (loss of kinase activity) [Ref4]. Animal models also provide some supporting evidence [discussed Ref4]. Consider inclusion in the current panel (probably with green rating) as well as other possibly relevant ones. Details provided below. [1]----- Shaheen et al (2016 - PMID: 26633546) studied patients with apparently novel phenotypes with positive family history consistent with AR inheritance due to consanguinity. Using autozygome analysis the authors determined the shared autozygome (ROH >1 Mb / Axiom SNP Chip) in families with multiple affected individuals. This analysis was followed by whole exome/genome sequencing. Using this approach, they managed to map the phenotype of interest to a single novel locus in some families, which was also the case in a large consanguineous family with 2 similarly affected cousins (11DG0424, 11DG1630). Within a 20 Mb region of homozygosity, followed by WES in a single affected individual and Sanger confirmation with compatible segregation studies in parents and 10 unaffected sibs, the authors identified a homozygous CDK9 missense SNV (NM_001261.3:c.673C>T / p.Arg225Cys) responsible for this phenotype. In silico predictions were concordant in favor of a deleterious effect. Features (detailed in the suppl.) included global DD (2/2), severe ID (1/1), cerebral and (mild) cerebellar atrophy (2/2), microcephaly (2/2), ocular anomalies (2/2, coloboma in 2/2, congenital cataract 2/2, etc), heart defects (2/2, PDA in both, ASD), variable genitourinary anomalies (2/2 incl. hydronephrosis, VUR/recurrent UTIs, kidney atrophy, abn. genitalia in 1), abnormalities of the limbs (2/2, bilateral talipes equinovarus : 2/2) or the skeleton (1/2 - butterfly vertebrae). One was reported to have some degree of growth delay (<10th centile for length, <5th for weight and OFC). There was no hearing defect reported (large ears in one case). Overall, the authors used the term CHARGE-like for this phenotype. [2]----- Maddirevula et al (2019 - PMID: 30237576) performed autozygome and exome analysis of individuals with suspected Mendelian disorders. They reported 3 individuals (18DG0161, 18DG0162, 18DG0165) born to 3 different consanguineous families (information in fig2) from Qatar, homozygous for CDK9 p.Arg225Cys. All presented a CHARGE-like phenotype with ophthalmologic findings (3/3 - abnormal ERG in one, congenital cataracts the other, visual impairment in the 3rd, though NO evidence of coloboma in at least two of them), heart defect (2/3 with VSD), choanal atresia (3/3), retarded growth/FTT (1/3) or global DD (3/3 - in suppl. table 1), (genito)urinary anomalies (1/3 - dysplastic atrophic kidney) or ear anomalies (3/3 - preauricular tags in 2/3, bilateral deafness 1/3, bilateral ossicular anomalies 1/3). Other features incl. epilepsy (2/3), brain MRI abnormalities (2/3), facial asymmetry in one, vertebral segmentation defect in 1/3. [3]----- Hu et al (2019 - PMID: 29302074) performed WES/WGS in 404 consanguineous families from Iran, having 2 or more offspring with ID. In this context they reported 2 females and a male (III:1,4,3 belonging to fam. M9100018 | suppl. text) born to first cousin parents from Iran. Features included DD (3/3 - walking at 3y, words at 4y), moderate ID (3/3 - WAIS-IV IQ of 40-43), short stature (3/3 below 3rd %le). Vision and hearing were normal. All three were homozygous for a missense SNV (NM_001261:c.280C>T, p.Arg94Cys) which was ultrarare in ExAC, with several in silico tools in favor of a deleterious effect. The authors commented that CDK9 is the catalytic core of transcription elongation factor p-TEFb essential for transcription elongation of numerous genes, Cdk9/Cyclin T1 complex may participate in neuronal differentiation, CDK9-cyclinK in maintenance of genomic integrity, with the protein encoded also interacting with AF4/FMR2. In addition the gene was commented to have ubiquitous expression with high protein expression in glial and neuronal cells of the cortex (based on Uniprot and Human Protein Atlas). [4]----- Nishina et al (2021 - PMID: 33640901) described an 8 y.o. male with facial asymmetry, ear/hearing anomalies (microtia, preauricular tags, bilateral hearing loss), ocular/vision anomalies (blepharophimosis, lacrimal obstruction, eyelid dermoids, duane-like anomaly, congenital cataracts, retinal dystrophy), cleft lip and palate, abnormalities of the limbs (finger contractures with associated absence of creases, cutaneous syndactyly, etc). Other features included cardiac dysrhythmia and undescended testes. Development was delayed with ID (walking 3y, words 7y, at 10y: could count to 20, 4 word sentences). There was no evidence of coloboma or choanal atresia. Trio exome revealed that the child was compound htz for 2 missense SNVs (NM_001261.3:c.862G>A / p.Ala288Thr and c.907C>T /p.Arg303Cys) with Sanger confirmation. These were ultrarare/not present in gnomAD. Both lied in the protein kinase catalytic domain of CDK9, with high conservation across different species and in silico predictions in favor of deleterious effect. In vitro studies in HEK293 cells demonstrated that the kinase activity for both variants was significantly reduced compared to wt. Kinase activity was also reduced for the Arg225Cys variant (reported in Refs 1 & 2). The authors briefly discuss evidence from zebrafish (regulates larval morphogenesis incl. brain, heart, eye, blood vessels) and mouse models. In the latter complete LoF is lethal while heterozygous LoF is associated with abnormal morphology of heart, skin and epididymis (PMIDs cited : 27715402, 30100824). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1561 | CDK9 |
Konstantinos Varvagiannis gene: CDK9 was added gene: CDK9 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CDK9 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CDK9 were set to 26633546; 30237576; 29302074; 33640901 Phenotypes for gene: CDK9 were set to Global developmental delay; Intellectual disability; Abnormality of vision; Congenital cataract; Iris coloboma; Abnormal heart morphology; Choanal atresia; Abnormality of the ear; Preauricular skin tag; Hearing impairment; Abnormality of the genitourinary system; Abnormality of limbs; Abnormality of the vertebrae; Abnormality of nervous system morphology; Seizures Penetrance for gene: CDK9 were set to Complete Review for gene: CDK9 was set to GREEN Added comment: There are 4 studies reporting on the phenotype associated with biallelic CDK9 pathogenic variants. DD and ID are part of the phenotype which appears to be relatively consistent. CDK9 encodes Cyclin-dependent kinase 9. There are 4 missense variants reported to date - one of which recurrent (NM_001261.3:c.673C>T / p.Arg225Cys) - with studies for 3 variants suggesting a LoF effect (loss of kinase activity) [Ref4]. Animal models also provide some supporting evidence [discussed Ref4]. Consider inclusion in the current panel (probably with green rating) as well as other possibly relevant ones. Details provided below. [1]----- Shaheen et al (2016 - PMID: 26633546) studied patients with apparently novel phenotypes with positive family history consistent with AR inheritance mode due to consanguinity. After autozygome analysis the authors determined the shared autozygome (ROH >1 Mb / Axiom SNP Chip) in families with multiple affected individuals. This analysis was followed by whole exome/genome sequencing. Using this approach, they managed to map the phenotype of interest to a single novel locus in some families, which was also the case in a large consanguineous family with 2 similarly affected cousins (11DG0424, 11DG1630). Within a 20 Mb region of homozygosity, followed by WES in a single affected individual and Sanger confirmation with compatible segregation studies in parents and 10 unaffected sibs, the authors identified a homozygous CDK9 missense SNV (NM_001261.3:c.673C>T / p.Arg225Cys) responsible for this phenotype. In silico predictions were concordant in favor of a deleterious effect. Features (detailed in the suppl.) included global DD (2/2), severe ID (1/1), cerebral and (mild) cerebellar atrophy (2/2), microcephaly (2/2), ocular anomalies (2/2, coloboma in 2/2, congenital cataract 2/2, etc), heart defects (2/2, PDA in both, ASD), variable genitourinary anomalies (2/2 incl. hydronephrosis, VUR reflux/recurrent UTIs, kidney atrophy, abn. genitalia in 1), abnormalities of the limbs (2/2, bilateral talipes equinovarus : 2/2) or the skeleton (1/2 - butterfly vertebrae). One was reported to have some degree of growth delay (<10th centile for length, <5th for weight and OFC). There was no hearing defect reported (large ears in 1/2). Overall, the authors used the term CHARGE-like phenotype. [2]----- Maddirevula et al (2019 - PMID: 30237576) performed autozygome and exome analysis of individuals with suspected Mendelian disorders. They reported 3 individuals (18DG0161, 18DG0162, 18DG0165) born to 3 different consanguineous families (information in fig2) from Qatar, homozygous for CDK9 p.Arg225Cys. All presented a CHARGE-like phenotype with features ophtalmologic findings (3/3 - abnormal ERG in one, congenital cataracts the other, visual impairment in the 3rd, though NO evidence of coloboma in at least two), heart defect (2/3 had VSD), choanal atresia (3/3), retarded growth/FTT (1/3) or global DD (3/3 - in suppl. table 1), (genito)urinary anomalies (1/3 - dysplastic atrophic kidney) or ear anomalies (3/3 - preauricular tags 2/3, bilateral deafness 1/3, bilat.ossicular anomalies 1/3). Other features incl. epilepsy (2/3), brain MRI abnormalities (2/3), facial asymmetry in one, vertebral segmentation defect in 1/3. [3]----- Hu et al (2019 - PMID: 29302074) performed WES/WGS in 404 consanguineous families from Iran, having 2 or more offspring with ID. In this context they reported 2 females and a male (III:1,4,3 belonging to fam. M9100018 - details in suppl. text) born to first cousin parents from Iran. Features included DD (3/3 - walking at 3y, words at 4y), moderate ID (3/3 - WAIS-IV IQ of 40-43), short stature (3/3 below 3rd %le). Vision and hearing were normal. All three were homozygous for a missense SNV (NM_001261:c.280C>T, p.Arg94Cys) which was ultrarare in ExAC, with severa in silico tools in favor of a deleterious effect. The authors commented that CDK9 is the catalytic core of transcription elongation factor p-TEFb essential for transcription elongation of numerous genes, Cdk9/Cyclin T1 complex may participate in neuronal differentiation, CDK9-cyclinK in maintenance of genomic integrity, with the protein encoded also interacted with AF4/FMR2. In addition the gene was commented to have ubiquitous expression with high protein expression in glial and neuronal cells of the cortex (based on Uniprot and Human Protein Atlas). [4]----- Nishina et al (2021 - PMID: 33640901) described an 8 y.o. male with facial asymmetry, ear/hearing anomalies (microtia, preauricular tags, bilateral hearing loss), ocular/vision anomalies (blepharophimosis, lacrimal obstruction, eyelid dermoids, duane-like anomaly, congenital cataracts, retinal dystrophy), cleft lip and palate, abnormalities of the limbs (finger contractures with associated absence of creases, cutaneous syndactyly, etc). Other features included cardiac dysrhythmia and undescended testes. Development was delayed with associated ID (walking 3y, words 7y, at 10y: could count to 20, 4 word sentences). There was no evidence of coloboma or choanal atresia. Trio exome sequencing revealed that the child was compound htz for 2 missense SNVs (NM_001261.3:c.862G>A / p.Ala288Thr and c.907C>T /p.Arg303Cys) with Sanger confirmation. These were ultrarare/not present in gnomAD. Both lied in the protein kinase catalytic domain of CDK9, with high conservation across different species and in silico predictions in favor of deleterious effect. In vitro studies in HEK293 cells demonstrated that the kinase activity for both variants was significantly reduced compared to wt. Kinase activity was also reduced for the Arg225Cys variant (reported in Refs 1 & 2). The authors briefly discuss evidence from zebrafish (regulates larval morphogenesis incl. brain, heart, eye, blood vessels) and mouse models. In the latter complete LoF is lethal while heterozygous LoF is associated with abnormal morphology of heart, skin and epididymis (PMIDs cited by the authors : 27715402, 30100824). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1556 | FBXW7 |
Konstantinos Varvagiannis gene: FBXW7 was added gene: FBXW7 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: FBXW7 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: FBXW7 were set to 33057194; 35395208; 30885698; 26482194; 19963109; 20332316 Phenotypes for gene: FBXW7 were set to Neurodevelopmental abnormality; Global developmental delay; Intellectual disability; Macrocephaly; Microcephaly; Abnormality of brain morphology; Abnormality of the corpus callosum; Abnormality of the cerebellum; Abnormality of the cardiovascular system; Seizures; Strabismus; Abnormality of the palate Penetrance for gene: FBXW7 were set to unknown Review for gene: FBXW7 was set to AMBER Added comment: While Kaplanis et al (2020 - Ref1), identified FBXW7 among 285 genes significantly associated with developmental disorders, a recent study by Stephenson et al (2022 - Ref2) describes the neurodevelopmental phenotype of 35 individuals making this gene relevant to the current panel. There are previous reports of dn/inh germline variants in individuals (likely 7) with tumor predisposition although a neurodevelopmental phenotype was not reported in most cases. There is currently no FBXW7-related phenotype in OMIM. The gene is included in the DD panel of G2P [associated with: FBXW7-related developmental disorder (monoallelic), confidence: definitive, citing the study by Kaplanis et al]. SysID lists FBXW7 among the candidate ID genes (same Ref.). The gene has a green rating for ID in PanelApp Australia (VCGS participating in the recent publication). Consider inclusion with amber/green rating. Also consider inclusion in other panels that may be relevant(macro/microcephaly, seizures, CHD, corpus callosum / cerebellar abnormalities, cleft palate, WT, etc). [1]------------ Kaplanis et al (2020 - PMID: 33057194), by combining exome data from 31,058 parent offspring trios from the DDD study, Radboudumc and GeneDx, identified 285 genes significantly associated with developmental disorders, 28 of which (incl. FBXW7) not previously robustly associated with these disorders. [2]------------ Stephenson et al (2022 - PMID: 35395208) provide clinical information on 35 individuals harboring germline monoallelic FBXW7 variants or chromosomal deletions spanning this gene. The phenotype corresponded to a phenotypically variable NDD characterized by hypotonia (in about 2/3), neurodevelopmental abnormality (34/35 - as discussed later), seizures (8/35), abnormal brain morphology (13/17 - in 7/17 abnormal CC, in 5/17 abn. cerebellum, etc), head circumference (macrocephaly in 10/35, microcephaly in 2/35). Additional features included abnormal palate or uvula morphology (10/35 - cleft palate in 3 from 2 families while 1 individual from a 3rd family had bifid uvula) or abnormal heart morphology (11/35), ophthalmologic features (e.g. strabismus in 5/35) or hearing impairment (2/35). There was no recognizable gestalt (deeply set eyes with upper eyelid fullness in 9/35). As for the DD/ID this ranged from borderline to severe, characterized as mild-moderate in 27/35, severe in 3/35. One individual did not present neurodevelopmental abnormality 1/35. FBXW7 encodes F-box and WD40 domain protein 7 which is part of the SCF E3 ligase complex (SKP1/CUL1/F-box protein) exerting a role of recognition and binding of target proteins for degradation by the ubiquitin proteasome system. In this way FBWX7 participates in regulating a network of proteins involved in cell division, growth, differentiation (as summarized by Roversi et al - Ref2). Most individuals were investigated by trio-WES/WGS (few with singleton WES or CMA only). 28 germline FBXW7 variants were identified incl. missense (N=21), pLoF (predicted or not to undergo NMD) and 2 deletions encompassing but not limited to FBXW7. Additional SNVs/CNVs (e.g. an inh intragenic DPP6 dup in one individual (#9) with deletion, other de novo 4q CNVs (#10), an inh 22q spanning partially an ISCA TS region, a CACNA1A and KMT2D SNV, etc) were reported in few individuals. Most variants arose dn (N=30) with two individuals displaying mosaicism (2/30) and three individuals having inherited the variant from their affected parent. CNVs had occurred dn. 3 missense SNVs were recurrent in unrelated individuals. All variants identified affected all FBXW7 isoforms. As the authors comment missense variants clustered at the C-terminal half of the protein with most (16/21) occurring within the WD40 domain. [The N-terminal part commented in the literature to affect localization]. The crystal structure of FBXW7 and SKP1 complex has been determined with CYCLIN E1/DISC1 as substrates, and in silico modeling revealed that all missense variants aligned with residues required for this interaction, or adjacent ones. All were absent from gnomAD, while missense variants from gnomAD (N=78) were not predicted have significant effect on the binding affinity. Variant studies revealed that most missense variants (6/7 tested - Arg689Gln being the exception) are unlikely to cause protein instability or degradation in vivo. Co-expression of these missense variants with CYCLIN E1 / E2, known FBXW7 substrates revealed that variants were less efficient at degrading the substrate with variants in the WD40 domain having greater impact (in some cases E1 / E2 - specific). Elav-Gal4 mediated neuronal knockdown of the Drosophila ortholog archipelago (ago) using 2 RNAi-s with different efficiency was shown to affect learning or compromise neuronal function (also related to the level of knockdown). The authors summarize results from animal models for the role of this gene in development and the nervous system. KO mice die in utero at E10.5 manifesting abn. of hematopoietic or vascular development and heart-chamber maturation(*). Some htz knock-in for human cancer variants, display perinatal lethality, abn lung, cleft palate (30%)(*),etc. Conditional gut specific deletion results in impaired differentiation of intestinal goblet cells (*)(constipation in 16/35 in cohort). KO limited to CNS and PNS results in defective sucking and morphological brain abnormalities. Haploinsufficiency in the nervous system was associated with impaired differentiation of neural stem cells (possibly through a Notch-mediated mechanism). KO in Schwann cells of the peripheral nervous system resulted in enhanced myelination. Excessive oligodendrocyte cells and hypermyelination (as a result of elevated Notch & mTOR signaling) are observed in homozygous mutant zebrafish or after morpholino-mediated fbxw7 knockdown. Overall, the authors propose haploinsufficiency or loss-of-function as the underlying mechanism. Finally, as the authors comment, FBXW7 is a tumor suppressor among the most commonly mutated genes in human cancer (3.5%). Germline variants have been previously reported in individuals with cancer (Wilms tumor, rhabdoid, etc - most summarized below). However, none of the 35 individuals in this cohort (oldest 44 y.o.) had any history of cancer. Reports of individuals with germline variants causing (monoallelic) disruption of FBXW7 - cases without DD/ID: [3]------------ Mahamdallie et al (2019 - PMID: 30885698) investigated with WES a cohort of 890 individuals with Wilms tumor (799 non-familial disease, 91 from WT pedigrees). In this context they identified 4 individuals having developed WT (ages: 28-76m) with FBXW7 dn or inherited LoF variants (710G>A / p.Trp237* dn - 1972C>T / p.Arg658* - inh:NA, 1017_1021del5, 670C>T - paternal / p.Arg224* inh:NA - RefSeq not provided). One additional individual with a missense variant (1753A>T / p.Ser585Cys - dn) had developed rhabdoid tumor. While the authors mentioned additional features for other subjects in their cohort, among the 5 individuals with FBXW7 variants, only one had hypotonia (ID_0592) and another (ID_7520) had two febrile convulsions. [4]------------ Roversi et al (2015 - PMID: 26482194) described the phenotype of a 34 y.o. female with syndromic presentation (macrocephaly, nephrotic syndrome due to FSGS, Hodgkin's lymphoma, Wilms tumor, ovarian cystadenoma, breast carcinoma) harboring a 157 kb deletion of 4q31.3. Eventual DD/ID was not reported despite detailed clinical description. The deletion spanned almost the entire FBXW7 gene and a pseudogene (hg19 - chr4:153205202-153362047). The authors provided evidence that the del affected the maternal allele as dn event (maternal mosaicism excluded). Expression of FBXW7 in patient-derived EBV lymphoblastoid cell line revealed decreased levels of expression compared to controls. At somatic level, the authors looked for eventual 2nd hit in tumor tissue (which was not the case) while they demonstrated decreased FBXW7 expression in a WT sample compared to normal renal tissue. Previously, variants in other genes candidate for the phenotype were ruled out (Sanger & MLPA for TP53, BRCA1/2, PALB2, WT1, 11p15 MS-MLPA, std karyotype). [5]------------ Kuiper et al (2015 - PMID: 19963109), in a 58 y.o. patient with recurrence of RCC, identified a constitutional translocation [t(3;4)(q21;q31)]. Using long-range PCR they defined the breakpoints at 3q21.3 (128379059 - hg18) between the PLXNA1 and C3orf56 genes while the chr4 breakpoint was located within the second intron of FBXW7 (pos. 153500813 - hg18). There were no additional phenotypes reported. [6]------------ Williams et al (2010 - PMID: 20332316) reported a patient with WT harboring germline variants in WT1 and FBXW7. While the phenotype was sufficiently explained by a germline stopgain WT1 variant with a frameshift WT1 variant (as 2nd hit) confined to the tumor, the authors identified a germline in-frame FBXW7 insertion in the same individual (c.45_46insCCT / p.Thr15_Gly16insPro - RefS : NA) [if correct corresponding to: https://gnomad.broadinstitute.org/variant/4-153332910-C-CAGG - 345/281696 alleles in gnomAD]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1544 | DTYMK |
Konstantinos Varvagiannis gene: DTYMK was added gene: DTYMK was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DTYMK was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DTYMK were set to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Global brain atrophy; Cardiorespiratory arrest Phenotypes for gene: DTYMK were set to 31271740; 34918187; 35346037 Penetrance for gene: DTYMK were set to Complete Review for gene: DTYMK was set to GREEN Added comment: 4 individuals (from 3 families) harboring biallelic DTYMK pathogenic variants have been reported. Consider inclusion in the current panel with green rating given consistent and relevant phenotype and evidence provided to date [effect of variants (LoF), pathogenesis, similar phenotypes in zebrafish model, etc]. Relevant studies are summarized below. ---- Lam et al (2019 - PMID: 31271740) described two siblings aged 25m and 7y, harboring biallelic DTYMK variants. The phenotype consisted of hypotonia, congenital microcephaly, DD, severe ID. Other shared features included raised serum lactate, pyruvate and alanine. The phenotype was more pronounced in the younger one (epilepticus during febrile illness, epilepsy on multiple anti-convulsants, evidence of regression, etc). Brain MRI revealed marked cerebral atrophy among the findings while a lactate peak was present in spectroscopy. The elder brother developed an episode of sudden onset coma with respiratory failure at the age of 7y. Quartet WES identified compound heterozygosity for a fs and a missense DTYMK variant (NM_012145.3:c.287_320del / p.Asp96Valfs*8 - c.295G>A / p.Ala99Thr). There were no additional findings. Previous genetic panel analysis for epilepsy was unremarkable for the 1st sib. There are two pathways for synthesis of dNTPs, the de novo pathway operating in the cytosol only and the salvage operating in both cytosol and mitochondria. DTYMK encodes (deoxy)thymidylate kinase which catalyzes conversion (phosphorylation) of dTMP to dTDP - a step right after convergence of both pathways - in the dTTP synthesis pathway. Mutations in TK2, an enzyme phosphorylating thymidine in mitochondria to dTMP have been associated with mitochondrial DNA depletion syndrome (MDDS). Given this and as the 2 sibs had raised serum lactate and pyruvate, the authors performed in silico analyses to calculate mtDNA/nDNA ratio dividing the respective read depths for mitochondrial and nuclear DNA obtained from WGS data of the two sibs (blood). This ratio was shown to be reduced in the more severely affected sib (65.5% of control) although this was not the case for the mildly affected brother (114.6%). As a control a non-MDDS mitochondrial cytopathy sample (corresponding to m.8993T>G) was used. The respective ratio which was calculated for a known POLG-related MDDS case was 15.6%. ---- Vanoevelen et al (2022 - PMID: 34918187) describe two unrelated children with hypotonia, absence of developmental progress, microcephaly, seizures (recurrent febrile seizures/myoclonic jerks). Severe cerebral atrophy (with unaffected cerebellum) was observed upon brain imaging. Other findings included puffy body/extremities. Both had complications following respiratory illness leading to demise. CNS pathology in the 1st individual revealed massive neuronal dropout, with sparing of dentate nucleus and brainstem. CMA in both cases was normal. This was also the case for extensive metabolic investigations (which provided no evidence of eventual mitochondrial dysfunction). WES revealed compound heterozygosity for 2 missense variants in the first individual (NM_012145.3:c.382G>A - p.Asp128Asn and c.242C>T - p.Pro81Leu). The second individual, born to consanguineous parents, was homozygous for c.242C>T / p.Pro81Leu. In silico predictions varied although each variant were (mostly) suggestive of a deleterious effect. Variants were both ultrarare without homozygotes in ExAC,. The authors generated a dtymk ko zebrafish model (hmz for a frameshift variant). Zebrafish exhibited markedly smaller eyes and pericardiac edema (3dpf-), twitching movements somewhat reminiscent of epilepsy (at 3dpf), prominent edema of brain and intestine. Head size was significantly smaller at a timepoint prior to brain edema (also after correction for length). Histology provided evidence of empty spaces in brain, suggestive of neurodegeneration, with high amounts of apoptotic cells. dTMPK activity was measured in zebrafish (at 5dpf) as well as in fibroblasts from one individual and in both cases, it was barely detectable and significantly lower compared to wt/htz zebrafish or to the activity in fibroblasts from the parents of the individual tested. In fibroblasts from the same individual with comparison to his parents, the authors demonstrated that DNA replication was impaired (using pulse-EdU staining to quantify cells in S-phase). Assessment of cell proliferation in the brain of dtymk ko zebrafish using phospo-Ser10-Histone H3 (pH3) staining was suggestive of severe proliferation defects in forebrain. Impaired biosynthesis of nucleotides for DNA synthesis/repair would be predicted to result in nucleotide pool imbalance, leading to incorporation of ribonucleotides in genomic DNA with - in turn - impairment of DNA replication and genomic instability (sensitivity to strand breakage). In line with this, genomic DNA of ko zebrafish following alkaline hydrolysis and alkaline gel electrophoresis was shown to migrate at lower position and to be more fragmented indicating increased sensitivity (due to incorporation of ribonucleotides). Visualization of DNA breakage by γH2AX staining, following UV-irradiation of zebrafish embryos revealed persistence of elevated γH2AX levels and DNA damage response signaling, interpreted as increase in unrepaired DNA breaks. mtDNA copy numbers in fibroblasts from the affected individual was somewhat but not significantly lower compared to his parents. Importantly, the copy numbers were similar to controls (N=5) which overall does not support mtDNA depletion as a consequence of DTYMK deficiency. Integrity of mtDNA did not appear to be compromised , with the mitochondrial genome migrating at the expected length of 16,5 kb with no indications of mtDNA deletions for both affected individual and his parents. Activity of the mitochondrial respiratory complexes I-V in fibroblasts from the affected individual was comparable to that of his parents. Overall, there was no evidence for mtDNA depletion (although not studied in muscle biopsy) while functional studies failed to demonstrate mitochondrial dysfunction. The authors discuss other disorders of impaired dTTP metabolism due to mutations in TYMP, RRM2B or CAD. ------ In a recent study using zebrafish model, Hu Frisk et al (2022 - PMID: 35346037) further demonstrate that Dtymk is essential for neurodevelopment providing evidence for expression of a compensatory thymidylate kinase-like enzyme at later stages of development (explaining survival of ko dtymk zebrafish despite the central role of this enzyme in dTTP generation). [Not further reviewed] Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1534 | ZBTB7A |
Konstantinos Varvagiannis gene: ZBTB7A was added gene: ZBTB7A was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: ZBTB7A was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZBTB7A were set to 31645653; 34515416 Phenotypes for gene: ZBTB7A were set to Global developmental delay; Intellectual disability; Macrocephaly; Abnormality of the lymphatic system; Sleep apnea; Increased body weight; Autism; Persistence of hemoglobin F; Abnormal leukocyte count; Recurrent infections; Umbilical hernia Penetrance for gene: ZBTB7A were set to unknown Review for gene: ZBTB7A was set to AMBER Added comment: Monoallelic pathogenic ZBTB7A variants cause Macrocephaly, neurodevelopmental delay, lymphoid hyperplasia, and persistent fetal hemoglobin (#619769). ---- Ohishi et al (2020 - PMID: 31645653) described the phenotype of a 6y5m-old male harboring a heterozygous, de novo ZBTB7A missense variant. Features included macrocephaly, mild intellectual disability (tIQ 65) and sleep apnea. Available hemoglobin levels (in the 1st month) supported high Hb and HbF levels. Other features included PDA and an umbilical hernia. Initial investigations incl. karyotype and CMA were normal. The ZBTB7A variant (NM_015898.3:c.1152C>G / p.Cys384Tyr) was identified following trio WES with a list of additional findings (in suppl.) not explaining the phenotype. This SNV, confirmed by Sanger sequencing, was absent from public db with several in silico predictions in favor of a deleterious effect. ZBTB7A on 19p encodes zinc finger- and BTB domain-containing protein 7 (or Pokemon). The authors performed a review of 19p13.3 microdeletion cases supporting a minimum region of overlap spanning PIAS4, ZBTB7A and MAP2K2 and common features of DD and ID, macrocephaly with prominent forehead, sleep apnea. The authors argue that loss of ZBTB7A explains part of - but probably not all - features of 19p13.3 microdeletions. ZBTB7A is known to repress expression of HBG1 and HBG2 (γ-globin), with the few available HbF patient measurements in line with this role. Based on the structure of the protein, Cys384 (along with 3 other residues) forms a coordinate bond with the Zn+2 ion, this bond predicted to be disrupted by Tyr. Further they favor a dominant negative effect given that ZBTB7A protein is known to form dimer via interaction at the BTB domain [hetero (variant+wt) and homodimers (variant+variant) having compromised function]. To support this notion, 3 previously reported somatic variants within the zinc-finger domain have been shown to exert a dominant-negative effect (PMID cited: 26455326). ---- In a collaborative study, von der Lippe et al (2022 - PMID: 34515416) identified 12 additional individuals (from 10 families) harboring monoallelic ZBTB7A missense/pLoF variants most commonly as de novo events. The authors describe a consistent phenotype with motor (9/11) and speech delay (9/12), cognitive impairment/ID (12/12 - commonly mild, ranged from specific learning difficulties to severe ID), macrocephaly (>90%le in 11/12, >97% in 7/12), lymphoid hypertrophy of pharyngeal tissue/adenoid overgrowth (12/12), sleep apnea (9/12). Autistic features were observed in 7/12. Other phenotypes included frequent upper airway infections (10/11), weight above 97th percentile (7/11). HbF levels were elevated in 4/5 individuals with available measurements (range: 2.2% to 11.2% - ref. for subjects above 6m of age : <2% ). Other hematological issues were observed in few individuals (abn. monocyte/neutrophil counts in 3-4). Cardiovascular issues were reported in 4 (2 fam). 3 subjects had umbilical hernia. There was no common dysmorphic feature. Various initial investigations were normal or did not appear to explain the NDD phenotype and incl. standard karyotype, CMA, targeted testing for genes/disorders previously considered (PTEN, FMR1, NSD1, BWS and PWS methylation studies, CFTR, etc). One male had a maternally inherited chrX dup not thought to explain his complex phenotype, while another had a concurrent diagnosis of thalassemia. Individuals were investigated with singleton (or trio) WES. Of note some individuals were DDD study participants. 8 had de novo ZBTB7A variants, incl. one who harbored 2 de novo missense SNVs several residues apart. 2 sibs had inherited a fs variant from their affected parent. For the latter as well as for another subject parental samples were unavailable. There were no other variants of interest upon exome analysis. 5 different missense, 2 nonsense and 3 fs variants were identified with pLoF all predicted to lead to NMD. All variants were absent from gnomAD (pLI of 0.96, LOEUF 0.33 and missense Z-score of 4.04) which lists one individual with htz LoF, likely not an artifact. Given this individual (and the familial case) the authors discuss on the mild phenotype and/or eventual reduced penetrance or underdiagnosis of the disorder. There was no difference in severity between those with missense/truncating variants. ZBTB7A transcription factor (or pokemon or lymphoma/leukemia-related factor) is widely expressed. It is involved in several activities being among others required to block Notch signaling which in turn drives T-cell at the expense of B-cell development. Notch pathway activation has been demonstrated in Zbtba7 ko mouse models. Finally, the authors discuss the role of notch signaling in thymus and the nervous system, as well as that ZBTB7A up/down-regulation known to repress/increase respectively HbF expression (several refs in text). ---- MGI (1335091) for Zbtb7a : "Mice homozygous for a knock-out allele die around E16.5 due to anemia and exhibit a cell autonomous defect in early B cell development". (Phenotypes from nervous system not commented on). ---- Apart from OMIM (#619769), ZBTB7A is included in the DD panel of G2P (ZBTB7A-associated developmental disorder / monoallelic_autosomal / absent gene product / confidence limited) as well as among the primary ID genes in SysID. In PanelApp Australia the gene is incl. with green rating in the ID and Macrocephaly gene panels. ---- Consider inclusion with amber or green rating (several individuals/families/variants, highly consistent phenotype, overlap with 19p microdeletions || variant effect not studied, animal models supporting contribution of the gene to the phenotype though no data on associated NDD ones). Please also consider inclusion in other relevant panels (macrocephaly, lymphatic disorders, ASD, etc). Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1534 | ATP2B1 |
Konstantinos Varvagiannis gene: ATP2B1 was added gene: ATP2B1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ATP2B1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ATP2B1 were set to 35358416; 35358416 Phenotypes for gene: ATP2B1 were set to Global developmental delay; Intellectual disability; Autism; Behavioral abnormality; Seizures; Abnormality of head or neck Penetrance for gene: ATP2B1 were set to unknown Review for gene: ATP2B1 was set to GREEN Added comment: Monoallelic missense/pLoF ATP2B1 variants have been reported in 12 unrelated individuals with DD/ID making this gene relevant to the current panel. Currently there is no associated phenotype in OMIM, G2P, SysID, PanelApp Australia. Based also on the evidence discussed below, please consider inclusion with green (rather than amber) rating. --- Rahimi et al (2022 - PMID: 35358416) describe 12 unrelated individuals with monoallelic ATP2B1 variants. Phenotype consisted of DD (12/12), ID [9/12 - mild or less commonly moderate, with 3 additional subjects "unclassified" likely due to their age (#6: 3y nonverbal/nonambulatory, could sit and roll / #8: 3y, sitting at 1y, 1st words:26m / #12: at 5y nonambulatory/nonverbal)]. Behavioral issues were observed in 8/11 (ASD in 5/11). Seizures were reported in 5/12 (one further had abnormal EEG). Minor features - albeit not consistent/without recognizable gestalt - were reported in 6. Anomalies of digits and marfanoid habitus were reported in 4 and 2. All subjects were investigated by singleton/trio exome sequencing. Previous investigations incl. karyotype, CMA, analysis of individual genes (e.g. FMR1, ZEB2) or metabolic workup were normal for several individuals with one having a concurrent diagnosis of mosaic (20%) XXY and another harboring an additional hmz variant for a liver disorder. 9 different missense and 3 nonsense ATP2B1 variants were identified, shown to have occurred de novo in all cases where parental samples were available (9/12). ATPase plasma membrane Ca+2 transporting 1, the protein encoded by ATP2B1, is an ATP-driven calmodulin-dependent Ca+2 pump which removes intracellular calcium from the cytosol. As the authors comment calcium pumps are thought to have a crucial role on neuronal function. All variants identified were absent from gnomAD with the exception of c.2365C>T / p.Arg789Cys (de novo) which is present once in the database. ATP2B1 has a pLI of 1 and a missense Z-score of 5.29. The variants affected several ATP2B1 isoforms. Variants were reported using NM_001001323.2, corresponding to ATP2B1a isoform which is mainly detected in brain (as also in GTEx). In silico predictions were in favor of a deleterious effect and structural modeling supported the role of the affected residues. The nonsense variants occurred in positions predicted to lead to NMD (not studied). Transfection of an ATP2B1-yellow fluorescent protein (YFP) expression plasmid for wt or variants in HEK293 cells, revealed membranous fluorescence for wt, significantly altered localization for 3 variants (Asp239Gly, Thr264Ile, Arg991Gln), shift to cytoplasmic localization for 4 others (Thr425Lys, Arg763Pro, Glu824Lys, Gln857Arg) with statistically non-significant effect for 2 others (His459Arg and Arg789Cys). Fluorometric [Ca+2]i analysis in HEK293 cells expressing wt or variant ATP2B1 revealed that all missense variants affected Ca+2 transport. This was not the case for wt ATP2B1 or for another missense variant used as control (drawn from gnomAD). Of note, a further (13th) affected individual with another missense variant (c.1793T>C / p.Ile598Thr) was excluded from the phenotypic analysis. The membrane localization and Ca+2 transport did not appear to be affected by this variant which was classified as VUS although it a different impact from those studied. Overall loss-of-function is thought to be the underlying mechanism based on the above (and supported by few reported cases with gross deletions spanning also ATP2B1). A dominant negative effect for missense variants (affecting heteromeric complex formation with neuroplastin or basigin) could not be completely excluded, but not supported either by the localization of the identified variants. In the supplement the authors include 3 DDD study participants previously reported to harbor de novo pLoF/missense variants though with few available clinical information (PMID: 33057194 - DDD13k.05076 : c.2883del / DDD13k.04028 : c2512A>C - p.Ile838Val / DDD13k.08944 : c.2129A>C - p.Asp710Ala). The authors discuss on the role of ATP2B1 on Ca+2 homeostasis in the CNS and neurodevelopment overall (also based on isoform expression in rat brain). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1530 | MAN2C1 |
Konstantinos Varvagiannis gene: MAN2C1 was added gene: MAN2C1 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: MAN2C1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: MAN2C1 were set to 35045343 Phenotypes for gene: MAN2C1 were set to Global developmental delay; Intellectual disability; Abnormality of nervous system morphology; Abnormality of the corpus callosum; Ventriculomegaly; Polymicrogyria; Abnormality of the face; Macrocephaly Penetrance for gene: MAN2C1 were set to unknown Review for gene: MAN2C1 was set to GREEN Added comment: Biallelic pathogenic MAN2C1 variants cause Congenital disorder of deglycosylation 2 (# 619775). Mild to moderate impairment of intellectual development is a feature in most patients as in the OMIM's clinical synopsis for this disorder. ---- Specifically, Maia et al (2022 - PMID: 35045343) report the clinical features based of 6 relevant individuals (4/6 aged 4-18years and 2/6 fetuses) from 4 families. These individuals had non-specific dysmorphic features (micro/retrognathia being the most common in 5/6), different congenital anomalies, variable degrees of ID (3/4), as well as brain MRI abnormalities (PMG in 3/6 from 3 fam, ventriculomegaly in 3/6 from 2 fam, callosal anomalies in 4/6 from 3 fam, cerebellar hypoplasia 2/6 - 2 fam, vermis hypoplasia 4/6 - 3 fam etc). Macrocephaly was reported for 2/6 individuals (2 fam). While ID was observed in 3/4 individuals of relevant age (mild in 1/4, moderate in 1/4, unk in 1/4), delayed motor and language development was reported for all (4/4). All individuals harbored biallelic MAN2C1 variants following exome sequencing (previous investigations not reported), and Sanger sequencing was used for validation and segregation (parents/sibs). There were no putative pathogenic variants in known disease genes. MAN2C1 encodes mannosidase, alpha, class 2c, member 1, an enzyme playing a role in deglycosylation of free oligosaccharides (fOSs). The latter are generated and released in the cytoplasm or the ER lumen during N-glycosylation of proteins. fOSs are generated from two different pathways (ERAD and LLO) with a defect in an enzyme of the NGLY1 already described to cause a NDD due to defect of deglycosylation. In a later step oligossaccharides are trimmed by the action of ENGase to form fOS containing one GlcNAc (N-Acetylglucosamine) residue (fOSGn1) at the reducing end. Processing of these fOSs by the cytosolic α-mannosidase (MAN2C1) converts Man7-9Gn1 to Man5Gn1 subsequently transported to lysosomes for degradation. Variants incl. 3 missense SNVs incl. c.2612G>C/p.Cys871Ser, c.2303G>A/p.Arg768Gln, c.607G>A/p.Gly203Arg, one splice variant (c.601-2A>G/p.Gly201Profs*10) and one indel (c.2733_2734del/p.His911Glnfs*67). [RefSeq NM_006715.3] Most were present in gnomAD with low AF ranging from 0.013% to 0.11% while c.2303G>A/p.Arg768 has an AF of 0.33% with 5 homozygotes(*) in the database. Conservation and in silico predictions supported their effect. For the variant affecting the splicing acceptor site (c.601-2A>G) studies in patient fibroblasts confirmed skipping of ex6. Fibroblasts from 2 sibs cmp htz for Arg768Gln and c.601-2A>G (Gly201Profs*10) were studied for protein levels, demonstrating 90% reduction in the amount of MAN2C1. There was no truncated protein observed upon immunoblot. Protein abundance was not affected in fibroblasts from the individual who was homozygous for Gly203Arg. Mannosidase activities were studied upon overexpression in a HEK293 model, with Gly203Arg presenting similar activity to WT and Arg768Gln exhibiting only a tiny residual activity. Cys871Ser showed increased activity compared to WT. Using fibroblasts from controls and the same individuals as above, the authors showed that pathogenic MAN2C1 variants caused defects in fOS processing (delayed processing of high oligomannose species, reduced production of M5Gn1 with M8 and M9Gn1/2 species remaining at high levels) supporting a total/partial loss of mannosidase activity for Arg768Gln and Gly203Arg. In MAN2C1-KO HAP1 cell lines, M7-M9Gn1 species accumulated while M5Gn1 - the product of MAN2C1 - were absent. Complementation of KO HAP1 cells with Gly203Arg, Arg768Gln and Cys871Ser suggested impaired fOS processing for Gly203Arg and Arg768Gln (with significant amounts of M7-M9Gn1 species). Cells complemented with Cys871Ser did not exhibit fOS processing defects. The authors speculate that Cys871Ser could affect a non-mannosidase function of the enzyme relevant to brain development or that it might lead to abnormal inter-subunit interactions or tetramer formation. Finally, Maia et al summarize findings in previously described Man2c1-KO mice (cited PMID: 24550399). These appeared normal, did not exhibit differences in growth or lifespan and did not present behavioral alterations. Man2c1-KO mice had CNS involvement with histological analyses in favor of neuronal and glial degeneration with multiple vacuoles in deep neocortical layers and telencephalic white matter tracts. Vacuolization was not observed upon brain histology for the 2 fetuses studied which Maia et al speculate may occur at a later stage. In KO mice there was considerable accumulation of Man8–9GlcNAc oligosaccharides. ---- G2P includes MAN2C1 in it's DD panel (confidence: strong, MAN2C1-associated neurodevelopmental disorder with cerebral malformations). In PanelApp Australia, this gene is rated green in the ID, polymicrogyria, cerebellar hypoplasia and fetal anomalies gene panels. Consider inclusion in the current panel with green (3 individuals/families/variants, role of the gene, NDD phenotype also reported for NGLY1-related disorder of deglycosylation, variant studies) or amber rating (ID not a universal feature, still DD observed in all affected individuals). Please consider adding this gene in other relevant panels (as in PanelApp Australia, also for corpus callosum abnormalities, metabolic disorders, etc). Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1529 | SLC38A3 |
