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| Intellectual disability - microarray and sequencing v5.532 | PLXNB2 |
Zornitza Stark gene: PLXNB2 was added gene: PLXNB2 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: PLXNB2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PLXNB2 were set to 38458752 Phenotypes for gene: PLXNB2 were set to Syndromic disease MONDO:0002254, PLXNB2 -related Review for gene: PLXNB2 was set to GREEN Added comment: 8 individuals from 6 families with core features of amelogenesis imperfecta and sensorineural hearing loss. Intellectual disability, ocular disease, ear developmental abnormalities and lymphoedema were also present in multiple cases. WES and WGS identified biallelic pathogenic variants in PLXNB2 (missense, nonsense, splice and a multiexon deletion variants). Variants segregated with disease. PLXNB2 is a large transmembrane semaphorin receptor protein, and semaphorin-plexin signalling controls cellular interactions that are critical during development as well as in adult life stages. Plxnb2 expression was detected in differentiating ameloblasts in mice. Human phenotype overlaps with that seen in Plxnb2 knockout mice. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.445 | ABCC9 | Sarah Leigh changed review comment from: Seven homozygous loss of function ABCC9 variants have been reported in seven unrelated cases of Intellectual disability and myopathy syndrome (OMIM:619719)(PMID: 31575858; 38217872). In vivo studies of abcc9 LoF in zebrafish, revealed an exacerbated motor response to pentylenetetrazole, a pro-convulsive drug, consistent with impaired neurodevelopment associated with an increased seizure susceptibility.(PMID: 38217872).; to: Seven homozygous loss of function ABCC9 variants have been reported in seven unrelated cases of Intellectual disability and myopathy syndrome (OMIM:619719)(PMID: 31575858; 38217872). In vivo studies of abcc9 LoF in zebrafish, revealed an exacerbated motor response to pentylenetetrazole, a pro-convulsive drug, consistent with impaired neurodevelopment associated with an increased seizure susceptibility.(PMID: 38217872). Heterozygous parents of the cases, did not show a consistent phenotype, although intrauterine death was reported in two families (PMID: 38217872). In family 4 the fetus was homozygous for c.1858C>T, p.(Arg620Ter) and in family 8 the parents were both heterozygous for c.2140_2141del, p.(Leu714SerfsTer7), but analysis of the fetus was not possible. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.389 | CLDN11 |
Achchuthan Shanmugasundram gene: CLDN11 was added gene: CLDN11 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: CLDN11 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CLDN11 were set to 33313762 Phenotypes for gene: CLDN11 were set to Leukodystrophy, hypomyelinating, 22, OMIM:619328 Review for gene: CLDN11 was set to GREEN Added comment: PMID:33313762 reported three unrelated individuals with early-onset spastic movement disorder, expressive speech disorder and eye abnormalities including hypermetropia. These patients exhibit global developmental delay, particularly motor and speech delay. Intellectual disability was maximally mild in two of three individuals and the intelligence is in a low-normal range in third individual, although IQ testing was not performed in them. Two different heterozygous de novo stop-loss variants were identified in these patients. One of the variants did not lead to a loss of CLDN11 expression on RNA level in fibroblasts indicating this transcript is not subject to nonsense-mediated decay and most likely translated into an extended protein. This gene has been associated with hypomyelinating leukodystrophy in OMIM, which includes global developmental delay and impaired intellectual development (mild) as clinical presentations. However, this gene has not yet been associated with phenotypes in Gene2Phenotype. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.315 | ZBTB47 |
Zornitza Stark gene: ZBTB47 was added gene: ZBTB47 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: ZBTB47 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: ZBTB47 were set to 37743782 Phenotypes for gene: ZBTB47 were set to Neurodevelopmental disorder (MONDO#0700092), ZBTB47-related Review for gene: ZBTB47 was set to GREEN Added comment: PMID 37743782: - 5 individuals with de novo missense variants, 4/5 have a recurring p.Gly477Lys. Probands have intellectual disability (5/5), seizures (5/5), hypotonia (5/5), gait abnormalities, and variable movement abnormalities (5/5). - Missense variants are positioned close to His and Cys residues involved in forming C2H2 zinc fingers. - No functional studies performed Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.161 | FEM1C |
Achchuthan Shanmugasundram changed review comment from: This gene should be rated RED as there is only one clear case of intellectual disability reported in literature. PMID:36336956 reported a 9 year-old boy with severe global developmental delay, lack of speech, pyramidal signs and limb ataxia and identified with a heterozygous de novo missense variant c.376G>C (p.Asp126His) in the FEM1C gene. Cognitive assessment performed at 9 years of age showed that he has moderate intellectual disability. De novo variant in the same residue (p.Asp126Val) has also been associated with an uncharacterised developmental disorder in PMID:28135719. An additional case with a diagnostically reported de novo variant in this gene and a compatible phenotype including intellectual disability and ataxia was identified in the internal Genomics England Clinical Variant Archive (CVA) by the Diagnostic Discovery initiative. This gene has not yet been associated with relevant phenotypes in OMIM or in Gene2Phenotype. Sources: Literature; to: PMID:36336956 reported a 9 year-old boy with severe global developmental delay, lack of speech, pyramidal signs and limb ataxia and identified with a heterozygous de novo missense variant c.376G>C (p.Asp126His) in the FEM1C gene. Cognitive assessment performed at 9 years of age showed that he has moderate intellectual disability. De novo variant in the same residue (p.Asp126Val) has also been associated with an uncharacterised developmental disorder in PMID:28135719. An additional case with a diagnostically reported de novo variant in this gene and a compatible phenotype including intellectual disability and ataxia was identified in the internal Genomics England Clinical Variant Archive (CVA) by the Diagnostic Discovery initiative. This gene has not yet been associated with relevant phenotypes in OMIM or in Gene2Phenotype. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.161 | FEM1C |
Achchuthan Shanmugasundram changed review comment from: This gene should be rated RED as there is only one clear case of intellectual disability reported in literature. PMID:36336956 reported a 9 year-old boy with severe global developmental delay, lack of speech, pyramidal signs and limb ataxia and identified with a heterozygous de novo missense variant c.376G>C (p.Asp126His) in the FEM1C gene. Cognitive assessment performed at 9 years of age showed that he has moderate intellectual disability. De novo variant in the same residue (p.Asp126Val) has also been associated with an uncharacterised developmental disorder in PMID:28135719. This gene has not yet been associated with relevant phenotypes in OMIM or in Gene2Phenotype. Sources: Literature; to: This gene should be rated RED as there is only one clear case of intellectual disability reported in literature. PMID:36336956 reported a 9 year-old boy with severe global developmental delay, lack of speech, pyramidal signs and limb ataxia and identified with a heterozygous de novo missense variant c.376G>C (p.Asp126His) in the FEM1C gene. Cognitive assessment performed at 9 years of age showed that he has moderate intellectual disability. De novo variant in the same residue (p.Asp126Val) has also been associated with an uncharacterised developmental disorder in PMID:28135719. An additional case with a diagnostically reported de novo variant in this gene and a compatible phenotype including intellectual disability and ataxia was identified in the internal Genomics England Clinical Variant Archive (CVA) by the Diagnostic Discovery initiative. This gene has not yet been associated with relevant phenotypes in OMIM or in Gene2Phenotype. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.2 | FEM1C |
Achchuthan Shanmugasundram gene: FEM1C was added gene: FEM1C was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: FEM1C was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: FEM1C were set to 36336956 Phenotypes for gene: FEM1C were set to Intellectual disability, MONDO:0001071 Review for gene: FEM1C was set to RED Added comment: This gene should be rated RED as there is only one clear case of intellectual disability reported in literature. PMID:36336956 reported a 9 year-old boy with severe global developmental delay, lack of speech, pyramidal signs and limb ataxia and identified with a heterozygous de novo missense variant c.376G>C (p.Asp126His) in the FEM1C gene. Cognitive assessment performed at 9 years of age showed that he has moderate intellectual disability. De novo variant in the same residue (p.Asp126Val) has also been associated with an uncharacterised developmental disorder in PMID:28135719. This gene has not yet been associated with relevant phenotypes in OMIM or in Gene2Phenotype. Sources: Literature |
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| Intellectual disability - microarray and sequencing v4.93 | DPYSL2 |
Achchuthan Shanmugasundram changed review comment from: This gene should be rated AMBER, as it has been associated with intellectual disability (ID) from two unrelated cases displaying monoallelic variants in DPYSL2/ CRMP2, and supported by functional studies. However, the evidence is not sufficient for green rating as there are variants reported in other (but different) genes in the two patients. PMID:35861646 reported two cases identified with heterozygous variants (patient1: c.1693C>T (p.Arg565Cys); patient 2: c.42C>A (p.Ser14Arg). These patients had overlapping phenotypes including dysmorphic features, severe global developmental delay and hypoplasia of the corpus callosum. In addition, patient 2 was bed-ridden and could not roll out and had a history of myoclonic seizures and status epilepticus. It should be noted that patient 1 is compound heterozygous for 2 missense variants in the EFCAB5 gene and was hemizygous for a maternally inherited missense variant in the GPKOW gene and patient 2 had 1 de novo missense variant in the COBLL1 gene and was compound heterozygous for 2 missense variants in the POTEF gene. The severity of the phenotypes between the two cases differs significantly and the additional variants may have possibly contributed to this phenotype. Brain-specific Crmp2 knockout mice display neuronal development deficits and behavioural impairments associated with hypoplasia of the corpus callosum. In addition, functional studies performed in zebrafish and cell lines that the CRMP2 variants lead to the loss-of-function of CRMP2 protein and can cause intellectual disability. Sources: Literature; to: This gene should be rated AMBER, as it has been associated with intellectual disability (ID) from two unrelated cases displaying monoallelic variants in DPYSL2/ CRMP2, and supported by functional studies. However, the evidence is not sufficient for green rating as there are variants reported in other (but different) genes in the two patients. PMID:35861646 reported two cases identified with heterozygous variants (patient1: c.1693C>T (p.Arg565Cys); patient 2: c.42C>A (p.Ser14Arg). These patients had overlapping phenotypes including dysmorphic features, severe global developmental delay and hypoplasia of the corpus callosum. In addition, patient 2 was bed-ridden and could not roll out and had a history of myoclonic seizures and status epilepticus. It should be noted that patient 1 is compound heterozygous for 2 missense variants in the EFCAB5 gene and was hemizygous for a maternally inherited missense variant in the GPKOW gene and patient 2 had 1 de novo missense variant in the COBLL1 gene and was compound heterozygous for 2 missense variants in the POTEF gene. The severity of the phenotypes between the two cases differs significantly and the additional variants may have possibly contributed to this phenotype. Brain-specific Crmp2 knockout mice display neuronal development deficits and behavioural impairments associated with hypoplasia of the corpus callosum. In addition, functional studies performed in zebrafish and cell lines that the CRMP2 variants lead to the loss-of-function of CRMP2 protein and can cause intellectual disability. This gene has not yet been associated with relevant phenotypes either in OMIM or in Gene2Phenotype. Sources: Literature |
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| Intellectual disability - microarray and sequencing v4.93 | DPYSL2 |
Achchuthan Shanmugasundram gene: DPYSL2 was added gene: DPYSL2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DPYSL2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: DPYSL2 were set to 27249678; 35861646 Phenotypes for gene: DPYSL2 were set to intellectual disability, MONDO:0001071; Aplasia/Hypoplasia of the corpus callosum, HP:0007370 Review for gene: DPYSL2 was set to AMBER Added comment: This gene should be rated AMBER, as it has been associated with intellectual disability (ID) from two unrelated cases displaying monoallelic variants in DPYSL2/ CRMP2, and supported by functional studies. However, the evidence is not sufficient for green rating as there are variants reported in other (but different) genes in the two patients. PMID:35861646 reported two cases identified with heterozygous variants (patient1: c.1693C>T (p.Arg565Cys); patient 2: c.42C>A (p.Ser14Arg). These patients had overlapping phenotypes including dysmorphic features, severe global developmental delay and hypoplasia of the corpus callosum. In addition, patient 2 was bed-ridden and could not roll out and had a history of myoclonic seizures and status epilepticus. It should be noted that patient 1 is compound heterozygous for 2 missense variants in the EFCAB5 gene and was hemizygous for a maternally inherited missense variant in the GPKOW gene and patient 2 had 1 de novo missense variant in the COBLL1 gene and was compound heterozygous for 2 missense variants in the POTEF gene. The severity of the phenotypes between the two cases differs significantly and the additional variants may have possibly contributed to this phenotype. Brain-specific Crmp2 knockout mice display neuronal development deficits and behavioural impairments associated with hypoplasia of the corpus callosum. In addition, functional studies performed in zebrafish and cell lines that the CRMP2 variants lead to the loss-of-function of CRMP2 protein and can cause intellectual disability. Sources: Literature |
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| Intellectual disability - microarray and sequencing v4.46 | BAP1 | Mafalda Gomes commented on gene: BAP1: Kry et al. (2022) performed trio-WES in a cohort with a rare syndromic NDD and identified de novo missense variants in 11 unrelated individuals. All individuals had DD or ID characterised notably by speech (11/11) and motor delay (6/11). Additional common characteristics were hypotonia, (7/11), seizures (6/11), and abnormal behaviour (8/10), including ASD, ADHD, and hypersensitivity. Almost all individuals showed dysmorphic facial features (10/11), and more than half (6/11) had skeletal malformations involving the hands, feet, or spine. Functional analysis showed that most of the variants cannot rescue the consequences of BAP1 inactivation, suggesting a loss-of-function mechanism. In T cells isolated from two affected children, H2A deubiquitination was impaired. In summary, this gene should be promoted to GREEN in this panel, with autosomal dominant mode of inheritance. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.18 | KLHL20 |
Arina Puzriakova Added comment: Comment on list classification: There is sufficient evidence to promote this gene to Green at the next GMS panel review. ----- Sleyp et al. 2022 (PMID: 36214804) reported on 14 patients with de novo missense variants who all presented with mild to severe ID, seizures, ASD, hyperactivity, and dysmorphic facial features. One variant (c.1069G>A, p.Gly357Arg) was recurrent in 11/14 cases but all variants clustered in the Kelch-type β-propeller domain (substrate binding surface) of the KLHL20 protein. No functional studies were performed but given the overlap in clinical presentation observed in patients with the same recurrent variant but also multiple different variants, its worth including as diagnostic-grade. |