Konstantinos Varvagiannis gene: SLC38A3 was added gene: SLC38A3 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: SLC38A3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC38A3 were set to 34605855 Phenotypes for gene: SLC38A3 were set to Infantile axial hypotonia; Global developmental delay; Intellectual disability; Seizures; Spasticity; Microcephaly; Cerebral atrophy; Cerebellar atrophy; Abnormality of the corpus callosum; Dysphagia; Constipation; Increased serum lactate; Hyperammonemia Penetrance for gene: SLC38A3 were set to Complete Review for gene: SLC38A3 was set to GREEN Added comment: Marafi et al (2021 - PMID: 34605855) describe the phenotype of 10 individuals, belonging to 7 families (6/7 consanguineous), harboring biallelic deleterious SLC38A3 variants. One subject (from fam3) was previously reported in the context of a larger cohort of consanguineous families investigated with exome sequencing (2017, PMID: 31130284). The phenotype overall corresponded to a DEE and features included axial hypotonia (10/10), severe global DD or ID (10/10), seizures (8/10, onset : 1w-15m, NOT observed in 2/10 aged 1y3m and 4y | s. types: tonic-clonic in 3/8, tonic 2/8, focal 2/8 with secondary generalization, myoclonic 1/8, gelastic 1/8 | EEG burst-suppression, hypsarrhythmia in few). Microcephaly was observed in (8/10) and was more commonly postnatal and/or progressive. Variable abnormalities were observed upon brain imaging incl. cerebral (5/10) or cerebellar atrophy (2/10) and abnormal CC (6/10), abnormal myelination for age (6/10). Other phenotypes included visual impairment (9/10), peripheral hypertonia (8/9) constipation (8/9) and dysphagia (7/9), FTT (4/8), movement disorder (3/10). Metabolic studies indicated (transient) elevation of lactate (7/8 - also pyruvate in 2) and elevated plasma ammonia (4/7). Individuals from the 1st family were investigated with ES, and the SLC38A3 splice site variant (NM_006841.6:c.855+1G>T) was the most likely candidate, additional SNVs not contributing to the NDD phenotype. Other affected subjects were ascertained through GeneMatcher/collaborations. In total, 3 different missense and 4 pLoF (1 fs, 2 nonsense, 1 splicing) variants were identified with individuals from 2 families being hmz or cmd htz for missense variants. Variants were absent/ultrarare with no homozygotes in public/in-house databases with several in silico predictions in favor of a deleterious effect. Regions of AOH (around SLC38A3/total) are provided for some individuals/families. Sanger sequencing was used for confirmation and segregation studies (apart from carrier parents in 7/7 fam, 11 unaffected sibs tested in 6/7 fam). The solute carrier (SLC) superfamily of transmembrane transporters - highly expressed in mammalian brain - is involved in exchange of amino-acids (AAs), nutrients, ions, neurotransmitters and metabolites etc across biological membranes with >100 SLC-encoding genes associated with NDDs. SLC38A3 specifically encodes SNAT3, a sodium-coupled neutral amino-acid transporter, principal transporter of Asn, His, Gln (precursor for GABA and glutamate), expressed in brain, liver, kidney, retina and pancreas. In the brain, it localizes to peri-synaptic astrocytes playing an important role in glutamate/GABA-glutamine cycle. While the pLoF variants are predicted to undergo NMD or result in non-functional protein, protein modelling suggested that missense ones affect protein activity or stability. Biochemical and metabolic screening was carried out for several individuals with plasma AAs reported normal (10/10), urinary OAs normal in 9/9, CSF AAs (incl. GABA/glutamine) normal in 2 sibs, CSF lactate normal in 1 indiv. studied. As discussed above plasma ammonia was elevated in 4/7 (2 fam), and 7/10 had elevated lactate and/or pyruvate (2/7). Untargeted metabolomic profiles performed in biofluids (plasma from 3 subjects, CSF:1, urine:1) were suggestive of altered AA and nitrogen metabolism. In particular, alterations in levels of AA known to be transported by SNAT3 were found. 676 molecules overall showed deviation in plasma samples, 630 in urine and 241 in CSF (albeit with no consistent pattern). Perturbations in several biochemical pathways were shown to occur (incl. Gln-,Asn- and His- pathways). Slc38a3-/- mice have reductions in brain glutamate and GABA neurotransmitters in homogenized brain tissue (GABA analytes being normal in plasma samples or the single CSF sample available from affected subjects). Snat3-deficient mice had elevation of plasma urea and normal ammonia levels (urea was low in all human samples and ranged from -2 to -3.5 SD in plasma, ammonia was elevated in 4/7). Slc38a3-/- mice have impaired growth, lethargy and ataxic gait, altered plasma AAs, normal glutamine in plasma with abundance in brain and exhibit early lethality. Plasma AAs were normal in 4 affected individuals, impaired growth observed in 4 and gait impairment was observed in 9/10. Hypoglycemia, previously reported in Slc38a3-/- mice, was not observed in any of the patients although this is presumably explained by diet/feeding intervals with abnormalities in pentose phosphate pathway in one individual hypothesized to be reflective of abn. glucose metabolism. The human phenotypes of microcephaly and seizures were not observed in mice. For mouse studies PMIDs cited by the authors : 27362266, 26490457. There is currently no SLC38A3-related phenotype reported in OMIM. In G2P this gene is incl. in the DD panel (biallelic, confidence: strong, SLC38A3-associated epileptic encephalopathy). SLC38A3 is listed among the primary ID genes in SysID. In PanelApp Australia, SLC38A3 is included with green rating in the epilepsy, ID and microcephaly panels. Consider inclusion with green rating (10 individuals, 7 families, 7 variants, role of SLCs and SLC38A3, alterations in AA/nitrogen metabolism etc) or amber rating (if discordances with mouse model considered). Please consider inclusion in other panels e.g. for microcephaly, CC abnormalities, metabolic disorders, etc. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1525 | CACNA2D1 |
Konstantinos Varvagiannis gene: CACNA2D1 was added gene: CACNA2D1 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: CACNA2D1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CACNA2D1 were set to 35293990; 28097321 Phenotypes for gene: CACNA2D1 were set to Abnormal muscle tone; Feeding difficulties; Global developmental delay; Intellectual disability; Seizures; Microcephaly; Abnormality of the corpus callosum; Cerebral atrophy; Abnormality of movement; Cortical visual impairment; Pain insensitivity Penetrance for gene: CACNA2D1 were set to Complete Review for gene: CACNA2D1 was set to GREEN Added comment: Consider inclusion in the current panel with green rating. Recent report of 2 unrelated individuals with DEE due to biallelic CACNA2D1 variants. Both referred to neurology/genetics for hypotonia/severe DD prior to onset of seizures. One further individual with hypotonia and severe ID (seizures not discussed, age unknown). Gene with established role, encoding α2δ-1 subunit of Cav channels. Studies for the variants support loss-of-function as the underlying effect. Eventual contribution of monoallelic variants to NDD-phenotypes discussed (and put in question) in Ref [1] below. There is currently no phenotype for CACNA2D1 in OMIM/G2P. In SysID this gene is listed among the candidates for ID, based on a previous report. CACNA2D1 is not currently included in the ID/epilepsy panels in PanelApp Australia. See also relevant review in epilepsy panel (Dr. H. Lord). Please consider also inclusion in other panels (e.g. microcephaly, corpus callosum, movement disorders, etc). [1] ---- Dahimene et al (2022 - PMID: 35293990) describe the phenotype of 2 unrelated individuals with biallelic CACNA2D1 variants. Overall, the phenotype corresponded to an early-onset DEE, characterized by abnormal muscle tone (axial hypotonia 2/2 with spasticity in extremities in 2/2), feeding difficulties (2/2), profound DD and ID (2/2), microcephaly (2/2 - approx. -2 SD in both), seizures (2/2 - 1st : onset 9m with absences and later generalized seizures, 2nd : onset 11m with hemi-clonic seizures and atypical absences). Other features included cortical visual impairment (2/2) and movement disorder (incl. choreiform movements 2/2, orofacial dyskinesia 2/2 and dystonic episodes 1/2). Brain MRI revealed corpus callosum anomalies (2/2) and cerebral atrophy (2/2). Both had echocardiography (abnormal in 1/2 - tiny PFO) and electrocardiography which was normal. Both exhibited insensibility to pain. Presentation is relevant to the current panel as first symptoms in the first 3 months with severe hypotonia and poor head control (2/2) with evaluation in neurology/genetics preceding onset of seizures in both. Trio ES was performed for both individuals and their (healthy) parents and revealed homozygosity for a fs variant in the first [NM_000722.3:c.818_822dup / p.(Ser275Asnfs*13)] and compound htz for a fs and a missense variant [c.13_23dup / p.(Leu9Alafs*5) and c.626G>A / p.(Gly209Asp)] in the second affected individual, respectively. Eventual additional variants were not discussed. Previous investigations are only provided for the 2nd and were all normal (karyotype, CMA, 15q methylation, epilepsy/neurometabolic gene panels). Voltage-gated calcium channels are heteromultimers comprising different subunits incl. an alpha-1 (α1), α2δ (alpha-2/delta), beta (β) and gamma (γ). CACNA2D1 is one of the 4 genes (CACNA2D1-4) encoding the alpha-2/delta subunit. Its product is post-translationally processed into 2 peptides, an alpha-2 and a delta subunit, held by a disulfide bond. Biallelic variants in CACNA2D2 - also encoding an alpha-2/delta subunit - cause cerebellar atrophy with seizures and variable developmental delay (# 618501). Variant studies support loss-of-function effect for the studied variants, notably by NMD for the fs one, and severe impairment of the Cav2 channel function for the missense one : - CACNA2D1 mRNA was reduced to 6-9% compared with control in fibroblasts from the 1st individual. mRNA levels for the 2nd subject were similar to control. - Quantification of the protein in whole-cell lysates from fibroblasts revealed lower α2δ levels compared to control (10-12% and 31-38% applying to the 1st and 2nd individual). - CACNA2D3 mRNA levels in fibroblasts from the 2nd patient were 2-7x higher compared to the 1st or controls suggesting a possible compensatory effect. CACNA2D2/4 mRNA levels were too low for quantification. - Gly209 lies within the gabapentin and amino-acid binding pocket and this residue is invariable in CACNA2D1/CACNA2D2 in all vertebrates and paralogs. - Transfection of tsA-201 cells with either WT or G209D HA-tagged α2δ revealed reduced cell surface expression for this missense variant (~80, for biotinylated form ~86%). - In tsA-201 cells transfected with HA-tagged Cav2.2/β1b and either α2δ-1-WT, no α2δ-1 or α2δ-1-G209D, WT resulted in increased 13x currents with no increase applying to G209D (or in absence of α2δ). Plasma membrane expression of double (GFP/HA) tagged Cav2.2 was increased upon co-expression with WT α2δ-1 which was not the case for α2δ-1-G209D. - In hippocampal neurons, double (GFP/HA)-tagged Cav2.2 could not be detected at the cell surface in the presence of α2δ-1-G209D (or no α2δ) in contrast with strong expression in presence of α2δ-1-WT. α2δ-1-G209D did not promote trafficking of Cav2.2 into hippocampal neurites, as indicated by reduced signals for both HA and GFP (for cell surface and total Cav2.2 respectively). - Co-expression of double (GFP/HA) tagged Cav2.2 with β1b and either HA-α2δ-1-WT or HA-α2δ-1-G209D in tsA-201 cells, revealed reduced complex formation of G209D with Cav2.2 Co-immunoprecipitated HA-α2δ-1-G209D had higher molecular weight compared to HA-α2δ-1-WT which suggests that α2δ-1-G209D remains as the uncleaved immature form (probably in the ER). Mouse model (several Refs in text): Mild cardiac phenotype and reduced ventricular myocyte Ca current density was observed in hmz ko mice. Similarly to the insensibility to pain human phenotype, mice had delayed neuropathic pain-related responses. Overexpression of a2δ-1 resulted in epileptiform EEG and behavioral arrest, overall supporting a critical role of α2δ-1 for mouse brain. The authors underscore that the parents of both patients (htz carriers) were healthy and review previous literature for association of monoallelic variants with epilepsy, ID and arrhythmogenic disorders (in suppl.) [Refs not here reviewed]. As for the NDD phenotype, CACNA2D1 is within a previously defined small region of overlap for 7q21.11 microdeletions associated with ID+/-epilepsy. The same study did not reveal de novo SNVs in any of the 3 contained genes within this SRO (HGF, CACNA2D1, PCLO) in 4293 patients with NDD [cited PMID: 28240412]. A frameshift variant (c.2625del) was identified in a 13-yo girl with infantile spasms and normal intelligence [cited PMID: 25877686]. A 1-bp insertion (c.659-2_659-1insT / not studied at the mRNA level) was identified in another 14-yo female with ID and epilepsy [cited PMID: 34356170]. The authors state that the phenotype (/differences) of these individuals as well as presence of pLoF CACNA2D1 variants in gnomAD [still pLI of 1] put in question pathogenicity of monoallelic variants for these phenotypes. The role of heterozygous missense variants described in relation to arrhythmogenic disorders is also discussed extensively (some downgraded to LB/VUS, others having a relatively high MAF and presence of 1-2 homozygotes in gnomAD). [2] ---- In an article cited by SysID for CACNA2D1 (2017 - PMID: 28097321), Reuter et al studied with WES and autozygosity mapping individuals with NDD belonging to consanguineous families. As in eTables1/3, a male - single affected individual born to consanguineous parents from Turkey (MR150) - was investigated by singleton ES. This individual was homozygous for a missense CACNA2D1 SNV [NM_000722.2:c.1514C>T;p.(Thr505Ile)]. Prior investigations are unavailable (although individuals with previously known P/LP CNVs were excluded). The phenotype - briefly reported - included hypotonia, severe ID, stereotypic behaviors, inguinal hernia and omphalocele. Presence of seizures was not commented on. The age of this individual was not reported. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1520 | PAN2 |
Konstantinos Varvagiannis gene: PAN2 was added gene: PAN2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PAN2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PAN2 were set to 29620724; https://doi.org/10.1038/s41431-022-01077-y Phenotypes for gene: PAN2 were set to Global developmental delay; Intellectual disability; Sensorineural hearing impairment; Abnormality of the genitourinary system; Abnormality of the cardiovascular system; Abnormality of blood and blood-forming tissues; EEG abnormality; Seizures; Anorectal anomaly; Abnormality of the skeletal system; Abnormality of the eye; Abnormality of head or neck Penetrance for gene: PAN2 were set to Complete Review for gene: PAN2 was set to AMBER Added comment: 1. Maddirevula et al (2018 - PMID: 29620724) first reported on the phenotype associated with biallelic pathogenic variants in PAN2. This concerned a male (15DG2222) born to consanguineous parents and exhibiting MCA, dysmorphic features and global DD (age of 34 m). Features incl. imperforate anus, metopic craniosynostosis, scoliosis, CHD (PFO, PDA, VSD), renal anomalies (duplicated collecting system) and abnormalities of the eye (posterior embryotoxon, maculopathy). As the other 411 individuals from the cohort, the child had 1st-tier testing genetic testing using a dysmorphology/skeletal dysplasia panel of 296 genes. Subsequent autozygome analysis (Axiom genotyping platform) was used to identify ROH (authors state "segregating within the family", in pedigree the proband was the single affected person and single child). WES revealed a PAN2 indel. [NM_001166279.1:c.3162delC / p.(Ser1055Profs*4)]. There were no additional studies. Role of PAN2 and animal models discussed as below. --- 2. Reuter et al. (2022 - https://doi.org/10.1038/s41431-022-01077-y) describe the phenotype of 5 additional individuals - from 3 unrelated families (2 consanguineous) - harboring biallelic PAN2 variants. The authors review the phenotype of the previously described case. Features included DD (6/6), ID (4/5 with relevant age in the mild-moderate range, 1/5 had borderline IF), sensorineural hearing loss (5/6) and incompletely penetrant congenital anomalies of the heart (4/6 - TOF, septal defects, Ao root dilat), urinary malformations (4/6 - hypoplasia/agenesis, anovesical fistula), ophthalmological anomalies (2/6 - Rieger, posterior embryotoxon, etc). EEG anomalies or seizures were noted in 4/6. Craniofacial feat. in >=2/6 included cleft palate/bifid uvula, ptosis, hypertelorism, abn. of the nose, low-set ears, short neck. There was no comprehensive evaluation for skeletal dysplasia despite short stature/skeletal anomalies in multiple individuals. Hematological anomalies were reported in 2, possibly explained by another concurrent diagnosis (of GSD) in one individual. WGS was performed for 1 individual, and WES for 4 members of the 2nd family and the proband in the 3rd. ROH identified in all 3 families (1 non-consanguineous but from the same region of Italy) are mentioned in the suppl. Sanger sequencing for parents and affected/unaffected sibs was mentioned for the 2 families with solo WGS/WES. One individual had a dual - previously established - diagnosis (of SLC37A4-related GSD) not related to his NDD. There were no other candidate variants except for VUS or variants in 'genes of uncertain significance'. The majority of mammalian mature mRNAs have polyA tails, added during RNA processing. PAN2 encodes a subunit of the Pan2-Pan3 deadenylation complex which shortens mRNA 3' polyA tails, regulating mRNA stability/translation efficiency. Specifically Pan2 is the catalytic subunit, while the interaction with Pan3 mediates efficient mRNA binding. Deadenylation in cytoplasm is mostly carried out by the Pan2-Pan3 or Ccr4-Not compexes. While perturbations of mRNA metabolism/decay are established causes of NDD and ID. In particular, monoallelic variants in genes of Ccr4-Not complex (inc. CNOT1/2/3) already causative of NDDs. All affected individuals were homozygous for pLoF PAN2 variants, namely (NM_001166279.2): c.2335G>T / p.(Glu779*) [Fam1], c.3408dupT / p.(Glu1137*) [Fam2], c.574-2A>G / p.? [Fam3]. Variants were absent from gnomAD (where PAN2 has a pLI:0.94, o/e:0.19). There were no variant studies performed. The splicing variant is predicted in silico to abolish the splice-acceptor site, with in-frame skippling of ex5 which codes a repeat within the WD40 domain. Previous studies in yeast have shown that this domain is important for sensing the length of the polyA tail, with absence of this domain resulting in impaired deadenylation of 90A tails (similarly to complete Pan2 del) [cited PMID: 31104843]. Overall PAN2 loss-of-function is thought to be the underlying disease mechanism. Partial functional redundancy of Pan2/Pan3 (initiation of deadenylation) and Ccr4-Not complexes (further shortening of polyA) is speculated to mitigate consequences of PAN2 LoF in humans. In yeast Pan2Δ, Ccr4Δ and Pan2Δ/Ccr4Δ have been studied with more severe phenotypes in double mutants where ability to shorten mRNA polyA tails was abolished [cited PMID:11239395]. In yeast extracts lacking Pan2p and Pan3p, transcripts were polyadenylated to >90-200 adenosines [cited PMID: 9774670] Mouse mutants (MGI:1918984) had increased heart weight, increased eosinophil cell number while homozygosity for a stopgain allele (by ENU mutagenesis) was shown to result in embyonic lethality. Finally, given the presence of thrombocytopenia and anemia in 3 individuals (2 families) as well as the link between mRNA deadenylation and telomere disease, telomere length analyses from WGS data were performed (TelSeq/Expansion Hunter dn), but there was no evidence for telomeric shortening. --- Currently, there is no PAN2-related phenotype in OMIM/G2P/SysID/PanelApp Australia. --- Consider inclusion in the ID panel with amber rating [>3 individuals/families/variants, though variant studies not performed (NMD/splicing) and authors of 2nd study recognize possibility of additional/concurrent diagnoses in individuals from consanguineous families, possibility of missed dn variants due to singleton WGS/WES in 2 fam. Also the presumed deadenylation defect not studied to date]. Please consider adding this gene to other panels - eg. for sens. hearing loss (5/6 - 3 fam), urinary tract anomalies (4/6 - 4 fam), congenital (4/6 - 3fam), anorectal malformations (2/6 - 2 families, incl. fistula or imperforate anus), clefting (2/6 - 1 fam), hematological disorders, etc. For the time being, not added in epilepsy panel as some individuals had only EEG anomalies, few had also clinical seizures not necessarily requiring treatment. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1520 | HIST1H4D |
Konstantinos Varvagiannis gene: HIST1H4D was added gene: HIST1H4D was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4D was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4D were set to 35202563 Phenotypes for gene: HIST1H4D were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4D were set to Complete Mode of pathogenicity for gene: HIST1H4D was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4D was set to AMBER Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1520 | HIST1H4E |
Konstantinos Varvagiannis gene: HIST1H4E was added gene: HIST1H4E was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4E was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4E were set to 35202563 Phenotypes for gene: HIST1H4E were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4E were set to unknown Mode of pathogenicity for gene: HIST1H4E was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4E was set to GREEN Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1520 | HIST1H4F |
Konstantinos Varvagiannis gene: HIST1H4F was added gene: HIST1H4F was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4F was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4F were set to 35202563 Phenotypes for gene: HIST1H4F were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4F were set to unknown Mode of pathogenicity for gene: HIST1H4F was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4F was set to AMBER Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1520 | HIST1H4I |
Konstantinos Varvagiannis gene: HIST1H4I was added gene: HIST1H4I was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4I was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4I were set to 35202563 Phenotypes for gene: HIST1H4I were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4I were set to unknown Mode of pathogenicity for gene: HIST1H4I was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4I was set to GREEN Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1518 | CPSF3 |
Konstantinos Varvagiannis gene: CPSF3 was added gene: CPSF3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CPSF3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CPSF3 were set to 35121750 Phenotypes for gene: CPSF3 were set to Failure to thrive; Abnormal muscle tone; Global developmental delay; Intellectual disability; Microcephaly; Seizures Penetrance for gene: CPSF3 were set to Complete Review for gene: CPSF3 was set to AMBER Added comment: Arnadottir (2022 - PMID: 35121750) describe the phenotype associated with biallelic CPSF3 pathogenic variants. Based on WGS of 56,969 Icelanders and imputing the genotype of another 153,054 chip-genotyped Icelanders, the authors identified missense variants with a deficit of homozygous carriers to what would be expected based on AF. (For variants with MAF>0.4%, for which >=3 hmz carriers would be expected by H-W equilibrium, no identified hmz carriers within this cohort/dataset). A total of 114 such missense variants was identified. 5 of these SNVs, among which a CPSF3 one (NM_016207.3:c.1403G>A / p.Gly468Glu), were however observed in a series of 764 individuals investigated with clinical WGS at the National University Hospital. The CPSF3 variant with a MAF of 0.41% (3 hmz expected but none observed in the population set) was found in homozygosity in 2 closely related individuals, both investigated for FTT, severe DD, ID, microcephaly, seizures but remaining unresolved following WGS with no other candidate variants. Using genealogical information from the db of deCODE genetics, the authors identified 3 couples from the 153k genotyped Icelanders where both partners were htz carriers for this SNV. These 3 couples had 10 offspring, 4 of whom deceased but with the same phenotypic features as above (hypotonia 4/4, ID 4/4, seizures 3/4, microcephaly 2/4). Paraffin embedded samples of 2 of these children and WG & Sanger sequencing confirmed hmz for Gly468Glu in 2 sibs, without other candidate variants. Samples of the 2 other individuals were N/A. Through GeneMatcher 2 additional first-cousin patients from Mexico were identified, being hmz for another CPSF3 variant (c.1061T>C/p.Ile354Thr) and having overlapping phenotype of abnormal muscle tone, ID, seizures and microcephaly. There were no other variants in WES analysis. mRNA studies in WBCs from Gly468Glu htz carriers did not reveal reduced levels and W.Blot of lymphocytes from a hmz individual confirmed expression, overall suggesting that the variant does not affect the protein levels but presumably the function. CPSF3 encodes cleavage and polyadenylation specificity factor 3, a 684 aa protein, subunit of the cleavage and polyadenylation specificity factor compex. As discussed, cleavage and polyadenylation of the 3' of pre-mRNAs is necessary before transport out of the nucleus with CPSF playing a crucial role in the process of cleavage. CPSF3 ko mice exhibit embryonic lethality, while in yeast mutations in key residues of the CPSF3 homolog are lethal. In gnomAD, CPSF3 has a pLI of 0, z-score of 3.61 with no homozygotes for pLoF variants in 141k individuals (or ~57k WGS Icelanders). The 2 missense variants concerned highly conserved residues (GERP ~5.8). Both are hypothesized to affect the ability of the protein to bind other factors involved in pre-mRNA cleavage. Overall the authors speculate that not only complete loss of CPSF3 would result in drastic phenotypic effects - as in the murine model - but also variants altering its enzymatic function. There is currently no CPSF3-related phenotype in OMIM, G2P, SysID, The gene is included with green rating in the ID, epilepsy and microcephaly panels in PanelApp Australia. Consider inclusion probably with amber rating (Highly consistent phenotype, biological function, evidence from animal models. 2 identified variants, authors state that follow-up functional studies are needed). Also consider inclusion in other possibly relevant panels. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1518 | NRCAM |
Konstantinos Varvagiannis gene: NRCAM was added gene: NRCAM was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: NRCAM was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: NRCAM were set to 35108495 Phenotypes for gene: NRCAM were set to Hypotonia; Hypertonia; Spasticity; Global developmental delay; Intellectual disability; Microcephaly; Behavioral abnormality; Neuropathy; Hearing abnormality; Abnormality of the eye; Abnormality of the skeletal system; Scoliosis; Abnormality of the face Penetrance for gene: NRCAM were set to Complete Review for gene: NRCAM was set to GREEN Added comment: Kurolap et al (2022 - PMID: 35108495) describe the phenotype of 10 individuals (from 8 families) with biallelic variants in NRCAM. Features included tone abnormalities (hypotonia in 4/10, hypertonia/spasticity in 4/10), DD (8/10 - 7 families) and cognitive impairment (in 7/10 - 6 fam), neuropathy (4/10 - incl. 2 sibs without DD/ID). Other phenotypes incl. FTT (2/8), microcephaly (3/6), variable behavioral issues (3/5), abnormalities from the eyes/vision (6/8 - cataract in 2), abnormal hearing (3/7) or skeletal findings (8/9 - incl. scoliosis in 5). Nonspecific facial features were reported in 5/8. Previous metabolic, genetic (incl. karyotype or CMA, FMR1, testing for Steinert disease or SMA) or other work-up (e.g. muscle biopsy) is reported for several subjects but was normal/non-diagnostic. All were investigated by WES/WGS which revealed biallelic NRCAM variants. Sanger sequencing was used for confirmation and segregation analyses, with compatible results in several affected/unaffected sibs tested. There were no alternative explanations for the NDD phenotype with the exception of one subject with a mosaic functionally characterized LP KRAS variant suspected to contribute to his phenotype. NRCAM encodes neuronal cell adhesion molecule (CAM). CAMs are membrane bound proteins with important role in tissue morphogenesis and maintenance. They mediate interactions between neighboring cells or cells and the extracellular matrix. The L1 subgroup of immunoglobulin CAMS - consisting of L1CAM, neurofascin, NRCAM, CHL1 - is the most abundant in the CNS with several critical functions in CNS development, among others in neural cell differentiation, axonal growth and guidance, myelination, synapse formation. Pathogenic L1CAM (XL) and NFASC variants (AR) are associated with NDD. Different missense (N=7), stopgain/frameshift (N=3), a splice variant (NM_001037132.2:c.2647-2A>G) as well as a deep intronic one (c.230+824G>C / rs575851831). Variants occurred in different domains with a cluster (42%) in the fibronectin III domain. Missense SNVs were ultrarare or not present in gnomAD, occurred in conserved residues, with several in silico predictions in favor of a deleterious effect. Structural modelling suggested that all substitutions occurred at residues exposed to solvent and possible abrogated interaction with other proteins. There were no expression studies performed at the mRNA/protein level. The splice variant is predicted to cause ex22 skipping leading to frameshift. The deep intronic variant is predicted to disrupt a site for spl. regulator SC35 and may cause activation of a cryptic acceptor site with inclusion of a cryptic exon. The zebrafish nrcama gene is the sole ortholog of human NRCAM, with another gene proposed as possible ortholog (nrcamb) mapping upon BLAST analysis to cntn1a. The authors performed CRISPR-Cas9 mutagenesis in zebrafish introducing a partial deletion of ex18 and 19. Mutant zebrafish were viable, displayed altered axonal projections and abnormal swimming behavior (increased movement in darkness). Currently, there is no NRCAM-associated phenotype in OMIM/G2P/SysID. PanelApp Australia includes NRCAM in its ID panel with green rating. Consider inclusion probably with green (>3 individuals/families/variants, segregation, gene in the L1-Ig CAM family causing NDD, zebrafish model) or amber rating (ID not a universal feature, variant effect not studied). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1518 | TIAM1 |
Konstantinos Varvagiannis gene: TIAM1 was added gene: TIAM1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TIAM1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TIAM1 were set to 35240055; 33328293 Phenotypes for gene: TIAM1 were set to Delayed speech and language development; Global developmental delay; Intellectual disability; Seizures; Behavioral abnormality; Abnormality of the endocrine system; Hypothyroidism; Abnormality of nervous system morphology Penetrance for gene: TIAM1 were set to Complete Review for gene: TIAM1 was set to AMBER Added comment: Lu et al (2022 - PMID: 35240055) describe 5 individuals (from 4 families) with biallelic TIAM1 missense variants. The phenotype overall corresponded to a neurodevelopmental disorder with DD (5/5), ID (4/4 individuals of relevant age - 3 families), speech delay (5/5), seizures (5/5 - onset: 2m-13y) and behavioral abnormalities (2/2, sibs with autism and ADHD). Several subjects had endocrine symptoms, namely hypothyroidism (N=3 - 2 families), Addison's disease (1) or hypomagnesemia (1). Non-consistent abnormalities were reported in (3/3) subjects who had a brain MRI. Previous investigations were mentioned for 3 individuals (incl. 2 sibs) and included normal CMA and/or metabolic workup. Singleton or trio exome sequencing (in one family) revealed biallelic missense TIAM1 variants. 6 different missense variants were reported, all ultra-rare or not present in gnomAD (also o/e:0.2, pLI:0.96), with CADD scores in favor of deleterious effect (NM_001353694.2): c.67C>T/p.Arg23Cys*, c.2584C>T/p.Leu862Phe*, c.983G>T/p.Gly328Val*, c.4640C>A/p.Ala1547Glu, c.1144G>C/p.Gly382Arg, c.4016C>T/p.Ala1339Val. TIAM1 encodes a RAC1-specific guanine exchange factor (GEF), regulating RAC1 signaling pathways that in turn affect cell shape, migration, adhesion, growth, survival, and polarity, and influence actin cytoskeletal organization, endocytosis, and membrane trafficking. RAC1 signaling plays important role in control of neuronal morphogenesis and neurite outgrowth (based on the summary by Entrez and authors). TIAM1 is highly expressed in human brain (GTEx). The authors provide evidence that sif, the Drosophila ortholog, is expressed primarily in neurons of the fly CNS (but not in glia). Using different sif LoF mutant flies they demonstrate that loss of sif impairs viability. Surviving flies exhibited climbing defects and seizure-like behaviors, both significantly rescued upon UAS-sif expression. Neuronal specific sif knockdown resulted in similar phenotypes to ubiquitous knockdown, while glial knockdown did not result in climbing defects. The semi-lethal phenotype could be fully rescued by expression of the fly sif cDNA, but only partially by human TIAM1 cDNA reference. Upon expression, 3 patient-variants (R23C, L862F, G328V) had variable rescue abilities similar to or lower (R23C) than TIAM1 Ref. TIAM1 Ref and variants could not rescue the neurological phenotypes though. Higher/ectopic expression of sif or TIAM1 Ref was toxic, which was also observed to a lesser extent for variants. Overall, the evidence provided suggests that the 3 variants tested induce partial LoF. In a recent study cited (PMID: 33328293), Tiam1 KO mice had simplified dendritic arbors, reduced spine density and diminished excitatory transmission in dentate gyrus. The authors comment that this mouse model presented only subtle behavioral abnormalities which they speculate may be secondary to GEF redundancy (eg. Tiam2). There is no TIAM1-associated phenotype in OMIM/G2P/SysID. TIAM1 is included in PanelApp Australia in the ID and epilepsy panels with green rating. Consider inclusion in the current panel with amber rating [As authors discuss: some phenotypic features differed in their small cohort and the contribution of other recessive conditions in 2 consanguineous families cannot be excluded. Also: in fig S1 only status of parents but not of affected/unaffected sibs is specified with the exception of Fam1]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1518 | HEATR3 |
Konstantinos Varvagiannis gene: HEATR3 was added gene: HEATR3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HEATR3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: HEATR3 were set to 35213692 Phenotypes for gene: HEATR3 were set to Anemia; Thrombocytopenia; Growth delay; Short stature; Abnormality of the skeletal system; Abnormality of finger; Abnormality of the thumb; Intellectual disability; Obesity; Abnormality of the face Penetrance for gene: HEATR3 were set to Complete Review for gene: HEATR3 was set to AMBER Added comment: O'Donohue et al (2022 - PMID: 35213692) describe the clinical features of 6 individuals (from 4 unrelated families) with biallelic pathogenic HEATR3 variants. These included bone marrow failure (anemia/anemia and thrombocytopenia at presentation), short stature/growth retardation (4/6), facial features (5/6 - in some: straight eyebrows, d-s palpebral fissures, synophrys) and skeletal findings incl. disproportionately short fingers/thumb anomaly. ID was reported in 4/6 individuals from 3 families (all: mild ID | 2/6 without ID). The phenotype corresponded overall to a variant form Diamond-Blackfan anemia (DBA, disorder caused by variants in genes encoding for ribosomal proteins) with additional features. The 1st family (2 affected sibs and parents) underwent WES, not diagnostic for DBA. Analysis suggested variants in HEATR3 (prioritized due to its potential role in ribosome biogenesis) and 4 additional genes as candidates. Collaboration in the European DBA consortium and national DBA consortia led to identification of additional families. HEATR3 encodes Heat-repeat-containing protein 3 or symportin, a protein that co-imports uL5 (encoded by RPL11) and uL18 (RPL5) in the nucleus where they assemble with 5S rRNA to form 5S RNP. The 5S RNP complex incorporates with maturing large ribosomal subunits to form the central protuberance. When 5S RNP is not incorporated, it accumulates and associates with Hdm2 ubiquitin ligase, the later normally targeting p53 proteasomal degradation. The following missense and splice variants were identified (NM_182922): - c.1751G>Α/p.(Gly584Glu) hmz - c.1337G>A/p.(Cys446Tyr) hmz - c.399+1G>T in trans with c.719C>T/p.(Pro240Leu) - c.400T>C/p.(Cys134Arg) hmz Variants were confirmed with Sanger sequencing. They were dispersed across HEATR3 without clustering although they affect residues either in the ARM (38-320) or HEAT (415-675) repeat domains, at positions evolutionary conserved, with in silico predictions in favor of a deleterious effect. With the exception of Cys134Arg (AF:4.11x10-6/no hmz), all were absent from gnomAD. Studies in yeast suggested that deletions in symportin gene (syo1) lead to a mild growth defect and accumulation of 40S subunits. Similarly, two yeast strains engineered to test for the effect of the p.Gly584Glu (yeast p.Gly522Glu/Ala) exhibited growth defect and ribosomal subunit imbalance, both restored by wt Syo1. HA-tagged HEATR3 in HeLa cells suggested that the co-translational capture mechanism to chaperone uL18 (RPL5) is conserved in human cells but was not observed upon expression of the p.Cys446Tyr variant. While HEATR3 transcription was not affected in LCLs from individuals hmz for Gly584Glu or Cys446Tyr, protein levels were barely detectable, suggesting destabilization of the protein. While uL18 accumulates in cytoplasm and nucleus with expected enrichment in nucleolus, upon siRNA knockdown of HEATR3 in HeLa cells this enrichment was lost. Studies in fibroblasts (Gly584Glu) demonstrated reduced uL18 nuclear staining. Overall, HEATR3 was suggested to be important for nuclear import of uL18 (though not for uL5). LCL studies demonstrated pre-rRNA processing defects in patient cells with accumulation of 32S and 12S pre-rRNAs, the former being reminiscent of accumulations observed in individuals with RPL5- and RPL11-related DBA. Expression of wt HEATR3 restored processing defects. LCLs from affected individuals revealed loss of free 60S subunits (as in yeast) with expression of wt cDNA restoring Nl levels. Western blots of LCLs demonstrated that the levels of uL5, uL18 and p53 were not affected (the latter also observed in RPL5-related DBA) Studies of bone marrow smears from 2 affected individuals allowed to conclude in a strong defect in erythroid cell proliferation. Currently, there is no HEATR3-associated phenotype in OMIM, PanelApp Australia, G2P or the SysID database. Consider inclusion in the ID panel with amber (mild ID in >3 individuals/families/variants although not universal feature) or green rating. Also consider inclusion in other possibly relevant panels eg. for cytopenias/congenital anemias, short stature, etc. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1506 | PDZD8 |
Konstantinos Varvagiannis changed review comment from: Al-Amri et al (2022 - PMID: 35227461) describe 4 affected individuals, belonging to 2 independent consanguineous families, harboring biallelic pLoF PDZD8 variants. The phenotype corresponded to a syndromic form of ID with autistic features. Animal models provide additional evidence for a role of the gene. Details are provided concerning 3 affected sibs born to consanguineous parents (Fam-A) and a male proband born to first cousin parents (Fam-B) from different countries of the Arabian Peninsula. Features included DD (4/4), ID (4/4 - moderate to severe), autistic features[*](4/4), other behavioral problems (3/4 - 2 families). Variable facial features were observed (4/4 - incl. hypertelorism 4/4, myopathic face, open mouth, low-set ears, ptosis). 3 sibs presented with myopathy[*](3/4 overall - 1 fam - see below), and marfanoid habitus was observed in 2 (2/4 - 1 fam). 2 sibs had epilepsy (2/4 - from 1 family). 1 individual had congenital heart defect. [* -also to consider for MOI]Autistic features were however observed in a parent and a htz sib. Mild myopathy/reduced facial expression was also observed in both parents. Contribution of another variant - also within the region of shared homozygosity - to the phenotype of myopathy was deemed to be possible within this family. Previous genetic testing was not reported. Homozygosity mapping in the 1st family identified 3 homozygous regions (2.57 - 28 Mb) shared by all affected sibs. Singleton WES revealed 2 candidate variants within these regions, a PDZD8 frameshift variant [NM_173791.5:c.2197_2200del;p.(S733*)] lying in the last exon and an ANKRD2 missense one (discussed above). The proband in Fam-B was hmz for a nonsense variant in ex2 (of 5), namely c.894C>G/p.(Y298*) considered to be the most likely cause of his phenotype following singleton WES. Sanger sequencing was used for validation and segregation studies confirming carrier status of the parents and compatible results in unaffected sibs (tested : 2 in Fam-A, 3 in Fam-B). Both variants were absent from gnomAD (the first also from a pool of 50 control individuals of the same origin) where PDZD8 has a pLI of 1 (5 different pLoF variants, none hmz). Expression was not studied for the 2 variants. As a result, it is not known whether they escape NMD (as could be expected for the variant in the last exon). PDZD8 encodes an endoplasmatic reticulum (ER) transmembrane protein (TM). As the authors discuss, it has been previously shown that depletion of PDZD8 in neurons impairs endosomal homeostasis, decreases proximity of ER-mitochondria and decreases Ca+2 uptake mitochondria following synaptic transmission-induced release from the ER (sev. refs. provided). The gene is highly expressed in the human brain (incl. subclasses of GABAergic / glutamatergic neurons in adult primary motor cortex). The authors analyzed RNA-seq data from the BrainSpan project, demonstrating stable expression in human brain from 8 wks after conception to adulthood. The gene is not expressed in blood. The authors performed in vivo functional studies. Knockdown of the orthologous gene (CG10362) in Drosophila via RNA interference was shown to result in impairment of long-term memory. Mice homozygous for a variant introducing a premature termination codon exhibited restricted growth, brain structural alterations (incl. relative reduction of the CC, as in one subject), spontaneous stereotypies, decreased anxiety-like behavior with deficits in spatial memory and impaired hippocampal neurophysiology. Currently, there is no associated phenotype in OMIM, Gene2Phenotype, SysID or PanelApp Australia. Overall, this gene can be considered for inclusion in the ID panel probably with amber rating pending further reports. Sources: Literature; to: Al-Amri et al (2022 - PMID: 35227461) describe 4 affected individuals, belonging to 2 independent consanguineous families, harboring biallelic pLoF PDZD8 variants. The phenotype corresponded to a syndromic form of ID with autistic features. Animal models provide additional evidence for a role of the gene. Details are provided concerning 3 affected sibs born to consanguineous parents (Fam-A) and a male proband born to first cousin parents (Fam-B) from different countries of the Arabian Peninsula. Features included DD (4/4), ID (4/4 - moderate to severe), autistic features[*](4/4), other behavioral problems (3/4 - 2 families). Variable facial features were observed (4/4 - incl. hypertelorism 4/4, myopathic face, open mouth, low-set ears, ptosis). 3 sibs presented with myopathy[*](3/4 overall - 1 fam - see below), and marfanoid habitus was observed in 2 (2/4 - 1 fam). 2 sibs had epilepsy (2/4 - from 1 family). 1 individual had congenital heart defect. [*] (also to consider for MOI) : Autistic features were however observed in a parent and a htz sib. Mild myopathy/reduced facial expression was also observed in both parents. Contribution of another variant - also within the region of shared homozygosity - to the phenotype of myopathy was deemed to be possible within this family. Previous genetic testing was not reported. Homozygosity mapping in the 1st family identified 3 homozygous regions (2.57 - 28 Mb) shared by all affected sibs. Singleton WES revealed 2 candidate variants within these regions, a PDZD8 frameshift variant [NM_173791.5:c.2197_2200del;p.(S733*)] lying in the last exon and an ANKRD2 missense one (discussed above). The proband in Fam-B was hmz for a nonsense variant in ex2 (of 5), namely c.894C>G/p.(Y298*) considered to be the most likely cause of his phenotype following singleton WES. Sanger sequencing was used for validation and segregation studies confirming carrier status of the parents and compatible results in unaffected sibs (tested : 2 in Fam-A, 3 in Fam-B). Both variants were absent from gnomAD (the first also from a pool of 50 control individuals of the same origin) where PDZD8 has a pLI of 1 (5 different pLoF variants, none hmz). Expression was not studied for the 2 variants. As a result, it is not known whether they escape NMD (as could be expected for the variant in the last exon). PDZD8 encodes an endoplasmatic reticulum (ER) transmembrane protein (TM). As the authors discuss, it has been previously shown that depletion of PDZD8 in neurons impairs endosomal homeostasis, decreases proximity of ER-mitochondria and decreases Ca+2 uptake mitochondria following synaptic transmission-induced release from the ER (sev. refs. provided). The gene is highly expressed in the human brain (incl. subclasses of GABAergic / glutamatergic neurons in adult primary motor cortex). The authors analyzed RNA-seq data from the BrainSpan project, demonstrating stable expression in human brain from 8 wks after conception to adulthood. The gene is not expressed in blood. The authors performed in vivo functional studies. Knockdown of the orthologous gene (CG10362) in Drosophila via RNA interference was shown to result in impairment of long-term memory. Mice homozygous for a variant introducing a premature termination codon exhibited restricted growth, brain structural alterations (incl. relative reduction of the CC, as in one subject), spontaneous stereotypies, decreased anxiety-like behavior with deficits in spatial memory and impaired hippocampal neurophysiology. Currently, there is no associated phenotype in OMIM, Gene2Phenotype, SysID or PanelApp Australia. Overall, this gene can be considered for inclusion in the ID panel probably with amber rating pending further reports. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1506 | PDZD8 |
Konstantinos Varvagiannis gene: PDZD8 was added gene: PDZD8 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PDZD8 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PDZD8 were set to 35227461 Phenotypes for gene: PDZD8 were set to Global developmental delay; Intellectual disability; Autistic behavior; Behavioral abnormality; Myopathy; Abnormality of the face; Hypertelorism; Seizures; Disproportionate tall stature Penetrance for gene: PDZD8 were set to Complete Review for gene: PDZD8 was set to AMBER Added comment: Al-Amri et al (2022 - PMID: 35227461) describe 4 affected individuals, belonging to 2 independent consanguineous families, harboring biallelic pLoF PDZD8 variants. The phenotype corresponded to a syndromic form of ID with autistic features. Animal models provide additional evidence for a role of the gene. Details are provided concerning 3 affected sibs born to consanguineous parents (Fam-A) and a male proband born to first cousin parents (Fam-B) from different countries of the Arabian Peninsula. Features included DD (4/4), ID (4/4 - moderate to severe), autistic features[*](4/4), other behavioral problems (3/4 - 2 families). Variable facial features were observed (4/4 - incl. hypertelorism 4/4, myopathic face, open mouth, low-set ears, ptosis). 3 sibs presented with myopathy[*](3/4 overall - 1 fam - see below), and marfanoid habitus was observed in 2 (2/4 - 1 fam). 2 sibs had epilepsy (2/4 - from 1 family). 1 individual had congenital heart defect. [* -also to consider for MOI]Autistic features were however observed in a parent and a htz sib. Mild myopathy/reduced facial expression was also observed in both parents. Contribution of another variant - also within the region of shared homozygosity - to the phenotype of myopathy was deemed to be possible within this family. Previous genetic testing was not reported. Homozygosity mapping in the 1st family identified 3 homozygous regions (2.57 - 28 Mb) shared by all affected sibs. Singleton WES revealed 2 candidate variants within these regions, a PDZD8 frameshift variant [NM_173791.5:c.2197_2200del;p.(S733*)] lying in the last exon and an ANKRD2 missense one (discussed above). The proband in Fam-B was hmz for a nonsense variant in ex2 (of 5), namely c.894C>G/p.(Y298*) considered to be the most likely cause of his phenotype following singleton WES. Sanger sequencing was used for validation and segregation studies confirming carrier status of the parents and compatible results in unaffected sibs (tested : 2 in Fam-A, 3 in Fam-B). Both variants were absent from gnomAD (the first also from a pool of 50 control individuals of the same origin) where PDZD8 has a pLI of 1 (5 different pLoF variants, none hmz). Expression was not studied for the 2 variants. As a result, it is not known whether they escape NMD (as could be expected for the variant in the last exon). PDZD8 encodes an endoplasmatic reticulum (ER) transmembrane protein (TM). As the authors discuss, it has been previously shown that depletion of PDZD8 in neurons impairs endosomal homeostasis, decreases proximity of ER-mitochondria and decreases Ca+2 uptake mitochondria following synaptic transmission-induced release from the ER (sev. refs. provided). The gene is highly expressed in the human brain (incl. subclasses of GABAergic / glutamatergic neurons in adult primary motor cortex). The authors analyzed RNA-seq data from the BrainSpan project, demonstrating stable expression in human brain from 8 wks after conception to adulthood. The gene is not expressed in blood. The authors performed in vivo functional studies. Knockdown of the orthologous gene (CG10362) in Drosophila via RNA interference was shown to result in impairment of long-term memory. Mice homozygous for a variant introducing a premature termination codon exhibited restricted growth, brain structural alterations (incl. relative reduction of the CC, as in one subject), spontaneous stereotypies, decreased anxiety-like behavior with deficits in spatial memory and impaired hippocampal neurophysiology. Currently, there is no associated phenotype in OMIM, Gene2Phenotype, SysID or PanelApp Australia. Overall, this gene can be considered for inclusion in the ID panel probably with amber rating pending further reports. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1500 | CHKA |
Konstantinos Varvagiannis gene: CHKA was added gene: CHKA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CHKA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CHKA were set to 35202461 Phenotypes for gene: CHKA were set to Abnormal muscle tone; Global developmental delay; Intellectual disability; Seizures; Microcephaly; Abnormality of movement; Abnormality of nervous system morphology; Short stature Penetrance for gene: CHKA were set to Complete Review for gene: CHKA was set to GREEN Added comment: Klöckner (2022 - PMID: 35202461) describe the phenotype of 6 individuals (from 5 unrelated families) harboring biallelic CHKA variants. Shared features incl. abnormal muscle tone(6/6 - hypertonia or hypotonia, 3/6 each), DD/ID (6/6,severe in 4, severe/profound in 2), epilepsy (6/6 - onset: infancy - 3y2m | epileptic spasms or GS at onset), microcephaly (6/6), movement disorders (3/6 - incl. dyskinesia, rigidity, choreoatetotic movements). 2/5 individuals exhibited MRI abnormalities, notably hypomyelination. Short stature was observed in 4/6. Eventual previous genetic testing was not discussed. Exome sequencing (quattro ES for 2 sibs, trio ES for 1 individual, singleton for 3 probands) revealed biallelic CHKA variants in all affected individuals. Sanger sequencing was performed for confirmation and segregation studies. Other variants (in suppl.) were not deemed to be causative for the neurodevelopmental phenotype. 3 different missense, 1 start-loss and 1 truncating variant were identified, namely (NM_0012772.2): - c.421C>T/p.(Arg141Trp) [3 hmz subjects from 2 consanguineous families], - c.580C>T/p.Pro194Ser [1 hmz individual born to consanguineous parents], - c.2T>C/p.(Met1?) [1 hmz individual born to related parents], - c.14dup/p.(Cys6Leufs*19) in trans with c.1021T>C/p.(Phe341Leu) in 1 individual. CHKA encodes choline kinase alpha, an enzyme catalyzing the first step of phospholipid synthesis in the Kennedy pathway. The pathway is involved in de novo synthesis of glycerophospholipids, phosphatidylcholine and phosphatidylethanolamine being the most abundant in eukaryotic membranes. CHKA with its paralog (CHKB) phosphorylates either choline or ethanolamine to phosphocholine or phosphoethanolamine respectively with conversion of ATP to ADP. As the authors comment, biallelic pathogenic variants in CHKB cause a NDD with muscular dystrophy, hypotonia, ID, microcephaly and structural mitochondrial anomalies (MIM 602541). [Prominent mitochondrial patterning was observed in a single muscle biopsy available from an individual with biallelic CHKA variants]. Other disorders of the Kennedy pathway (due to biallelic PCYT2, SELENOI, PCYT1A variants) present with overlapping features incl. variable DD/ID (no-severe), microcephaly, seizures, visual impairment etc. CHKA variants were either absent or observed once in gnomAD, affected highly conserved AAs with multiple in silico predictions in favor of a deleterious effect. In silico modeling suggests structural effects for several of the missense variants (Arg141Trp, Pro194Ser presumably affect ADP binding, Phe341 lying close to the binding site of phosphocholine). Each of the missense variants was expressed in yeast cells and W. Blot suggested expression at the expected molecular weight at comparative levels. The 3 aforementioned variants exhibited reduced catalytic activity (20%, 15%, 50% respectively). NMD is thought to underly the deleterious effect of the frameshift one (not studied). The start-loss variant is expected to result in significantly impaired expression and protein function as eventual utilization of the next possible start codon - occurring at position 123 - would remove 26% of the protein. Chka(-/-) is embryonically lethal in mice, suggesting that complete loss is not compatible with life. Reduction of choline kinase activity by 30% in heterozygous mice did not appear to result in behavioral abnormalities although this was not studied in detail (PMID cited: 18029352). Finally, screening of 1566 mouse lines identified 198 genes whose disruption yields neuroanatomical phenotypes, Chka(+/-) mice being among these (PMID cited: 31371714). There is no associated phenotype in OMIM, Gene2Phenotype or SysID. Overall this gene can be considered for inclusion in the ID and epilepsy panes with green or amber rating (>3 individuals, >3 variants, variant studies, overlapping phenotype of disorders belonging to the same pathway, etc). Consider also inclusion in the microcephaly panel (where available this seemed to be of postnatal onset). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1496 | SLC35F1 |
Zornitza Stark gene: SLC35F1 was added gene: SLC35F1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC35F1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: SLC35F1 were set to 33821533 Phenotypes for gene: SLC35F1 were set to Neruodevelopmental disorder, MONDO:0700092, SLC35F1-associated; Rett-like syndrome Review for gene: SLC35F1 was set to RED Added comment: WES identified a de novo heterozygous c.1037T>C; p.(I346T) (absent in gnomad v2 and v3) in a female described to have Rett-like syndrome. Global developmental delay, generalized tonic andtonic–clonic seizure, never acquired independent walking and developed spastictetraplegia in adulthood and limited speech No functional data Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1478 | FOXR1 |
Zornitza Stark gene: FOXR1 was added gene: FOXR1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: FOXR1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: FOXR1 were set to 34723967 Phenotypes for gene: FOXR1 were set to Postnatal microcephaly, progressive brain atrophy and global developmental delay Review for gene: FOXR1 was set to AMBER Added comment: 1 patient described with a de novo missense variant. Phenotypes include: postnatal microcephaly, progressive brain atrophy, skeletal abnormalities, brain abnormalities, ophthalmic abnormalities, neuromuscular abnormalities, and dysmorphic features. A variant in ATP1A3 was considered to have contributed to the final phenotype. In vitro functional evidence is supportive of pathogenicity (variant causes protein instability and abnormal nuclear aggregation). A mouse knockout has comparable phenotypes, and a severe survival deficit. Rated amber (1 patient, functional evidence, mouse model). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1395 | DHDDS |
Arina Puzriakova Added comment: Comment on mode of inheritance: MOI should be updated from 'Both mono- and biallelic' to 'Monoallelic' at the next GMS panel update. Monoallelic variants are associated with a neurodevelopmental disorder comprising DD/ID, epilepsy and a variable movement disorder phenotype - >3 unrelated individuals reported in literature. To date, only one individual with biallelic variants and ID has been reported (PMID: 27343064). This patient presented with glycosylation defects but no corroborating cases have been reported since. As only one patient has been described with biallelic inheritance and this phenotype, MOI should be set to 'Monoallelic' until evidence of additional cases emerges - biallelic variants would still be picked up by the Genomics England pipeline under this MOI. |
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| Intellectual disability - microarray and sequencing v3.1381 | CDH15 | Arina Puzriakova Added comment: Comment on list classification: Gene should be demoted to Red as there is limited evidence supporting this gene-disease association. The only cases reported to date with SNVs were discovered by targeted sequencing of CDH15. Clinical information was limited, describing only mild ID in some cases. There are also multiple benign LOF variants in population databases. Asymptomatic carriers lead authors to suggest incomplete penetrance but all identified variants are in gnomAD so are unlikely to be causal. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1348 | WDR11 |
Ivone Leong Added comment: Comment on list classification: Promoted from Red to Amber. This gene is associated with a relevant phenotype in Gene2Phenotype (probable) but not in OMIM. There is enough evidence to support a gene-disease association; however, the severity of ID in the patients described in PMID:34413497 does not fit the criteria for this panel (panel is for moderate to severe ID, patients have mild ID). Therefore, this gene has been given an Amber rating. The OFC of patients in PMID: 34413497 ranged from -3.09 SD to -4.93 SD) |
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| Intellectual disability - microarray and sequencing v3.1328 | RNF220 |
Ivone Leong Added comment: Comment on list classification: New gene added by Konstantinos Varvagiannis. This gene is currently not associated with a phenotype in OMIM or Gene2Phenotype. There are >3 cases for this gene; however, 3 of the cases described in PMID:33964137 are of Roma descent and haplotype analysis has shown that the variant found in these families are due to a founder effect (c.1094G>A, p.Arg365Gly). A separate Roma family also has the same variant (c.1094G>A, p.Arg365Gly). An Italian family with similar phenotypes has a different variant (c.1088G>A, p.Arg363Gly). The authors also report on in vitro and in vivo studies. There is enough evidence to support a gene-disease association; however, the ID severity in these patients do not meet the criteria (moderate to severe) for this panel (patients show mild (mostly) to moderate severity). Therefore, this gene has been given an Amber rating. |
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| Intellectual disability - microarray and sequencing v3.1276 | COPB2 |
Eleanor Williams changed review comment from: PMID: 34450031 - Marom et al 2021 describes 6 individuals from 5 families. In 4 families loss of function heterozygous variants in COPB2 were found. In the 5th family, two affected siblings were found to have a homozygous variant in COPB2. Osteopenia was noted in 4/5 families (5th unknown) and fractures in 2/5. Developmental delay was observed in all 6 individuals with variable severity. Severe intellectual disability, seizures and microcephaly was noted in the siblings with the homozygous variants. Copb2þ +/-mice exhibit low bone mass Sources: Literature; to: PMID: 34450031 - Marom et al 2021 describes 6 individuals from 5 families. In 4 families loss of function heterozygous variants in COPB2 were found. In the 5th family, two affected siblings were found to have a homozygous variant in COPB2. Osteopenia was noted in 4/5 families (5th unknown) and fractures in 2/5. Developmental delay was observed in all 6 individuals with variable severity. Severe intellectual disability, seizures and microcephaly was noted in the siblings with the homozygous variants. Copb2þ +/-mice exhibit low bone mass PMID: 29036432 - original report of microcephaly in the two siblings with the COPB2 homozygous variant. |
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| Intellectual disability - microarray and sequencing v3.1275 | COPB2 |
Eleanor Williams gene: COPB2 was added gene: COPB2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: COPB2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: COPB2 were set to 34450031 Phenotypes for gene: COPB2 were set to osteoporosis; developmental delay Review for gene: COPB2 was set to GREEN Added comment: PMID: 34450031 - Marom et al 2021 describes 6 individuals from 5 families. In 4 families loss of function heterozygous variants in COPB2 were found. In the 5th family, two affected siblings were found to have a homozygous variant in COPB2. Osteopenia was noted in 4/5 families (5th unknown) and fractures in 2/5. Developmental delay was observed in all 6 individuals with variable severity. Severe intellectual disability, seizures and microcephaly was noted in the siblings with the homozygous variants. Copb2þ +/-mice exhibit low bone mass Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1220 | PLXNA2 |
Konstantinos Varvagiannis changed review comment from: Altuame et al (2021 - PMID: 34327814) describe 3 individuals from 2 consanguineous Arab families with biallelic PLXNA2 variants. The index patient from the 1st family presented with CHD (hypoplastic right ventricle, ASD), DD and moderate ID (IQ of 40), failure to thrive as well as some dysmorphic features (obtuse mandibular angle, mild overbite, synophrys with downslanting p-f, strabismus, etc). There were additional features (eg. postaxial polydactyly) which were found in other affected and unaffected family members. Exome sequencing with autozygome analysis revealed homozygosity for a PLXNA2 stopgain variant (NM_025179:c.3603C>A / p.(Cys1201*)). Sanger confirmation was carried out and segregation analyses confirmed carrier status of the unaffected parents and a sib as well as a brother homozygous for the same variant. Clinical evaluation of the latter, following this finding revealed borderline intellectual functioning, ADHD, failure to thrive. There was no mandibular anomaly or overbite and no clinical evidence of CHD (no echo performed). The index patient from the 2nd consanguineous family was evaluated for ID (IQ of 63), with previous borderline motor development, ADHD and some dysmorphic features (obtuse mandibular angle and overbite). There was no clinical evidence of CHD (no echo performed). Exome sequencing with autozygosity mapping revealed a homozygous missense PLXNA2 variant (c.3073G>A / p.(Asp1025Asn), present only once in gnomAD (htz), with rather non-concordant in silico predictions SIFT 0.22, PolyPhen 0.682 and CADD 23.5. The aa was however highly conserved. Segregation analysis confirmed carrier state of the parents and 2 unaffected sibs, with a 3rd sib homozygous for the wt allele. As the authors discuss: *PLXNA2 belongs to the plexin family of genes, encoding transmbembrane proteins functioning as semaphorin receptors. It has predominant expression in neural tissue. The protein is thought to bind semaphorin-3A, -3C or -5 followed by plexin A2 dimerization, activation of its GTPase-activating protein domain, negative regulation of Rap1B GTPase and initiation of a signal transduction cascade mediating axonal repulsion/guidance, dendritic guidance, neuronal migration. *Murine Plxna2 knockout models display structural brain defects. In addition they display congenital heart defects incl. persistent truncus arteriosus and interrupted aortic arch. *Rare CNVs in adult humans with tetralogy of Fallot have suggested a potential role of PLXNA2 in cardiac development and CHD. *Expression and the role of PLXNA2 in human chondrocytes as well as a GWAS in 240 japanese patients with mandibular prognathism where PLXNA2 was suggested as a susceptibility locus. Overall, the authors recognize some common features (as for cognitive functioning, some dysmorphic features incl. obtuse mandibular angle and overbite in 2 unrelated subjects, failure to thrive 3/3) and provide plausible explanations for the variability / discordance of others eg: - Cyanotic heart disease explaining discordance in cognitive outcome among sibs - Incomplete penetrance for CHD (and/or ID or mandibular anomaly) as for few AR disorders and/or - Additional pathogenic variants explaining the CHD in the first subject. There is no associated phenotype in OMIM or G2P. SysID includes PLXNA2 among the candidate ID genes. Sources: Literature, Other; to: Altuame et al (2021 - PMID: 34327814) describe 3 individuals from 2 consanguineous Arab families with biallelic PLXNA2 variants. The index patient from the 1st family presented with CHD (hypoplastic right ventricle, ASD), DD and moderate ID (IQ of 40), failure to thrive as well as some dysmorphic features (obtuse mandibular angle, mild overbite, synophrys with downslanting p-f, strabismus, etc). There were additional features (eg. postaxial polydactyly) which were found in other affected and unaffected family members. Exome sequencing with autozygome analysis revealed homozygosity for a PLXNA2 stopgain variant (NM_025179:c.3603C>A / p.(Cys1201*)). Sanger confirmation was carried out and segregation analyses confirmed carrier status of the unaffected parents and a sib as well as a brother homozygous for the same variant. Clinical evaluation of the latter, following this finding revealed borderline intellectual functioning, ADHD, failure to thrive. There was no mandibular anomaly or overbite and no clinical evidence of CHD (no echo performed). The index patient from the 2nd consanguineous family was evaluated for ID (IQ of 63), with previous borderline motor development, ADHD and some dysmorphic features (obtuse mandibular angle and overbite). There was no clinical evidence of CHD (no echo performed). Exome sequencing with autozygosity mapping revealed a homozygous missense PLXNA2 variant (c.3073G>A / p.(Asp1025Asn), present only once in gnomAD (htz), with rather non-concordant in silico predictions SIFT 0.22, PolyPhen 0.682 and CADD 23.5. The aa was however highly conserved. Segregation analysis confirmed carrier state of the parents and 2 unaffected sibs, with a 3rd sib homozygous for the wt allele. As the authors discuss: *PLXNA2 belongs to the plexin family of genes, encoding transmbembrane proteins functioning as semaphorin receptors. It has predominant expression in neural tissue. The protein is thought to bind semaphorin-3A, -3C or -5 followed by plexin A2 dimerization, activation of its GTPase-activating protein domain, negative regulation of Rap1B GTPase and initiation of a signal transduction cascade mediating axonal repulsion/guidance, dendritic guidance, neuronal migration. *Murine Plxna2 knockout models display structural brain defects. In addition they display congenital heart defects incl. persistent truncus arteriosus and interrupted aortic arch. *Rare CNVs in adult humans with tetralogy of Fallot have suggested a potential role of PLXNA2 in cardiac development and CHD. *Expression and the role of PLXNA2 in human chondrocytes as well as a GWAS in 240 japanese patients with mandibular prognathism where PLXNA2 was suggested as a susceptibility locus. Overall, the authors recognize some common features (as for cognitive functioning, some dysmorphic features incl. obtuse mandibular angle and overbite in 2 unrelated subjects, failure to thrive 3/3) and provide plausible explanations for the variability / discordance of others eg: - Cyanotic heart disease explaining discordance in cognitive outcome among sibs - Incomplete penetrance for CHD (and/or ID or mandibular anomaly) as for few AR disorders and/or - Additional pathogenic variants possibly explaining the CHD in the first subject. There is no associated phenotype in OMIM or G2P. SysID includes PLXNA2 among the candidate ID genes. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1220 | PLXNA2 |
Konstantinos Varvagiannis gene: PLXNA2 was added gene: PLXNA2 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: PLXNA2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PLXNA2 were set to 34327814 Phenotypes for gene: PLXNA2 were set to Intellectual disability; Abnormality of the face; Failure to thrive; Abnormal heart morphology Penetrance for gene: PLXNA2 were set to Incomplete Review for gene: PLXNA2 was set to AMBER Added comment: Altuame et al (2021 - PMID: 34327814) describe 3 individuals from 2 consanguineous Arab families with biallelic PLXNA2 variants. The index patient from the 1st family presented with CHD (hypoplastic right ventricle, ASD), DD and moderate ID (IQ of 40), failure to thrive as well as some dysmorphic features (obtuse mandibular angle, mild overbite, synophrys with downslanting p-f, strabismus, etc). There were additional features (eg. postaxial polydactyly) which were found in other affected and unaffected family members. Exome sequencing with autozygome analysis revealed homozygosity for a PLXNA2 stopgain variant (NM_025179:c.3603C>A / p.(Cys1201*)). Sanger confirmation was carried out and segregation analyses confirmed carrier status of the unaffected parents and a sib as well as a brother homozygous for the same variant. Clinical evaluation of the latter, following this finding revealed borderline intellectual functioning, ADHD, failure to thrive. There was no mandibular anomaly or overbite and no clinical evidence of CHD (no echo performed). The index patient from the 2nd consanguineous family was evaluated for ID (IQ of 63), with previous borderline motor development, ADHD and some dysmorphic features (obtuse mandibular angle and overbite). There was no clinical evidence of CHD (no echo performed). Exome sequencing with autozygosity mapping revealed a homozygous missense PLXNA2 variant (c.3073G>A / p.(Asp1025Asn), present only once in gnomAD (htz), with rather non-concordant in silico predictions SIFT 0.22, PolyPhen 0.682 and CADD 23.5. The aa was however highly conserved. Segregation analysis confirmed carrier state of the parents and 2 unaffected sibs, with a 3rd sib homozygous for the wt allele. As the authors discuss: *PLXNA2 belongs to the plexin family of genes, encoding transmbembrane proteins functioning as semaphorin receptors. It has predominant expression in neural tissue. The protein is thought to bind semaphorin-3A, -3C or -5 followed by plexin A2 dimerization, activation of its GTPase-activating protein domain, negative regulation of Rap1B GTPase and initiation of a signal transduction cascade mediating axonal repulsion/guidance, dendritic guidance, neuronal migration. *Murine Plxna2 knockout models display structural brain defects. In addition they display congenital heart defects incl. persistent truncus arteriosus and interrupted aortic arch. *Rare CNVs in adult humans with tetralogy of Fallot have suggested a potential role of PLXNA2 in cardiac development and CHD. *Expression and the role of PLXNA2 in human chondrocytes as well as a GWAS in 240 japanese patients with mandibular prognathism where PLXNA2 was suggested as a susceptibility locus. Overall, the authors recognize some common features (as for cognitive functioning, some dysmorphic features incl. obtuse mandibular angle and overbite in 2 unrelated subjects, failure to thrive 3/3) and provide plausible explanations for the variability / discordance of others eg: - Cyanotic heart disease explaining discordance in cognitive outcome among sibs - Incomplete penetrance for CHD (and/or ID or mandibular anomaly) as for few AR disorders and/or - Additional pathogenic variants explaining the CHD in the first subject. There is no associated phenotype in OMIM or G2P. SysID includes PLXNA2 among the candidate ID genes. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1220 | VPS50 |
Konstantinos Varvagiannis gene: VPS50 was added gene: VPS50 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: VPS50 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: VPS50 were set to 34037727 Phenotypes for gene: VPS50 were set to Neonatal cholestatic liver disease; Failure to thrive; Profound global developmental delay; Postnatal microcephaly; Seizures; Abnormality of the corpus callosum Penetrance for gene: VPS50 were set to Complete Review for gene: VPS50 was set to AMBER Added comment: Schneeberger et al (2021 - PMID: 34037727) describe the phenotype of 2 unrelated individuals with biallelic VPS50 variants. Common features included transient neonatal cholestasis, failure to thrive, severe DD with failure to achieve milestones (last examination at 2y and 2y2m respectively), postnatal microcephaly, seizures (onset at 6m and 25m) and irritability. There was corpus callosum hypoplasia on brain imaging. Both individuals were homozygous for variants private to each family (no/not known consanguinity applying to each case). The first individual was homozygous for a splicing variant (NM_017667.4:c.1978-1G>T) and had a similarly unaffected sister deceased with no available DNA for testing. The other individual was homozygous for an in-frame deletion (c.1823_1825delCAA / p.(Thr608del)). VPS50 encodes a critical component of the endosome-associated recycling protein (EARP) complex, which functions in recycling endocytic vesicles back to the plasma membrane [OMIM based on Schindler et al]. The complex contains VPS50, VPS51, VPS52, VPS53, the three latter also being components of GARP (Golgi-associated-retrograde protein) complex. GARP contains VPS54 instead of VPS50 and is required for trafficking of proteins to the trans-golgi network. Thus VPS50 (also named syndetin) and VPS54 function in the EARP and GARP complexes, to define directional movement of their endocytic vesicles [OMIM based on Schindler et al]. The VPS50 subunit is required for recycling of the transferrin receptor. As discussed by Schneeberger et al (refs provided in text): - VPS50 has a high expression in mouse and human brain as well as throughout mouse brain development. - Mice deficient for Vps50 have not been reported. vps50 knockdown in zebrafish results in severe developmental defects of the body axis. Knockout mice for other proteins of the EARP/GARP complex (e.g. Vps52, 53 and 54) display embryonic lethality. Studies performed by Schneeberger et al included: - Transcript analysis for the 1st variant demonstrated skipping of ex21 (in patient derived fabriblasts) leading to an in frame deletion of 81 bp (r.1978_2058del) with predicted loss of 27 residues (p.Leu660_Leu686del). - Similar VPS50 mRNA levels but significant reduction of protein levels (~5% and ~8% of controls) were observed in fibroblasts from patients 1 and 2. Additionally, significant reductions in the amounts of VPS52 and VPS53 protein levels were observed despite mRNA levels similar to controls. Overall, this suggested drastic reduction of functional EARP complex levels. - Lysosomes appeared to have similar morphology, cellular distribution and likely unaffected function in patient fibroblasts. - Transferrin receptor recycling was shown to be delayed in patient fibroblasts suggestive of compromise of endocytic-recycling function. As the authors comment, the phenotype of both individuals with biallelic VPS50 variants overlaps with the corresponding phenotype reported in 15 subjects with biallelic VPS53 or VPS51 mutations notably, severe DD/ID, microcephaly and early onset epilepsy, CC anomalies. Overall, for this group, they propose the term "GARP and/or EARP deficiency disorders". There is no VPS50-associated phenotype in OMIM or G2P. SysID includes VPS50 among the ID candidate genes. Consider inclusion in other relevant gene panels (e.g. for neonatal cholestasis, epilepsy, microcephaly, growth failure in early infancy, corpus callosum anomalies, etc) with amber rating pending further reports. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1216 | IMPDH2 |
Zornitza Stark gene: IMPDH2 was added gene: IMPDH2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: IMPDH2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: IMPDH2 were set to 33098801 Phenotypes for gene: IMPDH2 were set to Neurodevelopmental disorder with dystonia Review for gene: IMPDH2 was set to GREEN Added comment: 6 unrelated individuals 1x individual in a dystonia cohort index case with infancy-onset dystonia and other neurological manifestations with a de-novo missense variant, c.338G>A (p.Gly113Glu) in IMPDH2, predicted to disrupt an invariant residue within the cystathionine-β-synthase (CBS) domain pair of the encoded protein. IMPDH2 encodes IMPDH2, a key enzyme in the purine biosynthetic pathway, expressed throughout the brain and not linked previously to any human Mendelian condition. 1x individual with a de-novo substitution, c.337G>A (p.Gly113Arg), was found in in-house whole-exome sequencing data from 500 individuals with neurodevelopmental disorders. Through GeneMatcher, de novo variants identified: 3 x missense: c.729G>C (p.Gln243His), c.619G>C (p.Gly207Arg), and c.619G>A (p.Gly207Arg) 1 x deletion: c.478_480delTCC (p.Ser160del) The six variants were predicted to be deleterious and none of them seen in control databases. All affected conserved amino acids and resided in and around the cystathionine-β-synthase domain pair. The described variants are situated in and around the CBS domain pair, a regulatory element in which clustering of pathogenic missense variants has already been shown for the homologue of IMPDH2, IMPDH1. All individuals shared similar neurodevelopmental phenotypes. Apart from the dystonia cohort index case, one participant had evidence of dystonic posturing. Modelling of the variants on 3D protein structures revealed spatial clustering near specific functional sites, predicted to result in deregulation of IMPDH2 activity. Additionally, thermal-shift assays showed that the c.619G>A (p.Gly207Arg) variant, identified as within the CBS domain pair, and c.729G>C (p.Gln243His), which is in close vicinity, affected the stability or folding behaviour of IMPDH2. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1195 | CEP85L |
Rachel Challis gene: CEP85L was added gene: CEP85L was added to Intellectual disability. Sources: NHS GMS Mode of inheritance for gene: CEP85L was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CEP85L were set to 32097629; 32097630 Phenotypes for gene: CEP85L were set to Intellectual disability; epilepsy, lissencephaly Penetrance for gene: CEP85L were set to unknown Review for gene: CEP85L was set to GREEN gene: CEP85L was marked as current diagnostic Added comment: Recommend adding as Green gene to GMS - R29 Intellectual disability panel. Monoallelic missense and loss of function variants in CEP85L are associated with Lissencephaly (OMIM 618873). Over 10 unrelated families have been described with de novo and inherited rare variants in CEP85L. Functional work in cell lines and knockdown of Cep85l in mice confirms the role of CEP85L in neuronal migration. PMID: 32097629 PMID: 32097630 Sources: NHS GMS |
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| Intellectual disability - microarray and sequencing v3.1170 | ASCC3 | Ivone Leong Added comment: Comment on list classification: Promoted from Red to Amber. New publication (https://doi.org/10.1016/j.xhgg.2021.100024) describing 11 individuals from 7 unrelated families (1 family was originally described in PMID: 21937992 and had mild ID). Patients had phenotypes ranging from mild to severe developmental dealys. As ID is not the prominant phenotype, this gene has been given an Amber rating. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1163 | SAMD9L |
Zornitza Stark gene: SAMD9L was added gene: SAMD9L was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SAMD9L was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: SAMD9L were set to 33710394 Phenotypes for gene: SAMD9L were set to Intellectual disability Review for gene: SAMD9L was set to RED Added comment: Missense variant reported de novo in a patient with moderate ID, in a large cohort study. Authors described it as a phenotype expansion as ataxia-pancytopenia not found in that patient. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1094 | UFSP2 |
Konstantinos Varvagiannis changed review comment from: Ni et al (2021 - PMID: 33473208) describe the phenotype of 8 children (belonging to 4 families - 2 of which consanguineous) homozygous for a UFSP2 missense variant [NM_018359.5:c.344T>A; p.(Val115Glu)]. Members of a broader consanguineous pedigree from Pakistan with 3 affected children with epilepsy and DD and ID underwent exome sequencing. All affected individuals were homozygous for the specific SNV with their parents (2 parent pairs, in both cases first cousins) being heterozygous. An unaffected sib was homozygous for the wt allele. Through genematching platforms 3 additional families with similarly affected individuals and homozygosity for the same variant were recruited. These additional families were from Pakistan (1/3) and Afganistan (2/3). Based on ROH analysis from the broader first pedigree and an additional family the authors concluded on a single shared region of homozygosity on chr 4q. Lack of ES data did not allow verification of whether 2/4 families shared the same haplotype with the other 2. The authors calculated the probability of the genotype-phenotype cosegragation occurring by chance (0.009) and this was lower than the recommended criterion (0.06) for strong evidence of pathogenicity. Shared features included abnormal tone in most (hypotonia 6/8, limb hypertonia 1/8), seizures (8/8 - onset 2d - 7m), severe DD with speech delay/absent speech (8/8), ID (8/8), strabismus (6/8). UFSP2 encodes UFM1-specific protease 2 involved in UFmylation, a post-translational protein modification. As summarized by the authors the cysteine protease encoded by this gene (as is also the case for UFSP1) cleaves UFM1 in the initial step of UFMylation. Apart from producing mature UFM1, the 2 proteases have also the ability to release UFM1 from UFMylated proteins, in the process of de-UFMylation. [several refs. provided] UFMylation is important in brain development with mutations in genes encoding other components of the pathway reported in other NDD disorders (incl. UFM1, UBA5, UFC1). Additional studies were carried to provide evidence for pathogenicity of this variant. Skin biopsies from 3 individuals were carried out to establish fibroblast cultures. Immunoblotting revealed reduced UFSP2 levels relative to controls. mRNA levels measured by qRT-PCR revealed no differences compared to controls altogether suggesting normal mRNA but reduced protein stability. The authors demonstrated increased levels of UFM1-conjugated proteins (incl. DDRGK1, or TRIP4). Ectopic expression of wt UFSP2 normalized the levels of UFMylated proteins in the fibroblasts which was not the case for the V115E variant. Further the variant was difficult to detect by immunoblotting consistent with an effect on protein destabilization. Although disruption of UFMylation induces ER stress, this was not shown to occur in patient fibroblast lines, when assessed for ER stress markers. Evaluation of data from the GTEx project, concerning UFSP2 as well as well as DDRGK1 or TRIP4 - an UFMylation target - revealed relevant expression in multiple regions of the human brain. Overall the authors provide evidence for defective de-UFMylation in patient fibroblasts (presence of increased UFMylation marks). The authors stress out that the effect of the variant in UFMylation in brain is unknown, as UFSP1 or other enzymes might compensate in the presence of hypomorphic UFSP2 mutants. Biallelic UFSP2 variants have previously been reported in 2 skeletal dysplasias [# 142669. BEUKES HIP DYSPLASIA; BHD and # 617974. SPONDYLOEPIMETAPHYSEAL DYSPLASIA, DI ROCCO TYPE; SEMDDR]. These disorders are not characterized by neurological dysfunction or epilepsy. The authors underscore the fact that variants identified in these disorders (Y290H, D526A, H428R) localize within the C-terminal catalytic (peptidase) domain [aa 278 – 461] while the variant here identified lies in the N-terminal substrate binding domain affecting protein stability/abundance. In OMIM, only the 2 aforementioned disorders are currently associated with biallelic UFSP2 mutations. There is no associated phenotype in G2P. SysID includes UFSP2 among the primary ID genes. You may consider inclusion in the current panel with amber/green rating. Sources: Literature; to: Ni et al (2021 - PMID: 33473208) describe the phenotype of 8 children (belonging to 4 families - 2 of which consanguineous) homozygous for a UFSP2 missense variant [NM_018359.5:c.344T>A; p.(Val115Glu)]. Members of a broader consanguineous pedigree from Pakistan with 3 affected children with epilepsy and DD and ID underwent exome sequencing. All affected individuals were homozygous for the specific SNV with their parents (2 parent pairs, in both cases first cousins) being heterozygous. An unaffected sib was homozygous for the wt allele. Through genematching platforms 3 additional families with similarly affected individuals and homozygosity for the same variant were recruited. These additional families were from Pakistan (1/3) and Afganistan (2/3). Based on ROH analysis from the broader first pedigree and an additional family the authors concluded on a single shared region of homozygosity on chr 4q. Lack of ES data did not allow verification of whether 2/4 families shared the same haplotype with the other 2. The authors calculated the probability of the genotype-phenotype cosegragation occurring by chance (0.009) and this was lower than the recommended criterion (0.06) for strong evidence of pathogenicity. Shared features included abnormal tone in most (hypotonia 6/8, limb hypertonia 1/8), seizures (8/8 - onset 2d - 7m), severe DD with speech delay/absent speech (8/8), ID (8/8), strabismus (6/8). UFSP2 encodes UFM1-specific protease 2 involved in UFmylation, a post-translational protein modification. As summarized by the authors the cysteine protease encoded by this gene (as is also the case for UFSP1) cleaves UFM1 in the initial step of UFMylation. Apart from producing mature UFM1, the 2 proteases have also the ability to release UFM1 from UFMylated proteins, in the process of de-UFMylation. [several refs. provided] UFMylation is important in brain development with mutations in genes encoding other components of the pathway reported in other NDD disorders (incl. UFM1, UBA5, UFC1). Additional studies were carried to provide evidence for pathogenicity of this variant. Skin biopsies from 3 individuals were carried out to establish fibroblast cultures. Immunoblotting revealed reduced UFSP2 levels relative to controls. mRNA levels measured by qRT-PCR revealed no differences compared to controls altogether suggesting normal mRNA but reduced protein stability. The authors demonstrated increased levels of UFM1-conjugated proteins (incl. DDRGK1, or TRIP4). Ectopic expression of wt UFSP2 normalized the levels of UFMylated proteins in the fibroblasts which was not the case for the V115E variant. Further the variant was difficult to detect by immunoblotting consistent with an effect on protein destabilization. Although disruption of UFMylation induces ER stress, this was not shown to occur in patient fibroblast lines, when assessed for ER stress markers. Evaluation of data from the GTEx project, concerning UFSP2 as well as well as DDRGK1 or TRIP4 - an UFMylation target - revealed relevant expression in multiple regions of the human brain. Overall the authors provide evidence for defective de-UFMylation in patient fibroblasts (presence of increased UFMylation marks). The authors stress out that the effect of the variant in UFMylation in brain is unknown, as UFSP1 or other enzymes might compensate in the presence of hypomorphic UFSP2 mutants. **Monoallelic** (correction to previous review) UFSP2 variants have previously been reported in 2 skeletal dysplasias [# 142669. BEUKES HIP DYSPLASIA; BHD and # 617974. SPONDYLOEPIMETAPHYSEAL DYSPLASIA, DI ROCCO TYPE; SEMDDR]. These disorders are not characterized by neurological dysfunction or epilepsy. The authors underscore the fact that variants identified in these disorders (Y290H, D526A, H428R) localize within the C-terminal catalytic (peptidase) domain [aa 278 – 461] while the variant here identified lies in the N-terminal substrate binding domain affecting protein stability/abundance. In OMIM, only the 2 aforementioned disorders are currently associated with biallelic UFSP2 mutations. There is no associated phenotype in G2P. SysID includes UFSP2 among the primary ID genes. You may consider inclusion in the current panel with amber/green rating. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1092 | UFSP2 |
Konstantinos Varvagiannis gene: UFSP2 was added gene: UFSP2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: UFSP2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: UFSP2 were set to 33473208 Phenotypes for gene: UFSP2 were set to Abnormal muscle tone; Seizures; Global developmental delay; Delayed speech and language development; Intellectual disability; Strabismus Penetrance for gene: UFSP2 were set to Complete Added comment: Ni et al (2021 - PMID: 33473208) describe the phenotype of 8 children (belonging to 4 families - 2 of which consanguineous) homozygous for a UFSP2 missense variant [NM_018359.5:c.344T>A; p.(Val115Glu)]. Members of a broader consanguineous pedigree from Pakistan with 3 affected children with epilepsy and DD and ID underwent exome sequencing. All affected individuals were homozygous for the specific SNV with their parents (2 parent pairs, in both cases first cousins) being heterozygous. An unaffected sib was homozygous for the wt allele. Through genematching platforms 3 additional families with similarly affected individuals and homozygosity for the same variant were recruited. These additional families were from Pakistan (1/3) and Afganistan (2/3). Based on ROH analysis from the broader first pedigree and an additional family the authors concluded on a single shared region of homozygosity on chr 4q. Lack of ES data did not allow verification of whether 2/4 families shared the same haplotype with the other 2. The authors calculated the probability of the genotype-phenotype cosegragation occurring by chance (0.009) and this was lower than the recommended criterion (0.06) for strong evidence of pathogenicity. Shared features included abnormal tone in most (hypotonia 6/8, limb hypertonia 1/8), seizures (8/8 - onset 2d - 7m), severe DD with speech delay/absent speech (8/8), ID (8/8), strabismus (6/8). UFSP2 encodes UFM1-specific protease 2 involved in UFmylation, a post-translational protein modification. As summarized by the authors the cysteine protease encoded by this gene (as is also the case for UFSP1) cleaves UFM1 in the initial step of UFMylation. Apart from producing mature UFM1, the 2 proteases have also the ability to release UFM1 from UFMylated proteins, in the process of de-UFMylation. [several refs. provided] UFMylation is important in brain development with mutations in genes encoding other components of the pathway reported in other NDD disorders (incl. UFM1, UBA5, UFC1). Additional studies were carried to provide evidence for pathogenicity of this variant. Skin biopsies from 3 individuals were carried out to establish fibroblast cultures. Immunoblotting revealed reduced UFSP2 levels relative to controls. mRNA levels measured by qRT-PCR revealed no differences compared to controls altogether suggesting normal mRNA but reduced protein stability. The authors demonstrated increased levels of UFM1-conjugated proteins (incl. DDRGK1, or TRIP4). Ectopic expression of wt UFSP2 normalized the levels of UFMylated proteins in the fibroblasts which was not the case for the V115E variant. Further the variant was difficult to detect by immunoblotting consistent with an effect on protein destabilization. Although disruption of UFMylation induces ER stress, this was not shown to occur in patient fibroblast lines, when assessed for ER stress markers. Evaluation of data from the GTEx project, concerning UFSP2 as well as well as DDRGK1 or TRIP4 - an UFMylation target - revealed relevant expression in multiple regions of the human brain. Overall the authors provide evidence for defective de-UFMylation in patient fibroblasts (presence of increased UFMylation marks). The authors stress out that the effect of the variant in UFMylation in brain is unknown, as UFSP1 or other enzymes might compensate in the presence of hypomorphic UFSP2 mutants. Biallelic UFSP2 variants have previously been reported in 2 skeletal dysplasias [# 142669. BEUKES HIP DYSPLASIA; BHD and # 617974. SPONDYLOEPIMETAPHYSEAL DYSPLASIA, DI ROCCO TYPE; SEMDDR]. These disorders are not characterized by neurological dysfunction or epilepsy. The authors underscore the fact that variants identified in these disorders (Y290H, D526A, H428R) localize within the C-terminal catalytic (peptidase) domain [aa 278 – 461] while the variant here identified lies in the N-terminal substrate binding domain affecting protein stability/abundance. In OMIM, only the 2 aforementioned disorders are currently associated with biallelic UFSP2 mutations. There is no associated phenotype in G2P. SysID includes UFSP2 among the primary ID genes. You may consider inclusion in the current panel with amber/green rating. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1033 | NCKAP1 | Arina Puzriakova Added comment: Comment on list classification: There is sufficient evidence to promote this gene to Green at the next GMS panel update. Guo et al 2020 (PMID:33157009) describe multiple families with inherited and de novo deleterious NCKAP1 variants. Neurodevelopmental features represent the core phenotypes, including autistic features, psychomotor delays, and ID or learning disabilities (10/16 individuals had a diagnosis of mild to severe ID) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.990 | RAD50 |
Arina Puzriakova edited their review of gene: RAD50: Added comment: - PMID: 33378670 (2020) - single patient described with bone marrow failure, immunodeficiency and developmental defects, who was compound heterozygous for a frameshift and premature stop codon (c.2165dup; p.Glu723Glyfs∗5 - maternally inherited) and in-frame deletion (c.3109_3111del; p.Glu1035del - de novo) in the RAD50 gene. Functional characterisation using patient-derived fibroblasts indicated defects in DNA replication, DNA repair, and DNA end resection; however, ATM-dependent DNA damage response remained intact. Studies in yeast modelling the variant corresponding to p.Glu1035del produced defects in both DNA repair and Tel1ATM-dependent signalling following thermal activation. This is the third case published with biallelic variants in the RAD50 gene. Although authors report 'developmental defects', it is unclear whether this individual displayed cognitive impairment. Therefore, maintaining the Red gene rating on this panel.; Changed rating: RED; Changed publications: 19409520, 32212377, 33378670; Changed phenotypes: Nijmegen breakage syndrome-like disorder, OMIM:613078; Changed mode of inheritance: BIALLELIC, autosomal or pseudoautosomal |
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| Intellectual disability - microarray and sequencing v3.963 | CDK19 |