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| Intellectual disability - microarray and sequencing v3.1733 | MTSS1L |
Arina Puzriakova gene: MTSS1L was added gene: MTSS1L was added to Intellectual disability. Sources: Literature new-gene-name, Q4_22_rating tags were added to gene: MTSS1L. Mode of inheritance for gene: MTSS1L was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: MTSS1L were set to 36067766 Phenotypes for gene: MTSS1L were set to Global developmental delay; Intellectual disability; Ophthalmological anomalies; Microcephaly; Mild facial dysmorphisms Review for gene: MTSS1L was set to GREEN Added comment: Huang et al. 2022 (PMID: 36067766) reported five unrelated individuals with the same heterozygous de novo variant (c.2011C>T; p.Arg671Trp) in MTSS2 (formally known as MTSS1L). Linkage analysis was not performed but given the variants arose de novo and the mixed ethnicity of the affected individuals (4 European, 1 Chinese) a founder effect can be ruled out. Subjects displayed a shared phenotype of GDD and/or ID, ophthalmological anomalies (most commonly nystagmus), microcephaly (primary in 2, relative in 3) and shared mild facial dysmorphisms. The single adult patient also presented with seizures and optic atrophy. Functional studies showed the variant leads to a decrease in mRNA level but does not impact protein levels of MTSS2. However, a Drosophila model demonstrated that loss of the fly ortholog results in defects in locomotor and visual functions which were rescued by human MTSS2 and only partially rescued by the MTSS2 c.2011C>T variant. Overexpression of the c.2011C>T variant caused similar phenotypes as the LoF mutant indicating a possible dominant-negative effect. 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 v3.1576 | 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 v3.1564 | 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 | 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 v3.1558 | SLC35B2 |
Konstantinos Varvagiannis gene: SLC35B2 was added gene: SLC35B2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC35B2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC35B2 were set to 35325049 Phenotypes for gene: SLC35B2 were set to Abnormality of the skeletal system; Short long bone; Short stature; Abnormality of epiphysis morphology; Scoliosis; Multiple joint dislocation; Global develpmental delay; Intellectual disability; CNS hypomyelination; Abnormality of the corpus callosum; Cerebral atrophy; Abnormality of the amniotic fluid Penetrance for gene: SLC35B2 were set to Complete Review for gene: SLC35B2 was set to AMBER Added comment: 2 unrelated individuals with biallelic SLC35B2 variants have been reported. DD and ID were part of the phenotype. There is currently no associated phenotype in OMIM/G2P/SysID. The gene has amber rating in the leukodystrophies panel of PanelApp Australia. Consider inclusion in the current panel (or other possibly relevant ones eg. for skeletal disorders, short stature, white matter disorders, corpus callosum, etc) with amber rating. --- Guasto et al (2022 - PMID:35325049) report 2 unrelated individuals with biallelic SLC35B2 variants. SLC35B2 encodes solute carrier family 35 (3'-phosphoadenosine 5'-phosphosulfate (PAPS) transporter), member B2. The protein is located in the Golgi membrane and serves as transporter of the activated nucleotide sulfate PAPS from the cytosol, where it is synthesized to the Golgi lumen. Another PAPS transporter is encoded by SLC35B3. In the Golgi apparatus PAPS serves as substrate of sulfotransferases for the addition sulfate to the covalently attached GAG chains of proteoglycans (PGs). The phenotype corresponded to a chondrodysplasia manifesting as severe pre- and postnatal growth retardation (height <-4 SD and -8 SD), early scoliosis, multiple joint dislocations (in one). There was severe DD affecting motor and expressive language development with associated ID. Brain imaging was suggestive of hypomyelinating leukodystrophy with thin corpus callosum and cerebral atrophy. One individual had a cleft palate in the context of Pierre Robin sequence. Both individuals were investigated with exome sequencing. The first individual - born to consanguineous parents - was homozygous for an in-frame del (NM_178148.3:c.1218_1220del, p.Leu407del) with Sanger sequencing confirming the variants, and heterozygosity in parents and 2 unaffected sibs. There was an initially identified hmz CUL7 variant (for 3M syndrome), which was not felt sufficient to explain the severity of the phenotype and notably ID. The 2nd proband was homozygous for a fs variant (c.1224_1225delAG / p.Arg408SerfsTer18 - leading to loss of the last 8 amino acids) occurring in the context of uniparental isodisomy [iUPD(6)] spanning the complete chr6 based on the exome data. Among the evidence presented for SLC35B2 and the variants : - SLC35B2 has high mRNA expression in fetal and adult mouse brain and other tissues. - Upon qPCR analysis of mRNA expression in human brain samples, the gene had expression across the brain (frontal lobe grey matter, subcortical frontal white matter/cerebellum). - High expression was shown upon analysis of mouse brain single cell RNA data (EMBL) in oligodendrocytes and microglial cells. - RT-PCR on mRNA from skin fibroblasts (both individuals) revealed significant decrease of SCL35B2 mRNA levels compared to controls. - Transfection of C-terminal c-myc tagged wt or mutant proteins in HEK293F cells, followed by western blotting did not reveal significant difference at the protein level. Wt SLC35B2 localized at the Golgi apparatus as suggested by colocalization with GM130 marker. The 2 variants however displayed only partial colocalization (/loss of localization specificity) with diffuse signal in the cell. - Chondroitin sulfate disaccharide sulfation was decreased upon HPLC disaccharide analysis in patient fibroblasts and bikunin (a circulating proteoglycan in blood) electrophoretic pattern in patient sera. - Disorders due to variants in genes implicated in proteoglycan biogenesis (e.g. XYLT1, B3GALT6, CHSY1) are associated with skeletal/connective tissue manifestations with DD/ID. - C-elegans model lacking pst-1 (SLC35B2 ortholog) provides support that the protein is required for migration, axonal guidance, and presynaptic development in a subset of neurons. - dsm-1 - the rat ortholog - is expressed in rat brain in D-serine and NMDA receptor rich regions. When expressed in Xenopus oocytes it accelerated the efflux of D-serine (a co-agonist for NMDA receptor). - Variants in other members of SLC superfamily (e.g. SLC17A5, SLC35A3, SLC29A3, SLC35A2) have been associated with brain-bone phenotypes. 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 v3.1529 | 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 | 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 v3.1506 | 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 v3.1455 | CLPB |
Arina Puzriakova Added comment: Comment on mode of inheritance: MOI should be updated from 'Biallelic' to 'Both mono- and biallelic' at the next GMS update. Association between biallelic variants and disease is well established, with more than 35 affected individuals reported. Recently, Wortmann et al. 2021 (PMID: 34140661) published six unrelated individuals with one of four different de novo monoallelic missense variants in CLPB. The phenotype strongly overlapped with that observed in the recessive disease, including mild to severe DD/ID in all cases. Some functional studies of heterozygous variants were performed. |
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| Intellectual disability - microarray and sequencing v3.1352 | SNIP1 | Sarah Leigh Added comment: Comment on list classification: Associated with relevant phenotype in OMIM and as possible Gen2Phen gene. A single (founder) variant NM_024700.4:c.1097A>G, p.(Glu366Gly) has been reported in over 30 cases of Psychomotor retardation, epilepsy, and craniofacial dysmorphism OMIM:614501 in the Amish community (PMIDs: 22279524; 34570759). Cases are homozygous for this variant and unaffected members of the families are heterozygous or wt. Overexpression of the equivalent mouse variant in mouse inner medullary collecting duct cells, resulted in a more aggregated appearance in the nucleus compared to wildtype. The variant protein maybe unstable as Western blots showed reduced levels of the variant protein (PMID: 22279524). Whole transcriptomic analysis of patient blood was performed in PMID: 34570759. This revealed 11 upregulated and 32 downregulated genes, of which 24 had previously been associated with neurological disease. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1220 | ARF3 |
Konstantinos Varvagiannis gene: ARF3 was added gene: ARF3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ARF3 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ARF3 were set to 34346499 Phenotypes for gene: ARF3 were set to Global developmental delay; Intellectual disability; Seizures; Morphological abnormality of the central nervous system Penetrance for gene: ARF3 were set to unknown Review for gene: ARF3 was set to AMBER Added comment: Sakamoto et al (2021 - PMID: 34346499) provide some evidence that monoallelic ARF3 pathogenic variants may be associated with a NDD with brain abnormality. Using trio exome sequencing, the authors identified 2 individuals with NDD harboring de novo ARF3 variants, namely: NM_001659.2:c.200A>T / p.Asp67Val and c.296G>T / p.Arg99Leu. Individual 1 (with Asp67Val / age : 4y10m), appeared to be more severelely affected with prenatal onset progressive microcephaly, severe global DD, epilepsy. Upon MRI there was cerebellar and brainstem atrophy. Individual 2 (Arg99Leu / 14y) had severe DD and ID (IQ of 23), epilepsy and upon MRI cerebellar hypoplasia. This subject did not exhibit microcephaly. Common facial features incl. broad nose, full cheeks, small philtrum, strabismus, thin upper lips and abnormal jaw. There was no evidence of systemic involvement in both. ARF3 encodes ADP-ribosylation factor 3. Adenosine diphosphate ribosylation factors (ARFs) are key proteins for regulation of cargo sorting at the Golgi network, with ARF3 mainly working at the trans-Golgi network. ARFs belong to the small GTP-binding protein (G protein) superfamily. ARF3 switches between an active GTP-bound form and an inactive GDP-bound form, regulated by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs) respectively. Members of the ARF superfamily regulate various aspects of membrane traffic, among others in neurons. There are 5 homologs of ARF families, divided in 3 classes. ARF3 and ARF1 belong to class I. Monoallelic ARF1 mutations are associated with Periventricular nodular heterotopia 8 (MIM 618185). In vivo, in vitro and in silico studies for the 2 variants suggest that both impair the Golgi transport system although each variant most likely exerts a different effect (gain-of-function for Arg99Leu vs loss-of-function/dominant-negative for Asp67Val). This was also reflected in somewhat different phenotype of the subjects with the respective variants. Common features included severe DD, epilepsy and brain abnormalities although Asp67Val was associated with diffuse brain atrophy as well as congenital microcephaly and Arg99Leu with cerebellar hypoplasia. Evidence to support the effect of each variant include: Arg99Leu: Had identical Golgi localization to that of wt Had increased binding activity with GGA1, a protein recruited by the GTP-bound active form of ARF3 to the TGN membrane (supporting GoF) In silico structural analysis suggested it may fail to stabilize the conformation of Asp26, resulting in impaired GTP hydrolysis (GoF). In transgenic fruit flies, evaluation of the ARF3 variant toxicity using the rough eye phenotype this variant was associated with increased severity of the r-e phenotype similar to a previously studied GoF variant (Gln71Leu) Asp67Val: Did not show a Golgi-like pattern of localization (similar to Thr31Asn a previously studied dominant-negative variant) Displayed decreased protein stability In silico structural analysis suggested that Asp67Val may lead to compromised binding of GTP or GDP (suggestive of LoF) In transgenic Drosophila eye-specific expression of Asp67Val (similar to Thr31Asn, a known dominant-negative variant) was lethal possibly due to high toxicity in very small amounts in tissues outside the eye. There is no associated phenotype in OMIM, G2P or SysID. 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 | CLCN3 |
Zornitza Stark gene: CLCN3 was added gene: CLCN3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CLCN3 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: CLCN3 were set to 34186028 Phenotypes for gene: CLCN3 were set to Neurodevelopmental disorder Mode of pathogenicity for gene: CLCN3 was set to Other Review for gene: CLCN3 was set to GREEN gene: CLCN3 was marked as current diagnostic Added comment: 11 individuals reported, 9 that carried 8 different rare heterozygous missense variants in CLCN3, and 2 siblings that were homozygous for an NMD-predicted frameshift variant likely abolishing ClC-3 function. All missense variants were confirmed to be de novo in eight individuals for whom parental data was available. The 11 individuals in the cohort share clinical features of variable severity. All 11 have GDD or ID and dysmorphic features, and a majority has mood or behavioural disorders and structural brain abnormalities: - Structural brain abnormalities on MRI (9/11) included partial or full agenesis of the corpus callosum (6/9), disorganized cerebellar folia (4/9), delayed myelination (3/9), decreased white matter volume (3/9), pons hypoplasia (3/9), and dysmorphic dentate nuclei (3/9). Six of those with brain abnormalities also presented with seizures. - Nine have abnormal vision, including strabismus in four and inability to fix or follow in the two with homozygous loss-of-function variants. - Hypotonia ranging from mild to severe was reported in 7 of the 11 individuals. - Six have mood or behavioural disorders, particularly anxiety (3/6). - Consistent dysmorphic facial features included microcephaly, prominent forehead, hypertelorism, down-slanting palpebral fissures, full cheeks, and micrognathia. The severity of disease in the two siblings with homozygous disruption of ClC-3 is consistent with the drastic phenotype seen in Clcn3 KO mice. The disease was more severe in two siblings carrying homozygous loss-of-function variants with the presence of GDD, absent speech, seizures, and salt and pepper fundal pigmentation in both individuals, with one deceased at 14 months of age. The siblings also had significant neuroanatomical findings including diffusely decreased white matter volume, thin corpora callosa, small hippocampi, and disorganized cerebellar folia. Supporting biallelic inheritance for LoF variants, disruption of mouse Clcn3 results in drastic neurodegeneration with loss of the hippocampus a few months after birth and early retinal degeneration. Clcn3−/− mice display severe neurodegeneration, whereas heterozygous Clcn3+/− mice appear normal. Patch-clamp studies were used to investigate four of the missense variants. These suggested a gain of function in two variants with increased current in HEK cells, however they also showed reduced rectification of voltage and a loss of transient current, plus decreased current amplitude, glycosylation and surface expression when expressed in oocytes, and were suspected to interfere with channel gating and a negative feedback mechanism. These effects were also shown to vary depending on pH levels. The current of the remaining two variants did not differ from WT. For heterozygous missense variants, the disruption induced may be at least partially conferred to mutant/WT homodimers and mutant/ClC-4 heterodimers. Both loss and gain of function in this gene resulted in the same phenotype. Green for mono-allelic variants, Amber/Red for bi-allelic. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1201 | CAMK4 |