Julia Baptista changed review comment from: De novo missense variants mapped to the kinase domain of CDK19 were described in 11 unrelated individuals (age range: 9 months to 14 years).Two recurrent changes at residues Tyr32 and Gly28 were identified. One additional case report (PMID:33568421) described a 10-month-old male patient who presented with a neurodevelopmental syndrome characterized by infantile spasms and a de novo missense variant c.92C>A (p.Thr31Asn) (also in the kinase domain). This brings the total of cases reported in the literature to 15.; to: De novo missense variants mapped to the kinase domain of CDK19 were described in 11 unrelated individuals (age range: 9 months to 14 years).Two recurrent changes at residues Tyr32 and Gly28 were identified. One additional case report (PMID:33568421) described a 10-month-old male patient who presented with a neurodevelopmental syndrome characterized by infantile spasms and a de novo missense variant c.92C>A (p.Thr31Asn) (also in the kinase domain). This brings the total of cases reported in the literature to 15. |
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| Intellectual disability - microarray and sequencing v3.751 | VPS4A |
Evan Reid changed review comment from: Multiple families (now 10) described with a consistent phenotype (we have termed it CIMDAG as an acronym for the major features). All have de novo heterozygous missense mutations of VPS4A, with a distinct mutational hotspot (R284) in many families. Mechanism is likely dominant negative. Haplo-insufficiency of VPS4A is tolerated and present in general population databases, so loss of function mutations likely do not cause this disease. Sources: Literature, Research; to: Multiple families (now 10) described with a consistent phenotype (termed CIMDAG as an acronym for the major features). All have de novo heterozygous missense mutations of VPS4A, with a distinct mutational hotspot (R284) in many families. Mechanism is likely dominant negative. Haplo-insufficiency of VPS4A is tolerated and present in general population databases, so loss of function mutations likely do not cause this disease. Sources: Literature, Research |
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| Intellectual disability - microarray and sequencing v3.751 | VPS4A |
Evan Reid gene: VPS4A was added gene: VPS4A was added to Intellectual disability. Sources: Literature,Research Mode of inheritance for gene: VPS4A was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: VPS4A were set to (PMID: 33186545; 33186543; 33460484) Phenotypes for gene: VPS4A were set to developmental delay; intellectual disability; cerebellar hypoplasia; pontine hypoplasia; thin corpus callosum; microcephaly; growth retardation; congenital anaemia; dyserythropeoitic anaemia; dystonia; congenital cataracts; deafness Penetrance for gene: VPS4A were set to Complete Mode of pathogenicity for gene: VPS4A was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: VPS4A was set to GREEN Added comment: Multiple families (now 10) described with a consistent phenotype (we have termed it CIMDAG as an acronym for the major features). All have de novo heterozygous missense mutations of VPS4A, with a distinct mutational hotspot (R284) in many families. Mechanism is likely dominant negative. Haplo-insufficiency of VPS4A is tolerated and present in general population databases, so loss of function mutations likely do not cause this disease. Sources: Literature, Research |
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| Intellectual disability - microarray and sequencing v3.681 | SMG8 |
Arina Puzriakova edited their review of gene: SMG8: Added comment: PMID: 33242396 (2020) - 9 affected individuals from 4 consanguineous families with different biallelic variants in the SMG8 gene. Clinical features include GDD (8/8), dysmorphic features (9/9) microcephaly (6/9), short stature (4/9), brain imaging anomalies (4/5), congenital heart disease (3/9) and cataract (3/8). Only two sibs from Family 2 had a formal ID diagnosis, but this can be inferred from the clinical reports of the other cases demonstrating severe language delays, difficulties to follow simple instructions or perform daily activities. ----- Several features described here overlap with those in the previously reported cases from PMID: 31130284 (e.g. microcephaly, ID, cataract, VSD); Changed rating: GREEN; Changed publications: 31130284, 33242396 |
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| Intellectual disability - microarray and sequencing v3.661 | RAP1B |
Ivone Leong Added comment: Comment on list classification: New gene added by Zornitza Stark (Australian Genomics). This gene is associated with a phenotype in Gene2Phenotype but not OMIM. PMID: 32627184 describes 2 patients. 36 yo patient of non-consanguineous parents. Had unclear pancytopenia, multiple congenital malformations, mild intellectual disability, endocrine disorders (short stature with growth hormone deficiency), dysmorphism and other features. Parents and sibling unaffected. 13 yo of non-consanguineous parents with thrombocytopenia, multiple congenital anomalies and learning difficulties. He had normal developmental milestones, walk was achieved at 14 months and there was no speech delay. He attended mainstream school with auxiliary help because of learning difficulties with graphism, syntaxic comprehension, logical reasoning and attention deficit. Parents and siblings unaffected. PMID: 26280580 describes another patient with variant in RAP1B. The clinical features can be found in supplementary table 2. The table lists ID, but doesn't say severity and lists a host of other features including short stature, facial dysmorphism and skeletal findings. All 3 cases seem to have a very wide spectrum of differing phenotypes and therefore, this gene has been given an Amber rating until further evidence is available. |
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| Intellectual disability - microarray and sequencing v3.654 | HS2ST1 | Ivone Leong Added comment: Comment on list classification: New gene added by Zornitza Stark (Australian Genomics). This gene is not associated with a relevant phenotype in OMIM or Gene2Phenotype. Only 2 of 3 unrelated families with affected individuals described in PMID: 33159882 were reported to have ID. The affected individuals in the third family could not be assessed for ID. Therefore, there is currently not enough evidence to support a gene-disease association. This gene has been given an Amber rating. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.644 | RAP1B |
Zornitza Stark gene: RAP1B was added gene: RAP1B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: RAP1B was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: RAP1B were set to 32627184; 26280580 Phenotypes for gene: RAP1B were set to Syndromic intellectual disability Review for gene: RAP1B was set to GREEN Added comment: Three unrelated individuals reported with de novo variants, some functional data. One of them described as Kabuki-like but lacks typical facial gestalt. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.599 | UPF1 |
Ivone Leong Added comment: Comment on list classification: New gene added by Zornitza Stark (Australian Genomics). PMID: 28539120 describes a patient with significant ID. The patient has SNVs in SQSTM1 and UPF1. The authors suggests that it is plausible that the haploinsufficiency of SQSTM1 may have caused neurofunctional defects, which the haploinsufficiency of UPF1 may have exacerbated. As the patient in the second case has another variant in another gene, there is not enough evidence to support a gene-disease association so this gene has been given an Amber rating. |
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| Intellectual disability - microarray and sequencing v3.569 | RNPC3 |
Ivone Leong gene: RNPC3 was added gene: RNPC3 was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: RNPC3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: RNPC3 were set to 24480542; 29866761; 32462814 Phenotypes for gene: RNPC3 were set to isolated growth hormone deficiency; ?Growth hormone deficiency, isolated, type V, 618160; developmental delay/intellectual deficiency and delayed puberty Review for gene: RNPC3 was set to RED Added comment: This gene is an Amber gene on the Growth failure in early childhood panel (v1.16). The following reviews are present for this gene on that panel: "Comment on list classification: Based on the available evidence and expert review, this gene has been promoted from Red to Amber. This gene is associated with a relevant phenotype on OMIM. The family described in PMIDs 24480542 and 29866761 are the same. The 3 sisters in this family had GH deficiency only. PMID: 32462814 had GH deficiency and almost undetectable levels of prolactin as well. Ivone Leong (Genomics England Curator), 15 Oct 2020 Two families reported. PMID 29866761: isolated growth deficiency and pituitary hypoplasia. PMID 32462814: growth hormone deficiency, central congenital hypothyroidism, congenital cataract, developmental delay/intellectual deficiency and delayed puberty. Full spectrum of phenotype unclear at present. Zornitza Stark (Australian Genomics), 5 Oct 2020" As only 1 affected family has developmental delay/intellectual deficiency, this gene is given a Red rating. Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v3.510 | FOXP4 |
Zornitza Stark gene: FOXP4 was added gene: FOXP4 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: FOXP4 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: FOXP4 were set to 33110267 Phenotypes for gene: FOXP4 were set to Neurodevelopmental disorder; multiple congenital abnormalities Review for gene: FOXP4 was set to AMBER Added comment: This gene is a little bit difficult to place, may be Green on Fetal Anomalies panel? Eight unrelated individuals reported, seven de novo missense, and one individual with a truncating variant. Detailed phenotypic information available on 6. Overlapping features included speech and language delays, growth abnormalities, congenital diaphragmatic hernia (2/6), cervical spine abnormalities, and ptosis. Intellectual disability described as mild in 2, some had normal intellect despite the early speech and language delays, hence Amber rating here. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.505 | NEMF | Arina Puzriakova Added comment: Comment on mode of inheritance: Set MOI to 'Biallelic' as currently only 1 case (total 14) with a monoallelic variant described but with normal intellectual development. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.446 | FGF14 |
Arina Puzriakova Added comment: Comment on list classification: Cognitive impairment has been reported in several patients, mostly mild but few cases with moderate deficits have also been described. However, the phenotype is mainly characterised by ataxia which would be the expected CI for diagnostic testing - FGF14 is already Green on Ataxia panels. The utility of calling variants in this gene in a cohort of ID patients without the ataxic component is unlikely to be of benefit, and therefore the rating has been kept Amber on this panel. |
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| Intellectual disability - microarray and sequencing v3.432 | C2CD3 |
Arina Puzriakova changed review comment from: - PMID: 24997988 (2014) - Two unrelated cases with OFD syndrome and biallelic variants (p.Arg62* and p.Cys1029Gly; p.Ala1304Valfs*3, respectively) in C2CD3. In a 4-year-old male, additional manifestations included severe microcephaly (-5 SD), severe ID, micropenis, and brain malformations including Molar Tooth Sign. In the second patient, a terminated foetus, severe microcephaly (-4 SD) was combined with canonical OFD symptoms, but assessment of ID was not possible. No functional studies of the variants; however, some data supporting a role of C2CD3 in cilium assembly and function. - PMID: 26092869 (2015) - Two unrelated individuals with biallelic variants in C2CD3. Clinical details are limited but both had features of Joubert syndrome (as JBTS screening study), as well as oral features including oral frenulae and/or cleft palate. No report on ID status, but could possibly be present in view of the JBTS diagnosis. One patient also harboured biallelic variants in TTC21B. - PMID: 26477546 (2015) - Compound het variants identified in two affected sibs with a classic form of JBTS and severe GDD but without any extraneural manifestations, as described in previous cases. - PMID: 27094867 (2016) - Two sibling fetuses with skeletal dysplasia, brain malformations but no microcephaly, in association with compound het variants in C2CD3. Due to termination of pregnancies, ID status could not be established. Analysis of patient-derived fibroblasts showed impaired cilium assembly. - PMID: 30097616 (2018) - Four individuals from three unrelated families with different biallelic variants in C2CD3. Each family exhibited distinct clinical phenotypes and severity of disease: Family 1: two sibs with a diagnosis of OFD including polydactyly, cleft palate and/or incomplete cleft lip, microcephaly, brain malformations and bilateral colobomas. GDD was noted in both sibs. Family 2: fetus with occipital encephalocele and a ventricular septal defect. Similar abnormalities were identified in another sib (also a terminated fetus), but DNA analysis was not performed on the latter. Family 3: one male with various fetal anomalies, and subsequent diagnosis of JBTS following identification of consistent findings on brain MRI. Other features included DD and bilateral retina colobomas.; to: - PMID: 24997988 (2014) - Two unrelated cases with OFD syndrome and biallelic variants (p.Arg62* and p.Cys1029Gly; p.Ala1304Valfs*3, respectively) in C2CD3. In a 4-year-old male, additional manifestations included severe microcephaly (-5 SD), severe ID, micropenis, and brain malformations including Molar Tooth Sign. In the second patient, a terminated foetus, severe microcephaly (-4 SD) was combined with canonical OFD symptoms, but assessment of ID was not possible. No functional studies of the variants; however, some data supporting a role of C2CD3 in cilium assembly and function. - PMID: 26092869 (2015) - Two unrelated individuals with biallelic variants in C2CD3. Clinical details are limited but both had features of Joubert syndrome (as JBTS screening study), as well as oral features including oral frenulae and/or cleft palate. No report on ID status, but could possibly be present in view of the JBTS diagnosis. One patient also harboured biallelic variants in TTC21B. - PMID: 26477546 (2015) - Compound het variants identified in two affected sibs with a classic form of JBTS and severe GDD but without any extraneural manifestations, as described in previous cases. - PMID: 27094867 (2016) - Two sibling fetuses with skeletal dysplasia, brain malformations but no microcephaly, in association with compound het variants in C2CD3. Due to termination of pregnancies, ID status could not be established. Analysis of patient-derived fibroblasts showed impaired cilium assembly. - PMID: 30097616 (2018) - Four individuals from three unrelated families with different biallelic variants in C2CD3. Each family exhibited distinct clinical phenotypes and severity of disease: Family 1: two sibs with a diagnosis of OFD including polydactyly, cleft palate and/or incomplete cleft lip, microcephaly, brain malformations and bilateral colobomas. GDD was noted in both sibs. Family 2: fetus with encephalocele and a ventricular septal defect. Similar abnormalities were identified in a sib (also a terminated fetus), but DNA analysis was not performed on the latter. Family 3: one male with various fetal anomalies, and subsequent diagnosis of JBTS following identification of consistent findings on brain MRI. Other features included DD and bilateral retina colobomas. |
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| Intellectual disability - microarray and sequencing v3.405 | NUP214 |
Eleanor Williams changed review comment from: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families one of Palestinian decent, the other Northern European (not Finnish descent). Each had two affected siblings in which neurological decline was seen after febrile events. The older son in family A, exhibited minor developmental delay from infancy. A homozygous missense variant was identified in NUP214 (p.Arg38Cys) in family A and segregated with the disease in available family members. In family B affected sisters were compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6). Functional studies with fibroblasts from one patient in family A showed a decrease in NUP214 and NUP88 levels compared to controls, PMID: 30758658 - Shamseldin et al 2019 - describe a multiplex consanguineous family in which four affected members presented with severe neonatal hypotonia, profound global developmental delay, progressive microcephaly and early death. Whole exome sequencing revealed the presence of a novel homozygous missense variant in NUP214, p.D154G. PMID: 29483668 - Egloff et al 2018 - report a 4-year-old girl presenting with developmental delay, growth retardation and facial dysmorphism. She was found to have a 9q deletion inherited from her healthy mother and a a hemizygous one-base pair deletion in the NUP214 gene inherited from her father. From patient leukocytes it was found that the expression level of the NUP214 transcript was significantly decreased and close to zero in the patient compared to the controls. ; to: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families one of Palestinian decent, the other Northern European (not Finnish descent). Each had two affected siblings in which neurological decline was seen after febrile events. The older son in family A, exhibited minor developmental delay from infancy. A homozygous missense variant was identified in NUP214 (p.Arg38Cys) in family A and segregated with the disease in available family members. In family B affected sisters were compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6). Functional studies with fibroblasts from one patient in family A showed a decrease in NUP214 and NUP88 levels compared to controls, PMID: 30758658 - Shamseldin et al 2019 - describe a multiplex consanguineous family in which four affected members presented with severe neonatal hypotonia, profound global developmental delay, progressive microcephaly and early death (<2 year old). Whole exome sequencing revealed the presence of a novel homozygous missense variant in NUP214, p.D154G. PMID: 29483668 - Egloff et al 2018 - report a 4-year-old girl presenting with developmental delay, growth retardation and facial dysmorphism. She was found to have a 9q deletion inherited from her healthy mother and a hemizygous one-base pair deletion in the NUP214 gene inherited from her father. From patient leukocytes it was found that the expression level of the NUP214 transcript was significantly decreased and close to zero in the patient compared to the controls. |
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| Intellectual disability - microarray and sequencing v3.405 | NUP214 |
Eleanor Williams changed review comment from: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families. Family A have first-cousin parents of Palestinian descent. The proband exhibited minor developmental delay from infancy, presented with ataxia, mental retardation, and intractable epilepsy and died at 11 years. He suffered deterioration in association with febrile illnesses. His cousin presented at 5.5 months with partially reversible encephalopathy and developmental regression after a febrile illness. Family B were sisters born to non-consanguineous parents of Northern European (non-Finnish) descent. The older sister had nystagmus at 2 months and mild hypotonia, but she was otherwise meeting milestones appropriately . At 15 months of age, she developed a fever that led to a rapid neurological decline, seizures, and abnormal movements. The younger sister presented at 7 months with failure to thrive and hyponatremia but was meeting developmental milestones appropriately. By 24 months of age, she had motor and speech delay, ataxic gait, and occasional very mild head bobbing. In family A a homozygous NUP214 p.Arg38Cys variant segregated with the disease in available family members. In family B the sisters were found to be compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6).; to: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families one of Palestinian decent, the other Northern European (not Finnish descent). Each had two affected siblings in which neurological decline was seen after febrile events. The older son in family A, exhibited minor developmental delay from infancy. A homozygous missense variant was identified in NUP214 (p.Arg38Cys) in family A and segregated with the disease in available family members. In family B affected sisters were compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6). Functional studies with fibroblasts from one patient in family A showed a decrease in NUP214 and NUP88 levels compared to controls, PMID: 30758658 - Shamseldin et al 2019 - describe a multiplex consanguineous family in which four affected members presented with severe neonatal hypotonia, profound global developmental delay, progressive microcephaly and early death. Whole exome sequencing revealed the presence of a novel homozygous missense variant in NUP214, p.D154G. PMID: 29483668 - Egloff et al 2018 - report a 4-year-old girl presenting with developmental delay, growth retardation and facial dysmorphism. She was found to have a 9q deletion inherited from her healthy mother and a a hemizygous one-base pair deletion in the NUP214 gene inherited from her father. From patient leukocytes it was found that the expression level of the NUP214 transcript was significantly decreased and close to zero in the patient compared to the controls. |
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| Intellectual disability - microarray and sequencing v3.382 | CTNND1 |
Eleanor Williams gene: CTNND1 was added gene: CTNND1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CTNND1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CTNND1 were set to 32196547 Review for gene: CTNND1 was set to GREEN Added comment: PMID: 32196547 - Alharatani et al 2020 - report an expanded phenotype for CTNND1 patients. They report 13 individuals from nine families with novel protein-truncating variants in CTNND1 identified by WES. The mutations were not previously described in blepharocheilodontic (BCD), orofacial cleft cases nor in gnomAD. 8 patients had de novo variants, 2 inherited from affected parents, 2 participants inherited a variant from a parent with a mild phenotype. 8/13 patients showed cleft palate. Additional phenotypic features seen include mild limb phenotypes (9/13), cardiovascular anomalies (6/13) and Developmental delay and other neurodevelopmental problems (8/13) Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.378 | SPTBN4 |
Arina Puzriakova Added comment: Comment on list classification: There is sufficient evidence to rate this gene Green at the next GMS panel update. Severe-to-profound DD and/or ID reported in all but one family with a milder phenotype (at least 9 total families described with different biallelic variants in SPTBN4). |
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| Intellectual disability - microarray and sequencing v3.370 | STS | Arina Puzriakova Added comment: Comment on publications: Added publication (PMID: 32139392) describing psychiatric/behavioural phenotypes in patients with ichthyosis caused by X-linked deletions spanning STS. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.369 | PRKD1 |
Arina Puzriakova changed review comment from: Gene included previously in context of publication by Sifrim et al. (2016) (PMID: 27479907). However, re-evaluation of this paper showed that only two of the three patients had ID, which may possibly be associated with microcephaly. The two individuals carried a c.1774G>A and c.896T>G variant, respectively; however, a third patient also harbouring the c.1774G>A variant did not display any neuropsychological signs (or microcephaly) at 4.86 years (see supplementary table 12). A recent report (PMID: 32817298, 2020) describes two additional unrelated cases with de novo variants, c.1774G>C and c.1808G>A, respectively. These patients shared cardiac and ectodermal abnormalities, as with the previously described patients; however, mental development was normal in both individuals.; to: Gene included previously in context of publication by Sifrim et al. (2016) (PMID: 27479907). However, re-evaluation of this paper showed that only two of the three patients had ID, which may possibly be associated with microcephaly. The two individuals carried a c.1774G>A and c.896T>G variant, respectively; however, a third patient also harbouring the c.1774G>A variant did not display any neuropsychological signs (or microcephaly) at 4.86 years (see supplementary table 12, and figure 3). A recent report (PMID: 32817298, 2020) describes two additional unrelated cases with de novo variants, c.1774G>C and c.1808G>A, respectively. These patients shared cardiac and ectodermal abnormalities, as with the previously described patients; however, mental development was normal in both individuals. |
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| Intellectual disability - microarray and sequencing v3.363 | NHP2 | Arina Puzriakova Added comment: Comment on list classification: Rating upgraded from Red to Amber as 2/3 cases described in literature present cognitive impairment. This does not yet meet the threshold for inclusion with a Green rating, but may be reviewed if further cases are published. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.330 | RAD50 |
Arina Puzriakova changed review comment from: Comment on list classification: Borderline ID in second patient (at age 15 estimated IQ: 85). Therefore, keeping rating Red awaiting further cases to clarify the relevance of ID to the overall phenotype. ; to: Comment on list classification: Note uncertainty regarding ID in the first patient - PMID:1887849 states 'lack of mental retardation', while a later report PMID:19409520 describes 'mild to moderate retardation of psychomotor development'. ID was borderline in the second patient (at age 15 estimated IQ: 85). Therefore, keeping rating Red awaiting further cases to clarify the relevance of ID to the phenotype associated with RAD50 variants. |
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| Intellectual disability - microarray and sequencing v3.315 | ZMYM2 |
Konstantinos Varvagiannis gene: ZMYM2 was added gene: ZMYM2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZMYM2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZMYM2 were set to 32891193 Phenotypes for gene: ZMYM2 were set to Abnormality of the urinary system; Global developmental delay; Intellectual disability; Microcephaly; Abnormality of the cardiovascular system; Autism; Seizures; Abnormality of the head or neck; Abnormality of the nail; Small hand; Short foot; Clinodactyly Penetrance for gene: ZMYM2 were set to unknown Review for gene: ZMYM2 was set to AMBER Added comment: Heterozygous pathogenic (pLoF) ZMYM2 variants have been reported in individuals with syndromic presentation including CAKUT (in several cases) and variable neurological manifestations among extra-renal features. DD and ID were reported in some of the families described to date as summarized below. You might consider inclusion with green/amber rating in the ID panel and green in the panel for CAKUT. -- Connaughton et al (2020 - PMID: 32891193) report on 19 individuals (from 15 unrelated families) with heterozygous pathogenic ZMYM2 variants. [Article not reviewed in detail]. Affected individuals from 7 families presented with CAKUT while all of them displayed extra-renal features. Neurological manifestations were reported in 16 individuals from 14 families (data not available for 1 fam), among others hypotonia (3/14 fam), speech delay (4/14 fam), global DD (9/14 fam), ID (4/14 fam), microcephaly (4/14 fam). ASD was reported in 4 fam (4 indiv). Seizures were reported in 2 fam (2 indiv). Variable other features included cardiac defects, facial dysmorphisms, small hands and feet with dys-/hypo-plastic nails and clinodactyly. 14 pLoF variants were identified, in most cases as de novo events (8 fam). In 2 families the variant was inherited from an affected parent. Germline mosaicism occurred in 1 family. The human disease features were recapitulated in a X. tropicalis morpholino knockdown, with expression of truncating variants failing to rescue renal and craniofacial defects. Heterozygous Zmym2-deficient mice also recapitulated the features of CAKUT. ZMYM2 (previously ZNF198) encodes a nuclear zinc finger protein localizing to the nucleus (and PML nuclear body). It has previously been identified as transcriptional corepressor interacting with nuclear receptors and the LSD1-CoREST-HDAC1 complex. It has also been shown to interact with FOXP transcription factors. The authors provide evidence for loss of interaction of the truncated ZMYM2 with FOXP1 (mutations in the latter having recently been reported in syndromic CAKUT). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.308 | FIBP | Arina Puzriakova Added comment: Comment on publications: Two publications (PMID: 26660953; 27183861) describing four individuals from two unrelated families. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.295 | ATP1A3 | Zornitza Stark edited their review of gene: ATP1A3: Added comment: Four additional individuals with dystonia, dysmorphism, encephalopathy with developmental delay, brain MRI abnormalities always including cerebellar hypoplasia, no hemiplegia, and neonatal onset. All had de novo missense variants. All are described to have global developmental delay, hence supporting upgrade in rating on this panel.; Changed rating: GREEN; Changed publications: https://doi.org/10.1212/NXG.0000000000000466; Changed phenotypes: Alternating hemiplegia of childhood 2, MIM#614820, Neurodevelopmental disorder; Set current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.262 | LMBRD2 |
Konstantinos Varvagiannis gene: LMBRD2 was added gene: LMBRD2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: LMBRD2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: LMBRD2 were set to 32820033; https://doi.org/10.1101/797787 Phenotypes for gene: LMBRD2 were set to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Abnormality of nervous system morphology; Abnormality of the eye Penetrance for gene: LMBRD2 were set to unknown Review for gene: LMBRD2 was set to AMBER Added comment: You may consider inclusion with green (13 individuals with dn missense SNVs overall, overlapping features for 10 with available phenotype / a recurring variant has been identified in 2 different studies) or amber rating (role of the gene not known, no variant studies, animal model probably not available). ► Malhotra et al (2020 - PMID: 32820033) report on 10 unrelated individuals with de novo missense LMBRD2 variants. Features included DD (9/10), ID (6/8 of relevant age), microcephaly (7/10), seizures (5/10 - >=3 different variants), structural brain abnormalities (e.g. thin CC in 6/9), highly variable ocular abnormalities (5/10) and dysmorphic features in some (7/10 - nonspecific). All had variable prior non-diagnostic genetic tests (CMA, gene panel, mendeliome, karyotype). WES/WGS revealed LMBRD2 missense variants, in all cases de novo. A single individual had additional variants with weaker evidence of pathogenicity. 5 unique missense SNVs and 2 recurrent ones (NM_001007527:c.367T>C - p.Trp123Arg / c.1448G>A - p.Arg483His) were identified. These occurred in different exons. Variants were not present in gnomAD and all had several in silico predictions in favor of a deleterious effect. There was phenotypic variability among individuals with the same variant (e.g. seizures in 1/3 and microchephaly in 2/3 of those harboring R483H). The gene has a pLI of 0 (although o/e ranges from 0.23 to 0.55), %HI of 15.13 and z-score of 2.27. The authors presume that haploinsufficiency may not apply, and consider a gain-of-function/dominant-negative effect more likely. As the authors comment LMBRD2 (LMBR1 domain containing 2) encodes a membrane bound protein with poorly described function. It is widely expressed across tissues with notable expression in human brain (also in Drosophila, or Xenopus laevis). It displays high interspecies conservation. It has been suggested (Paek et al - PMID: 28388415) that LMBRD2 is a potential regulator of β2 adrenoreceptor signalling through involvement in GPCR signalling. ► Kaplanis et al (2020 - https://doi.org/10.1101/797787) in a dataset of 31058 parent-offspring trios (WES) previously identified 3 individuals with developmental disorder, harboring c.1448G>A - p.Arg483His. These individuals (1 from the DDD study, and 2 GeneDx patients) appear in Decipher. [ https://decipher.sanger.ac.uk/ddd/research-variant/40e17c78cc9655a6721006fc1e0c98db/overview ]. The preprint by Kaplanis et al is cited by Malhotra et al, with Arg483His reported in 6 patients overall in both studies. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.255 | TAF1C |
Konstantinos Varvagiannis gene: TAF1C was added gene: TAF1C was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TAF1C was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TAF1C were set to 32779182 Phenotypes for gene: TAF1C were set to Global developmental delay; Intellectual disability; Spasticity; Strabismus; Seizures; Abnormality of nervous system morphology Penetrance for gene: TAF1C were set to Complete Review for gene: TAF1C was set to AMBER Added comment: Knuutinen et al (2020 - PMID: 32779182) report on 2 individuals from 2 consanguineous families, homozygous for TAF1C missense variants. Both presented with an early onset neurological phenotype with severe global DD, ID (2/2 - moderate and profound), spasticity (2/2), ophthalmic findings (strabismus 2/2, nystagmus 1/2). Epilepsy, abnormal brain MRI (cerebral and cerebellar atrophy and white matter hyperintensities) as well and additional findings were reported in one (always the same individual). Following a normal CMA, exome in the first case revealed a homozygous missense SNV (NM_005679.3:c.1165C>T / p.Arg389Cys) supported by in silico predictions. mRNA and protein levels were substantially reduced in fibroblasts from this subject. Only the patient and parents were tested for the variant but not 3 unaffected sibs (fig1). The second individual was homozygous for another missense variant (p.Arg405Cys) also supported by in silico predictions. The girl was the single affected person within the family with an unaffected sib and parents heterozygous for the variant. Several other unaffected relatives in the extended pedigree were either carriers for this variant or homozygous for the wt allele. TAF1C encodes the TATA-box binding protein associated factor (TAF) RNA polymerase I subunit. RNA polymerase I (Pol I) transcribes genes to produce rRNA. For Pol I to initiate transcription, two transcription factors are required : UBF (upstream binding factor encoded by UBTF) and SL1 (selectivity factor 1). The latter is formed by TBP (TATA-binding protein) and 3 Pol I-specific TBP-associated factors (TAFs). A recurrent de novo missense variant in UBTF (encoding the other Pol I transcription factor) causes a disorder with highly similar features. The specific variant acts through a gain-of-function mechanism (and not by LoF which appears to apply for TAF1C based on expression data). The authors hypothesize that altered Pol I activity and resulting ribosomal stress could cause the microcephaly and leukodystrophy (both reported in 1 - the same - individual). As a result, TAF1C may be considered for inclusion in the ID panel with amber rating pending further evidence. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.219 | ZNF407 |
Konstantinos Varvagiannis gene: ZNF407 was added gene: ZNF407 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZNF407 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: ZNF407 were set to 24907849; 32737394; 23195952 Phenotypes for gene: ZNF407 were set to Global developmental delay; Intellectual disability Penetrance for gene: ZNF407 were set to unknown Review for gene: ZNF407 was set to AMBER Added comment: You may consider inclusion of this gene probably with amber rating (or green if the evidence for biallelic variants is considered sufficient). Biallelic variants: - Kambouris et al. (2014 - PMID: 24907849) described 2 brothers with severe DD and ID, born to first cousin parents. Homozygosity mapping, following other non-diagnostic investigations (incl. aCGH), revealed 4 major homozygosity intervals. Exome sequencing in one identified 5 variants within these intervals, ZNF407 (c.5054C>G, p.Ser1685Trp) being the best candidate, supported also by segregation studies. The authors commented that zinc finger proteins act as transcriptional regulators, with mutations in genes encoding for other zinc finger proteins interfering with normal brain development. - Zahra et al. (2020 - PMID: 32737394) report on 7 affected individuals (from 3 families) homozygous or compound heterozygous for ZNF407 variants. Features included hypotonia, DD and ID (in all) and variable occurrence of short stature (6/6), microcephaly (in at least 5), behavioural, visual problems and deafness. Linkage analysis in the first family revealed a 4.4 Mb shared homozygosity region and exome (30x) revealed a 3-bp duplication, confirmed by Sanger sequencing and segregating with the disease (NM_001146189:c.2814_2816dup, p.Val939dup). Affected subjects from the 2 other families were each found to be homozygous (c.2405G>T) or compound heterozygous (c.2884C>G, c.3642G>C) for other variants. Segregation was compatible in all families. Other studies were not performed. The authors comment than only the 3-bp duplication fulfilled ACMG criteria for classification as LP, the other variants being all formally classified as VUS (also due to in silico predictions predicting a LB effect). In addition, while several features such as DD/ID and short stature appeared to be frequent among all patients reported, Zahra et all comment that there was partial clinical overlap with the sibs described by Kambouris et al (additional variants?). Monoallelic disruption of ZNF407: - Ren et al (2013 - PMID: 23195952) described an 8 y.o. boy with ID and ASD. The boy was found to harbor a de novo translocation between chromosomes 3 and 18 [46,XY,t(3;18)(p13;q22.3)]. Array CGH did not reveal any P/LP CNV. Delineation of the breakpoints (FISH, long-range PCR) revealed that the chr18 breakpoint disrupted intron 3 of ZNF407 (isoform 1) with the other breakpoint within a gene-free region of exon 3. There was a loss of 4-8 nt in chr18 and 2-6 in chr3. Sequencing of ZNF407 did not reveal additional variants. RNA isolation in blood followed by RT-PCR studied expression of all 3 ZNF407 isoforms (the intronic region being shared by isoforms 1 and 2). Expression of isoform 1 was shown to be significantly reduced compared to controls. Isoform 2 was undetectable (in blood) while isoform 3 expression was similar to controls. Sequencing of 105 additional patients with similar clinical presentation (ID & ASD) revealed 2 further individuals with de novo missense variants. - Based on the discussion by Kambouris et al (PMID: 24907849 - cited literature not here reviewed) ZNF407 may be deleted in patients with congenital aural atresia due to deletion of a critical region of 18q22.3 (though TSHZ1 is responsible for this phenotype) or 18q- although such deletions span several other genes (cited PMID: 16639285). In one case the breakpoint was shown to be disrupting ZNF407 (cited PMID: 24092497). - The denovo db and Decipher (research variant tab) list few individuals with de novo ZNF407 SNVs although these do not seem to allow conclusions. https://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=ZNF407 https://decipher.sanger.ac.uk/search/ddd-research-variants/results?q=znf407 Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.216 | NCAPD2 | Arina Puzriakova Added comment: Comment on list classification: Amber rating as only one patient has been described with severe ID. However, added to watchlist in case of new reports of more significant cases of ID. Gene has also been added with a Green rating on the Severe Microcephaly panel. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.184 | ATAD1 |
Arina Puzriakova changed review comment from: Not associated with any phenotype in G2P. Pathogenic variants have been described in seven affected individuals (three distinct consanguineous families) including a homozygous nonsense (c.826G>T; p.Glu276*), frameshift (c.1070_1071delAT; p.His357Argfs*15), and missense (c.162G>C; p.Gln54His) variant in the ATAD1 gene. Patients present with severe neurological features of essentially total absence of psychomotor development, encephalopathy, extreme hypertonia, non-responsiveness to stimuli, and death within the first few months of life. ; to: Not associated with any phenotype in G2P. Pathogenic variants have been described in seven affected individuals (three distinct consanguineous families) including a homozygous nonsense (c.826G>T; p.Glu276*), frameshift (c.1070_1071delAT; p.His357Argfs*15), and missense (c.162G>C; p.Gln54His) variant in the ATAD1 gene. Patients present with severe neurological features of essentially total absence of psychomotor development, encephalopathy, extreme hypertonia, non-responsiveness to stimuli, and death within the first few months of life. Knockout mouse model recapitulates phenotype. ATAD1 encodes Thorase, a mediator of AMPA receptor recycling; and therefore it was postulated that pathogenesis is a result of excessive AMPA receptor activity. Targeted therapy using perampanel, an AMPA receptor antagonist, ameliorated disease in both mice and humans, thus further supporting the role of ATAD1. |
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| Intellectual disability - microarray and sequencing v3.170 | CNPY3 |
Konstantinos Varvagiannis gene: CNPY3 was added gene: CNPY3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CNPY3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CNPY3 were set to 29394991; 30237576 Phenotypes for gene: CNPY3 were set to Epileptic encephalopathy, early infantile, 60 (MIM 617929) Penetrance for gene: CNPY3 were set to Complete Review for gene: CNPY3 was set to GREEN Added comment: Biallelic CNPY3 mutations cause Epileptic encephalopathy, early infantile, 60 (MIM 617929). The phenotype including among others hypotonia, intractable seizures, DD and ID has been first reported by Mutoh et al (2018 - PMID: 29394991) in 3 subjects from 2 families. Evidence was provided for the role of the gene (incl. mouse model) and pathogenicity of the identified variants (resulting in LoF). Another subject with similar features of hypotonia, DD, intractable epilepsy, feeding problems has been described briefly by Maddirevula et al (2019 - PMID: 30237576). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.170 | TMEM106B |
Konstantinos Varvagiannis gene: TMEM106B was added gene: TMEM106B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TMEM106B was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: TMEM106B were set to 29186371; 29444210; 32595021 Phenotypes for gene: TMEM106B were set to Leukodystrophy, hypomyelinating, 16 (MIM #617964) Penetrance for gene: TMEM106B were set to Complete Mode of pathogenicity for gene: TMEM106B was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: TMEM106B was set to GREEN Added comment: 6 unrelated individuals with Leukodystrophy, hypomyelinating, 16 (MIM #617964) due to a recurrent TMEM106B variant have been reported to date in the literature (Simons et al 2017 - PMID: 29186371, Yan et al 2018 - PMID: 29444210, Ikemoto et al 2020 - PMID: 32595021). While a 3 y.o. female described by Yan et al had DD (eg sitting at 9m, walking at 25m) with normal cognitive functioning, and a 38 y.o. female had borderline intellectual functioning (IQ 76), 4 affected individuals had ID. Among them, a 19 y.o. male with severe ID was also found to harbor a second de novo possibly damaging USP7 variant. Seizures have been reported in 2 unrelated subjects. [Clinical features are also summarized in table 1 - Ikemoto et al]. All harbored NM_001134232.2(TMEM106B):c.754G>A (p.Asp252Asn) which in almost all cases occurred as a de novo event. In a single case this variant was inherited from a mosaic parent with mild DD in infancy but normal cognition (reported by Simons et al). As discussed by Ito et al (2018 - PMID: 30643851) the encoded protein is a structural component of the lysosomal membrane, playing a role on lysosome acidification. Acidity of the lysosome mediates multiple aspects of lysosomal function. Ito et al, using patient-derived fibroblasts assessed mRNA and protein levels. These were unaltered compared with controls. While TMEM106B had been previously shown to affect lysosome number, morphology and acidification, Ito et al demonstrated increased number of lysosomes in patient cells as well as impaired acidification compared to controls. As commented lysosomes are required for generation of myelin. Recurrence of this missense variant, the presence of pLoF TMEM106B variants in gnomAD as well as the phenotypically normal Tmem106b null mice suggest that this variant may have a gain-of-function or dominant negative effect. Genes for other forms of hypomyelinating lipodystrophy (incl. PLP1) have green rating in the ID panel. Overall TMEM106B can be considered for the ID panel with green rating and the epilepsy panel with amber rating. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.170 | CEP120 |
Konstantinos Varvagiannis gene: CEP120 was added gene: CEP120 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CEP120 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CEP120 were set to 27208211 Phenotypes for gene: CEP120 were set to Joubert syndrome 31 (MIM 617761); Short-rib thoracic dysplasia 13 with or without polydactyly (MIM 616300) Penetrance for gene: CEP120 were set to Complete Review for gene: CEP120 was set to GREEN Added comment: Pathogenic CEP120 variants have been reported in recessive ciliopathies, namely Short-rib thoracic dysplasia 13 with or without polydactyly (MIM 616300) and Joubert syndrome 31 (MIM 617761). The former is associated with a severe/lethal outcome (4 unrelated infants described by Shaheen et al 2015 - PMID: 25361962, 2 fetuses reported by Roosing et al 2016 - PMID: 27208211). Roosing et al however, also provided details on 4 unrelated subjects with Joubert syndrome diagnosis. All presented with a neurologic phenotype of hypotonia, DD, cognitive impairment and exhibited a molar tooth sign. As a result, this gene can be considered for inclusion in the ID panel with green rating (>3 individuals/variants, consistent ciliopathy phenotype). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.170 | CCDC174 |
Konstantinos Varvagiannis gene: CCDC174 was added gene: CCDC174 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CCDC174 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CCDC174 were set to 26358778 Phenotypes for gene: CCDC174 were set to Hypotonia, infantile, with psychomotor retardation - IHPMR, 616816 Penetrance for gene: CCDC174 were set to Complete Mode of pathogenicity for gene: CCDC174 was set to Other Review for gene: CCDC174 was set to AMBER Added comment: Biallelic pathogenic CCDC174 variants cause Hypotonia, infantile, with psychomotor retardation - IHPMR (MIM 616816). Volodarsky et al [2015 - PMID: 26358778] describe 6 children from 2 unrelated families with - among others - severe hypotonia, psychomotor delay and abducens nerve palsy. All affected subjects were homozygous for a stoploss variant. Evidence from functional studies/animal model is provided supporting the role of the gene in this phenotype. Overall this gene can be considered for inclusion in the ID panel with amber rating (2 families, single founder variant, consistent phenotype, supportive studies) pending further reports. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.170 | ACOX2 |
Konstantinos Varvagiannis gene: ACOX2 was added gene: ACOX2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ACOX2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ACOX2 were set to 27647924; 27884763; 29287774 Phenotypes for gene: ACOX2 were set to Bile acid synthesis defect, congenital, 6 - 617308 Penetrance for gene: ACOX2 were set to unknown Review for gene: ACOX2 was set to RED Added comment: Biallelic pathogenic ACOX2 variants cause Bile acid synthesis defect, congenital, 6 (MIM 617308). Overall the phenotype corresponds to an IEM/peroxisomal disorder. As per 01-07-2020 there are 3 reports, briefly reviewed : - Vilarinho et al [2016 - PMID: 27647924] provided details on an 8-year-old boy with ID. - Monte et al [2017 - PMID: 27884763] described a 16 year old male with sustained elevation of transaminases *without* accompanying neurologic symptomatology (as they comment). - Ferdinandusse et al [2018 - PMID: 29287774] reported on a girl deceased at the age of few months. Please consider inclusion in the ID panel with amber/red rating pending further reports. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.170 | ABCA2 |
Konstantinos Varvagiannis gene: ABCA2 was added gene: ABCA2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ABCA2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ABCA2 were set to 30237576; 29302074; 31047799 Phenotypes for gene: ABCA2 were set to Intellectual developmental disorder with poor growth and with or without seizures or ataxia, 618808 Penetrance for gene: ABCA2 were set to Complete Review for gene: ABCA2 was set to GREEN Added comment: Biallelic pathogenic ABCA2 variants cause Intellectual developmental disorder with poor growth and with or without seizures or ataxia (MIM 618808). There are 3 relevant publications (01-07-2020) : - Maddirevula et al [2019 - PMID: 30237576] described briefly 2 unrelated subjects (16-2987, 16DG0071) both DD and seizures among other manifestations. - Hu et al [2019 - PMID: 29302074] reported 3 sibs (M8600615 - III:1-3) born to consanguineous parents (M8600615 - III:1-3) with DD/ID (formal confirmation of moderate ID, in those (2) evaluated). One also presented with seizures. - Aslam and Naz [2019 - PMID: 31047799] provided clinical details on 2 siblings born to consanguineous parents. ID was reported for the older sib but was absent in the younger one. Seizures were not part of the phenotype. All subjects harbored biallelic pLoF variants. N.B. : Steinberg et al [2015 - PMID: 25773295], within a cohort of patients with ALS, identified one with biallelic ABCA2 variants. As however Aslam and Naz comment, this person harbored a single pathogenic variant, with a second one rather unlikely to be pathogenic due to high allele frequency. Overall this gene can be considered for inclusion with green rating in both ID and epilepsy panels (each in >=3 unrelated individuals). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.170 | HERC2 |
Konstantinos Varvagiannis edited their review of gene: HERC2: Added comment: Please consider upgrading this gene to green in the current panel based on the following updated review (13-07-2020): Biallelic pathogenic HERC2 variants cause Mental retardation, autosomal recessive 38 (MIM 615516). The current review is based mostly on the information provided by Elpidorou et al (2020 - PMID: 32571899) summarizing the findings in several affected individuals as published in the literature. ID was a universal feature among them (27/27) and seizures were reported in some (9/27): - 22 subjects from Amish/Mennonite families were homozygous for p.Pro594Leu [NM_004667.5(HERC2):c.1781C>T] (Puffenberger et al 2012 - PMID: 23065719, Harlalka et al 2013 - PMID: 23243086, Abraham et al - PMID: 30902390) - 2 additional patients were homozygous for another missense SNV [NM_004667.5(HERC2):c.4625G>A - p.Arg1542His] (Abraham et al 2019 - PMID: 30902390) - 3 sibs born to consanguineous parents, homozygous for NM_004667.5:c.13767_13770delTGAA - p.(Asn4589LysTer4598)] as described by Elpidorou et al. - 1 male homozygous 286 kb deletion spanning several 5' exons of HERC2 as well as the first exons of OCA2 was described by Morice-Picard et al (2016 - PMID: 27759030). Despite a neurological presentation (axial hypotonia, peripheral hypertonia, extrapyramidal symptoms and uncoordinated movements) further information was not available. Apart from the cases summarized by Elpidorou et al, there have been few additional ones e.g. : - Trujillano et al (2017 - PMID: 27848944) reported briefly on a patient, homozygous for NM_004667.5:c.4676-1G>A displaying seizures, hypotonia, global DD, "Encephalopathy" and abnormality of the liver. - Yavarna et al (2015 - PMID: 26077850) provided few details with on an individual with primarily 'neurocognitive' phenotype but rather atypical presentation (MRI abnormalities, TGA, VSD, renal anomaly, growth retardation, hearing loss) due to p.Q3164X variant (recessive inheritance was specified). Several lines of evidence support an important role for the protein encoded (an E3 ubiquitin protein ligase, interacting also with UBE3A, involved in several cellular processes incl. cell cycle regulation, spindle formation during mitosis, mitochondrial functions, DNA damage responses by targeting proteins such as XPA) as well as the effect of the reported variants (mRNA studies, Western blot, detection of a fusion transcript in the case of the deletion, etc). Individuals from the Amish families displayed Angelman-like features (in line with HERC2-UBE3A interaction) with - among others - gait instability. Mouse models recapitulate some of these features (e.g. the movement disorder) as extensively discussed by Abraham et al. Overall this gene can be included in the ID and epilepsy panels with green rating. -----; Changed rating: GREEN; Changed publications: 23065719, 23243086, 30902390, 32571899, 27848944, 26077850, 27759030 |
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| Intellectual disability - microarray and sequencing v3.35 | SPTBN4 |
Konstantinos Varvagiannis gene: SPTBN4 was added gene: SPTBN4 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SPTBN4 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SPTBN4 were set to 28540413; 28940097; 29861105; 31230720; 31857255 Phenotypes for gene: SPTBN4 were set to Neurodevelopmental disorder with hypotonia, neuropathy, and deafness MIM#617519 Penetrance for gene: SPTBN4 were set to Complete Review for gene: SPTBN4 was set to GREEN Added comment: Biallelic pathogenic SPTBN4 variants cause Neurodevelopmental disorder with hypotonia, neuropathy, and deafness (MIM #617519). There are several reports on the phenotype of relevant affected individuals with severe/profound DD/ID in at least 9 individuals : - Knierim et al (2017 - PMID: 28540413) [1 affected individual] - Anazi et al (2017 - PMID: 28940097) [1] - Wang et al (2018 - PMID: 29861105) [6] - Pehlivan et al (2019 - PMID: 31230720) [1] A recent article by Häusler et al (2019 - PMID: 31857255) describes the phenotype of 2 sibs, both presenting with motor and speech delay, although the older one had reportedly 'normal' cognitive performance allowing attendance of regular school at the age of 6 years. Features include congenital hypotonia, severe DD and ID (in most as outlined above, ID was the primary indication for testing on several occasions), poor or absent reflexes and weakness secondary to axonal motor neuropathy, feeding and respiratory difficulties, hearing and visual impairment. Seizures have been reported in at least 4 unrelated individuals (3 by Wang et al / 1 by Pehlivan et al). Variants in most cases were nonsense/frameshift although biallelic missense variants have also been reported. Sibs in the report by Häusler et al harbored a homozygous splicing variant. SPTBN4 encodes a member of the beta-spectrin protein family that is expressed in the brain, peripheral nervous system, pancreas, and skeletal muscle. βIV spectrin links ankyrinG and clustered ion channels (at axon initial segments and nodes of Ranvier) to the axonal cytoskeleton. Pathogenic variants are proposed to disrupt the cytoskeletal machinery controlling proper localization of ion channels and function of axonal domains where ion channels are normally clustered in high density. Among the evidence provided : nerve biopsies from an affected individual displayed reduced nodal Na+ channels and no nodal KCNQ2 K+ channels / Loss of AnkyrinG and βIV spectrin in animal model resulted in loss of KCNQ2- and KCNQ3- subunit containing K+ channels. Apart from the ID / epilepsy panels please consider inclusion in other relevant ones. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.30 | CEP55 | Rebecca Foulger changed review comment from: PMID:32100459 (Barrie et al., 2020) describe 7 living individuals (5 families) with biallelic variants (compound het and homozygous splice site variant) in CEP55. Global/severe DD was seen in patient 2, and the 3 siblings (patients 5,6,7). Mild/delayed motor/speech development was seen in unrelated patients 3 and 4.; to: PMID:32100459 (Barrie et al., 2020) describe 7 living individuals (5 families) with biallelic variants (compound het and homozygous splice site variant) in CEP55. Global/severe DD was seen in patient 2, and the 3 siblings (patients 5,6,7). Mild/delayed motor & speech development was seen in unrelated patients 3 and 4. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.30 | CEP55 | Rebecca Foulger changed review comment from: PMID:32100459 (Barrie et al., 2020) describe 7 living individuals (5 families) with biallelic variants (compound het and homozygous splice site variant) in CEP55. Global/severe DD wax seen in patient 2, and the 3 siblings (patients 5,6,7). Mild/delayed motor/speech development was seen in unrelated patients 3 and 4.; to: PMID:32100459 (Barrie et al., 2020) describe 7 living individuals (5 families) with biallelic variants (compound het and homozygous splice site variant) in CEP55. Global/severe DD was seen in patient 2, and the 3 siblings (patients 5,6,7). Mild/delayed motor/speech development was seen in unrelated patients 3 and 4. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.30 | CEP55 | Rebecca Foulger commented on gene: CEP55: PMID:32100459 (Barrie et al., 2020) describe 7 living individuals (5 families) with biallelic variants (compound het and homozygous splice site variant) in CEP55. Global/severe DD wax seen in patient 2, and the 3 siblings (patients 5,6,7). Mild/delayed motor/speech development was seen in unrelated patients 3 and 4. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.3 | NDUFAF1 |
Zornitza Stark gene: NDUFAF1 was added gene: NDUFAF1 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: NDUFAF1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: NDUFAF1 were set to 17557076; 21931170; 24963768 Phenotypes for gene: NDUFAF1 were set to Mitochondrial complex I deficiency, nuclear type 11, MIM#618234 Review for gene: NDUFAF1 was set to GREEN gene: NDUFAF1 was marked as current diagnostic Added comment: Three unrelated families described, DD/ID part of the phenotype, specifically mentioned in two families, child in third family died in infancy from HOCM. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.3 | WDFY3 | Zornitza Stark edited their review of gene: WDFY3: Added comment: >10 individuals with heterozygous variants in this gene and mild/moderate intellectual disability now described in the literature. Some evidence for opposing effects on brain size depending on variant location.; Changed rating: GREEN; Changed publications: 31327001, 27008544; Set current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.3 | TENM3 |
Zornitza Stark gene: TENM3 was added gene: TENM3 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: TENM3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TENM3 were set to 30513139; 22766609; 27103084; 29753094 Phenotypes for gene: TENM3 were set to Microphthalmia, syndromic 15, MIM#615145; coloboma Review for gene: TENM3 was set to GREEN gene: TENM3 was marked as current diagnostic Added comment: At least four unrelated families described with syndromic microphthalmia and bi-allelic variants in this gene, ID is part of the phenotype. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.3 | SBF1 |
Zornitza Stark gene: SBF1 was added gene: SBF1 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: SBF1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SBF1 were set to 24799518; 23749797; 30039846; 28902413 Phenotypes for gene: SBF1 were set to Charcot-Marie-Tooth disease, type 4B3, MIM# 615284 Review for gene: SBF1 was set to GREEN Added comment: At least 4 families with multiple affected individuals described. Some have had central features including microcephaly and DD/ID, it is likely this gene causes a mixed picture. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | LYRM7 |
Zornitza Stark gene: LYRM7 was added gene: LYRM7 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: LYRM7 was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: LYRM7 were set to Mitochondrial complex III deficiency, nuclear type 8, MIM#615838 Review for gene: LYRM7 was set to GREEN gene: LYRM7 was marked as current diagnostic Added comment: Condition is characterised by progressive deterioration but some individuals described as developmentally delayed from birth. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | LAMB2 |
Zornitza Stark gene: LAMB2 was added gene: LAMB2 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: LAMB2 was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: LAMB2 were set to Pierson syndrome, MIM#609049 gene: LAMB2 was marked as current diagnostic Added comment: Cognitive impairment described in survivors. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | GLS |
Zornitza Stark gene: GLS was added gene: GLS was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: GLS was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: GLS were set to 30970188 Phenotypes for gene: GLS were set to Global developmental delay, progressive ataxia, and elevated glutamine, MIM# 618412 Review for gene: GLS was set to GREEN Added comment: Three unrelated individuals described with compound het variants, however, note one of these is a triplet expansion in the 5' UTR. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | DNM1L |
Zornitza Stark gene: DNM1L was added gene: DNM1L was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: DNM1L was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Phenotypes for gene: DNM1L were set to Encephalopathy, lethal, due to defective mitochondrial peroxisomal fission 1, MIM#614388 Mode of pathogenicity for gene: DNM1L was set to Other Review for gene: DNM1L was set to GREEN gene: DNM1L was marked as current diagnostic Added comment: Dominant and recessive disease described depending on domain affected; dominant negative effect of heterozygous missense variants. LoF/LoF or LoF/missense for AR variants. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | ALG14 |
Zornitza Stark gene: ALG14 was added gene: ALG14 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: ALG14 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ALG14 were set to 30221345; 23404334; 28733338 Phenotypes for gene: ALG14 were set to Myasthenic syndrome, congenital, 15, without tubular aggregates, MIM#616227; Intellectual disability Review for gene: ALG14 was set to GREEN gene: ALG14 was marked as current diagnostic Added comment: 5 individuals from unrelated families described in the literature: one with myasthenic syndrome, no report of ID; second with predominantly ID phenotype; and three more with a neurodegenerative phenotype. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | ADAMTS10 |
Zornitza Stark gene: ADAMTS10 was added gene: ADAMTS10 was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: ADAMTS10 was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: ADAMTS10 were set to Weill-Marchesani syndrome 1, recessive, MIM#277600 Review for gene: ADAMTS10 was set to AMBER Added comment: Mild intellectual disability is described in around 10% of affected individuals. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | DLL1 |
Konstantinos Varvagiannis gene: DLL1 was added gene: DLL1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DLL1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: DLL1 were set to 31353024 Phenotypes for gene: DLL1 were set to Global developmental delay; Intellectual disability; Morphological abnormality of the central nervous system; Seizures; Behavioral abnormality; Autism; Scoliosis Penetrance for gene: DLL1 were set to unknown Review for gene: DLL1 was set to GREEN Added comment: Heterozygous DLL1 pathogenic variants cause Neurodevelopmental disorder with nonspecific brain abnormalities and with or without seizures (# 618709). Fischer-Zirnsak et al (2019 - PMID: 31353024) reported on 15 affected individuals from 12 unrelated families. Most common features included DD/ID (12/14), ASD (6/14 - belonging to 6 families) or other behavioral abnormalities, seizures (6/14 - from 6 unrelated families) and various brain MRI abnromalities. As commented by OMIM (based on the same ref) "Cognitive function ranges from severely impaired to the ability to attend schools with special assistance". Among other features, scoliosis was observed in 4. The authors could not identify a distinctive facial gestalt. Variable initial investigations (where discussed/performed - also suggesting relevance to the current panel) included CMA, FMR1, FLNA, mitochondrial DNA analysis and metabolic work-up but had not revealed an alternative cause. The DLL1 variants were identified by WES (with the exception of a 122-kb microdeletion spanning DLL1 and FAM120B detected by CMA). Nonsense, frame-shift, splice-site variants in positions predicted to result to NMD were identified in most. One individual was found to harbor a missense variant (NM_005618.3:c.536G>T / p.Cys179Phe) and another the aforementioned microdeletion. The variant in several individuals had occurred as a de novo event. In 2 families, it was inherited from an also affected parent (an unaffected sib was non-carrier) while in 3 families parental studies were not possible/complete. In frame insertion of 4 residues was demonstrated for a splice site variant, from LCLs of the corresponding individual. For another individual, material was unavailable for mRNA studies. The missense variant affected a cysteine (of the DSL domain) conserved in all Notch ligands while AA changes affecting the same position of JAG1 (another Notch ligand) have been described in patients with Alagille s. Based on the variants identified and reports of deletions spanning DLL1 in the literature, haploinsufficiency is the proposed underlying mechanism. The gene has also a pLI of 1 and %HI of 4.65. DLL1 encodes the Delta-like canonical Notch ligand 1. Notch signaling is an established pathway for brain morphogenesis. Previous in vivo and in vitro studies have demonstrated the role of DLL1 in CNS. The gene is highly expressed in neuronal precursor cells during embryogenesis. Expression of Dll1 (and other molecules of the Notch signalling pathway) in an oscillatory/sustained pattern and cell-cell interactions important for this pathway have been demonstrated to play a role in neuronal differentiation. [Most discussed by Fischer-Zirnsak et al with several refs provided / also Gray et al., 1999 - PMID: 10079256 & OMIM]. Animal models as summarized by the authors: [Mouse] Loss of Dll1 in mice has been shown to increase neuronal differentiation, cause CNS hyperplasia and increased number of neurons (PMIDs cited: 9109488, 12397111, 20081190). Reduced Dll1 expression was associated with scoliosis and mild vertebral defects (cited PMIDs: 19562077, 14960495, 22484060 / among others Dll1 haploinsufficiency and dominant negative models studied). Scoliosis and vertebral segmentation defects were features in 4 and 1 individual, respectively in the cohort of 15. [Zebrafish] Homozygous mutations in dlA, the zebrafish ortholog, disrupted the Delta-Notch signaling and led to patterning defects in the hindbrain and overproduction of neurons (cited: 15366005). Please consider inclusion in other possibly relevant panels e.g. for ASD. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1143 | AFF3 |
Konstantinos Varvagiannis changed review comment from: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- Shimizu et al. (8/2019 - PMID: 31388108) describe an additional individual with de novo AFF3 missense variant. The phenotype overlaps with that summarized by Voisin et al. incl. mesomelic dysplasia with additional skeletal anomalies, bilateral kidney hypoplasia and severe DD at the age of 2.5 years. Seizures and pulmonary problems were not observed. Although a different RefSeq is used the variant is among those also reported by Voisin et al. [NM_002285.2:c.697G>A (p.Ala233Thr) corresponding to NM_001025108.1:c.772G>A (p.Ala258Thr)]. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article). [Review modified to add additional reference/case report]; to: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb deletion affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- Shimizu et al. (8/2019 - PMID: 31388108) describe an additional individual with de novo AFF3 missense variant. The phenotype overlaps with that summarized by Voisin et al. incl. mesomelic dysplasia with additional skeletal anomalies, bilateral kidney hypoplasia and severe DD at the age of 2.5 years. Seizures and pulmonary problems were not observed. Although a different RefSeq is used the variant is among those also reported by Voisin et al. [NM_002285.2:c.697G>A (p.Ala233Thr) corresponding to NM_001025108.1:c.772G>A (p.Ala258Thr)]. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article). [Review modified to add additional reference/case report] |
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| Intellectual disability - microarray and sequencing v2.1135 | SLC5A6 |
Konstantinos Varvagiannis changed review comment from: SLC5A6 encodes the sodium dependent multivitamin transporter (SMVT), a transporter of biotin, pantothenate and lipoate. The transporter has a major role in vitamin uptake in the digestive system (among others is the sole transporter for intestinal uptake of biotin which is not synthesized and but must be obtained from exogenous sources) as well as transport across the blood-brain barrier (SMVT being responsible for 89% of biotin transport) [several refs provided by Subramanian et al and Byrne et al]. 4 affected individuals from 3 families have been reported. Subramanian et al (2017 - PMID: 27904971) et al reported on a girl with feeding difficulties and failure to thrive (requiring nasogastric tube placement), microcephaly, DD (at 15m developmental age corresponding to 6m with features suggestive of spastic cerebral palsy), occurrence of multiple infections, osteoporosis and pathologic bone fractures. MRIs suggested brain atrophy, thin CC and hypoplasia of the pons. Metabolic (AA, OA) investigations and array-CGH were normal. Whole exome sequencing revealed presence of a missense (Arg123Leu - RefSeq not provided) and a nonsense (Arg94Ter) SLC5A6 variant. Serum biotin was normal although - at the time - the child was on parenteral and G-T nutrition. Following administration of biotin, pantothenic acid and lipoic acid the child demonstrated among others improved motor and verbal skills, head growth and normalization of immunoglobulin levels. Transfection of mutants in human derived intestinal HuTu-80 cells and brain U87 cells was carried out and a 3H-biotin assay showed no induction in biotin uptake confirming impaired functionality of the transporter. While wt protein displayed normal expression/membrane localization, Arg94Ter was poorly expressed with ectopic localization (cytoplasm). Arg123Leu was retained predominantly intracellularly, probably in the ER as was further supported by colocalization with DsRed-ER. Evidence from the literature is provided that deficiencies of the specific vitamins explain the clinical features (DD, microcephaly, immunological defect, osteopenia, etc). Schwantje et al (2019 - PMID: 31392107) described a girl with severe feeding problems, vomiting with blood (suspected Mallory-Weiss syndrome), poor weight gain and delayed gross motor development. The child presented an episode of gastroenteritis associated with reduced consciousness, circulatory insufficiency and metabolic derangement (hypoglycemia, severe metabolic acidosis, hyperammonemia, mild lactate elevation, ketonuria). Investigations some months prior to the admission (?) were suggestive of a metabolic disorder due to elevated plasma C3-carnitine, C5-OH-carnitine and elevated urinary excretion of 3-OH-isovaleric acid (biotinidase deficiency was considered in the DD but enzymatic activity was only marginally decreased). Biotin supplementation was initiated. Trio-exome sequencing (at 3yrs) demonstrated compound heterozygosity for 2 frameshift variants [NM_021095.2:c.422_423del / p.(Val141Alafs*34) and c.1865_1866del]. Following this result, increase of biotin supplementation and introduction of pantothenic acid, GI symptoms (incl. chronic diarrhea) resolved and the child displayed improved appetite and growth, yet a stable motor delay. The authors cite previous studies of conditional ko mice, displaying intestinal mucosal abnormalities and growth defects (similar to the child's problems), prevented by biotin and pantothenic acid supplementation. Byrne et al (2019 - PMID: 31754459) reported on a sibling pair with severe motor/speech developmental regression following a plateau (at 12m and 14m), development of ataxia and dyskinetic movements (both), seizures (one). Feeding difficulties, reflux and failure to thrive required N-G/gastrostomy feeding while both presented GI hemorrhage (in the case of the older sib, lethal). Other features in the youngest sib included brain MRI abnormalities (cerebral/cerebellar atrophy, thin CC, etc) and IgG deficiency. Biochemical, single-gene testing and mtDNA sequencing were not diagnostic. Exome in one, revealed presence of a frameshift [c.422_423del as above] and a missense variant (Arg400Thr). Sanger sequencing confirmed variants in both sibs and heterozygosity in parents. HeLa cells transfected with empty vector, wt or mut expression constructs confirmed significantly decreased 3H-biotin uptake for mut constructs compared to wt (and similar to empty vector). Parenteral triple vitamin replacement at the age of ~7 years resulted in improved overall condition, regain of some milestones, attenuation of vomiting, and resolution of peripheral neuropathy. Seizure were well-controlled (as was the case before treatment) despite persistence of epileptiform discharges. Again the authors cite studies of conditional (intestine-specific) SLC5A6 ko mice, with those viable (~1/3) demonstrating growth retardation, decreased boned density and GI abnormalities (similar to affected individuals). The phenotype could be rescued by oversupplementation of biotin and pantothenic acid (PMIDs cited: 23104561, 29669219). [Please consider inclusion in other relevant panels eg. metabolic disorders] Sources: Literature; to: SLC5A6 encodes the sodium dependent multivitamin transporter (SMVT), a transporter of biotin, pantothenate and lipoate. The transporter has a major role in vitamin uptake in the digestive system (among others is the sole transporter for intestinal uptake of biotin which is not synthesized but must be obtained from exogenous sources) as well as transport across the blood-brain barrier (SMVT being responsible for 89% of biotin transport) [several refs provided by Subramanian et al and Byrne et al]. 4 affected individuals from 3 families have been reported. Subramanian et al (2017 - PMID: 27904971) et al reported on a girl with feeding difficulties and failure to thrive (requiring nasogastric tube placement), microcephaly, DD (at 15m developmental age corresponding to 6m with features suggestive of spastic cerebral palsy), occurrence of multiple infections, osteoporosis and pathologic bone fractures. MRIs suggested brain atrophy, thin CC and hypoplasia of the pons. Metabolic (AA, OA) investigations and array-CGH were normal. Whole exome sequencing revealed presence of a missense (Arg123Leu - RefSeq not provided) and a nonsense (Arg94Ter) SLC5A6 variant. Serum biotin was normal although - at the time - the child was on parenteral and G-T nutrition. Following administration of biotin, pantothenic acid and lipoic acid the child demonstrated among others improved motor and verbal skills, head growth and normalization of immunoglobulin levels. Transfection of mutants in human derived intestinal HuTu-80 cells and brain U87 cells was carried out and a 3H-biotin assay showed no induction in biotin uptake confirming impaired functionality of the transporter. While wt protein displayed normal expression/membrane localization, Arg94Ter was poorly expressed with ectopic localization (cytoplasm). Arg123Leu was retained predominantly intracellularly, probably in the ER as was further supported by colocalization with DsRed-ER. Evidence from the literature is provided that deficiencies of the specific vitamins explain the clinical features (DD, microcephaly, immunological defect, osteopenia, etc). Schwantje et al (2019 - PMID: 31392107) described a girl with severe feeding problems, vomiting with blood (suspected Mallory-Weiss syndrome), poor weight gain and delayed gross motor development. The child presented an episode of gastroenteritis associated with reduced consciousness, circulatory insufficiency and metabolic derangement (hypoglycemia, severe metabolic acidosis, hyperammonemia, mild lactate elevation, ketonuria). Investigations some months prior to the admission (?) were suggestive of a metabolic disorder due to elevated plasma C3-carnitine, C5-OH-carnitine and elevated urinary excretion of 3-OH-isovaleric acid (biotinidase deficiency was considered in the DD but enzymatic activity was only marginally decreased). Biotin supplementation was initiated. Trio-exome sequencing (at 3yrs) demonstrated compound heterozygosity for 2 frameshift variants [NM_021095.2:c.422_423del / p.(Val141Alafs*34) and c.1865_1866del]. Following this result, increase of biotin supplementation and introduction of pantothenic acid, GI symptoms (incl. chronic diarrhea) resolved and the child displayed improved appetite and growth, yet a stable motor delay. The authors cite previous studies of conditional ko mice, displaying intestinal mucosal abnormalities and growth defects (similar to the child's problems), prevented by biotin and pantothenic acid supplementation. Byrne et al (2019 - PMID: 31754459) reported on a sibling pair with severe motor/speech developmental regression following a plateau (at 12m and 14m), development of ataxia and dyskinetic movements (both), seizures (one). Feeding difficulties, reflux and failure to thrive required N-G/gastrostomy feeding while both presented GI hemorrhage (in the case of the older sib, lethal). Other features in the youngest sib included brain MRI abnormalities (cerebral/cerebellar atrophy, thin CC, etc) and IgG deficiency. Biochemical, single-gene testing and mtDNA sequencing were not diagnostic. Exome in one, revealed presence of a frameshift [c.422_423del as above] and a missense variant (Arg400Thr). Sanger sequencing confirmed variants in both sibs and heterozygosity in parents. HeLa cells transfected with empty vector, wt or mut expression constructs confirmed significantly decreased 3H-biotin uptake for mut constructs compared to wt (and similar to empty vector). Parenteral triple vitamin replacement at the age of ~7 years resulted in improved overall condition, regain of some milestones, attenuation of vomiting, and resolution of peripheral neuropathy. Seizure were well-controlled (as was the case before treatment) despite persistence of epileptiform discharges. Again the authors cite studies of conditional (intestine-specific) SLC5A6 ko mice, with those viable (~1/3) demonstrating growth retardation, decreased boned density and GI abnormalities (similar to affected individuals). The phenotype could be rescued by oversupplementation of biotin and pantothenic acid (PMIDs cited: 23104561, 29669219). [Please consider inclusion in other relevant panels eg. metabolic disorders] Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1135 | SLC5A6 |
Konstantinos Varvagiannis gene: SLC5A6 was added gene: SLC5A6 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC5A6 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC5A6 were set to 27904971; 31392107; 31754459; 23104561; 29669219 Phenotypes for gene: SLC5A6 were set to Feeding difficulties; Failure to thrive; Global developmental delay; Developmental regression; Intellectual disability; Seizures; Microcephaly; Cerebral atrophy; Abnormality of the corpus callosum; Vomiting; Chronic diarrhea; Gastrointestinal hemorrhage; Abnormal immunoglobulin level; Osteopenia; Abnormality of metabolism/homeostasis Penetrance for gene: SLC5A6 were set to Complete Review for gene: SLC5A6 was set to GREEN Added comment: SLC5A6 encodes the sodium dependent multivitamin transporter (SMVT), a transporter of biotin, pantothenate and lipoate. The transporter has a major role in vitamin uptake in the digestive system (among others is the sole transporter for intestinal uptake of biotin which is not synthesized and but must be obtained from exogenous sources) as well as transport across the blood-brain barrier (SMVT being responsible for 89% of biotin transport) [several refs provided by Subramanian et al and Byrne et al]. 4 affected individuals from 3 families have been reported. Subramanian et al (2017 - PMID: 27904971) et al reported on a girl with feeding difficulties and failure to thrive (requiring nasogastric tube placement), microcephaly, DD (at 15m developmental age corresponding to 6m with features suggestive of spastic cerebral palsy), occurrence of multiple infections, osteoporosis and pathologic bone fractures. MRIs suggested brain atrophy, thin CC and hypoplasia of the pons. Metabolic (AA, OA) investigations and array-CGH were normal. Whole exome sequencing revealed presence of a missense (Arg123Leu - RefSeq not provided) and a nonsense (Arg94Ter) SLC5A6 variant. Serum biotin was normal although - at the time - the child was on parenteral and G-T nutrition. Following administration of biotin, pantothenic acid and lipoic acid the child demonstrated among others improved motor and verbal skills, head growth and normalization of immunoglobulin levels. Transfection of mutants in human derived intestinal HuTu-80 cells and brain U87 cells was carried out and a 3H-biotin assay showed no induction in biotin uptake confirming impaired functionality of the transporter. While wt protein displayed normal expression/membrane localization, Arg94Ter was poorly expressed with ectopic localization (cytoplasm). Arg123Leu was retained predominantly intracellularly, probably in the ER as was further supported by colocalization with DsRed-ER. Evidence from the literature is provided that deficiencies of the specific vitamins explain the clinical features (DD, microcephaly, immunological defect, osteopenia, etc). Schwantje et al (2019 - PMID: 31392107) described a girl with severe feeding problems, vomiting with blood (suspected Mallory-Weiss syndrome), poor weight gain and delayed gross motor development. The child presented an episode of gastroenteritis associated with reduced consciousness, circulatory insufficiency and metabolic derangement (hypoglycemia, severe metabolic acidosis, hyperammonemia, mild lactate elevation, ketonuria). Investigations some months prior to the admission (?) were suggestive of a metabolic disorder due to elevated plasma C3-carnitine, C5-OH-carnitine and elevated urinary excretion of 3-OH-isovaleric acid (biotinidase deficiency was considered in the DD but enzymatic activity was only marginally decreased). Biotin supplementation was initiated. Trio-exome sequencing (at 3yrs) demonstrated compound heterozygosity for 2 frameshift variants [NM_021095.2:c.422_423del / p.(Val141Alafs*34) and c.1865_1866del]. Following this result, increase of biotin supplementation and introduction of pantothenic acid, GI symptoms (incl. chronic diarrhea) resolved and the child displayed improved appetite and growth, yet a stable motor delay. The authors cite previous studies of conditional ko mice, displaying intestinal mucosal abnormalities and growth defects (similar to the child's problems), prevented by biotin and pantothenic acid supplementation. Byrne et al (2019 - PMID: 31754459) reported on a sibling pair with severe motor/speech developmental regression following a plateau (at 12m and 14m), development of ataxia and dyskinetic movements (both), seizures (one). Feeding difficulties, reflux and failure to thrive required N-G/gastrostomy feeding while both presented GI hemorrhage (in the case of the older sib, lethal). Other features in the youngest sib included brain MRI abnormalities (cerebral/cerebellar atrophy, thin CC, etc) and IgG deficiency. Biochemical, single-gene testing and mtDNA sequencing were not diagnostic. Exome in one, revealed presence of a frameshift [c.422_423del as above] and a missense variant (Arg400Thr). Sanger sequencing confirmed variants in both sibs and heterozygosity in parents. HeLa cells transfected with empty vector, wt or mut expression constructs confirmed significantly decreased 3H-biotin uptake for mut constructs compared to wt (and similar to empty vector). Parenteral triple vitamin replacement at the age of ~7 years resulted in improved overall condition, regain of some milestones, attenuation of vomiting, and resolution of peripheral neuropathy. Seizure were well-controlled (as was the case before treatment) despite persistence of epileptiform discharges. Again the authors cite studies of conditional (intestine-specific) SLC5A6 ko mice, with those viable (~1/3) demonstrating growth retardation, decreased boned density and GI abnormalities (similar to affected individuals). The phenotype could be rescued by oversupplementation of biotin and pantothenic acid (PMIDs cited: 23104561, 29669219). [Please consider inclusion in other relevant panels eg. metabolic disorders] Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1098 | CNOT2 |
Konstantinos Varvagiannis gene: CNOT2 was added gene: CNOT2 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: CNOT2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CNOT2 were set to 31512373; 31145527; 28135719; 28159701; 30768759; 21505450; 18076123; 22247066 Phenotypes for gene: CNOT2 were set to Intellectual developmental disorder with nasal speech, dysmorphic facies, and variable skeletal anomalies, MIM 618608 Penetrance for gene: CNOT2 were set to unknown Review for gene: CNOT2 was set to GREEN gene: CNOT2 was marked as current diagnostic Added comment: Heterozygous pathogenic CNOT2 variants cause Intellectual developmental disorder with nasal speech, dysmorphic facies, and variable skeletal anomalies (MIM 618608 - recently added disorder in OMIM). Larger 12q15 deletions, spanning CNOT2 have been reported in patients with similar phenotype. Relevant individuals - most discussed below - include 2 patients with truncating de novo mutation, 1 with de novo intragenic deletion, few with small deletions spanning also 2-3 additional proximal genes and others with larger 12q15 deletions encompassing CNOT2 and several other genes. Overall the phenotype - summarized by Uehara et al. (Ref1 - below) - seems to consist of language delay, mild motor delay (in most), some suggestive facial features (upslanted palpebral fissures, anteverted nares, thin upper lip and micrognathia). Nasal speech has also been reported in some individuals. As commented by Uehara et al. (Ref1), CNOT2 (CCR4-NOT transcription complex subunit 2) is a member of the carbon catabolite repressor 4 complex (CCR4-NOT), the latter having an important role in deadenylation of mRNA and global mRNA expression. Disruption of the complex - which can be caused by loss of one of its components - results in various human disorders incl. neural diseases. siRNA CNOT2 depletion has been shown to induce CCR4-NOT disruption (cited PMIDs: 16284618, 29438013, 31006510, 21299754). The type of variants (truncating, intragenic deletion, larger deletions) and the highly overlapping phenotypes in the respective patients suggest happloinsufficiency as the underlying mechanism. CNOT2 has also a pLI of 1 in gnomAD (o/e =0.06) and a %HI in Decipher of 4.39. The gene appears to have relevant expression (https://www.proteinatlas.org/ENSG00000111596-CNOT2/tissue). Animal models have not been discussed (or phenotypes possibly not sufficiently studied - MGI for Cnot2 : http://www.informatics.jax.org/marker/MGI:1919318). CNOT2 is not associated with any phenotype in G2P. It is listed among the ID candidate genes in SysID. This gene is included in gene panels for ID offered by some diagnostic laboratories (incl. Radboudumc). Overall CNOT2 could be considered for inclusion in the ID panel with amber (DD although outcome is not known, presumed dysfunction of the CCR4-NOT complex, variant studies or animal models not available) or green rating (sufficient cases and variants, consistent phenotype). ----- Individuals with CNOT2-only disruption: [1] PMID: 31512373 (Uehara et al., 2019) - A 6 y.o. male investigated for hypotonia, feeding problems, DD (speech and motor), macrocephaly (+3 SD) and some possibly suggestive facial/other features was found to harbor a de novo stopgain variant (NM_001199302.1: c.946A>T, p.Lys316Ter) after trio exome sequencing. The variant and its de novo occurrence were confirmed by Sanger sequencing. NMD was the predicted effect (variant in ex11 of 21 / effect not further studied). Previous metabolic work-up and chromosomal testing had not revealed an alternative diagnosis. [2] PMID: 31145527 (Alesi et al. 2019) - A 13 y.o. boy with hypotonia, failure to thrive, DD and following a specific schooling program for children with learning difficulties is reported. The authors comment on the facial phenotype (incl. upslanted p-f, anteverted nares, etc). Other features included valvular/supravalvular pulm. stenosis, mid aortic insufficiency, renal anomalies/failure, skeletal anomalies. Speech was nasal. CMA revealed an 85-kb 12q15 deletion spanning only CNOT2 (exons 3-15). Real-time PCR in proband and parents confirmed the variant and its de novo occurrence. [3] PMID: 28135719 (DDD study, 2017) - An individual with developmental disorder and a de novo (validated) frameshift variant was identified [DDD4K.00807 - NM_014515.5:c.1158del / p.(L387Sfs*3)]. Phenotype in Decipher incl. abnormality of head/neck, nervous, skeletal system and growth. [https://decipher.sanger.ac.uk/ddd/research-variant/16b4f7866652f08e25a194f65535b4c5#overview]. Individuals with disruption of additional proximal genes due to CNVs: [4] PMID: 28159701 (Alesi et al. 2017) - The authors report on a 29 y.o. individual with history of DD, learning difficulties, ID (WAIS-R IQ of 48 at the age of 17 y), some dysmorphic facial features. Additional features incl. recurrent infections, nasal voice as well as skeletal anomalies. CMA revealed a 742 kb microdeletion spanning CNOT2, KCNMB4 and PTPRB. Real-time PCR confirmed deletion and it's de novo occurrence in the proband. [5] PMID: 30768759 (Uehara et al. 2019) - A female investigated among others for global DD (walking/1st words at 24m), mild ID, submucosal cleft palate with some distinctive facial features (upslanted p-f, micrognathia, etc) was found to harbor a 1.32-Mb deletion of 12q15 encompassing CNOT2 and 14 other genes. Given the phenotypic resemblance to patients with 12q15 deletions, the previously defined smallest region of overlap (ref 4,6), the LoF SNV in Decipher the authors suggested that CNOT2 is the critical gene for the phenotype of 12q15 deletion syndrome. Larger deletions defining the smallest region of overlap [6] PMID: 21505450 (Vergult et al. 2011) - 3 patients with de novo microdeletions of ~ 2.5 Mb in size with a 1.34 MB common region of overlap are reported. Learning diability, DD, nasal speech and hypothyroidism were among the common features. [7] PMID: 18076123 (Schluth et al. 2008) - A girl with large (~10 Mb) de novo deletion of 12q15 - q21.2 identified by BAC array was described. The phenotype consisted of hypotonia, DD, moderate ID, growth delay and facial dysmorphic features. [8] PMID: 22247066 (Lopez et al. 2012) - A patient with ID and features of Floating-Harbor syndrome was found to harbor a 4.7 Mb de novo 12q15-q21.1 deletion spanning CNOT2 and 18 additional genes. [..] Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.1098 | NTNG2 |
Konstantinos Varvagiannis gene: NTNG2 was added gene: NTNG2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: NTNG2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: NTNG2 were set to 31372774; 31668703 Phenotypes for gene: NTNG2 were set to Central hypotonia; Global developmental delay; Intellectual disability; Behavioral abnormality; Microcephaly; Seizures Penetrance for gene: NTNG2 were set to Complete Review for gene: NTNG2 was set to GREEN Added comment: [1] Abu-Libdeh et al. (2019 - PMID: 31372774) reported 8 individuals from 4 unrelated consanguineous families of Arab Muslim origin, all homozygous for NM_032536.3:c.376dup - p.(Ser126PhefsTer241). Common features included hypotonia, failure to achieve milestones and developmental stagnation without regression during the first year (~9m) of life and severe ID. Minimal purposeful hand use (grasping and bringing objects to mouth), hand stereotypies and bruxism were also observed. Microcephaly and impaired growth were almost universal (with the exception of 2 having an OFC at ~10% percentile). Relevant previous investigations were normal in all and included MECP2, SMN1, aCGH, metabolic testing, etc. The variant was identified by exome in all, and Sanger confirmed with compatible segregation studies in parents and sibs. The variant was found within a shared haplotype of ~4.35 Mb, probably due to a founder effect. [2] Dias et al. (2019 - PMID: 31668703) described 16 individuals from 7 unrelated families from Iran, Mexico, Turkey, Egypt and Bangladesh. Parents were known to be consanguineous or shown to be distantly related. All patients were homozygous for missense variants private to each family (7 variants) identified following exome sequencing. Shared features incl. hypotonia, GDD, severe to profound ID and behavioral anomalies incl. autistic features/stereotypies (most), screaming/laughing spells (most), bruxism. Microcephaly (5/14), growth below average/FTT and GI problems were also observed. Epilepsy was reported in 5 individuals belonging to 4 different families in these 2 studies (5/24 overall / 4 variants). Netrin-G2, the encoded protein, is bound to the plasma membrane by GPI-anchors. Netrins-G2 and G1 (another member of the Netrin-G subfamily) are enriched in presynaptic terminals. Interaction with their cognate Netrin-G ligand trans-synaptic partners / receptors (NGL2, NGL1 respectively) has been shown to promote axon outgrowth, induce and maintain excitatory synapse formation. Complementary and non-overlapping expression in the developping and mature CNS has been shown for Netrin-G2/1 in mice (several references provided by Abu-Libdeh / Dias). Variant effect : The frameshift variant was not studied by Abu-Libdeh et al. Variants in the 2nd ref. were all missense, displayed no-specific localization and were suggested to affect protein stability and/or expression at the cell surface as 4/7 involved loss or addition of cystein residues (possibly creating unpaired cysteins) and 2 of the remaining 3 were predicted to affect the hydrophobic core. In line with this, overexpression of wt/variant constructs in HeLa cells demonstrated substantially decreased cell surface expression for all variants. Mouse models/phenotypes : Dias et al. showed that siRNA-mediated Ntng2 knockdown in N2a cells led to significant reduction in neurite number and length. Studied previously, Ntng2 knockout mice display impaired learning, memory, visual and motor functioning (PMID cited : 26746425). NTNG2 is not associated with any phenotype in OMIM/G2P. SysID lists it among the candidate ID genes, citing PMID: 29302074 (not here reviewed & NTNG2 not in the main text). Overall this gene can be considered for inclusion in the ID panel probably as green (>3 individuals/families/variants, consistent phenotype in both reports, role of the gene, in silico and in vitro studies, animal model, etc) or amber. [Please consider inclusion in other panels if relevant eg. ASD panel (many individuals having autistic / Rett-like features or epilepsy) or epilepsy (>3 individuals/families/variants although most families were also consanguineous)] Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1062 | APC2 |