Konstantinos Varvagiannis gene: CAMK4 was added gene: CAMK4 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: CAMK4 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CAMK4 were set to 30262571; 33098801; 33211350 Phenotypes for gene: CAMK4 were set to Global developmental delay; Intellectual disability; Autism; Behavioral abnormality; Abnormality of movement; Dystonia; Ataxia; Chorea; Myoclonus Penetrance for gene: CAMK4 were set to Complete Review for gene: CAMK4 was set to GREEN Added comment: 3 publications by Zech et al (2018, 2020 - PMIDs : 30262571, 33098801, 33211350) provide clinical details on 3 individuals, each harboring a private de novo CAMK4 variant. Overlapping features included DD, ID, behavoral issues, autism and abnormal hyperkinetic movements. Dystonia and chorea in all 3 appeared 3-20 years after initial symptoms. CAMK4 encodes Calcium/Calmodulin-dependent protein kinase IV, an important mediator of calcium-mediated activity and dynamics, particularly in the brain. It is involved in neuronal transmission, synaptic plasticity, and neuronal gene expression required for brain development and neuronal homeostasis (summary by OMIM based on Zech et al, 2018). The 473 aa enzyme has a protein kinase domain (aa 46-300) and a C-terminal autoregulatory domain (aa 305-341) the latter comprising an autoinhibitory domain (AID / aa 305-321) and a calmodulin-binding domain (CBD / aa 322-341) [NP_001735.1 / NM_001744.4 - also used below]. Variants in all 3 subjects were identified following trio-WES and were in all cases protein-truncating, mapping to exon 10 or exon 10-intron 10 junction, expected to escape NMD and cause selective abrogation of the autoinhibitory domain (aa 305-321) leading overall to gain-of-function. Variation databases include pLoF CAMK4 variants albeit in all cases usptream or downstream of this region (pLI of this gene in gnomAD: 0.51). Variants leading to selective abrogation of the autoregulatory domain have not been reported. Extensive evidence for the GoF effect of the variant has been provided in the first publication. Several previous studies have demonstrated that abrogation of the AID domain leads to consitutive activation (details below). Mouse models - though corresponding to homozygous loss of function - support a role for CAMKIV in cognitive and motor symptoms. Null mice display tremulous and ataxic movements, deficiencies in balance and sensorimotor performance associated with reduced number of Purkinje neurons (Ribar et al 2000, PMID: 11069976 - not reviewed). Wei et al (2002, PMID: 12006982 - not reviewed) provided evidence for alteration in hippocampal physiology and memory function. Heterozygous mutations in other genes for calcium/calmodulin-dependent protein kinases (CAMKs) e.g. CAMK2A/CAMK2B (encoding subunits of CAMKII) have been reported in individuals with ID. --- The proband in the first publication (PMID: 30262571) was a male with DD, ID, behavioral difficulties (ASD, autoaggression, stereotypies) and hyperkinetic movement disorder (myoclonus, chorea, ataxia) with severe generalized dystonia (onset at the age of 13y). Brain MRI demonstrated cerebellar atrophy. Extensive work-up incl. karyotyping, CMA, DYT-TOR1A, THAP1, GCH1, SCA1/2/3/6/7/8/12/17, Friedreich's ataxia and FMR1 analysis was negative.F Trio WES identified a dn splice site variant (c.981+1G>A) in the last exon-intron junction. RT-PCR followed by gel electrophoresis and Sanger in fibroblasts from an affected and control subject revealed that the proband had - as predicted by the type/location of the variant - in equal amount 2 cDNA products, a normal as well as a truncated one. Sequencing of the shortest revealed utilization of a cryptic donor splice site upstream of the mutated donor leading to a 77bp out-of-frame deletion and introduction of a premature stop codon in the last codon (p.Lys303Serfs*28). Western blot in fibroblast cell lines revealed 2 bands corresponding to the normal protein product as well as to the p.Lys303Serfs*28 although expression of the latter was lower than that of the full length protein. Several previous studies have shown that mutant CAMKIV species that lack the autoinhibitory domain are consitutively active (several Refs provided). Among others Chatila et al (1996, PMID: 8702940) studied an in vitro-engineered truncation mutant (Δ1-317 - truncation at position 317 of the protein) with functionally validated gain-of-function effect. To prove enhanced activity of the splicing variant, Zech et al assessed phosphorylation of CREB (cyclic AMP-responsive element binding protein), a downstream substrate of CAMKIV. Immunobloting revealed significant increase of CREB phosphorylation in patient fibroblasts compared to controls. Overactivation of CAMKIV signaling was reversed when cells were treated with STO-609 an inhibitor of CAMKK, the ustream activator of CAMKIV. Overall the authors demonstrated that loss of CAMKIV autoregulatory domain due to this splice variant had a gain-of-function effect. ---- Following trio-WES, Zech et al (2020 - PMID: 33098801) identified another relevant subject within cohort of 764 individuals with dystonia. This 12-y.o. male, harboring a different variant affecting the same donor site (c.981+1G>T), presented DD, ID, dystonia (onset at 3y) and additional movement disorders (myoclonus, ataxia) as well as similar behavior (ASD, autoaggression, stereotypies). [Details in suppl. p20]. ---- Finally Zech et al (2020 - PMID: 33211350) reported on a 24-y.o. woman with adolescence onset choreodystonia. Other features included DD, moderate ID, absence seizures in infancy, OCD with anxiety and later diagnosis of ASD. Trio WES revealed a dn stopgain variant (c.940C>T; p.Gln314*). ---- There is no associated phenotype in OMIM, G2P, PanelApp AUS. In SysID CAMK4 is listed among the current primary ID genes. ---- Please consider inclusion in other relevant panels. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1167 | RING1 |
Eleanor Williams gene: RING1 was added gene: RING1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: RING1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: RING1 were set to 29386386 Phenotypes for gene: RING1 were set to microcephaly; intellectual disability Review for gene: RING1 was set to RED Added comment: Not associated with any phenotype in OMIM. PMID: 29386386 - Pierce et al 2018 - report a 13 yo female with a de novo RING1 p.R95Q variant and syndromic neurodevelopmental disabilities. Early motor and language development were normal but were delayed after the first year of life. Cognitive testing showed a verbal IQ of 55 and a visual performance IQ of 63. Head circumference at birth was -4.9 SD, and -4.2 SD at age 13 which falls into the severe microcephaly category. C. elegans with either the missense mutation or complete knockout of spat-3 (the suggested RING1 ortholog) were defective in monoubiquitylation of histone H2A and had defects in neuronal migration and axon guidance. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1154 | EPHA7 |
Konstantinos Varvagiannis gene: EPHA7 was added gene: EPHA7 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: EPHA7 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: EPHA7 were set to 34176129; 19664229 Phenotypes for gene: EPHA7 were set to Global developmental delay; Intellectual disability; Delayed speech and language development; Behavioral abnormality Penetrance for gene: EPHA7 were set to Incomplete Review for gene: EPHA7 was set to AMBER Added comment: Lévy et al (2021 - PMID: 34176129) provide evidence that haploinssuficiency of EPHA7 results in a neurodevelopmental disorder. The authors report on 12 individuals belonging to 9 unrelated families, all harboring with 6q microdeletions spanning EPHA7. Overlapping features included DD (13/13), ID (10/10 - mild in most cases, individuals with larger CNVs/additional variants had more severe phenotype), speech delay and behavioral disorders. Variable other features incl. hypotonia (70%), non specific facial features, eye abnormalities (40%) and cardiac defects (25%). The CNVs ranged from 152 kb to few Mb in size but in 4 subjects (P5-8) were only minimal, involving only EPHA7. The 6q microdeletion included additional ID-related genes in at least one case (eg. ZNF292 in P12) while one subject (P4) harbored also a 7q11.23 Williams syndrome deletion. Confirmation (e.g. with FISH or qPCR) and segregation analyses were performed. 9 out of 12 individuals had inherited the deletion (5 subjects paternal, 4 maternal), in 1 subject (P12) this occured de novo, while for 2 others inheritance was not specified. Most deletions were inherited from an unaffected parent (in 6/7 families), with unclear contribution in a further one. Sequencing of an ID gene panel was performed for 5 subjects (P1-4 (sibs) and P9) and exome for 4 ones (P1,2,10,11). CNVs in all these subjects were not limited to EPHA7. These investigations did not reveal other variants responsible for the phenotype of these subjects. EPHA7 encodes ephrin receptor A7. As the authors comment, ephrin receptors are the largest family of transmembrane receptor tyrosine kinases. These receptors interact with membrane bound ephrins and binding activates the tyrosine kinase activity of the receptor. The authors discuss on previous studies suggesting an important role for EphA7 in brain development (modulation of cell-cell adhesion and repulsion, regulation of dendrite morphogenesis in early corticogenesis, role in dendritic spine formation later in development. EphA7 has also been proposed to drive neuronal maturation and synaptic function). Haploinsufficiency for other ephrins or ephrin receptors has been implicated in other NDDs. Finally the authors comment on a previous report of a de novo 2.16 Mb microdeletion spanning EPHA7 and another gene (TSG1). This deletion, reported by Traylor et al (2009 - PMID: 19664229) was identified in a 15-month old male with DD, microcephaly and dysmorphic features. Overall Lévy et al promote incomplete penetrance and variable expressivity with haploinsufficiency of this gene being a risk factor for NDD. [The gene has also an %HI of 2.76% and a pLI of 1]. In DECIPHER there are 2 indivuals (DDD participants) with de novo missense variants and abnormality of the nervous system. As a result this gene can 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 v3.1057 | CDH11 |
Arina Puzriakova Added comment: Comment on mode of inheritance: Association with biallelic variants well-established, with ID reported in all cases to date. On the other hand, DD/ID is variable in individuals with monoallelic variants (PMID: 33811546) - 7/19 cases (4 families) presented a developmental phenotype including very mild speech delays in 5/7, mild-moderate DD in 1/7, and global delay in 1/7 individuals. Overall, given the mostly mild degree of cognitive delay, as well as intra- and interfamilial reduced penetrance of this feature, there is currently not enough evidence to rate as Green on this panel for the monoallelic disease. |
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| Intellectual disability - microarray and sequencing v3.736 | RNU7-1 | Arina Puzriakova Phenotypes for gene: RNU7-1 were changed from Aicardi–Goutières syndrome-like to Aicardi–Goutières syndrome-like; Type I interferonopathy | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.734 | RNU7-1 | Arina Puzriakova reviewed gene: RNU7-1: Rating: GREEN; Mode of pathogenicity: None; Publications: 33230297; Phenotypes: Aicardi–Goutières syndrome-like, Type I interferonopathy; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 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 v3.666 | CSNK1G1 | Arina Puzriakova Added comment: Comment on list classification: Upgraded from Red to Amber as now at least 5 unrelated individuals reported (PMID: 33009664). All present developmental delay of varying severity, although a formal ID assessment was not performed. Tagged 'for-review' to evaluate relevance of the phenotypes to this panel. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.484 | PRKACB |
Konstantinos Varvagiannis gene: PRKACB was added gene: PRKACB was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PRKACB was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PRKACB were set to 33058759 Phenotypes for gene: PRKACB were set to Postaxial hand polydactyly; Postaxial foot polydactyly; Common atrium; Atrioventricular canal defect; Narrow chest; Abnormality of the teeth; Intellectual disability Penetrance for gene: PRKACB were set to unknown Mode of pathogenicity for gene: PRKACB 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: PRKACB was set to AMBER Added comment: ID was a feature in 2/4 individuals with PRKACB pathogenic variant reported to date. Please consider inclusion of PRKACB (and PRKACA) in other relevant gene panels e.g. for polydactyly, congenital heart defects. The disorder may be considered in the DD of ciliopathies. ----- Palencia-Campos et al (2020 - PMID: 33058759) report on the phenotype of 3 individuals heterozygous for PRKACA and 4 individuals heterozygous for PRKACB pathogenic variants. The most characteristic features in all individuals with PRKACA/PRKACB mutation, included postaxial polydactyly of hands (6/7 bilateral, 1/7 unilateral) and feet (4/7 bilateral, 1/7 unilateral), brachydactyly and congenital heart defects (CHD 5/7) namely a common atrium or AVSD. Two individuals with PRKACA variant who did not have CHD had offspring with the same variant and an AVSD. Other variably occurring features included short stature, limbs, narrow chest, abnormal teeth, oral frenula, nail dysplasia. One individual with PRKACB variant presented tumors. Intellectual disability was reported in 2/4 individuals with PRKACB variant (1/4: mild, 1/4: severe). The 3 individuals with PRKACA variant did not present ID. As the phenotype was overall suggestive of Ellis-van Creveld syndrome (or the allelic Weyers acrofacial dysostosis), although these diagnoses were ruled out following analysis of EVC and EVC2 genes. WES was carried out in all. PRKACA : A single heterozygous missense variant was identified in 3 individuals from 3 families (NM_002730.4:c.409G>A / p.Gly137Arg) with 1 of the probands harboring the variant in mosaic state (28% of reads) and having 2 similarly affected offspring. The variant was de novo in one individual and inherited in a third one having a similarly affected fetus (narrow thorax, postaxial polyd, AVSD). PRKACB : 4 different variants were identified (NM_002731.3: p.His88Arg/Asn, p.Gly235Arg, c.161C>T - p.Ser54Leu). One of the individuals was mosaic for the latter variant, while in all other cases the variant had occurred de novo. Protein kinase A (PKA) is a tetrameric holoenzyme formed by the association of 2 catalytic (C) subunits with a regulatory (R) subunit dimer. Activation of PKA is achieved through binding of 2 cAMP molecules to each R-subunit, and unleashing(/dissociation) of C-subunits to engage substrates. PRKACA/B genes encode the Cα- and Cβ-subunits while the 4 functionally non-redundant regulatory subunits are encoded by PRKAR1A/1B/2A/2B genes. The authors provide evidence that the variants confer increased sensitivity of PKA holoenzymes to activation by cAMP (compared to wt). By performing ectopic expression of wt or mt PRKACA/B (variants studied : PRKACA p.Gly137Arg / PRKACB p.Gly235Arg) in NIH 3T3 fibroblasts, the authors demonstrate that inhibition of hedgehog signaling likely underlyies the developmental defects observed in affected individuals. As for PRKACA, the authors cite another study where a 31-month old female with EvC syndrome diagnosis was found to harbor the aforementioned variant (NM_001304349.1:c.637G>A:p.Gly213Arg corresponding to NM_002730.4:c.409G>A / p.Gly137Arg) as a de novo event. Without additional evidence at the time, the variant was considered to be a candidate for this subject's phenotype (Monies et al 2019 – PMID: 31130284). Sources: Literature |
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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 v3.421 | ERF |
Arina Puzriakova Source Expert Review Red was added to ERF. Rating Changed from Amber List (moderate evidence) to Red List (low evidence) |
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| Intellectual disability - microarray and sequencing v3.420 | ITFG2 |