Konstantinos Varvagiannis gene: APC2 was added gene: APC2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: APC2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: APC2 were set to 31585108; 25753423; 19759310; 22573669 Phenotypes for gene: APC2 were set to Global developmental delay; Intellectual disability; Seizures; Morphological abnormality of the central nervous system Penetrance for gene: APC2 were set to Complete Review for gene: APC2 was set to GREEN gene: APC2 was marked as current diagnostic Added comment: Probably 14 individuals from 9 families (8 consanguineous) with biallelic APC2 LoF variants have been reported. ID and brain abnormalities were features in all, although the presentation was quite different between sibs in the first report (PMID: 25753423 - mild/mod ID, ventriculomegaly and CC anomalies, macrocephaly with variable height, Sotos-like facial features) and 12 subsequently described patients (PMID: 31585108 - severe ID, P>A lissencephaly/CC anomalies/ventriculomegaly/paucity of white matter in (almost) all, gT-C/myoclonic seizures in 8/12 with onset 3m-6y, OFC in the low percentiles). In all cases relevant alternative diagnoses (eg. macrocephaly/overgrowth syndromes - 1st report, mutations in other lissencephaly genes, metabolic disorders - 2nd) were ruled out. APC2 encodes Adenomatous polyposis coli protein 2, expressed in the CNS. All variants reported to date were LoF (stopgain/frameshift/splicing) and were supported by parental-only studies. Mutations in the 1st report as well as 4/8 variants from the 2nd report localized within the last exon (NM_005883.2 / longest of >=3 isoforms), although the 2nd report did not observe obvious genotype-phenotype correlations. Despite a pLI of 1 in gnomAD, Lee et al. comment that heterozygous carriers did not have any noticeable phenotype. They further note that carriers were not examined by brain MRI, though. 27 heterozygous high-confidence variants appear in individuals in gnomAD. Finally as commented on, APC2 is not mutated in colon cancer. Animal models: Apc -/- mice displayed disrupted neuronal migration, with defects of lamination of cerebral cortex and cerebellum supporting the observed brain abnormalities. In addition Apc2-deficient mice also presented impaired learning and memory abilities. Extensive additional studies have shown Apc2 co-localization with microtubules affecting their stabilization, distribution along actin fibers (all supporting a role in cytoskeletal organization) and regulation of Rac1 (a Rho GTPase). Generation of Neuro2a cells demonstrated abnormal localization mainly in cell bodies of mutant hAPC2 proteins (due to frameshift in the last exon / deletion of the C-terminal part) - different from wt (neurites, growth cones, cell bodies). The first patient report also provided evidence for Apc2 being a downstream effector of Nsd1, with Nsd1 knockdown brains displaying impaired migration / laminar positioning of cortical neurons (similar to Apc2-/- model) and rescued by forced expression of Apc2. Relevant articles: PMIDs: 19759310 and 22573669 (Shintani et al. 2009 & 2012) [mouse model] PMID: 25753423 (Almuriekhi et al. 2015) [2 individuals + mouse model] PMID: 31585108 (Lee et al. 2019) [12 individuals from 8 families] ----- In OMIM, the APC2-related phenotype is ?Sotos syndrome 3 (MIM 617169 - AR). G2P does not have any associated phenotype for this gene. In SysID, APC2 belongs to the Current primary ID genes. APC2 is included in gene panels for ID offered by some diagnostic laboratories (eg. Radboudumc, GeneDx). ----- Overall, this gene could be considered for inclusion in the ID panel probably as green (>3 individuals/families/variants, highly specific pattern of lissencephaly in 12/14, mouse model supporting migration defects and impaired learning/memory) rather than amber (differences between the 1st and the other families reported as for the OFC and presence of lissencephaly). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1047 | METTL5 |
Konstantinos Varvagiannis gene: METTL5 was added gene: METTL5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: METTL5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: METTL5 were set to 29302074; http://doi.org/10.1016/j.ajhg.2019.09.007; https://imgc2019.sciencesconf.org/data/abstract_book_complete.pdf Phenotypes for gene: METTL5 were set to Delayed speech and language development; Intellectual disability; Microcephaly; Behavioral abnormality Penetrance for gene: METTL5 were set to Complete Review for gene: METTL5 was set to GREEN Added comment: [1] - PMID: 29302074 : In a WES/WGS study of 404 consanguineous families with two or more offspring affected by ID, Hu et al. identified two sibs homozygous for a METTL5 missense variant [NM_014168:c.182G>A / p.Gly61Asp]. These 2 subjects, born to first cousin parents from Iran, presented with early learning impairment, aggressive behaviour, severe microcephaly (-7SD and -8SD) and ID formally evaluated to be in the severe range. Sanger confirmation of variants and segregation studies were performed for all available and informative members in families participating in the study. In silico predictions were all in favour of a deleterious effect (PolyPhen2, MutationTaster, SIFT, CADD) and the variant was absent from ExAC. The effect of the specific variant was studied in ref. 2 (below). [2] - DOI: 10.1016/j.ajhg.2019.09.007 : Richard et al. (2019) reported on 5 additional individuals from 2 consanguineous families. Common phenotype consisted of speech delay, moderate/severe ID (4/4), microcephaly (4/4 - though milder than in the first report), behavioral problems (ADHD, aggressiveness, autistic feat.) and possibly some overlapping facial features (nose and ear abnormalities). 3 sibs from the 1st family, from Pakistan, were homozygous for a frameshift variant (NM_014167.2:c.344_345delGA / p.Arg115Asnfs*19) while sibs from the 2nd family, from Yemen, were homozygous for p.Lys191Valfs*1 (c.571_572delAA). Confirmation and segregation studies supported a role for the variants. The authors performed additional studies for METTL5 and all 3 variants reported to date, notably: - Based on RNA-seq data from the Allen Brain Atlas, METTL5 is expressed in the developing and adult human brain (incl. cerebellar cortex, hippocampus and striatum). - Immunostaining in mouse brain demonstrated ubiquitous expression (postnatal day 30). - In rat hippocampal neurons, enrichment of METTL5 was found in the soma, the nucleus and pre- and post- synaptic regions. - Myc-/GFP-tagged METTL5 wt or mutants were transiently expressed in COS7 cells, and were found in the cytoplasm and nucleus. Levels of the 2 frameshift variants were significantly reduced compared with wt, although this was not the case for Gly61Asp. - Upon transfection of rat hippocampal neurons, METTL5-GFP tagged wt and mt proteins showed similar localicalization in nucleus and dendrites. - Western blot on HEK293T cells transfected with Myc-METTL5 wt or mt constructs demonstrated decreased amounts for the frameshift (but not the missense) variants while comparison after addition of a proteasome inhibitor or cyclohexamide suggested that this is not probably due to decreased mutant protein - rather than mRNA (NMD) - stability. - In zebrafish, morpholino knockdown of mettl5 led to reduced head size and head/body ratio (reproducing the microcephaly phenotype) and curved tails. Forebrain and midbrain sizes were also significantly reduced. Based on the ACMG criteria, Gly61Asp is classified as VUS (PM2, PP1, PP3) and the frameshift ones as pathogenic (PS3, PM2, PM4, PP1, PP3). The authors comment that METTL5 is an uncharacterized member of the methyltransferase superfamily (of 33 METTL proteins). Variants in other methyltransferase-like genes (mainly METTL23) have been associated with ID, while various histone-/DNA-/tRNA-/rRNA- methyltransferases such as EHMT1, DNMT3A, NSUN2, FTSJ1, etc have been implicated in ID. Given the role of methyltransferases in neurodevelopment and neuroplasticity, homology comparisons suggesting presence of relevant domain in METTL5 and accumulation of the protein in the nucleus, a role as epigenetic regulator is proposed (see also ref. 3). [3] - Conference abstract by Helmut et al. ["A novel m6A RNA methyltransferase in mammals - characterization of Mettl5 mutant mice in the German Mouse Clinic" - Oral presentation in the 33rd International Mammalian Genome Conference Sept. 2019 - available at : https://imgc2019.sciencesconf.org/data/abstract_book_complete.pdf ] The group using an in vitro methyltransferase assay, identified METTL5 as a m6A RNA methyltransferase. Generation of Mettl5-knockout mice using the CRISPR/Cas technology, suggested that homozygous mice are subviable, with lower body mass and abnormal growth of nasal bones in half. Homozygous mice were hypoactive and hypoexploratory during an open field test at the age of 8 weeks, while further alterations were observed in neurological functions. Phenotypic deviations were absent or very mild in heterozygous animals. As a result, the mouse model appeared to recapitulate relevant human phenotypes (microcephaly, ID and growth retardation). ---- There is no associated entry in OMIM (neither for the gene nor for a related disorder). G2P does not list any phenotype for this gene, either. METTL5 is included in the SysID database as a current primary ID gene (cited: 27457812, 28097321 / Given the shared co-authors with the study by Richard et al. as well as the overlapping variants, these articles probably report on the same individuals recently described in more detail). The gene is included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx). ---- Overall, METTL5 could be considered for inclusion in the ID panel probably as green (3 families, 3 variants, segregation, suggested role of the gene, relevant expression patterns, some evidence at the variant-level, zebrafish and mouse models) or amber (underlying effect of Gly61Asp unknown and variant classified as VUS). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1046 | PMPCA |
Konstantinos Varvagiannis gene: PMPCA was added gene: PMPCA was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PMPCA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PMPCA were set to 25808372; 26657514; 27148589; 30617178 Phenotypes for gene: PMPCA were set to Spinocerebellar ataxia, autosomal recessive 2 (MIM 213200) Penetrance for gene: PMPCA were set to Complete Review for gene: PMPCA was set to GREEN gene: PMPCA was marked as current diagnostic Added comment: Biallelic pathogenic PMPCA variants cause Spinocerebellar ataxia, autosomal recessive 2 (SCAR2 - MIM 213200). More than 20 individuals from several unrelated families have been reported. At least 6 different pathogenic variants have been identified. Loss of PMPCA function is the suggested mechanism. ID is a feature of the disorder. PMPCA encodes the α-subunit of mitochondrial processing peptidase (αMPP), a heterodimeric enzyme responsible for the cleavage of nuclear-encoded mitochondrial precursor proteins after import in the mitochondria (summary by Jobling et al and OMIM). Arguments for involvement of the gene include the highly similar phenotype, segregation studies, expression of the gene in fetal and relevant adult tissues (in brain/cerebellum/cerebellar vermis), lower protein levels demonstrated for some variants, abnormal processing of frataxin (in line with the role of αMPP) demonstrated in most cases, rescue of the maturation defect upon transduction of wt PMPCA cDNA, disruption of REDOX balance in patient cells, etc. Relevant studies are summarized below. PMPCA is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboud UMC, GeneDx, etc) and listed as a confirmed ID gene in SysID. It is not associated with any phenotype in G2P. As a result, this gene can be considered for inclusion in the current panel probably as green (or amber). ---- [1] - Jobling et al. (2015 - PMID: 25808372) described the phenotype of 17 individuals from 4 families, all presenting with non-progressive cerebellar ataxia and the majority with ID of variable severity (15/17 - relevant to the current panel). Individuals from 3 of the families - all of Lebanese origin - were homozygous for NM_015160.3:c.1129G>A (p.Ala377Thr). A further similarly affected subject was compound heterozygous for c.287C>T (p.Ser96Leu) and c.1543G>A (p.Gly515Arg). The homozygous variant in the first family was found within a 2.85 Mb linkage region on chr 9q34. An additional variant within this region (in CAMSAP1) was discarded following results in other families of the same origin. Semi-quantitative RT-PCR demonstrated fetal expression of the PMPCA as well as relatively higher expression in adult brain, cerebellum and cerebellar vermis. As for Ala377Thr, protein levels were shown to be lowest in affected individuals (LCLs, fibroblasts) and low - though somewhat higher - in carrier parents (LCL) compared to controls. RT-PCR on total RNA from LCLs did not show evidence of abnormal transcripts/additional splicing defect. Localization of mutant protein and morphology of mitochondrial reticulum was similar to controls. Maturation of frataxin - the protein depleted in Friedreich ataxia - was shown to be abnormal in patient lymphoblasts, compatible with the role of αMPP. In line with abnormal mitochondrial function, REDOX balance was increased in patient cells. [2] - Choquet et al. (2016 - PMID: 26657514) reported on 2 sibs - born to distantly related parents. The authors noted a phenotype corresponding to SCAR2 although the presentation was somewhat milder, intellectual disability was not a feature (despite some learning difficulties in one) and ataxia was progressive. WES demonstrated homozygosity for NM_015160:c.766G>A (p.Val256Met). Western blot in patient lymphoblasts showed αMPP levels similar to carriers and controls. Abnormal maturation (accumulation of specific isoforms) was shown for frataxin. [3] - Joshi et al. (2016 - PMID: 27148589) described the phenotype of 2 cousins belonging to a large Lebanese pedigree. Presentation in both was compatible with multisystem involvement incl. profound global DD, severe hypotonia, weakness, respiratory insufficiency, blindness suggestive of mitochondrial disorder. mtDNA, analyses of mitochondrial focused nuclear gene panel and aCGH were non-diagnostic. Both subjects were compound heterozygous for NM_015160.3:c.1066G>A (p.Gly356Ser) and c.1129G>A (p.Ala377Thr) following WES, with compatible segregation studies within the family. Western blot revealed PMPCA levels similar to control. Reduction of PMPCA staining and abnormally enlarged mitochondria were observed upon immunofluorescence in patient fibroblasts. Frataxin processing was abnormal. Lentiviral transduction of patient fibroblasts with wt PMPCA cDNA, led to increased PMPCA levels and correction of frataxin processing. [4] - Rubegni et al. (2019 - PMID: 30617178) report on a 7-y.o. boy with global DD, spastic-ataxic gait and 'low IQ'. MRI images were suggestive of cerebellar atrophy with hyperintensity in the striatum. The child was homozygous for c.553C>T / p.Arg185Trp (reference not specified, although the variant would be compatible with NM_015160.3). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.1022 | PIGP |
Konstantinos Varvagiannis gene: PIGP was added gene: PIGP was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PIGP was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PIGP were set to 28334793; 31139695 Phenotypes for gene: PIGP were set to Generalized hypotonia; Global developmental delay; Seizures; Intellectual disability; Feeding difficulties; Cortical visual impairment Penetrance for gene: PIGP were set to Complete Review for gene: PIGP was set to GREEN gene: PIGP was marked as current diagnostic Added comment: Johnstone et al. (2017 - PMID: 28334793) report on 2 sibs born to non-consanguineous parents of French-Irish ancestry. Both presented with seizures (onset at the age of 2 and 7 weeks respectively), hypotonia and profound DD. Other features included CVI and feeding difficulties. Extensive metabolic testing as well as prior genetic testing (ARX, STXBP1, MECP2, aCGH) in the family were non-diagnostic. WES suggested the presence of 2 PIGP variants with Sanger sequencing used for confirmation and segregation studies. PIGP encodes a subunit of the enzyme that catalyzes the first step of glycophosphatidylinositol (GPI) anchor biosynthesis. Mutations in other genes whose proteins are in complex with PIGP (PIGA, PIGC, PIGQ, PIGY, DPM2) lead to similar phenotypes. The phenotype overall was also overlapping with the inherited GPI deficiencies (belonging to the broader group of CDGs). PIGP has 2 isoforms, which differ by 24 amino acids due to utilization of alternative start codons [corresponding to NM_153681.2 (158 aa) and NM_153682.2 (134 aa)]. The variants identified affected both transcripts with the first SNV leading either to loss of the start codon (NM_153682.2:c.2T>C - p.Met1Thr) or to substitution of a methionine at position 25(NM_153681.2:c.74T>C;p.Met25Thr). The second variant led to frameshift in the last exon of both transcripts predicting a longer protein product (NM_153681.2:c.456delA / p.Glu153AsnfsTer34 or NM_153682.2:c.384delA / p.Glu129AsnfsTer34). Overall extensive studies demonstrated decreased levels of PIGP mRNA in patient fibroblast, decreased amounts of mutant protein in transfected HEK293 cells. The decreased levels of GPI-APs further supported the effect of variants : - mRNA levels in patient fibroblasts were reduced compared to controls. Conclusions could not be drawn from Western blot, since no antibodies could specifically detect PIGP. HEK293 cells transfected of mt or wt HA-tagged PIGP cDNA led to undetectable amounts for the first variant (both M1T/M25T) and a protein product of increased molecular weight for the frameshift one. - Flow cytometry of patient granulocytes indicated reduced signal of CD16 (a GPI-anchored protein) and FLAER (binding directly to the GPI anchor). - Reduced levels of GPI-APs were also observed in PIGP deficient HAP1 cells transfected with either wt, or mutant PIGP cDNA (of both isoforms for the M1T/M25T or isoform 2 for the frameshift mutation). -------- Krenn et al. (2019 - PMID: 31139695) described a patient born to non-consanguineous Polish parents. Features were highly similar to those reported by Johnstone et al. and incl. intractable infantile seizures (onset at 7m), hypotonia, severe DD and feeding difficulties. Metabolic work-up failed to identify an alternative diagnosis. WES revealed homozygosity for the frameshift variant reported by Johnstone et al. Sanger sequencing confirmed the variant and carrier state in both parents. Identified ROH of less than 7 Mb in the WES data, suggested a founder mutation rather than unreported consanguinity. The variant is present 9 times in gnomAD (AF of 3.2e-5 / no homozygotes). Flow cytometry of patient granulocytes, revealed markedly reduced expression of GPI-APs (CD157, CD59, FLAER) compared to parents/controls. ALP was normal in all aforementioned individuals (probably in line with PIGP being involved in the 1st step of the GPI anchor biosynthesis). -------- A further individual with phenotype of EIEE-55;GPIBD-14 is reported in LOVD [Individual #00246132]. This individual, born to consanguineous parents, was tested by WES and found to be homozygous for a frameshift variant, also affecting the last exon in both transcripts (NM_153681.2:c.384delA (p.Glu129ArgfsTer7) / NM_153682.2:c.312delA (p.Glu105ArgfsTer7). This was probably in agreement with segregation studies according to the respective entry. The specific variant is reported as pathogenic [variant ID #0000500090]. -------- ?Epileptic encephalopathy, early infantile, 55 (MIM 617599) is the corresponding phenotype in OMIM. There is no relevant G2P entry. PIGP is included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx). -------- As a result, PIGP can be considered for inclusion in the ID/epilepsy panels probably as green (3 individuals, role of the gene and similarity to other inherited GPI deficiencies, extensive supporting studies) or amber. (Please consider inclusion in other possibly relevant panels eg. CDGs, etc). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1021 | MED25 |
Konstantinos Varvagiannis changed review comment from: Please consider the 2 additional articles by Nair et al. (2019 - DOI: 10.1159/000494465 - PMID: 30800049 & DOI: 10.1159/000501114 - PMID: NA) reporting on 3 individuals from 2 consanguineous Lebanese families. All affected individuals were homozygous for a MED25 missense variant [NM_030973.3:c.518T>C / p.Ile173Thr], possibly a founder mutation in the Lebanese population. The phenotype presented some similarities with the previously described patients. The variant has a very low AF in gnomAD (0.00003470) and was also absent from the Saudi Variant Database. In silico predictions from PolyPhen2, PROVEAN, MutationTaster were suggestive of a probably damaging effect. The individual from the first report (PMID: 30800049) had an additional homozygous COQ8A variant, with some features fitting with the phenotype of AR primary CoQ10 deficiency type 4 and others negating this diagnosis. MED25 is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboudumc, Victorian Clinical Genetics and many others). It is not however included in the DD panel of G2P.; to: Please consider the 2 additional articles by Nair et al. (2019 - DOI: 10.1159/000494465 - PMID: 30800049 & DOI: 10.1159/000501114 - PMID: NA) reporting on 3 individuals from 2 consanguineous Lebanese families. All affected individuals were homozygous for a MED25 missense variant [NM_030973.3:c.518T>C / p.Ile173Thr], possibly a founder mutation in the Lebanese population. The phenotype presented some similarities with the previously described patients. The variant has a very low AF in gnomAD (0.00003470) and was also absent from the Saudi Variant Database. In silico predictions from PolyPhen2, PROVEAN, MutationTaster were suggestive of a probably damaging effect. The individual from the first report (PMID: 30800049) had an additional homozygous COQ8A variant, with some features fitting with the phenotype of AR primary CoQ10 deficiency type 4 and others negating this (possibly concurrent) diagnosis. MED25 is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboudumc, Victorian Clinical Genetics and many others). It is not however included in the DD panel of G2P. |
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| Intellectual disability - microarray and sequencing v2.1021 | PAK1 |
Konstantinos Varvagiannis changed review comment from: Horn et al. (2019 - doi.org/10.1093/brain/awz264) report on 4 additional individuals with de novo missense PAK1 pathogenic variants. ID, seizures and macrocephaly and walking difficulties were observed in all (4/4). ASD was reported in 3 (but was not among the features in the study by Harms et al). PAK1 encodes p21 protein-activated kinase 1. The protein has 2 major domains, an autoregulatory and a protein kinase domain. Homodimerization masks the active site of the kinase, leading to autoinhibition (inactive form). PAK1 is activated by dissociation into monomers upon binding of the GTP-bound forms of the Rho GTPases CDC42 and RAC1. TRIO and HACE1 are indirect regulators of PAK1, via RAC1. PAK1 in turn, activates LIMK1 which plays a critical role in dendritic spine morphogenesis and brain function. CDC42, RAC1, TRIO, HACE1 are all associated with neurodevelopmental disorders. Activation of RAC-PAK1-LIMK1 pathway has been demonstrated for Fragile-X syndrome (sharing ID, macrocephaly and seizures). Mutations in PAK3, another member of the group I PAK subfamily with similar activation mechanism to PAK1 (by CDC42 / RAC1), cause Mental retardation, X-linked 30/47 (MIM 300558) (Green rating in the current panel). 4 additional missense variants - further to the 2 previously described ones - were found, all as de novo events: c.397T>C (p.Ser133Pro) / c.361C>T p.(Pro121Ser) / c.328T>A p.(Ser110Thr) / c.1409T>G (p.Leu470Arg) [For the specific variants, cDNA and aa change are the same for both NM_001128620.1 and NM_002576]. The 3 former variants located within the autoinhibitory domain while the latter in the protein kinase domain though - again - close to the autoinhibitory one (in tertiary structure). A gain of function effect by reduced ability of autoinhibition (leading to autophosphorylation) and activation of PAK1 is the suggested mechanism. Gain of function is also supported by the fact that Pak1-/- do not exhibit neurodevelopmental anomalies / abnormal head size. PAK1 is not particularly intolerant to LoF variants as suggested by its pLI of 0.67. The corresponding phenotype in OMIM is Intellectual developmental disorder with macrocephaly, seizures, and speech delay (MIM 618158). The gene is part of the DD panel of G2P, associated with "Neurodevelopmental Disorder" (monoallelic, activating / disease confidence : probable). PAK1 is included in the gene panel for ID offered by Radboudumc.; to: Based on a further recent study, PAK1 can probably be upgraded to green in both ID and epilepsy gene panels: Horn et al. (2019 - doi.org/10.1093/brain/awz264) report on 4 additional individuals with de novo missense PAK1 pathogenic variants. ID, seizures and macrocephaly and walking difficulties were observed in all (4/4). ASD was reported in 3 (but was not among the features in the study by Harms et al). PAK1 encodes p21 protein-activated kinase 1. The protein has 2 major domains, an autoregulatory and a protein kinase domain. Homodimerization masks the active site of the kinase, leading to autoinhibition (inactive form). PAK1 is activated by dissociation into monomers upon binding of the GTP-bound forms of the Rho GTPases CDC42 and RAC1. TRIO and HACE1 are indirect regulators of PAK1, via RAC1. PAK1 in turn, activates LIMK1 which plays a critical role in dendritic spine morphogenesis and brain function. CDC42, RAC1, TRIO, HACE1 are all associated with neurodevelopmental disorders. Activation of RAC-PAK1-LIMK1 pathway has been demonstrated for Fragile-X syndrome (sharing ID, macrocephaly and seizures). Mutations in PAK3, another member of the group I PAK subfamily with similar activation mechanism to PAK1 (by CDC42 / RAC1), cause Mental retardation, X-linked 30/47 (MIM 300558) (Green rating in the current panel). 4 additional missense variants - further to the 2 previously described ones - were found, all as de novo events: c.397T>C (p.Ser133Pro) / c.361C>T p.(Pro121Ser) / c.328T>A p.(Ser110Thr) / c.1409T>G (p.Leu470Arg) [For the specific variants, cDNA and aa change are the same for both NM_001128620.1 and NM_002576]. The 3 former variants located within the autoinhibitory domain while the latter in the protein kinase domain though - again - close to the autoinhibitory one (in tertiary structure). A gain of function effect by reduced ability of autoinhibition (leading to autophosphorylation) and activation of PAK1 is the suggested mechanism. Gain of function is also supported by the fact that Pak1-/- do not exhibit neurodevelopmental anomalies / abnormal head size. PAK1 is not particularly intolerant to LoF variants as suggested by its pLI of 0.67. The corresponding phenotype in OMIM is Intellectual developmental disorder with macrocephaly, seizures, and speech delay (MIM 618158). The gene is part of the DD panel of G2P, associated with "Neurodevelopmental Disorder" (monoallelic, activating / disease confidence : probable). PAK1 is included in the gene panel for ID offered by Radboudumc. (Previous review below) |
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| Intellectual disability - microarray and sequencing v2.1021 | PAK1 |
Konstantinos Varvagiannis edited their review of gene: PAK1: Added comment: Horn et al. (2019 - doi.org/10.1093/brain/awz264) report on 4 additional individuals with de novo missense PAK1 pathogenic variants. ID, seizures and macrocephaly and walking difficulties were observed in all (4/4). ASD was reported in 3 (but was not among the features in the study by Harms et al). PAK1 encodes p21 protein-activated kinase 1. The protein has 2 major domains, an autoregulatory and a protein kinase domain. Homodimerization masks the active site of the kinase, leading to autoinhibition (inactive form). PAK1 is activated by dissociation into monomers upon binding of the GTP-bound forms of the Rho GTPases CDC42 and RAC1. TRIO and HACE1 are indirect regulators of PAK1, via RAC1. PAK1 in turn, activates LIMK1 which plays a critical role in dendritic spine morphogenesis and brain function. CDC42, RAC1, TRIO, HACE1 are all associated with neurodevelopmental disorders. Activation of RAC-PAK1-LIMK1 pathway has been demonstrated for Fragile-X syndrome (sharing ID, macrocephaly and seizures). Mutations in PAK3, another member of the group I PAK subfamily with similar activation mechanism to PAK1 (by CDC42 / RAC1), cause Mental retardation, X-linked 30/47 (MIM 300558) (Green rating in the current panel). 4 additional missense variants - further to the 2 previously described ones - were found, all as de novo events: c.397T>C (p.Ser133Pro) / c.361C>T p.(Pro121Ser) / c.328T>A p.(Ser110Thr) / c.1409T>G (p.Leu470Arg) [For the specific variants, cDNA and aa change are the same for both NM_001128620.1 and NM_002576]. The 3 former variants located within the autoinhibitory domain while the latter in the protein kinase domain though - again - close to the autoinhibitory one (in tertiary structure). A gain of function effect by reduced ability of autoinhibition (leading to autophosphorylation) and activation of PAK1 is the suggested mechanism. Gain of function is also supported by the fact that Pak1-/- do not exhibit neurodevelopmental anomalies / abnormal head size. PAK1 is not particularly intolerant to LoF variants as suggested by its pLI of 0.67. The corresponding phenotype in OMIM is Intellectual developmental disorder with macrocephaly, seizures, and speech delay (MIM 618158). The gene is part of the DD panel of G2P, associated with "Neurodevelopmental Disorder" (monoallelic, activating / disease confidence : probable). PAK1 is included in the gene panel for ID offered by Radboudumc.; Changed rating: GREEN; Changed publications: 30290153, doi.org/10.1093/brain/awz264; Set current diagnostic: yes |
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| Intellectual disability - microarray and sequencing v2.1004 | AFF3 | Rebecca Foulger changed review comment from: As noted by Konstantinos Varvagiannis, Voisin et al., 2019 (not yet in PubMed) describe de novo missense variants in the degron of AFF3 (a region required for its degradation) in 10 unrelated individuals with symptoms including ID. 4 different missense variants were identified (p.A258S, p.A258T, p.A258V and p.V260G). Although there are sufficient cases with a relevant phenotype, I have rated as Amber pending publication of the 2019 article: as OMIM note in their correspondance on AFF3, information changes from the initial bioRxiv upload to peer-reviewed publication. Therefore updated rating of AFF3 from Red to Amber, added 'watchlist' tag (in addition to missense tag), and will re-curate when the paper is published.; to: As noted by Konstantinos Varvagiannis, Voisin et al., 2019 (not yet in PubMed) describe de novo missense variants in the degron of AFF3 (a region required for its degradation) in 10 unrelated individuals with symptoms including ID. 4 different missense variants were identified (p.A258S, p.A258T, p.A258V and p.V260G). Although there are sufficient cases with a relevant phenotype (plus the individual reported in PMID:18616733), I have rated as Amber pending publication of the Voisin 2019 article: as OMIM note in their correspondance on AFF3, information changes from the initial bioRxiv upload to peer-reviewed publication. Therefore updated rating of AFF3 from Red to Amber, added 'watchlist' tag and 'missense' tag, and will re-curate when the paper is published. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.998 | PIGU | Rebecca Foulger commented on gene: PIGU: PIGU (together with other PIGx genes) were discussed with members of the GMS Neurology Specialist Test Group on the Webex call Thursday 8th August 2019 to discuss R59 Early onset or syndromic epilepsy. Agreed that there is enough evidence to rate PIGU Green on the 'Genetic epilepsy syndromes' panel (402). Therefore applied Green rating to the ID panel also: although PIGU is not yet associated with a disorder in OMIM or Gene2Phenotype, there are sufficient unrelated cases described in PMID:31353022. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.996 | AFF3 |
Konstantinos Varvagiannis changed review comment from: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article).; to: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- Shimizu et al. (8/2019 - PMID: 31388108) describe an additional individual with de novo AFF3 missense variant. The phenotype overlaps with that summarized by Voisin et al. incl. mesomelic dysplasia with additional skeletal anomalies, bilateral kidney hypoplasia and severe DD at the age of 2.5 years. Seizures and pulmonary problems were not observed. Although a different RefSeq is used the variant is among those also reported by Voisin et al. [NM_002285.2:c.697G>A (p.Ala233Thr) corresponding to NM_001025108.1:c.772G>A (p.Ala258Thr)]. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article). [Review modified to add additional reference/case report] |
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| Intellectual disability - microarray and sequencing v2.996 | WDR37 |
Konstantinos Varvagiannis gene: WDR37 was added gene: WDR37 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: WDR37 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: WDR37 were set to 31327510; 31327508 Phenotypes for gene: WDR37 were set to Global developmental delay; Intellectual disability; Seizures; Abnormality of the eye; Abnormality of nervous system morphology; Hearing abnormality; Abnormality of the cardiovascular system; Abnormality of the skeletal system; Abnormality of the genitourinary system Penetrance for gene: WDR37 were set to unknown Review for gene: WDR37 was set to GREEN Added comment: Two concurrent publications by Reis et al. and Kanca et al. (2019 - PMIDs: 31327510, 31327508) report on the phenotype of individuals with de novo WDR37 mutations. The study by Reis et al. provides clinical details on 4 affected individuals, while 5 further are described by Kanca et al. 4 different de novo variants were reported in these individuals who appear to be unrelated in (and between) the 2 studies [NM_014023.3]: - c.356C>T (p.Ser119Phe) [Reis indiv. 1 - 3y, Kanca proband 3 - 5m2w] - c.389C>T (p.Thr130Ile) [Reis indiv. 2 - 22m , Kanca proband 5 - 6w] - c.374C>T (p.Thr125Ile) [Reis indiv. 3 - 8y , Kanca proband 1 - 7y] - c.386C>G (p.Ser129Cys) [Reis indiv. 4 - unkn age, Kanca probands 2 and 4, 6.5y and 19y] Common features included DD/ID (severity relevant for the current panel), seizures (9/9), ocular anomalies (corneal opacity/Peters anomaly, coloboma, microphthalmia etc.) and variable brain, hearing, cardiovascular, skeletal and genitourinary anomalies. Some facial and/or other dysmorphic features (incl. excess nuchal skin / webbed neck) were also frequent among affected individuals. Feeding difficulties and growth deficiency were also among the features observed. The function of WDR37 is not known. Variants demonstrated comparable protein levels and cellular localization compared to wt. Reis et al. provide evidence using CRISPR-Cas9 mediated genome editing in zebrafish, to introduce the Ser129Cys variant observed in affected individuals as well as novel missense and frameshift variants. Poor growth (similar to the human phenotype) and larval lethality were noted for missense variants. Head size was proportionately small. Ocular (coloboma/corneal) or craniofacial anomalies were not observed. Zebrafish heterozygous for LoF variants survived to adulthood. Based on these a dominant-negative mechanism was postulated for missense alleles. RNA-seq analysis in zebrafish showed upregulation of cholesterol biosynthesis pathways (among the most dysregulated ones). Previous data in mice, suggest a broad expression pattern for Wdr37 with enrichment in ocular and brain tissues, significant associations in homozygous mutant mice for decreased body weight, grip strength, skeletal anomalies and possible increase (p =< 0.05) in ocular (lens/corneal) and other anomalies [BioGPS and International Mouse Phenotyping Consortium cited]. CG12333 loss (the Drosophila WDR37 ortholog) causes increased bang sensitivity in flies (analogous to the human epilepsy phenotype), defects in copulation and grip strength, phenotypes that were rescued by human reference but not variant cDNAs. As discussed by Kanca et al. based on data from Drosophila and mice, limited phenotypic similarity of CNVs spanning WDR37 and adjacent genes with the reported individuals and the presence of LoF variants in control populations haploinsufficiency appears unlikely. Gain-of-function is also unlikely, as expression of human variants in flies did not exacerbate the observed phenotypes. A dominant-negative effect is again proposed. WDR37 is not associated with any phenotype in OMIM/G2P. As a result WDR37 can be considered for inclusion in the ID and epilepsy panels with green (relevant phenotype, sufficient cases, animal models) or amber rating. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.965 | DEGS1 | Rebecca Foulger commented on gene: DEGS1: PMID:31186544: Dolgin et al., 2019 describe four individuals from a consanguineous family. All four had mild to severe ID, spastic quadriplegia, scoliosis and epilepsy in most. WES identified a homozygous missense variant in DEGS1 (in isoforms N219S, N255S). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.963 | ATN1 |
Catherine Snow changed review comment from: As reviewed on the Genetic epilepsy syndromes (Version 1.178). Advice from the clinical team was that as phenotype is relevant it can be rated as Green. Konstantinos Varvagiannis reviewed Palmer et al. (2019 - PMID: 30827498) who describes 8 individuals all with de novo variants in a specific and highly evolutionary conserved histidine-rich 16 amino acid motif encoded by exon 7 of ATN1. The pedigree analysis showed that all individuals are unrelated with different ancestry, all except one had undergone trio sequencing. All individuals have DD/ID and 5/8 have seizures therefore making it applicable to the epilepsy panel. ATN1 is in OMIM but is associated with the STR, it is in Gene2Phenotype as probable based on this paper. ATN1_CAG STR is Green in a large number of panels and there are a number of publications associated with the STR. This is the first publication where variants within the gene and not the STR have been associated with this phenotype; to: As reviewed on the Genetic epilepsy syndromes (Version 1.178). Advice from the clinical team was that as phenotype is relevant it can be rated as Green. Konstantinos Varvagiannis reviewed Palmer et al. (2019 - PMID: 30827498) who describes 8 individuals all with de novo variants in a specific and highly evolutionary conserved histidine-rich 16 amino acid motif encoded by exon 7 of ATN1. The pedigree analysis showed that all individuals are unrelated with different ancestry, all except one had undergone trio sequencing. All individuals have DD/ID. ATN1 is in OMIM but is associated with the STR, it is in Gene2Phenotype as probable based on this paper. ATN1_CAG STR is Green in a large number of panels and there are a number of publications associated with the STR. This is the first publication where variants within the gene and not the STR have been associated with this phenotype |
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| Intellectual disability - microarray and sequencing v2.951 | POU3F3 |
Konstantinos Varvagiannis gene: POU3F3 was added gene: POU3F3 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: POU3F3 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: POU3F3 were set to https://doi.org/10.1016/j.ajhg.2019.06.007; 24550763 Phenotypes for gene: POU3F3 were set to Generalized hypotonia; Delayed speech and language development; Global developmental delay; Intellectual disability; Autistic behavior Penetrance for gene: POU3F3 were set to unknown Review for gene: POU3F3 was set to GREEN gene: POU3F3 was marked as current diagnostic Added comment: Snijders Blok et al. (2019, DOI: https://doi.org/10.1016/j.ajhg.2019.06.007) report on 19 individuals with heterozygous POU3F3 variants. Features included hypotonia in some, DD/ID (19/19) with impairment in speech and language skills, and autism-like symptoms with formal ASD diagnosis in 7(/19). Epilepsy was reported for 2 individuals. Overlapping facial features were noted among these individuals. POU3F3 encodes a member of the class III POU family of transcription factors expressed in the central nervous system (Sumiyama et al. 1996, PMID: 8703082 cited in OMIM) and as the authors comment holds a role in regulation of key processes, eg. cortical neuronal migration, upper-layer specification and production and neurogenesis (PMIDs cited: 11859196, 12130536, 22892427, 17141158). In almost all subjects (17/19) the variant had occurred as a de novo event, while one individual had inherited the variant from a similarly affected parent. In total 12 nonsense/frameshift variants, 5 missense ones as well as 1 in-frame deletion were identified following (mostly) trio exome sequencing. All variants were absent from gnomAD, with in silico predictions in favour of pathogenicity. The few missense variants and the in-frame deletion were found either in the POU-specific (NM_006236.2:c.1085G>T / p.Arg362Leu found in 2 subjects) or the POU-homeobox domain (where 2 variants affected the same residue, namely p.Arg407Gly/Leu, the other variant was p.Asn456Ser). POU3F3 is an intronless gene and as a result truncating variants are not subject to NMD. The gene appears to be intolerant to LoF variants (pLI of 0.89 in gnomAD). Western blot analysis of YFP-tagged POU3F3 variants (in HEK293 cell lysates) showed that the YFP-fusion proteins were expressed and had the expected molecular weights. For several truncating variants tested as well as the in-frame deletion, aberrant subcellular localization pattern was demonstrated although this was not the case for 4 missense variants. In vitro studies were carried out and suggested that POU3F3, as is known to be the case for POU3F2, is able to activate an intronic binding site in FOXP2. Using a luciferase assay, transcriptional activation was severely impaired for truncating variants tested, significantly lower for many missense ones with the exception of those affecting Arg407 in which case luciferase expression was either similar to wt (for Arg407Gly) or even increased in the case of Arg407Leu. As the authors comment, both loss- and gain- of function mechanisms may underly pathogenicity of variants. The ability of mutant proteins to form dimers either with wt or themselves was tested. Dimerization capacity was intact for most missense variants but was lost/decreased for truncating variants. The in-frame deletion resulted in impaired dimerization with wt, although homo-dimerization was found to be normal. --- Dheedene et al. (2014 - PMID: 24550763) had previously reported on a boy with ID. aCGH had demonstrated a de novo 360-kb deletion of 2q12.1 spanning only POU3F3 and MRPS9 the latter encoding a mitochondrial ribosomal protein (which would be most compatible with a - yet undescribed - recessive inheritance pattern / disorder). --- POU3F3 is not associated with any phenotype in OMIM/G2P. The gene is included in gene panels for ID offered by some diagnostic laboratories (incl. Radboudumc, among the principal authors of the study). --- As a result POU3F3 seems to fulfill criteria for inclusion in the current panel probably as green [DD/ID was a universal feature - severity of ID was relevant in 5/10 individuals for whom details were available, functional evidence provided] or amber. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.935 | USP7 | Rebecca Foulger Added comment: Comment on list classification: USP7 was rated Green by Konstantinos Varvagiannis. Not currently associated with a disorder in OMIM, but has a 'possible' Disease confidence in Gene2Phenotype for the disorder: Intellectual disability, autism, epilepsy, aggressive behaviour, hypotonia, and hypogonadism (based on PMID:26365382). There is now a 2019 paper in addition to PMID:26365382 (PMID:30679821). In total, 22/23 individuals have an ID/DD phenotype, and 23/23 have speech delay. However, the Tyr143Ter variant described by both PMID:26365382 and PMID:30679821 is a VUS, and the microdeletions in other patients cover additional genes (PMID:26365382, Figure 5). Plus three patients in PMID:30679821 harbour variants in additional genes. Therefore although the phenotype is relevant, I have updated the rating from Red to Amber until there is more evidence that USP7 variants are causative. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.903 | CSNK2B | Rebecca Foulger commented on gene: CSNK2B: PMID:30655572: Nakashima et al, 2019 describe 4 patients with ID, DD and seizures. Two of the patients had variants in CSNK2B: c.533_534insGT, p.(Pro179Tyrfs*49) in Malaysian Patient 3, and c.494A>G, p.(His165Arg) in Japanese Patient 4. Both had seizures within 2 months of age. Both variants occurred de novo. In each patient, only 1 likely candidate variant was proposed. Functional assays suggested that Pro179Tyrfs*49 mutant protein was produced but showed disrupted interaction with CSNK2A1. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.893 | ITPA | Ivone Leong Added comment: Comment on list classification: Promoted from red to green. ITPA is associated with a phenotype in OMIM but not in Gene2Phenotype. There are 5 unrelated families (PMID: 26224535, 30816001) with affected individuals who have global developmental delay with different variants in ITPA. PMID: 19498443 describes a knockout mouse model of Itpa, which had growth retardation. Therefore, there is enough evidence to promote this gene to green status. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.811 | TCF20 | Rebecca Foulger Added comment: Comment on list classification: Updated rating from Amber to Green following recent external review by Konstantinos Varvagiannis (Dec 2018 and Feb 2019). The Torti et al., 2019 article (PMID:30739909) describes 27 individuals from 24 families with novel TCF20 variants. All 27 individuals had developmental delay/intellectual disability (DD/ID). Together with the individual in PMID:30525188 (Snoeijen-Schouwenaars et al 2019, Supplementary Table 2) and the additional evidence listed by Konstantinos Varvagiannis, these papers provide additional cases since the Amber rating in July 2018, and support that ID is a consistent feature amongst TCF20 patients. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.800 | ZNF142 |