Konstantinos Varvagiannis gene: ITFG2 was added gene: ITFG2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ITFG2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ITFG2 were set to 28397838; https://doi.org/10.1038/s41525-020-00150-z Phenotypes for gene: ITFG2 were set to Neurodevelopmental abnormality; Intellectual disability; Developmental regression; Ataxia Penetrance for gene: ITFG2 were set to Complete Review for gene: ITFG2 was set to AMBER Added comment: ITFG2 was suggested to be a candidate gene for autosomal recessive ID in the study by Harripaul et al (2018 - PMID: 28397838). The authors performed microarray and exome sequencing in 192 consanguineous families and identified a homozygous ITGF2 stopgain variant (NM_018463.3:c.472G>T / p.Glu158*) along with 3 additional variants segregating with ID within an investigated family (PK51). Cheema et al (2020 - https://doi.org/10.1038/s41525-020-00150-z) report briefly on a male, born to consanguineous parents presenting with NDD, seizures, regression and ataxia. There was a similarly affected female sibling. Evaluation of ROH revealed a homozygous ITFG2 nonsense variant [NM_018463.3:c.361C>T / p.(Gln121*)]. Families in this study were investigated by trio WES or WGS. Evaluation of data of the same lab revealed 3 additional unrelated subjects with overlapping phenotypes, notably NDD and ataxia. These individuals were - each - homozygous for pLoF variants [NM_018463.3:c.848-1G>A; NM_018463.3:c.704dupC, p.(Ala236fs), NM_018463.3:c.1000_1001delAT, p.(Ile334fs)]. As discussed in OMIM, ITFG2 encodes a subunit of the KICSTOR protein complex, having a role in regulating nutrient sensing by MTOR complex-1 (Wolfson et al 2017 - PMID : 28199306). Please consider inclusion in the ID panel with amber rating, pending further details. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.420 | SHMT2 |
Konstantinos Varvagiannis gene: SHMT2 was added gene: SHMT2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SHMT2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SHMT2 were set to 33015733 Phenotypes for gene: SHMT2 were set to Congenital microcephaly; Infantile axial hypotonia; Spastic paraparesis; Global developmental delay; Intellectual disability; Abnormality of the corpus callosum; Abnormal cortical gyration; Hypertrophic cardiomyopathy; Abnormality of the face; Proximal placement of thumb; 2-3 toe syndactyly Penetrance for gene: SHMT2 were set to Complete Review for gene: SHMT2 was set to GREEN Added comment: García‑Cazorla et al. (2020 - PMID: 33015733) report 5 individuals (from 4 families) with a novel brain and heart developmental syndrome caused by biallelic SHMT2 pathogenic variants. All affected subjects presented similar phenotype incl. microcephaly at birth (5/5 OFC < -2 SD though in 2/5 cases N OFC was observed later), DD and ID (1/5 mild-moderate, 1/5 moderate, 3/5 severe), motor dysfunction in the form of spastic (5/5) paraparesis, ataxia/dysmetria (3/4), intention tremor (in 3/?) and/or peripheral neuropathy (2 sibs). They exhibited corpus callosum hypoplasia (5/5) and perisylvian microgyria-like pattern (4/5). Cardiac problems were reported in all, with hypertrophic cardiomyopathy in 4/5 (from 3 families) and atrial-SD in the 5th individual (1/5). Common dysmorphic features incl. long palpebral/fissures, eversion of lateral third of lower eylids, arched eyebrows, long eyelashes, thin upper lip, short Vth finger, fetal pads, mild 2-3 toe syndactyly, proximally placed thumbs. Biallelic variants were identified following exome sequencing in all (other investigations not mentioned). Identified variants were in all cases missense SNVs or in-frame del, which together with evidence from population databases and mouse model might suggest a hypomorphic effect of variants and intolerance/embryonic lethality for homozygous LoF ones. SHMT2 encodes the mitohondrial form of serine hydroxymethyltransferase. The enzyme transfers one-carbon units from serine to tetrahydrofolate (THF) and generates glycine and 5,10,methylene-THF. Mitochondrial defect was suggested by presence of ragged red fibers in myocardial biopsy of one patient. Quadriceps and myocardial biopsies of the same individual were overall suggestive of myopathic changes. While plasma metabolites were within N range and SHMT2 protein levels not significantly altered in patient fibroblasts, the authors provide evidence for impaired enzymatic function eg. presence of the SHMT2 substrate (THF) in patient but not control (mitochondria-enriched) fibroblasts , decrease in glycine/serine ratios, impared folate metabolism. Patient fibroblasts displayed impaired oxidative capacity (reduced ATP levels in a medium without glucose, diminished oxygen consumption rates). Mitochondrial membrane potential and ROS levels were also suggestive of redox malfunction. Shmt2 ko in mice was previously shown to be embryonically lethal attributed to severe mitochondrial respiration defects, although there was no observed brain metabolic defect. The authors performed Shmt2 knockdown in motoneurons in Drosophila, demonstrating neuromuscular junction (# of satellite boutons) and motility defects (climbing distance/velocity). Overall this gene can be considered for inclusion with (probably) green rating in gene panels for ID, metabolic / mitochondrial disorders, cardiomyopathy, congenital microcephaly, corpus callosum anomalies, etc. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides produced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration in mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could be ruled out that the de novo and maternally inherited variants were on the same allele, as phase was not been determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could be ruled out that the de novo and maternally inherited variants were on the same allele, as phase was not been determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis gene: NEMF was added gene: NEMF was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: NEMF was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: NEMF were set to 32934225 Phenotypes for gene: NEMF were set to Hypotonia; Global developmental delay; Intellectual disability; Axonal neuropathy; Ataxia; Abnormal brain imaging; Kyphosis; Scoliosis; Tremor; Respiratory distress Penetrance for gene: NEMF were set to Complete Review for gene: NEMF was set to GREEN Added comment: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.314 | LMNB1 |
Konstantinos Varvagiannis gene: LMNB1 was added gene: LMNB1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: LMNB1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: LMNB1 were set to 32910914 Phenotypes for gene: LMNB1 were set to Global developmental delay; Intellectual disability; Microcephaly; Short stature; Seizures; Abnormality of the corpus callosum; Cortical gyral simplification; Feeding difficulties; Scoliosis Penetrance for gene: LMNB1 were set to unknown Mode of pathogenicity for gene: LMNB1 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: LMNB1 was set to GREEN Added comment: Cristofoli et al (2020 - PMID: 32910914) report 7 individuals (from 5 families) harboring mostly de novo LMNB1 variants. The common phenotype consisted of primary microcephaly (7/7 ranging from -4.4 to -10 SD), DD/ID (7/7), relative short stature in most (+0.7 to -4 SD). Additional features included brain MRI abnormalities (abnormal CC in 3, simplified gyral pattern in 3, small structurally normal brain, etc), seizures (4 individuals from 2 families), limb spasticity (1/7), cortical visual impairment (in 3), feeding difficulties (5/7), scoliosis (4/7). Non-overlapping dysmorphic features were reported in some. Variants were identified by WES or custom-designed gene panel and included 3 missense variants, 1 in-frame deletion and a splice variant. The in-frame deletion was inherited from a similarly affected parent in whom the variant occurred as a dn event. The splice SNV(NM_005573.3:c.939+1G>A) occurred in 3 sibs and was present as mosaic variant (15%) in the parent. This variant was predicted to result to extension of exon 5 by 6 amino-acids (samples were unavailable for mRNA studies). LMNB1 encodes a B-type lamin (the other being encoded by LMNB2). A- and B- type lamins are major components of the nuclear lamina. As the authors comment, LMNB1 is expressed in almost all cell types beginning at the earliest stages of development. Lamin-deficient mouse models support an essential role of B-type lamins in organogenesis, neuronal migration, patterning during brain development. Functional studies performed, demonstrated impaired formation of LMNB1 nuclear lamina in LMNB1-null HeLa cells transfected with cDNAs for 3 missense variants. Two variants (Lys33Glu/Arg42Trp) were shown to result in decreased nuclear localization with increased abundance in the cytosolic fraction. In patient derived LCLs these variants led to abnormal nuclear morphology. A missense variant in another domain (Ala152Gly - 1st coil domain) resulted also in lower abundance of lamin B1, irregular lamin A/C nuclear lamina, as well as more condensed nuclei (HeLa cells). LMNB1 duplications or missense mutations increasing LMNB1 expression are associated with a different presentation of AD leuodystrophy. A variant previously associated with leukodystrophy (Arg29Trp) was shown to behave differently (present in the nuclear extract but not in the cytosol, lamin B1 to A/C ratio in nuclear extract was not significantly altered compared to wt as was the case for Arg42Trp, Lys33Glu). Given the pLI score of 0.55 as well as the phenotype of individuals with deletions (not presenting microcephaly) the authors predict that a dominant-negative effect applies (rather than haploinsufficiency). Consider inclusion in the following panels : DD/ID (green), epilepsy (amber - 4 of 7 patients belonging to 2 families), primary microcephaly (green), callosome (amber/green - 3 individuals belonging to 3 families), mendeliome (green), etc. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.262 | TASP1 |
Arina Puzriakova Added comment: Comment on list classification: Sufficient cases for a GREEN rating at the next major review. Associated with phenotype in OMIM, and a possible gene for Developmental delay, happy demeanor, distinctive facial features, and congenital anomalies in G2P. Four unrelated patients with homozygous LOF variants in this gene all exhibited a consistent phenotype which included global developmental delay. All variants segregated with disease, but no functional studies of the variants or patient cells were not performed. |
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| Intellectual disability - microarray and sequencing v3.256 | PISD | Arina Puzriakova reviewed gene: PISD: Rating: ; Mode of pathogenicity: None; Publications: 31263216, 30858161, 30488656, 3561949; Phenotypes: Liberfarb syndrome, 618889; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.251 | ERF | Arina Puzriakova commented on gene: ERF | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 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 v3.196 | LYRM7 |
Arina Puzriakova changed review comment from: PMID: 24014394 (2013) - Homozygous variant (c.73G>A) in LYRM7 identified in a patient with normal initial development until the first 20 months of life, when she presented rapid deterioration which included severe psychomotor regression. Functional studies performed in yeast indicate functional impairment. PMID: 26912632 (2016) - Six distinct homozygous variants in the LYRM7 gene were identified in seven affected individuals (including 2 sibs). Initial cognitive development was delayed in three patients and borderline in one.; to: PMID: 24014394 (2013) - Homozygous variant (c.73G>A) in LYRM7 identified in a patient with normal initial development until the first 20 months of life, when she presented rapid deterioration which included severe psychomotor regression. Functional studies performed in yeast indicate functional impairment. PMID: 26912632 (2016) - Six distinct homozygous variants in the LYRM7 gene were identified in seven affected individuals (including 2 sibs). Initial cognitive development was delayed in three patients and borderline in one. Continued development was delayed to variable degrees in five individuals, and all were said to have impaired intelligence at the time of the most recent assessment (aged 2.5-16 yrs). PMID: 28694194 (2017) - Three affected family members with homozygosity for a splice site deletion (c.243_244+2delGAGT) in LYRM7. Development was normal for the first few months of life, however all experienced a rapidly progressive clinical course which included profound impairment of psychomotor and mental functions. |
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| Intellectual disability - microarray and sequencing v3.170 | TBC1D2B |
Konstantinos Varvagiannis gene: TBC1D2B was added gene: TBC1D2B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TBC1D2B was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TBC1D2B were set to 32623794 Phenotypes for gene: TBC1D2B were set to Global developmental delay; Intellectual disability; Seizures; Gingival overgrowth; Behavioral abnormality; Abnormality of the mandible; Abnormality of brain morphology; Abnormality of the eye; Hearing abnormality Penetrance for gene: TBC1D2B were set to Complete Review for gene: TBC1D2B was set to AMBER Added comment: Harms et al (2020 - PMID: 32623794) report on 3 unrelated individuals with biallelic pLoF TBC1D2B variants. Features included cognitive impairment (mild ID in one case, regression at the age of 12y in another, hypotonia and delayed milestones in a third aged 8m), seizures (3/3 - variable age of onset) and/or gingival overgrowth (2/3 - prior to initiation of AEDs). Other findings included behavioral abnormalities, mandibular anomalies, abnormal brain imaging and ophthalmologic or (rarely) audiometric evaluations. All were born to non-consanguineous couples and additional investigations were performed in some. Variants were identified by WES or trio WGS, with Sanger confirmation/compatible segregation analyses. In line with the pLoF variants, mRNA studies in fibroblasts from 2 unrelated affected individuals demonstrated significantly reduced (~80-90%) TBC1C2D mRNA levels compared to controls, restored following cycloheximide treatment. Protein was absent in patient fibroblasts. TBC-domain containing GTPase activating proteins are known as key regulators of RAB GTPase activity. TBC1D2B was shown to colocalize with RAB5-positive endocytic vesicles. CRISPR/Cas9-mediated ko of TBC1D2B in HeLa cells suggested a role in EGF receptor endocytosis and decreased cell viability of TBC1D2B-deficient HeLa cells upon serum deprivation. Genes encoding other TBC domain-containg GTPase-activating proteins, e.g. TBC1D7 and TBC1D20, TBC1D24 are associated with recessive neurodevelopmental disorders (with ID and/or seizures) and the pathophysiological defect in TBC1D2B-related disorder (deficit in vesicle trafficking and/or cell survival) is proposed to be similar to that of TBC1D24. Overall this gene can be considered for inclusion with amber/green rating in the ID panel and green in epilepsy panel. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.35 | YIF1B |
Konstantinos Varvagiannis gene: YIF1B was added gene: YIF1B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: YIF1B was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: YIF1B were set to 32006098 Phenotypes for gene: YIF1B were set to Central hypotonia; Failure to thrive; Microcephaly; Global developmental delay; Intellectual disability; Seizures; Spasticity; Abnormality of movement Penetrance for gene: YIF1B were set to Complete Review for gene: YIF1B was set to GREEN Added comment: AlMuhaizea et al (2020 - PMID: 32006098) report on the phenotype of 6 individuals (from 5 families) with biallelic YIF1B truncating variants. Affected subjects presented hypotonia, failure to thrive, microcephaly (5/6), severe global DD and ID (as evident from best motor/language milestones achieved - Table S1) as well as features suggestive of a motor disorder (dystonia/spasticity/dyskinesia). Seizures were reported in 2 unrelated individuals (2/6). MRI abnormalities were observed in some with thin CC being a feature in 3. Variable initial investigations were performed including SNP CMA, MECP2, microcephaly / neurotransmitter disorders gene panel testing did not reveal P/LP variants. YIF1B variants were identified in 3 families within ROH. Following exome sequencing, affected individuals were found to be homozygous for truncating variants (4/5 families being consanguineous). The following 3 variants were identified (NM_001039672.2) : c.186dupT or p.Ala64fs / c.360_361insACAT or p.Gly121fs / c.598G>T or p.Glu200*. YIF1B encodes an intracellular transmembrane protein. It has been previously demonstrated that - similarly to other proteins of the Yip family being implicated in intracellular traffic between the Golgi - Yif1B is involved in the anterograde traffic pathway. Yif1B KO mice demonstrate a disorganized Golgi architecture in pyramidal hippocampal neurons (Alterio et al 2015 - PMID: 26077767). The rat ortholog interacts with serotonin receptor 1 (5-HT1AR) with colocalization of Yif1BB and 5-HT1AR in intermediate compartment vesicles and involvement of the former in intracellular trafficing/modulation of 5-HT1AR transport to dendrites (PMID cited: 18685031). Available mRNA and protein expression data (Protein Atlas) suggest that the gene is widely expressed in all tissues incl. neuronal cells. Immunochemistry data from the Human Brain Atlas also suggest that YIF1B is found in vesicles and localized to the Golgi apparatus. Immunohistochemistry in normal human brain tissue (cerebral cortex) demonstrated labeling of neuronal cells (Human Protein Atlas). Functional/network analysis of genes co-regulated with YIF1B based on available RNAseq data, suggest enrichement in in genes important for nervous system development and function. Please consider inclusion in other panels that may be relevant (e.g. microcephaly, etc). Sources: Literature |
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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 v3.3 | WNT1 | Zornitza Stark reviewed gene: WNT1: Rating: GREEN; Mode of pathogenicity: None; Publications: 26671912; Phenotypes: Osteogenesis imperfecta, type XV, OMIM# 615220; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | FTL | Zornitza Stark reviewed gene: FTL: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Neurodegeneration with brain iron accumulation 3, MIM#606159, Hyperferritinemia-cataract syndrome, MIM#600886, L-ferritin deficiency, dominant and recessive, MIM#615604; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | ERF | Zornitza Stark reviewed gene: ERF: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Chitayat syndrome, MIM#617180, Craniosynostosis 4, MIM#600775; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | C4orf26 | Zornitza Stark reviewed gene: C4orf26: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Amelogenesis imperfecta, type IIA4, MIM# 614832; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | SUPT16H |
Konstantinos Varvagiannis gene: SUPT16H was added gene: SUPT16H was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SUPT16H was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: SUPT16H were set to http://dx.doi.org/10.1136/jmedgenet-2019-106193 Phenotypes for gene: SUPT16H were set to Global developmental delay; Intellectual disability; Abnormality of the corpus callosum Penetrance for gene: SUPT16H were set to Complete Review for gene: SUPT16H was set to AMBER Added comment: Bina et al (2020 - http://dx.doi.org/10.1136/jmedgenet-2019-106193) report on 4 unrelated individuals with heterozygous SNVs affecting SUPT16H as well as 1 further with microdeletion spanning this gene. The phenotype consisted of DD with subsequent ID in a subset of them (ages of the cohort: 2y-14y), autistic features in few, abnormalities of the corpus callosum (for 3 with available MRI images), variable gastrointestinal problems in some, and possibly minor dysmorphic features. SUPT16H encodes a subunit of the FACT (facilitates chromatin transcription) complex, a chromatin-specific factor required for transcription elongation as well as for DNA replication and repair (OMIM citing Belotserkovskaya et al. 2003 - PMID: 12934006). The 2 subunits of the complex [Spt16 (encoded by SUPT16H) and SSRP1] are essential for histone regulation. As the authors note, Spt16 interacts with the histone dimer H2A-H2B during transcription to allow RNA polymerase access to previously coiled DNA [cited PMIDs : 9489704, 10421373 / A recent study by Liu et al 2019 (PMID: 31775157) appears highly relevant]. SUPT16H has a Z-score of 5.1 in gnomAD and a pLI of 1 (%HI of 22.56 in Decipher). SNVs : 4 de novo missense SNVs were identified following exome sequencing (NM_007192.3:c.484A>G or I162V / L432P / N571S / R734W), all absent from gnomAD and mostly predicted to be deleterious (I162V predicted benign, tolerated, disease-causing by PolyPhen2, SIFT, MutationTaster respectively and had a CADD score of 13.61). Prior work-up for these individuals (incl. CMA in some / MS-MLPA for Angelman s. in 1 / metabolic investigations) had (probably) not revealed an apparent cause, with small CNVs inherited from healthy parents (a 4q13.3 dup / 20q13.2 del - coordinates not provided). There were no studies performed for the identified variants. CNVs : A 5th individual reported by Bina et al was found to harbor a 2.05 Mb 14q11.2 deletion spanning SUPT16H. The specific deletion also spanned CHD8 while the same individual harbored also a 30.17 Mb duplication of 18p11.32q12.1. CNVs spanning SUPT16H reported to date, also span the (very) proximal CHD8. [Genomic coordinates (GRCh38) for SUPT16H and CHD8 as provided by OMIM : 14:21,351,471-21,384,018 / 14:21,385,198-21,456,122]. Haploinsufficiency of CHD8 is associated with a distinctive syndrome with overgrowth and ID (Douzgou et al 2019 - PMID: 31001818). The phenotype of SUPT16H-CHD8 duplications is discussed in other studies/reviews. [Smol et al 2020 - PMID: 31823155 / Smyk et al 2016 - PMID: 26834018]. Animal models were not commented on by Bina et al (possibly not available for mouse : http://www.informatics.jax.org/marker/MGI:1890948 / https://www.mousephenotype.org/data/genes/MGI:1890948 ). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.0 | PUM1 |
Konstantinos Varvagiannis commented on gene: PUM1: 5 unrelated individuals with de novo pathogenic PUM1 variants have been reported in the literature. DD (5/5), ID (4/5 - relevant severity to the current panel), seizures (4/4 - absence/tonic-clonic, abnormal EEG) and variable other features (incl. facial dysmorphism, ataxia, cryptorchidism) appear to be part of the phenotype. 9 individuals with deletions spanning PUM1 and proximal genes presented similar features. [1] PMID: 29474920 - Gennarino et al (2018) [2] PMID: 30903679 - Bonnemason-Carrere et al (2019) [3] PMID: 31859446 - Voet et al (2019) [with review of the literature] SNVs in relevant individuals were identified by exome sequencing and were in all cases de novo. Arg1147Trp was a recurrent variant reported in 3 unrelated subjects with ID and seizures (Refs 1,2,3 / NM_001020658.1:c.3439C>T). A nonsense variant was reported in an additional one with DD, ID, seizures and additional features (c.2509C>T / p.Arg837* - Ref3). One individual with a de novo missense variant (c.3416G>A / p.Arg1139Trp) with DD and ataxia, though without ID was reported in Ref1. Details on 9 individuals with 0.3 - 5.6 Mb deletions spanning PUM1 and other genes are provided in Ref1. Features also included DD, ID, seizures, ataxia, etc. Extensive initial investigations were reported for individuals in Refs 2 and 3 (various investigations incl. karyotype, SNP-array, targeted sequencing of OPHN1, KANSL1 or of a small panel of ID genes, biopsies and/or metabolic work-up) to rule out alternative causes. These only revealed a likely benign CNV and a GRIA3 SNV of uncertain significance in the case of an individual harboring the recurrent Arg1147Trp variant [Ref2]. Role of the gene (from OMIM): Pumilio proteins, such as PUM1, negatively regulate gene expression by repressing translation of mRNAs to which they bind (Lee et al., 2016). A clinically significant PUM1 target is ataxin (ATXN1; 601556), mutation in which causes spinocerebellar ataxia-1 (SCA1; 601556). Variant studies: - Arg1147Trp was shown to be associated with normal PUM1 mRNA levels, but reduced (to ~43%) PUM1 protein levels in patient fibroblasts. ATXN1 mRNA and protein levels, as well as protein and/or mRNA levels of other PUM1 targets were shown to be increased (Ref1). - In Ref1, in vitro transfection assays with wt or mt PUM1 were performed in HEK293T cells to evaluate repression of ATXN1 and E2F3. While overexpression of wt and Arg1147Trp were able to reduce ATXN1 and E2F3 levels, Arg1139Trp was not able to repress ATXN1 or E2F3. - Upon overexpression in mouse hippocampal neurons, PUM1 missense mutations (among others Arg1139Trp and Arg1147Trp) were shown to alter neuronal morphology. Overall haploinsufficiency is the proposed mechanism for the disorder for which the acronym PADDAS is used (Pumilio1-associated developmental disability, ataxia and seizure). Milder mutations reducing PUM1 levels by 25% are associated with adult-onset ataxia without ID (PRCA or Pumilio1-related cerebellar ataxia) [Ref1]. Mouse models: The role of PUM1 was first suggested in mouse models where Pum1 mutations were shown to lead to a SCA1-like phenotype (PMID cited : 12086639 - Watase et al 2002) further shown to be caused by increased Atxn1 mRNA and protein levels (PMID cited : 25768905 - Gennarino et al 2015). The mouse model seems to recapitulate several of the features observed in affected individuals : Pum1 homozygous ko mice display among others hyperactivity, progressive cerebellar signs, spontaneous seizures as also observed in affected individuals (PMID cited : 25768905 - Gennarino et al 2015). Cryptorchidism was observed in 2 patients similar to testicular hypoplasia reported in Pum1 ko mice (PMID cited : 22342750 - Chen et al 2012). - Heterozygous mice were evaluated in Ref1 with 69% or 75% exhibiting spontaneous seizures by the end of 30 or 35 wks respectively, with abnormal EEG activity already by 16 wks. Additional individuals with PUM1 variants and a relevant phenotype of ID with or without seizures have been reported as part of the DDD study or as external submissions to Decipher and ClinVar : https://decipher.sanger.ac.uk/search?q=PUM1#research-variants/results [ DDD4K.01387 participant ] https://decipher.sanger.ac.uk/search?q=pum1#consented-patients/results [ external submission(s) ] https://www.ncbi.nlm.nih.gov/clinvar/variation/431110/ [ splice-site variant in an individual with ID submitted prior to the 1st publication on the disorder ] |
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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 v3.0 | CXorf56 |
Konstantinos Varvagiannis gene: CXorf56 was added gene: CXorf56 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: CXorf56 was set to X-LINKED: hemizygous mutation in males, monoallelic mutations in females may cause disease (may be less severe, later onset than males) Publications for gene: CXorf56 were set to 29374277; 31822863 Phenotypes for gene: CXorf56 were set to ?Mental retardation, X-linked 107, 301013 Penetrance for gene: CXorf56 were set to unknown Review for gene: CXorf56 was set to AMBER Added comment: Verkerk et al (2018 - PMID: 29374277) reported on a three-generation family with five males and one female presenting mild non-syndromic ID. Segregation was compatible with X-linked inheritance. Multipoint linkage analysis with XL microsatellite markers demonstrated a linkage peak at Xq23-24 with LOD score of 3.3. Haplotype analysis and utilization of additional STR markers allowed narrowing to a region of 7.6 Mb containing 92 genes. WGS in 3 affected males (spanning 3 generations) and 1 unaffected male and application of relevant filters for rare protein affecting variants within this region - present only in affected but absent in the unaffected individual - suggested a CXorf56 frameshift variant in exon 2 [NM_022101.3:c.159_160insTA / p.(Asp54*)] as the only relevant for this phenotype. Sanger sequencing was performed for 25 family members with all 5 affected males and 1 affected female harboring this insertion and 8 unaffected females (also) shown to be carriers. X-chromosome inactivation studies demonstrated that unaffected females had skewed inactivation (76-93%) of the variant allele, while the single affected female did not have a skewed XCI pattern (54%). In EBV-transformed lymphoblasts grown with/without cycloheximide, mRNA levels were shown to be significantly lower in the affected female compared to unaffected ones (and corrected upon treatment with cycloheximide). mRNA levels were also significantly lower in cell lines from an affected male, with expression showing significant increase after treatment with cycloheximide. These results confirmed that nonsense-mediated decay applies. The variant was absent from ExAC (where CXorf56 has a pLI of 0.93) and 188 healthy Dutch individuals. The function of CXorf56 is not known. The gene appears to be expressed in brain and a (broad) range of other tissues [ https://gtexportal.org/home/gene/CXORF56 ]. Immunostaining in 8-week old murine brain, showed that the protein is present in the nucleus and cell soma of most neurons in brain cortex and cerebellum. Upon transfection of human CXorf56 cDNA in mouse primary hippocampal neurons, the protein localized in the nucleus, dendrites (co-localizing with Map2) and dendritic spines. As the authors note, the latter may suggest a role in synaptic function. Overexpression in HEK293T cells demonstrated predominantly nuclear localization. Mouse : Based on MGI (and an article by Cox et al. - PMID: 20548051 / both cited by the authors) male chimeras hemizygous for a gene trapped allele have abnormal midbrain-hindbrain boundary morphology, decreased forebrain size, while a subset hemizygous for a different gene trapped allele show growth delay [ http://www.informatics.jax.org/marker/MGI:1924894 ]. ----- Rocha et al (2019 - PMID: 31822863) report on 9 affected individuals with mild to severe ID belonging to 3 unrelated families. Additional features in this cohort - observed in some - included abnormal reflexes, fine tremor, seizures (in 3), abnormal gait, etc. In the 1st family, 3 males presented with (severe/severe/moderate) ID and 2 females with mild ID. Following a normal CMA and FMR1 testing, trio plus exome sequencing revealed a CXorf56 in-frame deletion [NM_022101.3:c.498_503del / p.(Glu167_Glu168del)]. Sanger sequencing in 9 members, confirmed presence of the variant in one unaffected mother, all her affected sons (2) and daughers(2) and an affected grandson and absence in 2 remaining unaffected daughters. Skewing of XCI was seen in blood cells from affected females (97 and 83%) while the unaffected mother had complete inactivation of the carrier X-chromosome. The authors commented that even minor reductions in CXorf56 (suggested by XCI in affected females) may be detrimental and/or that inactivation for this gene may be different than that of AR gene (which was studied instead) or in other tissues. In family 2, an affected mother (with learning difficulties) and her 2 sons - the most severely affected presenting moderate ID - harbored a frameshift variant [c.303_304delCTinsACCC / p.(Phe101Leufs*20)]. A male with ID belonging to a 3rd family, for which no further information was available, was found to harbor the c.498_503del variant (also discussed above) as a de novo event. It has been commented that individuals with Xq24 deletions spanning CXorf56 present with ID, although (all) such deletions reported in the literature also span the neighboring UBE2A gene, associated with Mental retardation, X-linked syndromic, Nascimento-type (MIM #300860). ----- In OMIM, the CXorf56-related phenotype is ?Mental retardation, X-linked 107 (# 301013), based only on the report by Verkerk et al. This gene is included in gene panels for ID offered by some diagnostic laboratories (incl. Radboudumc). ----- Overall, CXorf56 can be considered for inclusion in the ID panel either with amber (function of the gene unknown, skewed XCI also in affected females in the 2nd reference) or with green rating (several individuals from 4 families, compatible segregation studies and females presenting a milder phenotype than males or unaffected, LOD score in the 1st report, studies confirming lower mRNA levels and NMD, gene expressed in human brain, expression in mouse brain cortex and cerebellum, evidence from transfection studies in mouse hippocampal neurons). [Note : penetrance was here set to unknown / It was complete for males, incomplete for females]. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.1135 | TRAPPC4 |