Konstantinos Varvagiannis gene: ZNF142 was added gene: ZNF142 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZNF142 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ZNF142 were set to 31036918 Phenotypes for gene: ZNF142 were set to Global developmental delay; Intellectual disability; Seizures; Tremor; Dystonia Penetrance for gene: ZNF142 were set to unknown Review for gene: ZNF142 was set to GREEN Added comment: Khan et al. (2019 - PMID: 31036918) describe the phenotype of 7 females from 4 families, harboring biallelic likely pathogenic ZNF142 variants. Overlapping features included cognitive impairment (ID in 6/7 from 3 families, borderline intellectual functioning was reported one occasion), speech impairement and motor impairment (7/7), and variably penetrant seizures (5/7), tremor (4/7) and dystonia (3/7). Most individuals (5/7) had experienced at least one episode of seizures (tonic-clonic) though seizures were recurrent in 3 sibs. Other disorders with ID (eg. Angelman syndrome, Rett syndrome, chromosomal disorders) or movement disorders as a feature were previously ruled out for many subjects. 6 individuals were homozygous or compound heterozygous for LoF (stopgain or frameshift) variants. One individual harbored 2 missense SNVs in the compound heterozygous state. Variants reported include (NM_001105537.2): c. 817_818delAA (p.Lys273Glufs*32), c.1292delG (p.Cys431Leufs*11), c.3175C>T (p.Arg1059*), c.4183delC (p.Leu1395*), c.3698G>T (p.Cys1233Phe), c.4498C>T (p.Arg1500Trp) with the LoF variants predicted to result in NMD. Expression or functional studies were not carried out. ZNF142 encodes a C2H2 domain-containing transcription factor. Mutations in other zinc finger proteins (ZNF/zfp) have been reported in several neurodevelopmental disorders impacting the CNS (eg. ZBTB20 and ZBTB11 heterozygous and biallelic mutations, respectively) and/or presenting with movement disorders among their manifestations (eg. YY1). As the authors comment, homozygous ablation of the orthologous (Zfp142) locus in mice results in behavioral and neurological phenotypes [MGI ref.ID: J:211773 cited - http://www.informatics.jax.org/marker/reference/J:211773 (though Zfp142 or its locus do not seem to appear in the list)]. ZNF142 is not - at least commonly - included in gene panels for ID offered by diagnostic laboratories. It is not associated with any phenotype in OMIM, nor in G2P. As a result, this gene can be considered for inclusion in the current panel as probably as green (individuals from 3 families, appropriate degree of ID for the current panel) or amber (if further evidence would be required). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.742 | WARS2 |
Konstantinos Varvagiannis gene: WARS2 was added gene: WARS2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: WARS2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: WARS2 were set to 28236339; 28650581; 28905505; 29783990; 29120065 Phenotypes for gene: WARS2 were set to Neurodevelopmental disorder, mitochondrial, with abnormal movements and lactic acidosis, with or without seizures, 617710 Penetrance for gene: WARS2 were set to unknown Review for gene: WARS2 was set to GREEN gene: WARS2 was marked as current diagnostic Added comment: Several individuals with biallelic pathogenic WARS2 variants have been published to date. DD and ID have been reported among others in most of the affected individuals (only the respective features are commented on below): PMID: 28236339 (Musante et al. 2017) : 2 sibs compound heterozygous for NM_201263.2:c.325delA (p.Ser109Alafs*159) and c.37T>G (p.Trp13Gly). DD with ID were features in both. PMID: 28650581 (Theisen et al. 2017) : The authors report on 1 individual with DD, ID and seizures was found to harbor in the compound heterozygous state NM_0158360.3:c.938A>T (p.K313M) and c.298_300delCTT (p.L100del). PMID: 28905505 (Wortmann et al. 2017) : Details on 6 individuals from 5 unrelated families are provided. DD and ID were observed in 5 of these individuals (Fam 2-5). Severe, neonatal presentation was the case for an additional subject. Confirmed occurrence of epilepsy was reported for 3 individuals from 2 families (and suspected in a further one). Using NM_0158360.3 variants were the following : Fam1 : c.91-8725_348+27113del36096 (p.Lys31_Glndel116) in trans with c.1045G>C (p.Val349Leu) Fam2 : c.797del (p.Pro266Argfs*10) in trans with c.938A>T (p.Lys313met) [in 2 individuals] Fam3 : c.231C>G (p.His77Gln) in trans with c.1054G>A (p.Glu352Lys) Fam4 : c.532G>C (p.Val178Leu) in homozygous state Fam5 : c.134G>T (p.Gly45Val) in trans with c.938A>T (p.Lys313Met) PMID: 29783990 (Vantroys et al. 2018) : The authors report on 1 individual with DD, ID and seizures (among other features), compound heterozygous for c.797del (p.Pro266Argfs*10) and c.938A>T (p.Lys313met), similar to subjects from family 2 in PMID: 28905505. PMID: 29120065 (Burke et al. 2018) : One 17-year-old boy with infantile-onset Parkinsonism but not DD/ID is described in this study. This individuals was found to harbor in the following variants in the compound heterozygous state: NM_015836.3: c.37T>G (p.Trp13Gly) and c.683C>G (p.Ser228Trp). Probably 7 missense variants, 3 frameshift ones and an intragenic deletion have been reported in individuals with DD/ID (overview in fig 4. - in PMID: 29783990). - p.Pro266Argfs*10 is located in the last exon of the gene (NM_015836.3). - p.Trp13Gly (c.37T>G using either NM_201263.2 or NM_015836.3 as ref) has been commented to be a functional polymorphism 'uncovered' by the presence of a LoF allele in trans in affected individuals (AF : 0.003265 and 6 homozygotes in gnomAD) - p.Lys313Met is possibly the most frequently reported variant as discussed by Vantroys et al. WARS2 encodes mitochondrial tryptophanyl-tRNA synthetase (a cytoplasmic form is encoded by WARS). As commented in most of the articles, aminoacyl-tRNA synthetases (ARS) are a group of enzymes responsible for ligating amino acids to cognate tRNA molecules. Mutations in mitochondrial ARSs lead to impaired intramitochondrial translation affecting OXPHOS complexes (with mitochondrial-encoded subunits). Mutations in all 19 mitochondrial ARSs have been linked to disorders affecting different organ systems with variable severity and phenotypic presentation (summarized by Vantroys et al.). Several lines of evidence have been provided to support a role for specific variants (eg. reduced WARS2 amounts upon Western blot, or impaired mitochondrial localization depending on the different variants and their effect) or WARS2 (expression in brain, impaired aminoacylation, abnormalities in OXPHOS enzymes/biosynthesis , etc). Alternative causes (disorders of the differential diagnosis) have been ruled out on most - if not all - occasions. As commented by Wortmann et al. the clinical spectrum appears to be broad as for the age of onset, features and clinical course (as happens to be the case for some other disorders due deficiencies of other ARSs). The same authors state that apart from elevated lactate which is suggestive of mitochondrial dysfunction, no specific metabolite was found to be altered in affected individuals. Phenotypic variability even between individuals with the same genotype has been reported. Eg. severe neonatal presentation with lactic acidosis/hypoglycaemia was the case for 2 sibs in family 2 from Wortmann et al. but the clinical course was different for the subject reported by Vantroys et al. (DD/ID with seizure onset at the age of 6 yrs). As a result, investigations (and selection of gene panel) may not be straightforward. In addition consideration of this gene in the epilepsy panel seems to be relevant given that seizures were noted in at least 5 individuals (from 4 families - 28650581, 28905505, 29783990) and severe adverse effects of valproate administration occurred in the subject reported by Vantroys et al. ----------- The associated phenotype in OMIM is Neurodevelopmental disorder, mitochondrial, with abnormal movements and lactic acidosis, with or without seizures (# 617710). WARS2 is not associated with any disorder in G2P. This gene is included in panels for ID offered by some diagnostic laboratories. ----------- As a result, WARS2 can be considered for inclusion in the ID and epilepsy panels as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.740 | ITCH | Ivone Leong Added comment: Comment on publications: PMID: 20170897 describes a large Amish family with 10 affected individuals from 8 consanguineous and related families with multisystem autoimmune disease with facial dysmorphism. The affected individuals have organomegaly, failure to thrive, developmental delay, dysmorphic features, and autoimmune inflammatory cell infiltration of the lungs, liver, and gut. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.689 | NECAP1 | Ivone Leong Added comment: Comment on list classification: NECAP1 has been given an amber gene rating based on the evidence provided by Konstantinos Varvagiannis. As patients from the cases described in PMID: 24399846, 30525121 are from Saudi Arabia and have the same variant, these are counted as a single piece of evidence. Therefore, there are not enough evidence to promote this gene to a green rating at this stage. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.650 | KCNQ3 | Ivone Leong Added comment: Comment on list classification: Promoted from amber to green, based on the expert reviews already provided. There are also >3 unrelated cases of patients with different variants in the KCNQ3 gene who have the described phenotype. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.646 | KCNK4 | Ivone Leong Added comment: Comment on list classification: Given an amber rating as there is currently only one report detailing 3 unrelated patients (2 Italian and 1 of European ancestry) who have variants (2 patients have the same missense variant and the third patient has a different missense variant). The paper also describe some in vitro cell studies. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.611 | CYFIP2 |
Konstantinos Varvagiannis gene: CYFIP2 was added gene: CYFIP2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CYFIP2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CYFIP2 were set to 29534297; 29667327; 30664714; 25432536; 27524794; 12818175; 20537992 Phenotypes for gene: CYFIP2 were set to Epileptic encephalopathy, early infantile 65, 618008 Penetrance for gene: CYFIP2 were set to unknown Review for gene: CYFIP2 was set to GREEN gene: CYFIP2 was marked as current diagnostic Added comment: Heterozygous pathogenic variants in CYFIP2 cause Epileptic encephalopathy, early infantile, 65 (MIM 618008) -------------- [Apologies for any eventual mistakes esp.as for the functional evidence]: Nakashima et al. (2018 - PMID: 29534297) report on 4 unrelated individuals with early-onset epileptic encephalopathy due to de novo missense CYFIP2 variants. The phenotype consisted of early-onset intractable seizures (diagnosis of West syndrome in 2, Ohtahara syndrome in further individuals) with hypotonia (3/4), DD/ID (4/4) and microcephaly (3/4). All variants affected Arg87 residue (NM_001037333.2:c.259C>T or p.Arg87Cys in 2 individuals, the 2 other subjects harbored Arg87Leu and Arg87Pro respectively). CYFIP2 encodes the cytoplasmic FMRP interacting protein 2. CYFIP2 (similar to CYFIP1) is a component of the WAVE regulatory complex (WRC) which has been shown to play a role in actin remodeling, axon elongation, dendritic morphogenesis and synaptic plasticity (several PMIDs cited). In the inactive state of the WRC complex, CYFIP2 binds to the VCA domain of WAVE. GTP-bound Rac1 (GTPase) leads to release of the VCA domain from CYFIP2 which allows binding of this domain to the Arp2/3 complex (active WRC state) and in turn stimulates actin polymerization and lamellipodia formation. Using lymphoblastoid cell lines from affected individuals and healthy controls and CYFIP2 expression was evaluated by Western Blot and was found to be similar between the 2 groups. Additional studies suggested weaker binding of the WAVE1 VCA domain to mutant CYFIP2 compared to WT CYFIP2 (upon transfection of HEK293T cells). This could possibly favor activation of WRC (/the WAVE signalling pathway). As a result a gain-of-function effect on the WAVE signalling pathway is suggested as a possible mechanism. Using B16F1 mouse melanoma cells lamellipodia formation (process in which CYFIP2 has previously been implicated) was not shown to be impaired in the case of mutant CYFIP2. However aberrant accumulation of F-actin (and co-localization with mutant CYFIP2) was observed in the present study. Only large 5q deletions spanning CYFIP2 (and several other genes) have been described to date. Cyfip2 heterozygous knockout in mice results in abnormal behavior and memory loss. WAVE activity was enhanced (despite reduced WAVE protein production). Homozygous Cyfip2 loss is lethal (PMIDs cited by the authors: 25432536, 27524794). Impaired axonal growth, guidance and branching is noted in Drosophila mutants (CYFIP1/2 ortholog) (PMID cited: 12818175). The authors comment that Cyfip2 (nev) mutant zebrafish show a similar phenotype to mutant flies (PMID cited: 20537992). -------------- Peng et al. (2018 - PMID: 29667327) in a study of 56 Chinese families with West Syndrome (epileptic/infantile spasms, hypsarrhytmia and ID) identified 1 individual with the Arg87Cys CYFIP2 variant as a de novo occurrence. -------------- Zweier et al. (2019 - DDD study among the co-authors - PMID: 30664714) report on 12 unrelated subjects with heterozygous pathogenic de novo CYFIP2 variants. The common phenotype consisted of tone abnormalities (12/12), DD/ID (12/12) and seizures (12/12 though a single individual had experienced a single episode of febrile seizure). Absolute or relative microcephaly and/or additional features were also noted in several individuals. 7 missense variants (4 occurrences of the Arg87Cys variant) as well as splice variant (shown to lead to exon skipping) are reported, as de novo events in these individuals. The splice variant was expected to escape NMD producing a truncating protein. Although the variants are distantly located in the primary structure, spatial clustering (in the tertiary structure) is suggested by in silico modelling (all in proximity at the CYFIP2-WAVE1 interface). CYFIP2 appears to be intolerant to both missense and LoF variants (Z-score of 6.15 and pLI of 1 respectively in ExAC). The authors comment that haploinsufficiency as a mechanism is rather unlikely given the absence of small CNVs or variants predicted to lead to NMD. Again, a gain-of-function effect of these variants on WAVE activation (partial-loss-of function in terms of WRC stabilization and/or conformation of the VCA region in the inactive state) is proposed. -------------- CYFIP2 is not associated with any phenotype in G2P. The gene is included in gene panels for intellectual disability offered by some diagnostic laboratories (eg. participants in these studies). -------------- As a result this gene could be considered for inclusion in this panel as green. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.595 | NUS1 |
Konstantinos Varvagiannis gene: NUS1 was added gene: NUS1 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: NUS1 was set to BOTH monoallelic and biallelic (but BIALLELIC mutations cause a more SEVERE disease form), autosomal or pseudoautosomal Publications for gene: NUS1 were set to 25066056; 29100083; 24824130; 30348779 Phenotypes for gene: NUS1 were set to #617082 - ?Congenital disorder of glycosylation, type 1aa; #617831 - Mental retardation, autosomal dominant 55, with seizures; Abnormality of extrapyramidal motor function Penetrance for gene: NUS1 were set to unknown Review for gene: NUS1 was set to AMBER gene: NUS1 was marked as current diagnostic Added comment: Mutations in NUS1 have been implicated in recessive as well as dominant forms of ID (1 and 3 unrelated individuals respectively). The latter individuals presented with a developmental and epileptic encephalopathy with ID. At least 2 of these individuals had tremor and other movement disorders. A recent study proposes that NUS1 variants contribute to Parkinson's disease (1 individual with de novo variant affecting the canonical splice site, 26 additional individuals with missense variants - for which segregation studies where not however performed). ID is not commented on for these individuals. NUS1 is included in the DD panel of G2P, associated with "Epilepsy and intellectual disability". (Monoallelic LoF variants / Disease confidence : probable). This gene is included in gene panels for ID offered by diagnostic laboratories (incl. Radboudumc). Associated phenotypes in OMIM and others discussed in the literature are summarized below (to my understanding). As a result, NUS1 can be considered for inclusion in the ID panel probably as amber. -------- Recessive - [MIM #617082 - ?Congenital disorder of glycosylation, type 1aa] : Park et al. (2014 - PMID: 25066056) report on an individual homozygous for a NUS1 missense variant (R290H) and suggest that biallelic variants cause a congenital disorder of glycosylation. The authors based in studies in yeast, mice and man provide evidence that NUS1 encodes the Nogo-B receptor (NgBR), a subunit of cis-prenyltransferase (cis-PTase), important for its activation. cis-PTase catalyzes one of the reactions for dolichol biosynthesis. Dolichol, in turn, is a carrier of glycans for N-linked glycosylation, O-mannosylation and GPI anchor biosynthesis. Genetic defects in the dolichol biosynthetic pathway have been linked to other forms of CDG and/or other recessive or dominant neurodevelopmental disorders (eg. SRD5A3- and DHDDS-related disorders). Similarities are provided at the cellular level between different organisms. Heterozygous knockout mice appear normal. Homozygosity is associated with embryonic lethality before E6.5. Conditional knockout in mouse embryonic fibroblasts led to accumulation of free cholesterol, decreased cis-PTase activity, and mannose incorporation in protein (the first & third rescued by transduction with lentiviral human NgBR). In patient fibroblasts protein levels appeared similar to controls. Interaction with Nogo-B (and hCIT - the product of DHDDS) was not affected. As in mice, accumulation of free cholesterol was observed in cells, with decreased cis-PTase activity and mannose incorporation. LAMP-1 and ICAM-1 were hypoglycosylated in patient fibroblasts. Altered dolichol profiles in serum and urine were observed in carriers of the NUS1 variant, similarly to what described in individuals with DHDDS LoF variants. ---------- Dominant - [MIM #617831 - Mental retardation, autosomal dominant 55, with seizures]. Hamdan et al. (2017 - PMID: 29100083) report on 3 unrelated individuals with developmental and epileptic encephalopathy (onset: 10m - 2.5y) and ID. Two individuals harbored de novo LoF variants while a third subject had a deletion of exon 2. Movement disorders were noted in all 3 and included tremor (2 subjects) or ataxia (1 additional subject). The authors cite a previous study on 6q22.1 deletions the critical region of which encompassed only NUS1 and the promoter of SLC35F1 (Szafranski et al. - PMID: 24824130). Haploinsufficiency is discussed as a possible mechanism (pLI of 0.87). A more severe phenotype due to dramatic reduction of NUS1 activity is proposed for the previously reported patient with CDG. ---------- Other: Guo et al. (2018 - PMID: 30348779) suggest that NUS1 pathogenic variants contribute to Parkinson's disease. By performing WES in 39 individuals with early onset Parkinson's disease and their unaffected patients (and sibs) the authors identified 1 individual with de novo insertion affecting a NUS1 canonical splice site. RT-PCR demonstrated increased mRNA levels compared with controls. Skipping of 91 bp of exon 3 was demonstrated. Study in 2 large sporadic PD-patient (N=1852+3237)/control cohorts (N=1565+2858) suggested association between NUS1 non-synonymous variants and PD (P=1.01e-5, OR:11.3). Other genetic causes of PD were excluded in 26 additional individuals with NUS1 missense variants. Phenotypes of all 27 individuals are provided in Dataset_S04. NUS1 has been found to be differentially expressed in PD mouse models. RNAi-mediated knockdown of Tango14 (the Drosophila NUS1) resulted in impaired climbing activity, reduction in brain dopamine levels and abnormal apoptotic signals in brain. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.588 | PTRH2 |
Konstantinos Varvagiannis gene: PTRH2 was added gene: PTRH2 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PTRH2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PTRH2 were set to 25574476; 27129381; 25558065; 28328138; 28175314 Phenotypes for gene: PTRH2 were set to Infantile-onset multisystem neurologic, endocrine, and pancreatic disease (MIM 616263) Penetrance for gene: PTRH2 were set to Complete Review for gene: PTRH2 was set to GREEN gene: PTRH2 was marked as current diagnostic Added comment: Biallelic pathogenic variants in PTRH2 cause Infantile-onset multisystem neurologic, endocrine, and pancreatic disease (MIM 616263). Several affected individuals have been reported to date. ID was a feature in the majority. Hu et al. (2014 - PMID:25574476) reported on 2 sibs born to consanguineous Yazidian-Turkish family, homozygous for a frameshift variant [NM_016077.4(PTRH2):c.269_270delCT (p.Ala90Glyfs)]. In PMID: 27129381 (2016) the same group reported on 5 additional individuals, from 2 unrelated consanguineous (Tunesian / Saudi-Arabian) pedigrees. These subjects were homozygous for a missense variant [NM_016077.4(PTRH2):c.254A>C (p.Gln85Pro)]. A summary of the features observed in all 7 cases is provided in table 1 of the latter article. ID was a feature in all 6 individuals for whom this information was available (6/7). Phenotypic variability even among individuals with the same variant is underscored. mRNA studies for both variants have shown similar levels compared to controls, with reduced protein upon Western blot (for both). In Ptrh2-null mouse model a similar to the human phenotype is observed (muscle weakness and wasting, ataxia, cerebelar atrophy, etc.) (PMIDs:25574476 and 28175314). Alazami et al. (PMID: 25558065 - 2015) report on an additional individual homozygous for the p.Gln85Pro variant. This boy presented with intellectual disability (clinical details provided in the supplement). Sharkia et al. (PMID: 28328138) describe 3 sibs homozygous for the p.Gln85Pro variant. The index patient was reported to have normal intelligence upon formal testing which also appeared to be the case for her 2 sisters. Apart from the 2 variants observed in the published patients, 2 further variants have been submitted in ClinVar as likely pathogenic, namely : NM_016077.4(PTRH2):c.253C>T (p.Gln85Ter) and NM_001015509.2(PTRH2):c.114dup (p.Gly39Trpfs). PTRH2 is not associated with any phenotype in G2P. This gene is included in gene panels for intellectual disability offered by diagnostic laboratories (incl. Radboudumc). As a result it can be considered for inclusion in the ID panel as green (or amber). [As several individuals presented with ataxia, demyelinating sensorimotor neuropathy, sensorineural hearing loss and other possibly relevant phenotypes, consider inclusion in the respective gene panels]. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.584 | AIMP2 |
Konstantinos Varvagiannis gene: AIMP2 was added gene: AIMP2 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: AIMP2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: AIMP2 were set to 29215095 Phenotypes for gene: AIMP2 were set to Leukodystrophy, hypomyelinating, 17 (MIM 618006) Penetrance for gene: AIMP2 were set to Complete Review for gene: AIMP2 was set to AMBER gene: AIMP2 was marked as current diagnostic Added comment: Biallelic pathogenic variants in AIMP2 cause Leukodystrophy, hypomyelinating, 17 (MIM 618006). 3 individuals from 2 unrelated consanguineous families, of Indian origin have been reported (all in PMID: 29215095). The phenotype consisted of feeding difficulties, lack of development with intellectual disability and seizures as well as brain MRI abnormalities (cerebral and cerebellar atrophy, hypo-intensities of the basal ganglia on T2w sequences). Severe microcephaly was observed in 2 patients for whom this information was available (birth measurements not specified). All patients described to date were homozygous for a nonsense variant [NM_006303.3:c.105C>A or p.(Tyr35Ter)] which appears to be a founder mutation in this population. Quantitative reverse transcription PCR demonstrated reduced mRNA levels in peripheral lymphocytes, but this decrease was not significant compared to controls (the authors presume low level of NMD). Previous mouse models provide some - but not substantial - support. The authors note marked similarity with the phenotype associated with AIMP1 (Leukodystrophy, hypomyelinating, 3 - MIM 260600), another auxiliary protein of the macromolecular multienzyme multi-tRNA synthetase complex. AIMP1 is listed in the current panel as green. AIMP2 is not associated with any phenotype in G2P. This gene is included in gene panels for ID offered by some diagnostic laboratories (incl. Radboudumc). As a result, AIMP2 can be considered for inclusion in this panel probably as amber. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.579 | PUS3 |
Konstantinos Varvagiannis gene: PUS3 was added gene: PUS3 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PUS3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PUS3 were set to 27055666; 30308082 Phenotypes for gene: PUS3 were set to Global developmental delay; Intellectual disability; Microcephaly Penetrance for gene: PUS3 were set to Complete Review for gene: PUS3 was set to AMBER gene: PUS3 was marked as current diagnostic Added comment: PUS3 (Pseudouridylate synthase 3) is proposed as a gene related to ID in a recent publication on PUS7. Biallelic mutations in this gene are associated in OMIM with ?Mental retardation, autosomal recessive 55 (MIM 617051). PMID: 27055666 reports on 3 sisters from a consanguineous Saudi Arabian family with failure to thrive, DD/ID, microcephaly and some common (coarse) facial features. These individuals were homozygous for a stopgain mutation in the last exon of the gene. Pseudouridylation appeared to be defective (as has also been the case with other genes related to ID, eg. PUS7). PMID: 30308082 describes 1 individual born to consanguineous Palestinian parents, homozygous for a further LoF variant. Despite the localisation of this variant (again in the last exon of the gene) qPCR analyses were suggestive of degradation of the abnormal transcript possibly by NMD. The phenotype consisted of DD/ID and microcephaly. In a further publication (http://dx.doi.org/10.7124/bc.0008D6) Gulkovskyi et al. report on 2 siblings with ID, born to non-consanguineous Ukranian parents. Pathogenicity of the variant is disputed. [NM_031307.4:c.212A>G or p.(Tyr71Cys) is found in an apparent homozygous state in the sibs but was only found in their father. De novo occurence in the maternal allele is proposed although the possibility of microdeletion missed by aCGH or other plausible mechanisms are not considered. This variant has maximum pathogenicity scores in silico (not discussed) and has an allele frequency of 0.00006717 in gnomAD. The authors did not perform studies of pseudouridylation but examined for the presence of hypoproteinemia, observed in some disorders affecting this process). PUS3 is not associated with any phenotype in G2P but is associated with disease in OMIM. The gene is included in gene panels for ID offered by various diagnostic laboratories (including Radboudumc). PUS1 is included in the current panel as green and PUS7 has been suggested for inclusion. As a result, these gene can be considered for inclusion as amber (2 families) or green (given the supportive functional studies and/or the proposed role for the gene). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.579 | METTL23 |
Konstantinos Varvagiannis gene: METTL23 was added gene: METTL23 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: METTL23 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: METTL23 were set to 24501276; 24626631 Phenotypes for gene: METTL23 were set to Mental retardation, autosomal recessive 44 (MIM 615942) Penetrance for gene: METTL23 were set to Complete Review for gene: METTL23 was set to GREEN gene: METTL23 was marked as current diagnostic Added comment: Biallelic pathogenic variants in METTL23 cause Mental retardation, autosomal recessive 44 (MIM 615942). Reiff et al. (PMID: 24501276) report on a consanguineous pedigree of Yemeni origin with 7 individuals presenting intellectual disability. Clinical details are provided for 3 subjects from one branch of the family. Findings included moderate (2/3) or severe (1/3) ID, seizures (2/3) and some common facial features. Seizures were not observed in individuals from other branch of the family. The affected individuals were homozygous for a 4-bp deletion. Bernkopf et al. (PMID: 24626631) report on a consanguineous family from Pakistan with 2 affected sibs as well as a non-consanguineous family from Austria with 4 affected sibs. The parents in the latter family originated from a small - geographically isolated - village. Individuals from the Pakistani family were homozygous for a nonsense variant, while the sibs from the Austrian family for a frameshift variant. Mild ID was noted in all. In total 3 different LoF variants have been reported. Extensive functional studies have been performed in both articles. METTL23 (methyltransferase like 23) is expressed at low-to-moderate levels in the developping human brain. Bernkopf et al. suggest that METTL23 is indeed a methyltransferase. The gene has 7 transcripts of which one is non-coding. 3 transcripts encode isoform 1 and 3 other encode isoform 2. The variant reported by Reiff et al. affects the coding region of 3 (of the 6 coding) transcripts (corresponding to isoform 1) and the 5'-UTR of the other 3 transcripts. It is however shown that this first coding exon (specific to isoform 1) is expressed in the developing human brain, though at lower levels than downstream exons common to both isoforms. In addition, only isoform 1 appears to be conserved in most other species. The variants described by Bernkopf et al. affect all 6 coding trancripts and as a result both isoforms. [However, the individuals reported by Bernkopf et al. were less severely affected compared to those reported by Reiff et al.] Nonsense-mediated decay appeared unlikely since mRNA levels for both isoforms in lymphoblasts from affected individuals were similar to controls (upon qRT-PCR) [The specific nonsense variant tested would be expected to be subject to NMD given its localization]. METTL23 is not associated with any phenotype in G2P. This gene is included in gene panels for intellectual disability offered by various diagnostic laboratories. As a result, METTL23 can be considered for inclusion in the ID panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.579 | MAST1 |
Konstantinos Varvagiannis gene: MAST1 was added gene: MAST1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MAST1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: MAST1 were set to 30449657; 28135719; 25666757; 27479843 Phenotypes for gene: MAST1 were set to Global developmental delay, Intellectual disability, Abnormality of the corpus callosum, Cerebellar hypoplasia, Abnormality of the cerebral cortex, Seizures; Global developmental delay, Intellectual disability, Microcephaly, Autism, Seizures Penetrance for gene: MAST1 were set to unknown Review for gene: MAST1 was set to GREEN gene: MAST1 was marked as current diagnostic Added comment: PMID: 30449657 reports on 6 unrelated individuals with de novo mutations in MAST1. All these 6 individuals were investigated for a strikingly similar phenotype of enlarged corpus callosum (CC), cerebellar hypoplasia, cortical malformation with associated DD/ID. Seizures were a feature in 2/6 (one further had EEG anomalies without clinical seizures). Three of them harbored an in-frame deletion of 1 amino-acid (3 different indels reported - all in a specific domain) while 3 others had a missense variant (NM_014975.2:c.1549G>A or p.Gly517Ser). Mast1 has embryonic expression in murine models with postnatal decrease. Similarly qPCR of human fetal brain cDNA demonstrated expression at 13 and 22 gestational weeks. A murine model for L278del recapitulated the brain (incl. CC) and cerebellar phenotype while Mast1 knockout mice do not present similar morphological defects. While Western blot in murine brain lysates demonstrated absence of Mast1 in knockout and reduction in the L278del, Mast1 transcript levels for L278del were similar to wildtype. Other Mast proteins (Mast1 & Mast2) were significantly reduced upon western blot while this was not reflected in their mRNA levels, suggesting a dominant-negative effect, at least for the L278del. 4 additional individuals with somewhat different phenotype consisting DD/ID and microcephaly/autism are described in the supplement. All 4 had de novo missense variants but did not display the CC-cerebral and cerebellar anomalies. Four different (additional to Gly517Ser) missense SNVs were observed. Several additional individuals exist in the denovo-db (among others DDD participant DDD4K.02310 published in 28135719, 25666757 - McMichael et al. commented in the article, 27479843, etc.). [http://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=Mast1] Epilepsy was a feature in 4/10 individuals (with an additional one with EEG anomalies without clinical seizures). One further individual from PMID:23934111 (in denovo-db) had seizures. As the authors comment (and as evident from the 6+4 reported patients) the related neurodevelopmental phenotype may be more complex. MAST1 is not related to any phenotype in G2P, nor in OMIM. The gene is included in gene panels for ID offered by different diagnostic laboratories. As a result, this gene can be considered for inclusion in this panel as green. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.579 | RPIA |
Konstantinos Varvagiannis gene: RPIA was added gene: RPIA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: RPIA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: RPIA were set to 14988808; 20499043; 28801340; 30088433 Phenotypes for gene: RPIA were set to Ribose 5-phosphate isomerase deficiency, MIM 608611. Penetrance for gene: RPIA were set to unknown Review for gene: RPIA was set to GREEN gene: RPIA was marked as current diagnostic Added comment: Biallelic pathogenic variants in RPIA cause Ribose 5-phosphate isomerase deficiency, MIM 608611. PMID: 14988808 is the first report on the disorder with molecular (incl. genetic) confirmation of the diagnosis. A patient initially investigated for early developmental delay, leukoencephalopathy, seizures with onset at 4 years, with subsequent neurologic regression and peripheral neuropathy at the age of 7, was suspected to have a disorder of the pentose phosphate pathway on the basis of highly elevated polyols on brain MRS and body fluid analysis. Reduced ribose 5-phosphate isomerase activity was shown in fibroblasts. Genetic testing demonstrated the presence of a missense (NM_144563.2:c.404C>T / NP_653164.2:p.Ala135Val - previously referred to as A61V) as well as a frameshift variant (NM_144563.2:c.762delG / NP_653164.2:p.Asn255Ilefs). Additional extensive supportive functional studies were published a few years later (PMID: 20499043). [This patient was initially described in PMID: 10589548]. PMID: 28801340 is a report on a second patient. This individual presented with delayed early development (independent walking and speech achieved at 2 and 5 years respectively), seizures and regression at the age of 7 with MRI white matter abnormalities. Review of magnetic resonance spectroscopy (MRS) was suggestive of elevated polyols (arabitol and ribitol). In line with this, genetic testing revealed a homozygous missense variant in RPIA (NM_144563.2:c.592T>C or p.Phe198Leu). Urine analysis confirmed elevated excretion of polyols, thus confirming the diagnosis. PMID: 30088433 reports on a boy with neonatal onset leukoencephalopathy and developmental delay having undergone early metabolic testing and aCGH (the latter at the age of 16 months). Persistance of his delay motivated exome sequencing at the age of approx. 4.5 years which demonstrated 2 RPIA variants (NM_144563.2:c.253G>A or p.Ala85Thr and NM_144563.2:c.347-1G>A). Measurement of ribitol and arabitol in urine demonstrated significant elevations (>20x) consistent with this diagnosis. RPIA is included in gene panels for intellectual disability offered by various diagnostic laboratories. As a result this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.576 | PPP1R21 |
Konstantinos Varvagiannis gene: PPP1R21 was added gene: PPP1R21 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PPP1R21 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PPP1R21 were set to 29808498; 28940097 Phenotypes for gene: PPP1R21 were set to Generalized hypotonia; Feeding difficulties; Profound global developmental delay; Abnormality of the face; Abnormality of vision; Abnormal heart morphology; Abnormality of the respiratory system; Hepatosplenomegaly Penetrance for gene: PPP1R21 were set to Complete Review for gene: PPP1R21 was set to GREEN Added comment: Biallelic pathogenic variants in PPP1R21 have been reported so far in 9 individuals from 7 unrelated families. All (7 different) variants reported to date are truncating. PMID: 29808498 is the first detailed clinical description on the related phenotype. 3 individuals from 3 families are reported. One of these individuals was previously included in a larger patient cohort (in PMID: 28940097). In a subsequent further publication, Rehman et al. (https://doi.org/10.1002/humu.23694) describe 6 additional patients from 4 unrelated consanguineous families. Again, these individuals were homozygous for truncating mutations. The authors summarize the findings in their patients as well as the previously reported ones. Common features included feeding difficulties, hypotonia with severe global DD and mildly coarsened facial features (all were observed in 9/9), visual anomalies (8/9), respiratory problems (7/9), cardiac anomalies (4/9) and hepato-/splenomegaly (3/7). Brain MRI anomalies were observed in the majority. DD was severe in all and ID (which is not explicitly mentioned) was evident from the clinical description of several individuals (eg. in PMID: 29808498). In total 7 loss-of-function variants have been reported. The authors in the first article, underscore the possibility of less severe phenotypes associated to biallelic missense variants (although none has been reported so far). Functional studies have shown great reduction (but not complete absence) of PPP1R21 mRNA levels in patient fibroblasts compared to controls. A role of PPP1R21 in the endosomal-lysosomal function is demonstrated in line with the presence of myelin figures in patient fibroblasts as well as some phenotypic similarities to neurometabolic/lysosomal storage disorders. Most variants reported in the most recent publication except one (NM_001135629.2:c.1607dupT) seem to affect all 3 PPP1R21 isoforms (which also seems to be the case for previously published variants). c.1607dupT appears to be the single truncating variant affecting 2 (of 3) isoforms. This variant was however shown to have severely reduced expression in fibroblasts upon qPCR, absent protein staining, and increase in myelin figures. The protein is expressed in embryonic mouse cortex. Overall, this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.576 | GRIN2D |
Konstantinos Varvagiannis gene: GRIN2D was added gene: GRIN2D was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: GRIN2D was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: GRIN2D were set to 27616483; 30280376 Phenotypes for gene: GRIN2D were set to Epileptic encephalopathy, early infantile, 46 (MIM 617162) Penetrance for gene: GRIN2D were set to unknown Review for gene: GRIN2D was set to GREEN gene: GRIN2D was marked as current diagnostic Added comment: Heterozygous pathogenic variants in GRIN2D cause Epileptic encephalopathy, early infantile, 46 (MIM 617162). As commented in the previous review, PMID: 27616483 is the first report on 2 unrelated individuals with severe epileptic encephalopathy (onset of seizures at the age of 2 and 4 months). Severe DD with ID was noted in both. Each of these individuals were heterozygous for the same missense variant (NM_000836.2:c.1999G>A p.Val667Ile) as a de novo event. Functional studies demonstrated a gain-of-function effect. GRIN2D encodes for an NMDA receptor subunit, and the gain-of-function effect shown for this variant suggests that NMDAR antagonists might be useful as adjuvant therapy (some improvement noted in both individuals). [The mode of pathogenicity selected here may be modified as more evidence on further variants becomes available. GRIN2D appears to be intolerant also to LoF mutations with a pLI of 1. Both LoF and GoF mutations have been described for genes encoding other NMDAR subunits]. PMID: 30280376 reports on 3 additional unrelated patients with developmental and epileptic encephalopathy and pathogenic or likely pathogenic missense variants in GRIN2D. Three additional missense variants are reported (Met681Ile, Ser694Arg, Asp449Asn). Parental studies were possible only for the patient with Met681Ile (de novo) as well as for the individual with Ser694Arg (only one parent available though). Significant developmental delay was evident in all prior to the onset of seizures (1m/2y/3y respectively) and subsequent developmental stagnation/regression with ID. The phenotype of these 3 individuals as well as of the 2 previously described is summarized in table 1 of the latter article. GRIN2D is a probable DD gene in G2P and is included in gene panels for ID offered by diagnostic laboratories. Several other genes for NMDA receptor subunits (eg. GRIN2A, GRIN2B, GRIN1) and relevant/similar phenotypes are included in this panel as green. As a result, this gene can be considered for inclusion in the ID panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.564 | PRR12 |
Konstantinos Varvagiannis gene: PRR12 was added gene: PRR12 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PRR12 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PRR12 were set to 29556724; 26163108 Phenotypes for gene: PRR12 were set to Global developmental delay; Intellectual disability; Abnormality of the iris; Abnormality of vision; Behavioral abnormality Penetrance for gene: PRR12 were set to unknown Review for gene: PRR12 was set to GREEN gene: PRR12 was marked as current diagnostic Added comment: PMID: 29556724 (Leduc et al. 2018) reports on 3 unrelated individuals with de novo pathogenic variants in PRR12. The common phenotype consisted of DD/ID (3/3), iris anomalies (colobomas in 2/3 with stellate iris patern in all) as well as additional vision problems and behavioral anomalies. 3 different loss-of-function variants are reported. These variants affected the longer transcript (Ensembl ENST00000418929.6 or NM_020719 - short : ENST00000615927.1) with a single one affecting both. PRR12 appears to be intolerant to loss-of-function muatations (pLI of 1). Some LoF variants exist in ExAC/gnomAD although the majority appear to be low-quality variants. As commented by the authors 2 individuals with de novo variants exist in Decipher (1 in-frame deletion and a missense SNV - both variants appear in fig.2 of the article) [a few more DDD study participants in the denovo-db all from PMID: 28135719 : http://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=PRR12]. Alternative explanations for the phenotype (eg. CHARGE syndrome, etc) were ruled out in many individuals in the article. Functional studies have not been performed. // PMID: 26163108 (Córdova-Fletes al. 2015) is a previous report cited by Leduc et al. One individual with balanced translocation [t(10;19)] with disruption of PRR12 is described. This individual presented with ID and behavioral anomalies (without details on eventual coloboma or other iris anomalies). The translocation was balanced and led to fusion of PRR12 with LMIZ1. The breakpoint was located within intron 11 (PRR12 is a 14-exon gene) with fusion of PRR12 exon 11 with ZMIZ1 exon 8 upon RT-PCR. Both PRR12/ZMIZ1 products were predicted to be truncated due to frameshift and introduction of premature stop codon. [Surprisingly qPCR and Western blot in patient LCLs were suggestive of increased PRR12 expression compared to controls suggesting either a compensation mechanism or longer half-life/accumulation of the aberrant PRR12]. Expression of wt PRR12 was highest during embryonic development in mouse/rat brain cells suggesting a role in early CNS development. The transcript studied (corresponding to the longest human transcript) was exclusively located in the nucleus compared to a shorter one located primary in the nucleus but also outside suggesting that PRR12 might be involved in regulation of transcription. In line with this several genes linked to neurodevelopmental processes/neuronal communication appeared be dysregulated in lymphoblastoid cell lines (LCLs) from the translocation patient. A role for ZMIZ1 is similarly discussed. // PRR12 is included in gene panels for ID offered by diagnostic laboratories. // As a result, this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.561 | MAB21L1 |
Konstantinos Varvagiannis gene: MAB21L1 was added gene: MAB21L1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: MAB21L1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: MAB21L1 were set to 27103078 Phenotypes for gene: MAB21L1 were set to Global developmental delay; Intellectual disability; Cerebellar hypoplasia; Abnormality of the eye; Abnormality of the genital system Penetrance for gene: MAB21L1 were set to Complete Review for gene: MAB21L1 was set to GREEN gene: MAB21L1 was marked as current diagnostic Added comment: Bruel et al. (PMID: 27103078) report on a boy, born to consanguineous Algerian parents, homozygous for a frameshift MAB21L1 variant. Rad et al. (http://dx.doi.org/10.1136/jmedgenet-2018-105623) describe 10 additional individuals from 5 unrelated consanguineous families (from Iran, Lebanon and Turkey). These subjects were homozygous for truncating variants appart from a patient with a missense one [NM_005584.4:c.698A>C or p.(Gln233Pro)]. All 11 individuals presented with a common phenotype consisting of DD/ID (in 9/11 for whom this information was available), cerebellar, ocular and genital anomalies as well as similar facial features. In total 6 different variants (5 truncating and 1 missense SNV) have been reported. There are no functional studies performed appart from in silico visualisation for the missense variant and protein interaction network analysis for MAB21L1. Previous studies in Mab21l1 knockout mice suggest ocular as well as preputial gland anomalies. ID appears to be a feature for biallelic mutations in MAB21L2, another member of the male abnormal 21 (MAB21)-like proteins (gene rated green in this panel - associated phenotype : Microphthalmia/coloboma and skeletal dysplasia syndrome, MIM 615877). MAB21L1 is included in gene panels for intellectual disability offered by some diagnostic laboratoires. As a result, this gene can be considered for inclusion in this panel as green (or amber) Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.558 | ODC1 |
Konstantinos Varvagiannis gene: ODC1 was added gene: ODC1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: ODC1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ODC1 were set to 30239107; 30475435 Phenotypes for gene: ODC1 were set to Global developmental delay; Intellectual disability; Macrocephaly; Alopecia; Ectodermal dysplasia Penetrance for gene: ODC1 were set to unknown Review for gene: ODC1 was set to GREEN Added comment: PMIDs 30239107 and 30475435 report on 5 cases of de novo truncating ODC1 variants in unrelated families. One concerned a stillborn male. The 4 remaining individuals presented with a similar phenotype consisting of alopecia and other ectodermal anomalies, DD/ID, relative or absolute macrocephaly and common facial features. DD/ID was severe in some instances and many of these individuals had extensive prior testing for other disorders (Fragile-X, PTEN, SLC2A1, chromosomal disorders, etc). ODC1 (ornithine decarboxylase 1) converts enzymatically ornithine to putrescine. All variants reported to date are truncating but lead to gain-of-function. Specifically they affect a 37 amino acid c-terminal destabilization region critical for the degradation of ODC1 and - as a result - lead to increased levels of ODC1 as well as putrescine. A mouse model with identical phenotype has been described several years ago. The role of ODC inhibitors is extensively discussed in both publications. As a result, ODC1 can be considered for inclusion in the ID panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.556 | DDX59 |