Konstantinos Varvagiannis gene: TRAPPC4 was added gene: TRAPPC4 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TRAPPC4 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TRAPPC4 were set to 31794024 Phenotypes for gene: TRAPPC4 were set to Feeding difficulties; Progressive microcephaly; Intellectual disability; Seizures; Spastic tetraparesis; Abnormality of the face; Scoliosis; Cortical visual impairment; Hearing impairment Penetrance for gene: TRAPPC4 were set to Complete Review for gene: TRAPPC4 was set to GREEN Added comment: Van Bergen et al. (2019 - PMID: 31794024) report on 7 affected individuals from 3 famillies (only 1 of which consanguineous), all homozygous for a TRAPPC4 splicing variant. Overlapping features included feeding difficulties, progressive microcephaly, severe to profound developmental disability (7/7 - DD also prior to the onset of seizures / regression also reported in 3), epilepsy (7/7 - onset in the first year), spastic quadriparesis. Other findings in some/few incl. scoliosis, cortical visual and hearing impairment. Some facial features were shared (eg. bitemporal narrowing, long philtrum, open mouth with thin tented upper lip, pointed chin, etc). Brain imaging demonstrated abnormalities in those performed (among others cerebral with/without cerebellar atrophy). Work-up prior to exome sequencing was normal (highly variable incl. metabolic testing, CMA, MECP2, CDKL5, mitochondrial depletion studies, etc). Exome of affected individuals (and parents +/- affected sibs in some families) revealed a homozygous TRAPPC4 splicing variant [NM_016146.5:c.454+3A>G / chr11:g.118890966A>G (hg19)]. Sanger sequencing confirmed variant in affecteds, heterozygosity in parents and compatible genotypes with disease status in sibs/other members. Families were of Caucasian/Turkish and French-Canadian ethnicities. SNP array to compare haplotypes between affecteds in 2 families did not reveal a shared haplotype (/founder effect) and the variant is present in gnomAD (68/281054 - no hmz) in many populations (European/Asian/African/Latino) [https://gnomad.broadinstitute.org/variant/11-118890966-A-G]. mRNA studies in fibroblasts from an affected individual confirmed the splicing defect (2 RT-PCR products corresponding to wt and a shorter due to skipping of exon 3, the latter further confirmed by Sanger sequencing. The shorter transcript is not present in controls). qPCR revealed that the normal transript in patient fibroblasts was present at 6% of the level observed in control fibroblasts (or 54% in the case of a heterozygote parent compared to controls). Western blot in patient fibroblasts, revealed presence of full-length protein in significantly reduced levels compared to fibroblasts from carrier parents or controls. There was no band using an antibody targeting the N-terminal region of the protein prior to exon 3, suggesting that NMD applies (skipping of ex3 is also predicted to lead to frameshift). TRAPPC4 encodes one of the core proteins of the TRAPP complex. Use of different accessory proteins leads to formation of 2 distinct complexes (TRAPPII / III). The complex has an important role in intracellular trafficking. Both TRAPPII & TRAPPIII have a function in the secretory pathway, while complex III has a role also in autophagy. Core proteins are important for the complex stability. The TRAPP complex serves as a GEF for Ypt/Rab GTPases [several refs in article]. Mutations in genes for other proteins of the complex lead to neurodevelopmental disorders with associated ID ('TRAPPopathies' used by the authors / TRAPPC12, C6B, C9 green in the current panel). Western blot suggested that levels of other TRAPP subunits (TRAPPC2 or C12) under denaturing conditions, although PAGE/size exclusion chromatography suggested that the levels of fully-assembled TRAPP complexes were lower in affected individuals. Studies in patient fibroblasts showed a secretory defect (between ER, Golgi and the plasma membrane) which was restored upon lentiviral transduction with wt TRAPPC4 construct. Basal and starvation-induced autophagy were also impaired in patient fibroblasts (increased LC3 marker and LC3-positive structures / impaired co-localization with lysosomes) partly due to defective autophagosome formation (/sealing). TRAPPC4 is the human orthologue of the yeast Trs23. In a yeast model of reduced Trs23 (due to temperature instability) the authors demonstrated impaired assembly of the TRAPP core. The yeast model recapitulated the autophagy as well as well as the secretory defect observed in patient fibroblasts. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1134 | OXR1 |
Konstantinos Varvagiannis gene: OXR1 was added gene: OXR1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: OXR1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: OXR1 were set to https://doi.org/10.1016/j.ajhg.2019.11.002 Phenotypes for gene: OXR1 were set to Central hypotonia; Global developmental delay; Delayed speech and language development; Intellectual disability; Seizures; Abnormality of the cerebellum Penetrance for gene: OXR1 were set to Complete Review for gene: OXR1 was set to GREEN Added comment: Wang et al (2019 - https://doi.org/10.1016/j.ajhg.2019.11.002 ) report on 5 individuals (from 3 families) with biallelic OXR1 LoF variants. Common features included hypotonia (4/5), severe global DD (5/5) and speech delay (5/5), ID (5/5), epilepsy (5/5) with cerebellar dysplasia/atrophy (5/5) and in some scoliosis. All were investigated by exome sequencing and were found to harbor biallelic loss-of-function variants (2 splice-site, a stopgain and a frameshift one) either in homozygosity (2 consanguineous families) or in compound heterozygosity. In all cases parental segregation studies were compatible and in one family, an unaffected sib shown to be carrier. Althouhgh OXR1 has been shown to affect several processes (among others DNA lesions induced by oxidative stress in E.coli, neuronal maintenance, mitochondrial morphology and DNA maintenance, etc), its mechanism of action is still not well defined. There are 6 RefSeq transcripts, the longest (NM_018002.3) encoding 3 protein domains (LysM, GRAM, TLDc). The TLDc domain is encoded by all transcripts. Identified variants affected (probably all - fig1D) transcripts expressed in the CNS, namely NM_018002.3, NM_001198532.1, NM_181354.4. The 3 transcripts not expressed in the CNS are NM_001198533.1, NM_001198534.1 and NM_001198535.1. Western blot with 2 different antibodies which would bind upstream of the truncation site failed to detect presence of truncated proteins in 2 affected individuals from 2 families. The Drosophila homolog of OXR is mustard (mtd). The authors provide evidence that loss of mtd is lethal. This was however rescued by expression of an 80kb fly BAC clone covering mtd, or the fly mtd-RH isoform cDNA, or a short human OXR1 cDNA containing only the TLDc domain or a human NCOA7 cDNA. The latter is another human mtd homolog which also contains the TLDc domain. As a result the TLDc domain compensated sufficiently for loss of mtd. Flies that survived displayed bang sensitivity and climbing defects the former assay being suggestive of susceptibility to seizures and the latter of impaired neurological/muscular function. The authors provided evidence that mtd is broadly expressed in the fly CNS. RNAi mediated mtd knockdown specific to neurons (elav/nSyb-GAL4 expression of mtd RNAi) led to lethal eclosion defects for RNAis targeting most (18)/all(23) mtd isoforms. Lifespan was increased upon expression of human OXR1 cDNA. Neuronal loss and vacuolization was demonstrated and additional experiments in R7 photoreceptors showed presence of aberrant lysosomal structures (autolysosomes, autophagosomes and/or endolysosomes). Aberrant lysosomal structures were also observed in fibroblasts from affected individuals (accumulation of lysosomes and/or presence of highly aberrant compartments with content typical of lysosomal dysfunction). Overall the data presented suggest a critical role for OXR1 in lysosomal biology. Although previous reports suggested that OXR1 is involved in oxidative stress resistance, studies performed by the authors suggested that oxidative stress is probably not the driver of the mutant fly defects. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1098 | AP1B1 |
Konstantinos Varvagiannis gene: AP1B1 was added gene: AP1B1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: AP1B1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: AP1B1 were set to 31630788; 31630791 Phenotypes for gene: AP1B1 were set to Failure to thrive; Abnormality of the skin; Hearing abnormality; Abnormality of copper homeostasis; Global developmental delay; Intellectual disability Penetrance for gene: AP1B1 were set to Complete Review for gene: AP1B1 was set to AMBER Added comment: Boyden et al. (2019 - PMID: 31630788) and Alsaif et al (2019 - PMID: 31630791) report on the phenotype related to biallelic AP1B1 mutations. Common features included failure to thrive, ichthyosis (with variable palmoplantar keratoderma/erythroderma/abnormal hair) and hearing loss. Each study focused on different additional features eg. thrombocytopenia or photophobia in all individuals reported by Boyden et al, while Alsaif et al. focused on abnormal copper metabolism (low plasma copper and ceruloplasmin) observed in all 3 affected individuals and enteropathy/hepatopathy observed in 2 sibs. DD was observed in all 3 individuals (2 families) reported by Alsaif et al. and patient 424 reported by Boyden et al. ID was noted in all individuals of relevant age (2 from 2 families) in the study by Alsaif. Boyden commented that ID is not part of the phenotype. The adult (424) - despite his early DD - was noted to have normal intellect and had graduated college. The other patient (1325) was last followed up at 11 months (still DD was not reported). AP1B1 encodes one of the large subunits (β1) of the adaptor protein complex 1. Each of the AP complexes is a heterotetramer composed of two large (one of γ, α, δ, ε and β1-β4 for AP-1 to AP-4 respectively), one medium (μ1-μ4) and one small (σ1-σ4) adaptin subunit. The complex is involved in vesicle-mediated transport. Variants were confirmed in probands and carrier parents (NM_001127.3): Boyden Pat424 (33y) : c.430T>C (p.Cys144Arg) in trans with c.2335delC (p.Leu779Serfs*26) Boyden Pat1325 (11m) [consanguineous Ashkenazi Jewish family] : homozygosity for c.2374G>T (p.Glu792*) Alsaif sibs P1,P2 (4y4m, 1y5m) [consanguineous - Pakistani origin] : homozygous for a chr22 75 kb deletion spanning only the promoter and ex1-2 of AP1B1 Alsaif P3 (4y6m) [consanguineous - Saudi origin] : homozygous for a c.38-1G>A Variant / additional studies : 22q 75-kb deletion: PCR deletion mapping and Sanger delineated the breakpoints of the 22q12.2 del to chr22:29758984-29815476 (hg?). Complete absence of transcript upon RT-PCR (mRNA from fibrolasts). Splicing variant (c.38-1G>A): RT-PCR confirmed replacement of the normal transcript by an aberrant harboring a 1 bp deletion (r.40del). Stopgain variant (c.2374G>T): Western blot demonstrated loss of AP1B1 (and marked reduction also for AP1G1) in cultured keratinocytes of the homozygous patient. Loss-of-function is the effect predicted by variants. Vesicular defects were observed in keratinocytes of an affected individual (homozygous for the nonsense variant). Rescue of these vesicular defects upon transduction with wt AP1B1 lentiviral construct confirmed the LoF effect. [Boyden et al.] ATP7A and ATP7B, two copper transporters, have been shown to depend on AP-1 for their trafficking. Similar to MEDNIK syndrome, caused by mutations in AP1S1 and having an overlapping phenotype with AP1B1 (also including hypocupremia and hypoceruloplasminemia), fibroblasts from 2 affected individuals (from different families) demonstrated abnormal ATP7A trafficking. [Alsaif et al.] Proteomic analysis of clathrin coated vesicles (2 ind from 2 fam) demonstrated that AP1B1 was the only AP1/AP2 CCV component consistently reduced in 2 individuals (from 2 families). [Alsaif et al.] Boyden et al. provided evidence for abnormal differentiation and proliferation in skin from an affected individual. In addition E-cadherin and β-catenin were shown to be mislocalized in keratinocytes from this affected individual. Loss of ap1b1 in zebrafish is not lethal but lead to auditory defects (/vestibular deficits). The inner ears appear to develop normally, although there is progressive degeneration of ear epithelia. There are no behavioral/neurological phenotypes listed for mouse models. [ http://www.informatics.jax.org/marker/MGI:1096368 ]. AP1B1 is not associated with any phenotype in OMIM/G2P/SysID. Overall this gene could be considered for inclusion in the ID panel probably with amber rating. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1098 | FDFT1 |
Konstantinos Varvagiannis gene: FDFT1 was added gene: FDFT1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: FDFT1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: FDFT1 were set to 29909962 Phenotypes for gene: FDFT1 were set to Profound global developmental delay; Intellectual disability; Seizures; Abnormality of nervous system morphology; Cortical visual impairment; Abnormality of the skin; Abnormality of the face Penetrance for gene: FDFT1 were set to Complete Review for gene: FDFT1 was set to AMBER Added comment: Biallelic pathogenic FDFT1 variants cause Squalene synthase deficiency (MIM 618156). 3 individuals from 2 families (and 3 variants) have been reported. DD, ID and seizures are part of the phenotype (3/3). The metabolic profile observed is specific and highly suggestive of disruption of the cholesterol biosynthesis pathway (at the specific level) while the clinical presentation is similar to other disorders of the pathway (SLO). The effect of 2 variants has been studied in detail (in one case mis-splicing demonstrated and in the other regulatory effect). Overall, this gene could be considered for inclusion in the ID/epilepsy panel with amber rating. As the gene is currently present only in the DDG2P panel, please consider adding it to relevant ones (eg. IEMs, undiagnosed metabolic disorders, etc). [Details provided below]. ---- Coman et al. (2018 - PMID: 29909962) reported on 3 relevant individuals from 2 unrelated families. The phenotype consisted of seizures (3/3 - neonatal onset - generalized), profound DD (ID can be inferred from the description in the supplement), variable brain MRI abnormalities (white matter loss, hypoplastic CC), cortical visual impairment, dry skin with photosensitivity as well facial dysmorphic features. Male subjects presented genital anomalies (cryptorchidism/hypospadias). FDFT1 encodes squalene synthase, the enzyme which catalyzes conversion of farnesyl-pyrophosphate to squalene - the first specific step in cholesterol biosynthesis. A specific pattern of metabolites was observed in all, similar to a pattern previously observed in animal models/humans treated with squalene synthase inhibitor or upon loading with farnesol (in animals). Overall the pattern was suggestive of a cholesterol biosynthesis defect at the level of squalene synthase as suggested by increased total farnesol levels (farnesyl-pyrophosphate + free farnesol), reduced/normal squalene, low plasma cholesterol as well as other metabolites. Clinical features also resembled those observed in Smith-Lemli-Opitz syndrome (another disorder of cholesterol biosynthesis). WES was carried out in affected individuals and their parents and revealed for sibs of the first family, compound heterozygosity for a maternally inherited 120-kb deletion spanning exons 6-10 of FDFT1 and CTSB and a paternally inherited FDFT1 variant in intron 8 (TC deletion/AG insertion). Variant studies for the latter included: - Minigene splice assay demonstrating retention of 22 bp in intron 8. - Partial splicing defect with both nl and mis-spliced cDNA (patient fibroblasts) - Reduced protein levels in lymphoblasts/fibroblasts from both sibs upon Western blot. Contribution of the CTSB deletion was considered unlikely (carrier mother was unaffected). As for the 2nd family, WES data allowed identification of a homozygous deep-intronic (although this is transcript-specific) 16-bp deletion in the proband. Parents were carriers. For the specific variant : - cDNA studies failed to detect 3 (of 10) isoforms which are normally present in control fibroblasts. Eventual NMD (which would be predicted if the deletion resulted in splicing defect) was eliminated given the absent effect of cyclohexamide addition, thus suggesting a regulatory effect. - Given a predicted promoter/enhancer effect of the deleted region, a luciferase assay performed, suggested that the sequence had promoter capacity, with the construct containing the 16-bp deletion showing reduced promoter activity. Fdft1 knockout mice demonstrate embryonic lethality around mid-gestation while they exhibit severe growth retardation and defective neural tube closure. In G2P FDFT1 is associated with 'Defect in Cholesterol Biosynthesis' (confidence:possible/biallelic/LoF). The gene belongs to the Current primary ID gene group of SysID. It is not commonly included in gene panels for ID offered by diagnostic laboratories. 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 v2.1024 | GABRA2 |
Rebecca Foulger commented on gene: GABRA2: Summary of evidence (refer to Konstantinos Varvagiannis' review for further details): PMID:29422393, Orenstein et al., 2018 report a male of unrelated Ashkenazi Jewish parents with EIEE-78 and a de novo heterozygous variant in GABRA2 (N335H). Development was severely delayed. Functional studies were not performed but the variant was absent in ExAC and gnomAD controls. PMID:29961870, Butler et al. 2018 report an 11 year old girl with EIEE-78 and a de novo heterozygous variant in GABRA2 (T292K). Development was delayed, the patient was nonverbal and had profound intellectual disability plus microcephaly. PMID:31032849, Maljevic et al., 2019 decribe 5 patients (3 sporadic cases and 2 siblings) with four novel de novo GABRA2 missense variants (Val284Ala, Leu291Val, Met263Thr, Phe325Leu). All patients showed some degree of ID (mild to profound). https://doi.org/10.1101/678219: Sanchis-Juan et al., 2019 identified a de novo missense variant in GABRA2 gene (Pro280Leu) in a 10 year old girl with EIEE and developmental delay. At age-10, she had severe impairment of language, hand stereotypies, disruptive behavior and repetitive movements. |
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| Intellectual disability - microarray and sequencing v2.1022 | GABRA2 |
Konstantinos Varvagiannis changed review comment from: Heterozygous pathogenic GABRA2 variants cause Epileptic encephalopathy, early infantile, 78 (MIM 618557) [new OMIM entry]. At least 8 relevant individuals have been reported to date in the following studies: - Orenstein et al. (2018 - PMID: 29422393) - 1 individual - Butler et al. (2018 - PMID: 29961870) - 1 subject - Maljevic et al. (2019 - PMID: 31032849 - 3 unrelated children as well as 2 affected sibs - Sanchis-Juan et al. (2019 - bioRxiv / https://doi.org/10.1101/678219) - 1 further patient In all affected individuals the variants were missense and - in almost all cases - had occurred as de novo events. The 2 sibs reported by Maljevic however, had inherited a missense variant from their unaffected mosaic parent. Clinical descriptions for individuals from the 3 studies are provided in OMIM and also summarized in the suppl. table 1 by Sanchis-Juan et al. (https://www.biorxiv.org/content/biorxiv/early/2019/06/21/678219/DC2/embed/media-2.xlsx). Seizures, DD and ID (relevant to the current panel) are among the reported features. Functional studies have been performed for most of the variants and are summarized for each one in the OMIM entry for GABRG2 and the aforementioned table as well. The following variants have been reported (NM_000807.2): c.1003A>C - p.Asn335His (dn) / c.875C>A - Thr292Lys (dn) / c.871C>G - p.Leu291Val (dn) / c.788T>C - p.Met263Thr (dn) / c.851T>C - p.Val284Ala (dn) / c.975C>A - p.Phe325Leu (inherited from mosaic parent) / c.839C>T - p.Pro280Leu (dn - Sanchis-Juan et al). As commented by Jenkins and Escayg (2019 - PMID: 31032848 / both among the authors of the 1st report) as well as by Sanchis-Juan et al., both loss- and gain- of function effects explain the pathogenicity of the various mutations reported to date. [In gnomAD GABRA2 has a Z-score for missense variants of 3.13 as well as a pLI of 1]. ------ GABRA2 is not associated with any phenotype in G2P. This gene is not commonly included in gene panels for ID offered by diagnostic laboratories. ------ As a result, GABRA2 can be considered for inclusion in the epilepsy and ID panels probably as green (several relevant individuals, several reported variants with supporting functional studies for most, etc.). [Consider inclusion in other possibly relevant gene panels eg. for ASD which was feature in some patients at relevant age and/or among those evaluated].; to: Heterozygous pathogenic GABRA2 variants cause Epileptic encephalopathy, early infantile, 78 (MIM 618557) [new OMIM entry]. At least 8 relevant individuals have been reported to date in the following studies: - Orenstein et al. (2018 - PMID: 29422393) - 1 individual - Butler et al. (2018 - PMID: 29961870) - 1 subject - Maljevic et al. (2019 - PMID: 31032849 - 3 unrelated children as well as 2 affected sibs - Sanchis-Juan et al. (2019 - bioRxiv / https://doi.org/10.1101/678219) - 1 further patient In all affected individuals the variants were missense and - in almost all cases - had occurred as de novo events. The 2 sibs reported by Maljevic however, had inherited a missense variant from their unaffected mosaic parent. Clinical descriptions for individuals from the 3 studies are provided in OMIM and also summarized, Maljevic - Table 1 (7 patients) and/or in the suppl. table 1 by Sanchis-Juan et al. (8 patients) (https://www.biorxiv.org/content/biorxiv/early/2019/06/21/678219/DC2/embed/media-2.xlsx). Seizures, DD and ID (relevant to the current panel) are among the reported features. Functional studies have been performed for most of the variants and are summarized for each one in the OMIM entry for GABRG2 and the aforementioned table as well. The following variants have been reported (NM_000807.2): c.1003A>C - p.Asn335His (dn) / c.875C>A - Thr292Lys (dn) / c.871C>G - p.Leu291Val (dn) / c.788T>C - p.Met263Thr (dn) / c.851T>C - p.Val284Ala (dn) / c.975C>A - p.Phe325Leu (inherited from mosaic parent) / c.839C>T - p.Pro280Leu (dn - Sanchis-Juan et al). As commented by Jenkins and Escayg (2019 - PMID: 31032848 / both among the authors of the 1st report) as well as by Sanchis-Juan et al., both loss- and gain- of function effects explain the pathogenicity of the various mutations reported to date. [In gnomAD GABRA2 has a Z-score for missense variants of 3.13 as well as a pLI of 1]. ------ GABRA2 is not associated with any phenotype in G2P. This gene is not commonly included in gene panels for ID offered by diagnostic laboratories. ------ As a result, GABRA2 can be considered for inclusion in the epilepsy and ID panels probably as green (several relevant individuals, several reported variants with supporting functional studies for most, etc.). [Consider inclusion in other possibly relevant gene panels eg. for ASD which was feature in some patients at relevant age and/or among those evaluated]. |
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| Intellectual disability - microarray and sequencing v2.1022 | GABRA2 |
Konstantinos Varvagiannis gene: GABRA2 was added gene: GABRA2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: GABRA2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: GABRA2 were set to 29422393; 29961870; 31032849; 31032848; doi.org/10.1101/678219 Phenotypes for gene: GABRA2 were set to Epileptic encephalopathy, early infantile, 78 (MIM 618557) Penetrance for gene: GABRA2 were set to unknown Review for gene: GABRA2 was set to GREEN Added comment: Heterozygous pathogenic GABRA2 variants cause Epileptic encephalopathy, early infantile, 78 (MIM 618557) [new OMIM entry]. At least 8 relevant individuals have been reported to date in the following studies: - Orenstein et al. (2018 - PMID: 29422393) - 1 individual - Butler et al. (2018 - PMID: 29961870) - 1 subject - Maljevic et al. (2019 - PMID: 31032849 - 3 unrelated children as well as 2 affected sibs - Sanchis-Juan et al. (2019 - bioRxiv / https://doi.org/10.1101/678219) - 1 further patient In almost all affected individuals, the variants were missense and had occurred as de novo events. The 2 sibs reported by Maljevic however, had inherited a missense variant from their unaffected mosaic parent. Clinical descriptions for individuals from the 3 studies are provided in OMIM and also summarized in the suppl. table 1 by Sanchis-Juan et al. (https://www.biorxiv.org/content/biorxiv/early/2019/06/21/678219/DC2/embed/media-2.xlsx?download=true). Seizures, DD and ID (relevant to the current panel) are among the reported features. Functional studies have been performed for most of the variants and are summarized for each one in the OMIM entry for GABRG2 and the aforementionned table as well. The following variants have been reported (NM_000807.2): c.1003A>C - p.Asn335His (dn) / c.875C>A - Thr292Lys (dn) / c.871C>G - p.Leu291Val (dn) / c.788T>C - p.Met263Thr (dn) / c.851T>C - p.Val284Ala (dn) / c.975C>A - p.Phe325Leu (inherited from mosaic parent) / c.839C>T - p.Pro280Leu (dn - Sanchis-Juan et al). As commented by Jenkins and Escayg (2019 - PMID: 31032848 / both among the authors of the 1st report) as well as by Sanchis-Juan et al., both loss- and gain- of function effects explain the pathogenicity of the various reported (all) missense mutations. [In gnomAD GABRA2 has a Z-score for missense variants of 3.13 as well as a pLI of 1]. ------ GABRA2 is not associated with any phenotype in G2P. This gene is not commonly included in gene panels for ID offered by diagnostic laboratories. ------ As a result, GABRA2 can be considered for inclusion in the epilepsy and ID panels probably as green (several relevant individuals, several reported variants with supporting functional studies for most, etc.). [Consider inclusion in other possibly relevant gene panels eg. for ASD which was feature in some patients at relevant age and/or among those evaluated]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1021 | KATNB1 |
Konstantinos Varvagiannis gene: KATNB1 was added gene: KATNB1 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: KATNB1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: KATNB1 were set to 25521378; 25521379; 26640080 Phenotypes for gene: KATNB1 were set to Lissencephaly 6, with microcephaly (MIM 616212) Penetrance for gene: KATNB1 were set to Complete Review for gene: KATNB1 was set to GREEN gene: KATNB1 was marked as current diagnostic Added comment: Biallelic pathogenic KATNB1 variants cause Lissencephaly 6, with microcephaly (MIM 616212). At least 13 affected individuals from 9 (mostly consanguineous) families have probably been reported in the following articles: - Mishra-Gorur et al. (2014 - PMID: 25521378) [7 individuals from 5 unrelated families] - Hu et al. (2014 - PMID: 25521379) [5 individuals from 3 families] - Yigit el al. (2016 - PMID: 26640080) [1 subject born to consanguineous parents] The phenotype appears to be relevant to the current panel. Several different variants have been reported to date. Extensive studies as for the impact of mutations at the cellular level as well as animal models (zebrafish, mouse, drosophila) support involvement of KATNB1. These arguments, provided mainly by the first two studies, are summarized in the respective OMIM entry for the disorder : https://omim.org/entry/616212 (variants and their effect are discussed in the entry for KATNB1 - https://omim.org/entry/602703). The individual reported by Yigit el al. was a 5 year-old girl with - among others - severely delayed psychomotor development. The child was found to harbor a homozygous splice site variant (removing the acceptor AG signature). Confirmation of the variant and segregation studies were performed with Sanger sequencing. cDNA studies were carried out and demonstrated aberrant splicing. KATNB1 is not associated with any disorder in G2P. The gene is included in panels for ID offered by several diagnostic laboratories (incl. Radboudumc). As a result, this gene can be considered for inclusion in the current panel probably as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.977 | FRMPD4 |
Catherine Snow changed review comment from: Further paper identified to indicated FRMPD4 is relevant to ID. PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was heterozygous for the same micro deletion. Family 3, two half-siblings (p.Arg286Ter) Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported. Some functional work performed but only for the frameshift variant that was reported in family 1. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only hetrozygous carrier who displays ID features.; to: Further paper identified to indicated FRMPD4 is relevant to ID. PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was heterozygous for the same micro deletion. Family 3, two half-siblings (p.Arg286Ter) Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported. Some functional work performed but only for the frameshift variant that was reported in family 1. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only heterozygous carrier who displays ID features. |
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| Intellectual disability - microarray and sequencing v2.977 | FRMPD4 |
Catherine Snow changed review comment from: Further paper identified to indicated FRMPD4 is relevant to ID. PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was hetrozygous for the same micro deletion. Family 3, two half-siblings, p.Arg286Ter . Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported Some functional work on mice performed. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only hetrozygous carrier who displays ID features.; to: Further paper identified to indicated FRMPD4 is relevant to ID. PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was heterozygous for the same micro deletion. Family 3, two half-siblings (p.Arg286Ter) Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported. Some functional work performed but only for the frameshift variant that was reported in family 1. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only hetrozygous carrier who displays ID features. |
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| Intellectual disability - microarray and sequencing v2.977 | FRMPD4 |
Catherine Snow changed review comment from: Further paper identified to indicated FRMPD4 is relevant to ID. PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was hetrozygous for the same micro deletion Family 3, two half-siblings, p.Arg286Ter . Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported Some functional work on mice performed. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only hetrozygous carrier who displays ID features.; to: Further paper identified to indicated FRMPD4 is relevant to ID. PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was hetrozygous for the same micro deletion. Family 3, two half-siblings, p.Arg286Ter . Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported Some functional work on mice performed. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only hetrozygous carrier who displays ID features. |
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| Intellectual disability - microarray and sequencing v2.977 | FRMPD4 |
Catherine Snow changed review comment from: PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was hetrozygous for the same micro deletion Family 3, two half-siblings, p.Arg286Ter . Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported Some functional work on mice performed. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only hetrozygous carrier who displays ID features.; to: Further paper identified to indicated FRMPD4 is relevant to ID. PMID: 29267967 provides details of four unrelated families, two families, family 1 and 4 had already been identified and reported in PMID:25644381. Family 2, two brothers, had a micro deletion of exon 2, their mother was hetrozygous for the same micro deletion Family 3, two half-siblings, p.Arg286Ter . Their unaffected mother was heterozygous for the same deletion, a hetrozygous sister was mildly disabled. No further segregation information for the two families was reported Some functional work on mice performed. Requesting support from clinical team as limited information on the extended families and the female affected in family 3 is the only hetrozygous carrier who displays ID features. |
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| Intellectual disability - microarray and sequencing v2.938 | CTBP1 |
Konstantinos Varvagiannis changed review comment from: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green.; to: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential (Cited: Kim and Youn 2009 - PMID: 19136938). ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. |
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| Intellectual disability - microarray and sequencing v2.938 | CTBP1 |
Konstantinos Varvagiannis changed review comment from: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1 ). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. Sources: Literature; to: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.938 | CTBP1 |