Konstantinos Varvagiannis gene: DDX59 was added gene: DDX59 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: DDX59 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DDX59 were set to 23972372; 28711741; 29127725 Phenotypes for gene: DDX59 were set to Orofaciodigital syndrome V, 174300 Penetrance for gene: DDX59 were set to Complete Review for gene: DDX59 was set to GREEN Added comment: Biallelic mutations in DDX59 cause Orofaciodigital syndrome V, 174300. PMID: 23972372 reports on 6 individuals from 2 consanguineous Arab families. All 6 presented with palatal anomalies (cleft palate or bifid uvula), lobulated tongue, facial anomalies (frontal bossing and hypertelorism) as well as intellectual disability. Individuals from the first family were homozygous for the Val367Gly (NM_001031725.4:c.1100T>G) variant while those from the second were homozygous for Gly534Arg (NM_001031725.4:c.1600G>A), both predicted to be pathogenic in silico. Immunoblot demonstrated reduced levels of the Val367Gly variant in patient fibroblasts (the other variant was probably not tested). Ddx59 was shown to be expressed in lips, palatal shelves and developing limb buds of mouse embryos. PMID: 28711741 describes 3 further patients (from two consanguineous Pakistani families), presenting the cardinal features of orofaciodigital syndrome (though polydactyly was only reported in one of the three). Developmental delay was reported in all (in the first family one of the sibs had more severe delay with no speech at the age of 7 years, in the patient from the other family speech was limited to 2 words at school age). Affected individuals from both families were found to harbor a SNV leading to loss of a stop codon, thus extending the reading frame by 21 codons. PMID: 29127725 reports on two sibs with a diagnosis of orofaciodigital syndrome born to non-consanguineous parents. ID was a feature in both. These individuals were homozygous for a frameshift variant. Reverse transcription PCR/semiquantitative PCR demonstrated reduction of the mutant transcript compared to the levels in wt controls (suggestive of incomplete NMD). Functional studies showed possible perturbation of the Sonic Hedgehog pathway. DDX59 expression in CNS from control post-mortem human brains was confirmed to be high (based on data generated in a previous study). Studies in Drosophila suggest reduced lifespan and neuronal defects secondary to mutations in mahe (the Drosophila homolog of DDX59). As a result this gene can be considered for inclusion in the ID panel as green. Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.556 | DPH1 |
Konstantinos Varvagiannis gene: DPH1 was added gene: DPH1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: DPH1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DPH1 were set to 25558065; 26220823; 29362492; 29410513 Phenotypes for gene: DPH1 were set to Developmental delay with short stature, dysmorphic features, and sparse hair, 616901 Penetrance for gene: DPH1 were set to Complete Review for gene: DPH1 was set to GREEN gene: DPH1 was marked as current diagnostic Added comment: Biallelic mutations in DPH1 cause Developmental delay with short stature, dysmorphic features, and sparse hair, MIM 616901. Overall 11 patients from 6 different families have probably been reported in detail. DD/ID is a universal feature. In PMID 25558065, Alazami et al. identified 1 patient from the same consanguineous Saudi Arabian family (of 8 total similarly affected individuals) homozygous for the Leu234Pro (NM_001383.3:c.701T>C) variant. This individual was part of a large cohort of patients with neurogenetic disorders from consanguineous families. The phenotype is not described in detail. In PMID 26220823 Louks et al. report on 4 patients from 3 families belonging to the same genetic isolate from North America and provide details on 4 of the individuals identified by Alazami et al. The individuals identified in this study were homozygous for Met6Lys which was however predicted to be benign and tolerated (by PolyPhen2 and SIFT respectively) in silico. DD/ID, unusual skull shape, ectodermal anomalies were universal (8/8) with additional features including short stature (7/8), renal (4/6) or cardiac anomalies (3/8). Some facial features appeared to be common, too. Functional studies were not performed. However Dph1 pathogenic variants in mice result in restricted growth, craniofacial and developmental defects similar to the human phenotypes (PMIDs 14744934 and 24895408 are cited). PMIDs 29362492 and 29410513 report on 3 further patients with similar (as well as some additional) features including DD/ID. The individual in the first article was compound heterozygous for a missense (Leu164Pro) and a frameshift variant (c.289delG) while 2 sibs born to consanguineous parents in the second article were homozygous for a frameshift variant (c.1227delG). The phenotype appears to be consistent among all the published patients. DPH1 is included in gene panels for intellectual disability offered by different diagnostic laboratories. As a result, this gene can be considered for inclusion in this panel as green. Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.555 | COG6 |
Konstantinos Varvagiannis gene: COG6 was added gene: COG6 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: COG6 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: COG6 were set to 26260076; 20605848; 23430903; 23606727; 28139241; 28742265; 29445937; 29709711 Phenotypes for gene: COG6 were set to Congenital disorder of glycosylation, type IIl, 614576; Shaheen syndrome, 615328 Penetrance for gene: COG6 were set to Complete Review for gene: COG6 was set to GREEN gene: COG6 was marked as current diagnostic Added comment: DD/ID is an almost universal feature of individuals with biallelic COG6 mutations, whether this is associated with a type II transferrin IEF pattern (as in Congenital disorder of glycosylation, type IIl, 614576) or not (as in Shaheen syndrome, 615328). More than 15 patients from several different families have been reported to date. PMID: 26260076 is a collaborative study reporting on new patients as well as on individuals previously described up to 2015 by Lubbehusen et al. (2010 - PMID: 20605848), Huybrechts et al. (2012 - PMID: 23430903) as well as Shaheen et al. (2013 - PMID: 23606727). As summarized in table 1 of this article, developmental disability was a feature in 8/10, although for a further 2/10 this was probably not relevant (both deceased too early). The following articles are additional reports although there might be some overlap (applicable for the Saudi patients) : PMIDs: 28139241 (individuals with diagnosis of CDG from Spain), 28742265 (cohort of CDG patients from Saudi Arabia), 29445937 (case report of Saudi subject), 29709711 (Chinese individual with COG6-CDG). All types of variants have been observed including missense, stopgain and frameshift ones, as well as variants leading to aberrant splicing [eg. positions -2, -9, -24]. The deep intronic variant (position -24) in the individuals reported by Shaheen and others is considered a founder mutation in the Saudi population. Individuals homozygous for the latter variant have detectable levels of the normal transcript, although 75% of the produced transcript (upon RT-PCR analysis) correspond to retention of 37 intronic nucleotides leading to frameshift and introduction of a premature stop codon. This was also confirmed with Western blot. Given the detectable levels of the normal transcript, it has been proposed that Shaheen syndrome represents the mildest end of the spectrum COG6-related disorders. COG6 is included in gene panels for intellectual disability offered by different diagnostic laboratories. As a result this gene can be considered for inclusion in this panel as green. Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.552 | SCAPER | Louise Daugherty Added comment: Comment on phenotypes: added phenotype and MIM from OMIM : Tatour et al. (2017) PMID: 28794130 describes 4 patients from 3 unrelated families with intellectual disability disorder and retinitis pigmentosa and identified homozygosity or compound heterozygosity for mutations in the SCAPER gene. Noting that the retinal phenotype associated with null SCAPER mutations is not congenital but presents around the second decade of life, the authors suggested that in the retina, SCAPER does not play a developmental role, but rather is important for photoreceptor function and/or maintenance. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.550 | UFM1 |
Konstantinos Varvagiannis gene: UFM1 was added gene: UFM1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: UFM1 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: UFM1 were set to 28931644; 29868776 Phenotypes for gene: UFM1 were set to Leukodystrophy hypomyelinating 14, 617899 Penetrance for gene: UFM1 were set to Complete Review for gene: UFM1 was set to GREEN Added comment: Biallelic UFM1 mutations cause Leukodystrophy hypomyelinating 14, MIM 617899. PMID: 28931644 is the first report on 16 individuals from 14 families with shared Roma ethnic background. All subjects were found to harbor a UFM1 promoter 3 basepair deletion in the homozygous state. All patients demonstrated a severe phenotype including lack of development and severe epileptic encephalopathy while their MRI images demonstrated hypomyelination with atrophy of the basal ganglia and the cerebellum. The promoter deletion was detected by exome sequencing. Previously a 0.8 Mb homozygous region was identified to be shared by all the patients in whom a SNP array was performed. Alternative causes, notably TUBB4A mutations and deletions/duplications were excluded. 3 individuals had Sanger sequencing of all coding regions within the homozygous interval to rule out other - eventually missed - variants. PMID: 29868776 reports 4 additional individuals from 2 consanguineous families (one from Ethiopia, for the other this was not specified). All 4 patients were homozygous for the c.241C>T (NM_016617.3) or p.(Arg81Cys) variant which was shown to be hypomorphic upon functional studies. The phenotype consisted of developmental delay (4/4 or 20/20 including the patients from the previous report with which comparison is made in table 2 of the article) with microcephaly (4/4 or 20/20) and seizures (4/4 or 16/20) as well as MRI abnormalities. Failure to thrive and/or short stature were also among the most common features. UFM1 (as well as UFC1 also discussed in the same article) participate in ufmylation, with mutations in other enzymes of the same process (notably UBA5 - gene rated Green in the ID and epilepsy panels) having already been described in neurodevelopmental disorders. As a result, this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.545 | UFC1 |
Konstantinos Varvagiannis gene: UFC1 was added gene: UFC1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: UFC1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: UFC1 were set to 29868776 Phenotypes for gene: UFC1 were set to Neurodevelopmental disorder with spasticity and poor growth, 618076 Penetrance for gene: UFC1 were set to Complete Review for gene: UFC1 was set to GREEN Added comment: Biallelic UFC1 mutations cause Neurodevelopmental disorder with spasticity and poor growth, MIM 618076. PMID: 29868776 describes 7 individuals (most) born to consanguineous Saudi families (in one case the parents were not consanguineous but originated from the same tribe) as well as a further individual born to distantly related Swiss parents. One of these patients was previously briefly published by the same authors (PMID: 27431290). The phenotype consisted of developmental delay (8/8 - usually profound), failure to thrive (8/8), short stature and microcephaly (both observed in 7/8), seizures (4/8) and variable brain MRI anomalies in some of these subjects. Overall, two UFC1 missense variants are reported [NM_016406.3:c.317C>T or p.(Thr106Ile) and c.68G>A or p.(Arg23Gln) the former in the Saudi individuals]. Functional studies demonstrated the hypomorphic nature of the variants. UFC1 (as well as UFM1 also discussed in the same article) participate in ufmylation, with mutations in other enzymes of the same process (notably UBA5 - gene rated Green in the ID and epilepsy panels) having already been described in neurodevelopmental disorders. As a result this gene can be considered for inclusion in the ID panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.537 | GNB5 |
Konstantinos Varvagiannis gene: GNB5 was added gene: GNB5 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: GNB5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: GNB5 were set to 27523599; 27677260; 28697420; 29368331 Phenotypes for gene: GNB5 were set to Intellectual developmental disorder with cardiac arrhythmia, 617173; Language delay and ADHD/cognitive impairment with or without cardiac arrhythmia, 617182 Penetrance for gene: GNB5 were set to Complete Review for gene: GNB5 was set to GREEN gene: GNB5 was marked as current diagnostic Added comment: Biallelic GNB5 pathogenic variants cause Intellectual developmental disorder with cardiac arrhythmia (MIM 617173) or language delay and ADHD/cognitive impairment with or without cardiac arrhythmia (MIM 617182). PMID: 27523599 is the first report on the associated phenotype. A total of 9 individuals from 6 different families (from various ethnic backgrounds) are described. The common features included hypotonia (noted in 6 out of 9 patients), intellectual disability (9/9 - in 3 cases mild, in 6 severe), heart rate disturbance (9/9 - in most cases sick sinus syndrome), seizures (4/9), ophthalmological problems (nystagmus in 6 out of 7 for whom this information was available) as well as gastric problems (5/8 with G-E reflux). The 6 variants (summarized in table S1) included : 2 nonsense mutations, 1 synonymous (demonstrated to affect splicing and leading to retention of 25 intronic bp), 2 further splice variants (positions +1 and +3) and a missense one (S81L). Nonsense mediated decay was the case for the product of the synonymous/splice variant as well as for a stopgain one. As noted by the authors, individuals homozygous for the S81L variant had a less severe phenotype - among others - with mild degree of intellectual disability. Functional studies included knockout of gnb5 in zebrafish, which was able to reproduce the human neurological, cardiac and ophthalmological phenotypes. Alternative causes for these phenotypes (incl. chromosomal or metabolic disorders) were ruled out. Affected individuals might benefit interventions for their heart rate disturbance as appears to be the case in the article as well as subsequent studies. PMID: 27677260 describes an extended consanguineous Saudi family with 5 individuals homozygous for the S81L variant. Common features included severe language delay, ADHD, but normal cognition in those available for evaluation. Seizures were not reported. Pathogenicity of the S81L variant is further supported by functional studies. PMID: 28697420 describes in detail 2 individuals from a large consanguineous pedigree confirmed to be homozygous for a single nucleotide deletion in GNB5. The phenotype included severe DD/ID, seizures, sinus bradycardia with frequent sinus pauses and ophthalmological problems. Sinus arrhythmia and or seizures were documented in several other relatives deceased and unavailable for testing. PMID: 28327206 reports on 2 subjects previously included in PMID: 27523599. PMID: 29368331 describes a child with severe developmental delay, nystagmus and sinus arrhythmia necessitating a pacemaker. EEG was abnormal although no frank seizures were observed. The child was compound heterozygous for a novel missense variant (R246Q) as well a 5 basepair deletion. GNB5 is included in diagnostic gene panels for intellectual disability offered by different laboratories. As a result this gene can be considered for inclusion in this panel as green. Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.535 | ATP6V1A |
Konstantinos Varvagiannis gene: ATP6V1A was added gene: ATP6V1A was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: ATP6V1A was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ATP6V1A were set to 29668857; 28065471 Phenotypes for gene: ATP6V1A were set to # 618012 EPILEPTIC ENCEPHALOPATHY, INFANTILE OR EARLY CHILDHOOD, 3; IECEE3 Penetrance for gene: ATP6V1A were set to unknown Review for gene: ATP6V1A was set to GREEN Added comment: Heterozygous mutations in ATP6V1A cause Epileptic encephalopathy, infantile or early childhood, type 3 (MIM 618012). PMID: 29668857 reports 4 individuals from 4 families with de novo pathogenic variants in ATP6V1A. The phenotype was consistent with a developmental encephalopathy with epilepsy. All patients were found to harbor missense variants. The variants resulted in altered lysosomal homeostasis, abnormal neuritogenesis and synaptic density. However in one of the variants tested (p.Asp100Tyr) pathogenicity was mediated by loss-of-function mechanism while for another (p.Asp349Asn) by gain-of-function mechanism. Differences in severity were noted, with two variants (incl. Asp100Tyr) being associated with a more severe phenotype and the two other (incl. Asp349Asn) with milder degrees of ID and epilepsy. Biallelic ATP6V1A mutations cause Cutis laxa type IID (MIM 617403). PMID: 28065471 is the first report on 3 individuals from 3 different families (2 of which were consanguineous). All patients were homozygous for ATP6V1A pathogenic variants. All three presented with hypotonia, one (or possibly two) with developmental delay and two with seizures although the developmental phenotype is not further commented on. (Additional patients described in the article harbored mutations in other genes and were not considered). As a result, this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.531 | NFIB |
Konstantinos Varvagiannis gene: NFIB was added gene: NFIB was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: NFIB was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: NFIB were set to 30388402 Phenotypes for gene: NFIB were set to Global developmental delay; Intellectual disability; Macrocephaly Penetrance for gene: NFIB were set to unknown Review for gene: NFIB was set to GREEN Added comment: Schanze et al. (PMID: 30388402) report on the phenotype related to NFIB haploinsufficiency. 10 individuals with intragenic NFIB or larger deletions encompassing also other genes as well as 8 individuals with nucleotide variants (5 loss-of-function and 3 missense ones) are described. Intellectual disability was a universal feature while macrocephaly was noted in the majority of the patients. The phenotype of individuals deletions was similar to the phenotype of intragenic mutations as also seems to be the case with the degree of ID. Functional studies support loss of function for the pathogenic missense variants reported. Cortical-specific knockout of Nfib in mice results in enlargement of the cortex. While most of the variants occurred as de novo events, a few individuals had inherited a variant (deletion or nucleotide variant) from a similarly affected parent. As a result, this gene can be considered for inclusion in the ID panel as green. Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.530 | DCPS |
Konstantinos Varvagiannis gene: DCPS was added gene: DCPS was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: DCPS was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DCPS were set to 25712129; 25701870; 30289615 Phenotypes for gene: DCPS were set to Al-Raqad syndrome (OMIM 616459) Penetrance for gene: DCPS were set to Complete Review for gene: DCPS was set to GREEN gene: DCPS was marked as current diagnostic Added comment: Biallelic pathogenic DCPS variants cause Al-Raqad syndrome (OMIM 616459). 7 patients from 3 families have been reported to date, all summarized in PMID 30289615 (first reports on the disorder - PMIDs : 25712129, 25701870). Most individuals belong to consanguineous families although a compound heterozygous patient belonging to a broader consanguineous family (in PMID 25701870) and a further individual was born to unrelated parents originating from the same region (in PMID 30289615) have been described. Overall, 2 splice site and 2 missense variants have been reported. Functional studies were carried out and support pathogenicity of the variants in the first 2 studies. Developmental delay and intellectual disability are universal features. DCPS is included in gene panels for intellectual disability offered by different diagnostic labs. As a result this gene can be considered for inclusion in this panel as green. Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.530 | RHOBTB2 |
Konstantinos Varvagiannis gene: RHOBTB2 was added gene: RHOBTB2 was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: RHOBTB2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: RHOBTB2 were set to 29276004; 29768694; 26740508 Phenotypes for gene: RHOBTB2 were set to Global developmental delay; Intellectual disability; Seizures; Postnatal microcephaly Penetrance for gene: RHOBTB2 were set to unknown Mode of pathogenicity for gene: RHOBTB2 was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: RHOBTB2 was set to GREEN gene: RHOBTB2 was marked as current diagnostic Added comment: PMID: 29276004 reports on 10 unrelated patients with de novo pathogenic missense variants in RHOBTB2. The phenotype in all individuals was compatible with a developmental and epileptic encephalopathy including early-onset seizures, severe intellectual disability, postnatal onset microcephaly (6/10) and movement disorders (8/10). The variants occured as de novo events and clustered within the BTB-domain encoding region (within and between the 2 BTB domains). Three missense variants were recurrent and/or concerned the same residue (p.Arg483His in 4 individuals, Arg511Gln was reported in 2, and Arg511Trp was was found in another 2 individuals). Functional studies in HEK293 cells suggested increased abundance of the mutant protein secondary to decreased proteasome degradation. Using Drosophila as a model organism, altered expression of RhoBTB (the single ortholog of the 3 vertebrate paralogs, closest to RHOBTB2) was shown to result in neurological phenotypes. RhoBTB overexpression in particular was associated with increased bang sensitivity (which was not the case or milder in the case if knockdown of this gene) and impaired performance upon the negative geotaxis assay, similar to the human neurological phenotypes. Altered RhoBTB dosage was shown to be associated with impaired dendrite development. As commented by the authors, these results as well as the clustering of missense variants and the pLI score of 0.51 reported for RHOBTB2 are consistent with altered protein function (due to the missense variants) rather than haploinsufficiency or loss-of-function. PMID: 29768694 describes 3 additional individuals, all found to harbor de novo missense variants again within the BTB-domain encoding region. Two of the variants had been reported in the previous study (Arg511Gln and Arg483His) while the third was a private one (Arg507Cys). The phenotype was similar to the previous descriptions. Functional studies were suggestive of impaired degradation of the mutant protein by the CUL3 complex although this was not secondary to decreased binding with CUL3. PMID: 26740508 (cited by the two aforementioned publications) reports briefly on an individual with de novo missense variant in the same region of RHOBTB2 (Asn510Asp) and Rett-like phenotype. RHOBTB2 is included in gene panels for intellectual disability offered by different diagnostic laboratories. As a result the gene can be considered for inclusion in the intellectual disability and epilepsy panels as green. Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.510 | EMC1 |
Konstantinos Varvagiannis gene: EMC1 was added gene: EMC1 was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: EMC1 was set to BOTH monoallelic and biallelic (but BIALLELIC mutations cause a more SEVERE disease form), autosomal or pseudoautosomal Publications for gene: EMC1 were set to 26942288; 29271071 Phenotypes for gene: EMC1 were set to Cerebellar atrophy, visual impairment, and psychomotor retardation, MIM 616875 Penetrance for gene: EMC1 were set to Complete Review for gene: EMC1 was set to GREEN gene: EMC1 was marked as current diagnostic Added comment: Harel et al. (PMID: 26942288) describe 7 individuals from 3 families with biallelic pathogenic variants in EMC1. In the first family, a single individual (born to non-consanguineous parents) was found to harbor a homozygous frameshift variant in a small (approx. 100 kb) stretch of absence of heterozygosity. The patients in the other two families were homozygous for missense variants (private to each family) in the context of parental consanguinity. The common phenotype was suggestive of a progressive neurodegenerative disorder and consisted of hypotonia, severe developmental delay with marked speech delay, diminished deep tendon reflexes, cerebellar atrophy, vision as well as skeletal problems. Seizures were a feature in one subject. One further patient from an additional (fourth) family was found to have a similar but milder phenotype and was only found to harbor a de novo missense variant in EMC1 following trio exome sequencing. Sanger sequencing of the promoter region as well as CNV calling from the exome data failed to reveal other variants in this specific individual. Similarly to what has been observed in other genes the authors propose that both monoallelic and biallelic pathogenic variants may be causative of the specific phenotype, though the presentation may be more severe in case of biallelic variants. Altogether this study reports 1 homozygous frameshift and 3 missense variants (2 of the latter found in homozygous state and one as a de novo heterozygous mutation). // Geetha et al. (PMID: 29271071) describe an individual born to consanguineous parents presenting with hypotonia, developmental delay, and cerebellar atrophy as well as early onset epilepsy. Exome sequencing demonstrated a homozygous splice variant in EMC1. This variant was demonstrated to result to retention of intron 11 upon RNA sequencing. This was predicted to lead to premature truncation of the protein. // EMC1 is associated in OMIM with Cerebellar atrophy, visual impairment, and psychomotor retardation (MIM 616875) for which an autosomal recessive inheritance mode is retained. // Apart from the variants reported in the previous studies [p.Pro874Argfs*21, p.Thr82Met, p.Gly868Arg, p.Gly471Arg, c.1212+1G>A - NM_015047.2] further variants have been submitted in ClinVar as likely pathogenic (Variation IDs : 521479, 445564). // The gene has been included in intellectual disability gene panels offered by a few other diagnostic labs. // As a result this gene can be considered for inclusion in the panel as green (or amber). Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.510 | CACNA1E |
Konstantinos Varvagiannis gene: CACNA1E was added gene: CACNA1E was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: CACNA1E was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CACNA1E were set to 29942082 Phenotypes for gene: CACNA1E were set to Global developmental delay; Intellectual disability; Seizures; Dystonia; Congenital contracture; Macrocephaly Penetrance for gene: CACNA1E were set to Incomplete Mode of pathogenicity for gene: CACNA1E was set to Other Review for gene: CACNA1E was set to GREEN Added comment: Helbig et al. (https://doi.org/10.1016/j.ajhg.2018.09.006) report on 30 individuals with pathogenic variants in CACNA1E. The phenotype was consistent with a developmental and epileptic encephalopathy, with hypotonia, early-onset and refractory seizures, severe to profound developmental delay and intellectual disability. Additional relatively common features included hyperkinetic movement disorder (severe dystonia which was observed in 40%, other dyskinesias in another 20%), congenital joint contractures of variable degree and joint involvement (approx. 40% of individuals) and macrocephaly (approx. 40%). There were no common facial dysmorphic features observed. Of note, epilepsy was not a feature in 4 cases (age 1 to 4 years) so few of these individuals may be investigated for their developmental delay/intellectual disability or other features. Missense variants: All the 30 subjects described harbored a missense variant in CACNA1E which in all cases where parental studies were possible (29/30) occurred as a de novo event. There were 4 recurrent variants, explaining the phenotype in 20 patients in total while the rest of the individuals had private mutations. Functional studies were performed and suggested a gain-of-function effect for these variants (increased calcium inward currents). Loss-of-function (LoF) variants: Apart from the main cohort of patients, the authors note the presence of 3 individuals with such variants incl.: - one individual with a nonsense variant present in the mosaic state (6/22 reads) in peripheral blood. - one individual with a frameshift variant inherited from his unaffected parent. - one individual with a nonsense variant for whom parental studies were not possible. The authors comment that these indivdiduals presented with milder phenotype compared to those with missense variants. More information on these subjects is provided in the supplement as the article focuses on missense SNVs. As the authors also note, several LoF variants exist in gnomAD, although the gene appears to be LoF intolerant (pLI=1). Penetrance: Seems to be complete for missense SNVs and possibly incomplete for LoF ones. --- A previous study by Heyne et al. (PMID: 29942082) implicated de novo variants (DNVs) in CACNA1E with neurodevelopmental disorders for the first time. This study however does not provide clinical details on the phenotype of the affected individuals, while it seems to present overlap as to the individuals reported (eg. includes subjects from the DDD study and others). --- Details as to a few - possibly further - de novo coding variants reported to date can be found at the denovo-db: http://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=CACNA1E --- As a result this gene can be considered for inclusion in this panel as green. Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.510 | VARS |
Konstantinos Varvagiannis gene: VARS was added gene: VARS was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: VARS was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: VARS were set to 26539891; 29691655; 30275004 Phenotypes for gene: VARS were set to # 617802. NEURODEVELOPMENTAL DISORDER WITH MICROCEPHALY, SEIZURES, AND CORTICAL ATROPHY; NDMSCA Penetrance for gene: VARS were set to Complete Review for gene: VARS was set to GREEN gene: VARS was marked as current diagnostic Added comment: PMID: 26539891 is the first report on individuals with biallelic pathogenic variants in VARS. 3 individuals from 2 consanguineous families are briefly reported. The phenotype was similar in all 3, consisting of severe developmental delay, microcephaly, seizures and cortical atrophy. Subjects from the first family were homozygous for a missense variant in the tRNA synthetase catalytic domain [p.(L885F)]. The patient from the second family was homozygous for a missense SNV affecting the anticodon-binding domain [p.(R1058Q)]. PMID: 29691655 reports on a further patient born to non-consanguineous parents, with 2 in-trans pathogenic variants in VARS. The phenotype consisted of progressive microcephaly (OFC at birth -2SD, at the age of 2 months -4SD), global developmental delay, seizures and progressive cerebral and cerebellar atrophy. An affected brother presented with more severe phenotype (OFC -6SD at birth and -8SD at 2 months of age), seizures, hearing loss but was deceased and unavailable for genetic testing. cDNA studies demonstrated absence of the reference allele for the missense mutation downstream the splice variant (in line with a reduced or absent mRNA allele harboring the splice variant). Similarly, mRNA expression studies demonstrated 50-60% reduction in the transcripts (due to NMD of the allele with the splice SNV). Western blot showed severe reduction in protein levels (more pronounced compared to what would be expected by mRNA expression) presumably secondary to decreased protein stability due to the missense variant. Severe defects in aminoacylation were further confirmatory of a pathogenic role of these variants. The missense variant was affecting the anticodon-binding domain, important for aminoacylation. PMID: 30275004 reports on 2 siblings with developmental delay, intellectual disability, severe speech impairment and microcephaly, similar to what has been described for the disorder. Clinical findings were somewhat different from previous studies in that microcephaly was acquired, while seizures and cortical atrophy were not part of the phenotype. Both sibs were compound heterozygous for 2 missense variants, though only one of these mutations affected the anticodon binding domain and the other was in the N-terminal region of the protein. Previous metabolic studies and extensive genetic testing (karyotype, CMA, MECP2, FMR1) was normal. Epilepsy was a feature in 4 of the 6 individuals for whom genetic testing was possible (or 5/7 in total). VARS belongs to the family of amino acyl-tRNA synthetases (ARSs). Mutations in several cytoplasmic ARSs are associated with severe neurological manifestations including seizures, intellectual disability associated with microcephaly. VARS is included in gene panels for intellectual disability (but not for epilepsy) offered by different diagnostic labs. As a result this gene can be considered for inclusion in the ID and epilepsy panel as green (or amber). Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.510 | ADAT3 |
Konstantinos Varvagiannis gene: ADAT3 was added gene: ADAT3 was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: ADAT3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ADAT3 were set to 23620220; 26842963; 30296593; 29796286 Phenotypes for gene: ADAT3 were set to # 615286. MENTAL RETARDATION, AUTOSOMAL RECESSIVE 36; MRT36 Penetrance for gene: ADAT3 were set to Complete Review for gene: ADAT3 was set to GREEN gene: ADAT3 was marked as current diagnostic Added comment: Initially reported in PMID 23620220, the findings in several individuals with biallelic ADAT3 pathogenic variants (including also those from the first report) are summarized in PMID 26842963. A total of 39 individuals from 19 consanguineous families are described in the two studies. These individuals were homozygous for a specific missense variant (probably a Saudi Arabian founder mutation). The common phenotype consists of intellectual disability (39/39 patients) and strabismus (32/39). Additional features included failure to thrive (33/39), microcephaly (22/39), short stature (11 of 15 individuals for whom this was information was available). Epilepsy was observed in some of these individuals (6/39). A few facial features were more common, although there was no distinct facial gestalt. // PMID 30296593 reports on 2 additional subjects born to consanguineous parents and found to be homozygous for the same missense variant. These individuals presented with features similar to the previous reports (although none of them was reported to have seizures). // Of note, the variant is either referred to as V144M (using NM_138422.2 or NM_138422.3) or as V128M (using NM_138422.1 as a reference / c.382G>A) as in the initial report. [ClinVar : https://www.ncbi.nlm.nih.gov/clinvar/variation/183301/#summary-evidence] PMID 29796286 describes a 6-year-old female, born to consanguineous Iranian parents, investigated for developmental delay,intellectual disability, behavioral difficulties as well as microcephaly. A homozygous 8-basepair duplication in ADAT3 was identified by exome and was further confirmed by Sanger sequencing. This individual did not have seizures. // This gene is included in DD/ID (but not epilepsy) panels offered by different diagnostic labs. // As a result this gene can be considered for inclusion in the intellectual disability panel as green. Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.510 | PIGG |
Konstantinos Varvagiannis gene: PIGG was added gene: PIGG was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: PIGG was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PIGG were set to 26996948; 28581210 Phenotypes for gene: PIGG were set to # 616917 MENTAL RETARDATION, AUTOSOMAL RECESSIVE 53; MRT53 Penetrance for gene: PIGG were set to Complete Review for gene: PIGG was set to GREEN gene: PIGG was marked as current diagnostic Added comment: PMID: 26996948 reports on 5 individuals from 3 families, with biallelic pathogenic variants in PIGG. Individuals from first family, were born to consanguineous parents from Egypt and were homozygous for a stopgain variant [p.(Gln310*)]. The patient from the second family had a rare missense SNV [p.(Arg669Cys)] and a de novo microdeletion affecting PIGG on her other allele. In the third family (consanguineous parents from Pakistan), two affected sibs were found to be homozygous for a splice variant. The phenotype consisted of hypotonia, early-onset seizures and intellectual disability. Ataxia was an additional feature in one of the families. Seizures, were observed in most of patients but do not appear to be a universal feature as they were absent in one of the sibs from the third family (10 years of age), while the other had a single episode by the age of 12 years. In vitro testing of lymphoblastoid cell lines (generated from individuals from the 1st and 3rd family) indicated that the variants abolished completely the function of PIGG, whereas the surface level of GPI anchored proteins was normal. // PMID: 28581210 describes the phenotype of 2 sibs from Palestine, homozygous for a stopgain variant [p.(Trp547*)]. Hypotonia, feeding difficulties, severe non-progressive ataxia (with cerebellar hypoplasia), intellectual disability and seizures were common features. Differences in severity and/or additional features might be explained by other homozygous variants (the girl had a concurrent diagnosis of MCAD deficiency). The authors demonstrated that the PIGG transcript levels were significantly lower (approximately half) in the two siblings compared to their parents, while the transcripts with the mutation in the heterozygous parents were very low due to nonsense-mediated decay. Patient fibroblasts showed decreased surface level of GPI-anchored proteins, in contrast with what was noted in lymphoblastoid cells in the previous study. // PIGG has been included in gene panels for intellectual disability offered by different diagnostic labs. // As a result this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.510 | MAP1B |
Konstantinos Varvagiannis gene: MAP1B was added gene: MAP1B was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: MAP1B was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: MAP1B were set to 30150678; 29738522 Phenotypes for gene: MAP1B were set to Intellectual disability Penetrance for gene: MAP1B were set to unknown Review for gene: MAP1B was set to AMBER Added comment: In PMID 30150678 the authors report on a family with 5 individuals diagnosed with intellectual disability (ID, IQ <= 70 and associated impairments in adaptive function) and 3 further relatives with IQ below 70, not fulfilling the criteria for a clinical diagnosis of ID. A frameshift variant in MAP1B segregated with the ID/low IQ phenotype. This variant was not found in 31463 Icelanders for whom whole genome sequencing data were available. The authors confirmed association of MAP1B loss-of-function (LoF) variants by demonstrating the presence of 2 other stopgain mutations in 2 further families. Among the 6 mutation carriers in these families, the average IQ was 81 with 2 of these subjects fulfilling the criteria for intellectual disability. 3 of the 6 mutation carriers had a diagnosis of autism spectrum disorder. Carriers demonstrated 24% less white matter volume (-2.1 SD) and 47% less corpus callosum volume (-2.4 SD) compared to controls. Mean full-scale IQ, performance IQ and verbal IQ were 68.3 (with a SD of 10.5), 66.4 (SD of 9.3) and 74.5 (SD of 14.8) in MAP1B LoF carriers. All 3 LoF variants reported result in a truncated but stable MAP1B protein as demonstrated by western blot analysis. MAP1B undergoes post-translational modification and is cleaved (at position 2206) into a heavy chain and a light chain. The authors note that all LoF variants lead to truncation prior to the cleavage site. As commented by the authors, LoF variants are found in publicly available databases at a frequency of approx. 1 in 10000. One individual with de novo frameshift variant in Decipher ( https://decipher.sanger.ac.uk/search?q=gene%3AMAP1B#research-variants/results ). De novo and inherited MAP1B variants have previously been described in individuals with periventricular nodular heterotopia (PMID: 29738522). This was also a feature in 9 individuals in the previous ID study. Although PMID 30150678 is entitled "MAP1B mutations cause intellectual disability and extensive white matter deficit", intellectual disability was not a feature in all individuals or was rather mild when present. Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.510 | NSD2 |
Konstantinos Varvagiannis gene: NSD2 was added gene: NSD2 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: NSD2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: NSD2 were set to 29892088; 29760529; 29884796; 30244530 Phenotypes for gene: NSD2 were set to Intrauterine growth retardation; Growth delay; Microcephaly; Muscular hypotonia; Neurodevelopmental delay; Intellectual disability Penetrance for gene: NSD2 were set to unknown Review for gene: NSD2 was set to GREEN gene: NSD2 was marked as current diagnostic Added comment: PMID: 29892088 reports on 2 individuals with de novo SNVs affecting NSD2 (WHSC1). Both individuals presented with pre- and postnatal growth retardation, hypotonia, developmental delay / intellectual disability, as well as microcephaly. The authors suggest partial overlap with the phenotype of Wolf-Hirschhorn syndrome (WHS). Seizures are not part of the phenotype.The first subject had a splice site mutation while the second individual had a stopgain variant (affecting the PWWP domain). PMID: 29760529 describes a further patient with de novo nonsense mutation in NSD2. The boy was evaluated for probable growth delay ("low physical development"), hypotonia, psychomotor delay and microcephaly. The variant affected the SET domain. Three individuals with de novo likely loss-of-function (two frameshift and one stop gained) variants in Decipher [ https://decipher.sanger.ac.uk/search?q=NSD2#research-variants/results ]. A further patient with de novo frameshift mutation in NSD2 and a phenotype overlapping WHS reported in ClinVar [ https://www.ncbi.nlm.nih.gov/clinvar/variation/547999/ ] PMID: 29884796 (Zollino M and Doronzio PN) comments that NSD2 (WHSC1) is a neurodevelopmental gene with a role in growth delay, intellectual disability and dysmorphic facial features. PMID: 30244530 describes patients with 4p16.3 microdeletions spanning (exclusively) NSD2 and reviews the literature on patients with small microdeletions reported to date. All relevant individuals present with developmental delay and (rather mild) intellectual disability apart from other characteristics such as microcephaly, growth retardation and some facial features also observed in WHS. In Decipher one individual (286913) with a single CNV spanning exclusively NSD2 presenting with IUGR, failure to thrive, feeding difficulties, postnatal microcephaly, hypotonia, developmental delay as well as possibly relevant facial features. The gene is included in ID gene panels offered by various labs (either as NSD2 or WHSC1). As a result it can be considered for inclusion in the panel as green. Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.458 | KDM1A | Louise Daugherty edited their review of gene: KDM1A: Added comment: Recommendation that this gene should be Green. Three patients https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4902791/, there is functional characterisation of the three described mutations https://www.ncbi.nlm.nih.gov/pubmed/27094131?dopt=Abstract and the patients seem to share a similar phenotype, which recapitulates features of other deleterious mutations in better-characterised lysine demethylase and chromatin remodelling genes. There is also a recurrent de novo variant p.Tyr831Cys which has been reported in two separate "autism spectrum" patients in large cohort studies. The gene is also extensively constrained against both missense and LOF variation in humans http://exac.broadinstitute.org/gene/ENSG00000004487. I think what's been reported so far is probably robust enough to use the gene clinically.Pers comm. Ian Berry (NHS Leeds Genetics Laboratory); Changed rating: GREEN | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.420 | AP1S1 |
Louise Daugherty edited their review of gene: AP1S1: Added comment: New gene added by external expert review, who notes French Canadian (founder effect); however, Sephardic Jewish family also reported with a different variant. ID is part of the phenotype, added publication to support gene-disease association. The patients cases described in the literature to date are likely to be linked to a founder effect. 5 children from 3 families all from Quebec, Canada (with the same mutation) and 1 patient from a consanguineous Sephardic-Jewish background has been described (a different mutation in AP1S1). However, this gene was rated Green on the Vici Syndrome and other autophagy disorders panel for MEDNIK syndrome after discussion with Emma Baple (South West GMC and Genomics England); as there is a second, independent case with a different variant, plus functional data, so this gene can be green on the ID panel, since intellectual disability is part of the phenotype; Changed rating: GREEN |
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| Intellectual disability - microarray and sequencing v2.407 | ORC1 | Louise Daugherty Added comment: Comment on list classification: Although variants of ORC1 can result in microcephaly phenotype, there is no strong evidence for ID. single patient with ORC1 variants was described in this paper HERE, they had mild intellectual disability. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.398 | ISCA-37424-Loss |
Louise Daugherty Region: ISCA-37424-Loss was added Region: ISCA-37424-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37424-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for Region: ISCA-37424-Loss were set to 25217958; 20345475; 21248748; 24550761 Phenotypes for Region: ISCA-37424-Loss were set to PMID 20345475 macrocephaly, hypertelorism, and arachnodactyly, and neurodevelopmental delay that includes failure to thrive, hypotonia, and feeding difficulties in the neonatal period, and receptive and expressive language delay with global neurodevelopmental delay after the neonatal period. PMID: 21248748 developmental delay, mainly affecting speech. In addition, macrocephaly, mild facial dysmorphisms, cerebellar anomalies, cardiac defects and congenital breast aplasia; PMID: 25217958 none specified; PMID: 24550761 age-appropriate language development evaluated by a standardized test at an age of 2 years and 3 months. The boy was born with a cleft palate - a feature not present in any of the patients described before, phenotype of patients with an LCR3/4-flanked 10q22.3q23.2 deletion can be rather variable |
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