Konstantinos Varvagiannis gene: CTBP1 was added gene: CTBP1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CTBP1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CTBP1 were set to 27094857; 28955726; 31041561 Phenotypes for gene: CTBP1 were set to Generalized hypotonia; Global developmental delay; Intellectual disability; Ataxia; Abnormality of dental enamel Penetrance for gene: CTBP1 were set to unknown Mode of pathogenicity for gene: CTBP1 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: CTBP1 was set to GREEN gene: CTBP1 was marked as current diagnostic Added comment: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1 ). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.938 | TRPM3 |
Konstantinos Varvagiannis changed review comment from: Dyment et al. (2019 - https://doi.org/10.1038/s41431-019-0462-x) report on 7 unrelated individuals with a recurrent de novo TRPM3 missense variant [NM_020952.4:c.2509G>A - NP_066003.3:p.(Val837Met)] as well as an additional individual with a further de novo missense variant [c.2810C>A or p.(Pro937Gln) - same ref. sequences]. Overlapping features included hypotonia (7/8 - in one case mixed tone abnormality), DD/ID (8/8 - all individuals at appropriate age - degree relevant), EEG-confirmed epilepsy (7/8). Autism-like features were observed in 4 (out of 6 for whom this information was reported). Other features were noted in a minority (or were private to certain) of these individuals. Different clinical types of seizures were reported incl. absence, generalized-toni-clonic, infantile spasms as well as subclinical ones. Onset was in infancy or early childhood. In all individuals the variant was found following trio exome sequencing. The first variant fulfilled ACMG criteria to be classified as pathogenic due to it's de novo occurrence, prevalence in affected individuals (>=6 affected individuals and in the same time) absence from population databases, in silico predictions in favour of pathogenicity (PS2, PS4_Moderate, PM2, PP3). The Pro937Gln variant is however classified as a VUS. The subject harboring this variant had an additional de novo variant in another gene (DDB1) not associated with any phenotype, to date. Several other genetic causes had previously been ruled out for most individuals by other investigations : aCGH was normal in all, FMR1 testing in 6 subjects, genes (PHF6, MECP2, MCT8) or smaller panels for ID (the latter in 3 subjects), mtDNA or testing of nuclear genes for mitochondrial disorders, etc. TRPM3 encodes transient receptor potential (TRP) cation channel, subfamily M, member 3. TRP channels are a superfamily of gated cation channels sensitive to various physical or chemical stimuli (Clapham 2003 - PMID: 14654832 cited) eg. temperature or pain. The gene is highly expressed in the brain in humans and other vertebrates (Grimm et al. 2003 - PMID : 12672799 and GTEx - https://gtexportal.org/home/gene/TRPM3). Animal models : In rat brain, expression is initially restricted to neurons but later - as myelination progresses - shifts to oligodendrocytes (cited : Hoffmann et al. 2010 - PMID: 20163522). Most subjects had normal brain MRI appart from one individual with nonspecific white matter hyperintensities and another with possible mild cerebral volume loss. Trpm3 -/- mice show attenuated nocifensive behavior after heat or dermal injection of pregnenolone sulfate. Heat or pain insensitivity was reported only for 2 individuals. Functional studies were not carried out, although some hypotheses are proposed following in silico modeling of the TRPM3 variants using an available structure for TRPM7. As discussed by Dyment et al., happloinsufficiency appears to be unlikely given the presence of LoF variants in ExAC/gnomAD (pLI of 0), some intragenic copy number variants in DGV. In addition, pathogenicity of deletions spanning only TRPM3 or additional proximal genes was not evident in 2 cases: - In the first case a exon 1-9 deletion was found in 2 brothers with Becker muscular dystrophy due to DMD intragenic duplication and autism/cognitive impairment though the TRPM3 deletion was found also in unaffected family members. The deletion was also found in unaffected relatives. A multiple hit hypothesis was hypothesized for this family. [Pagnamenta et al. 2011 - PMID: 21484199] - Kuniba et al. [2009 - PMID: 19343044] reported a 1.27-Mb deletion spanning TRPM3, KLF9, SMC5 and MAMDC2 in a patient with Kabuki syndrome working diagnosis. Segregation studies were however not possible. At the time, the molecular etiology of Kabuki syndrome (KMT2D/KDM6A) was not known. ----- TRPM3 is not associated with any phenotype in OMIM or G2P. This gene is included in panels for ID offered by some diagnostic laboratories (eg. GeneDx participating in the above study). ----- As a result, TRPM3 seems to fulfill criteria for inclusion in the ID/epilepsy panels probably as green (# of individuals, degree of ID relevant, EEG-confirmed epilepsy) or amber (if further functional evidence would be required). [Please consider eligibility for inclusion in other possibly relevant panels eg. autism, etc]. Sources: Literature; to: Dyment et al. (2019 - https://doi.org/10.1038/s41431-019-0462-x) report on 7 unrelated individuals with a recurrent de novo TRPM3 missense variant [NM_020952.4:c.2509G>A - NP_066003.3:p.(Val837Met)] as well as an additional individual with a further de novo missense variant [c.2810C>A or p.(Pro937Gln) - same ref. sequences]. Overlapping features included hypotonia (7/8 - in one case mixed tone abnormality), DD/ID (8/8 - all individuals at appropriate age - degree relevant), EEG-confirmed epilepsy (7/8). Autism-like features were observed in 4 (out of 6 for whom this information was reported). Other features were noted in a minority (or were private to certain) of these individuals. Different clinical types of seizures were reported incl. absence, generalized-toni-clonic, infantile spasms as well as subclinical ones. Onset was in infancy or early childhood. In all individuals the variant was found following trio exome sequencing. The first variant fulfilled ACMG criteria to be classified as pathogenic due to it's de novo occurrence, prevalence in affected individuals (>=6 affected individuals and in the same time) absence from population databases, in silico predictions in favour of pathogenicity (PS2, PS4_Moderate, PM2, PP3). The Pro937Gln variant is however also present once in gnomAD (1/251370 alleles or AF:3.98e-6) and is classified as VUS according to the ACMG criteria. The subject harboring this variant had an additional de novo variant in another gene (DDB1) not associated with any phenotype, to date. Several other genetic causes had previously been ruled out for most individuals by other investigations : aCGH was normal in all, FMR1 testing in 6 subjects, genes (PHF6, MECP2, MCT8) or smaller panels for ID (the latter in 3 subjects), mtDNA or testing of nuclear genes for mitochondrial disorders, etc. TRPM3 encodes transient receptor potential (TRP) cation channel, subfamily M, member 3. TRP channels are a superfamily of gated cation channels sensitive to various physical or chemical stimuli (Clapham 2003 - PMID: 14654832 cited) eg. temperature or pain. The gene is highly expressed in the brain in humans and other vertebrates (Grimm et al. 2003 - PMID : 12672799 and GTEx - https://gtexportal.org/home/gene/TRPM3). Animal models : In rat brain, expression is initially restricted to neurons but later - as myelination progresses - shifts to oligodendrocytes (cited : Hoffmann et al. 2010 - PMID: 20163522). Most subjects had normal brain MRI appart from one individual with nonspecific white matter hyperintensities and another with possible mild cerebral volume loss. Trpm3 -/- mice show attenuated nocifensive behavior after heat or dermal injection of pregnenolone sulfate. Heat or pain insensitivity was reported only for 2 individuals. Functional studies were not carried out, although some hypotheses are proposed following in silico modeling of the TRPM3 variants using an available structure for TRPM7. As discussed by Dyment et al., happloinsufficiency appears to be unlikely given the presence of LoF variants in ExAC/gnomAD (pLI of 0), some intragenic copy number variants in DGV. In addition, pathogenicity of deletions spanning only TRPM3 or additional proximal genes was not evident in 2 cases: - In the first case a exon 1-9 deletion was found in 2 brothers with Becker muscular dystrophy due to DMD intragenic duplication and autism/cognitive impairment though the TRPM3 deletion was found also in unaffected family members. The deletion was also found in unaffected relatives. A multiple hit hypothesis was hypothesized for this family. [Pagnamenta et al. 2011 - PMID: 21484199] - Kuniba et al. [2009 - PMID: 19343044] reported a 1.27-Mb deletion spanning TRPM3, KLF9, SMC5 and MAMDC2 in a patient with Kabuki syndrome working diagnosis. Segregation studies were however not possible. At the time, the molecular etiology of Kabuki syndrome (KMT2D/KDM6A) was not known. ----- TRPM3 is not associated with any phenotype in OMIM or G2P. This gene is included in panels for ID offered by some diagnostic laboratories (eg. GeneDx participating in the above study). ----- As a result, TRPM3 seems to fulfill criteria for inclusion in the ID/epilepsy panels probably as green (# of individuals, degree of ID relevant, EEG-confirmed epilepsy) or amber (if further functional evidence would be required). [Please consider eligibility for inclusion in other possibly relevant panels eg. autism, etc]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.938 | TRPM3 |
Konstantinos Varvagiannis gene: TRPM3 was added gene: TRPM3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TRPM3 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: TRPM3 were set to doi.org/10.1038/s41431-019-0462-x Phenotypes for gene: TRPM3 were set to Generalized hypotonia; Global developmental delay; Intellectual disability; Seizures; Autistic behavior Penetrance for gene: TRPM3 were set to unknown Mode of pathogenicity for gene: TRPM3 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: TRPM3 was set to GREEN gene: TRPM3 was marked as current diagnostic Added comment: Dyment et al. (2019 - https://doi.org/10.1038/s41431-019-0462-x) report on 7 unrelated individuals with a recurrent de novo TRPM3 missense variant [NM_020952.4:c.2509G>A - NP_066003.3:p.(Val837Met)] as well as an additional individual with a further de novo missense variant [c.2810C>A or p.(Pro937Gln) - same ref. sequences]. Overlapping features included hypotonia (7/8 - in one case mixed tone abnormality), DD/ID (8/8 - all individuals at appropriate age - degree relevant), EEG-confirmed epilepsy (7/8). Autism-like features were observed in 4 (out of 6 for whom this information was reported). Other features were noted in a minority (or were private to certain) of these individuals. Different clinical types of seizures were reported incl. absence, generalized-toni-clonic, infantile spasms as well as subclinical ones. Onset was in infancy or early childhood. In all individuals the variant was found following trio exome sequencing. The first variant fulfilled ACMG criteria to be classified as pathogenic due to it's de novo occurrence, prevalence in affected individuals (>=6 affected individuals and in the same time) absence from population databases, in silico predictions in favour of pathogenicity (PS2, PS4_Moderate, PM2, PP3). The Pro937Gln variant is however classified as a VUS. The subject harboring this variant had an additional de novo variant in another gene (DDB1) not associated with any phenotype, to date. Several other genetic causes had previously been ruled out for most individuals by other investigations : aCGH was normal in all, FMR1 testing in 6 subjects, genes (PHF6, MECP2, MCT8) or smaller panels for ID (the latter in 3 subjects), mtDNA or testing of nuclear genes for mitochondrial disorders, etc. TRPM3 encodes transient receptor potential (TRP) cation channel, subfamily M, member 3. TRP channels are a superfamily of gated cation channels sensitive to various physical or chemical stimuli (Clapham 2003 - PMID: 14654832 cited) eg. temperature or pain. The gene is highly expressed in the brain in humans and other vertebrates (Grimm et al. 2003 - PMID : 12672799 and GTEx - https://gtexportal.org/home/gene/TRPM3). Animal models : In rat brain, expression is initially restricted to neurons but later - as myelination progresses - shifts to oligodendrocytes (cited : Hoffmann et al. 2010 - PMID: 20163522). Most subjects had normal brain MRI appart from one individual with nonspecific white matter hyperintensities and another with possible mild cerebral volume loss. Trpm3 -/- mice show attenuated nocifensive behavior after heat or dermal injection of pregnenolone sulfate. Heat or pain insensitivity was reported only for 2 individuals. Functional studies were not carried out, although some hypotheses are proposed following in silico modeling of the TRPM3 variants using an available structure for TRPM7. As discussed by Dyment et al., happloinsufficiency appears to be unlikely given the presence of LoF variants in ExAC/gnomAD (pLI of 0), some intragenic copy number variants in DGV. In addition, pathogenicity of deletions spanning only TRPM3 or additional proximal genes was not evident in 2 cases: - In the first case a exon 1-9 deletion was found in 2 brothers with Becker muscular dystrophy due to DMD intragenic duplication and autism/cognitive impairment though the TRPM3 deletion was found also in unaffected family members. The deletion was also found in unaffected relatives. A multiple hit hypothesis was hypothesized for this family. [Pagnamenta et al. 2011 - PMID: 21484199] - Kuniba et al. [2009 - PMID: 19343044] reported a 1.27-Mb deletion spanning TRPM3, KLF9, SMC5 and MAMDC2 in a patient with Kabuki syndrome working diagnosis. Segregation studies were however not possible. At the time, the molecular etiology of Kabuki syndrome (KMT2D/KDM6A) was not known. ----- TRPM3 is not associated with any phenotype in OMIM or G2P. This gene is included in panels for ID offered by some diagnostic laboratories (eg. GeneDx participating in the above study). ----- As a result, TRPM3 seems to fulfill criteria for inclusion in the ID/epilepsy panels probably as green (# of individuals, degree of ID relevant, EEG-confirmed epilepsy) or amber (if further functional evidence would be required). [Please consider eligibility for inclusion in other possibly relevant panels eg. autism, etc]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.857 | MED12L |
Konstantinos Varvagiannis gene: MED12L was added gene: MED12L was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MED12L was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: MED12L were set to 31155615 Phenotypes for gene: MED12L were set to Motor delay; Delayed speech and language development; Intellectual disability; Behavioral abnormality; Abnormality of the abdomen; Seizures; Abnormality of the corpus callosum Penetrance for gene: MED12L were set to unknown Review for gene: MED12L was set to AMBER Added comment: Nizon et al. (2019 - PMID: 31155615) report on 7 unrelated individuals with nucleotide or copy-number variants in MED12L. Features included motor delay (4/7), speech impairment (7/7) with ID of variable degrees (7/7 - mild to severe). Variable behavioral abnormalities (ASD in 4/7, aggressive behavior, ADHD, etc), functional GI anomalies, corpus callosum abnormalities and seizures were among other features noted in some/few. There was no recognizable facial phenotype. Nucleotide variants included 1 stopgain, 1 frameshift and 2 splice site variants. 3 CNVs were reported (two 3q25.1 microduplications of 460- and 147-kb respectively and one microdeletion of 291-kb) although all spanned also other genes. De novo occurrence was shown for 2 CNVs and 2 SNVs, as parental samples were unavailable for 3 of the subjects. Contribution of other genetic (eg. an inherited 22q11.2 microduplication, VUS in other genes) or environmental factors could not be ruled out for few individuals. Among the arguments provided: MED12L encodes a subunit of the kinase module of the mediator complex, a complex required for transcription by RNA polymerase II. Mutations in other subunits of the kinase module (eg. MED12, MED13L, etc) have been implicated in intellectual disability. The protein is localized in the nucleus. The gene is mainly expressed in the brain. The functional effect of 2 CNVs was evaluated using the recovery of RNA synthesis assay, an assay reflecting global transcriptional activity. Fibrobast studies from one individual with microdeletion and one further subject with microduplication demonstrated decreased RNA synthesis compared to controls. Decreased RNA synthesis was also observed in cell lines from individuals with mutations in other genes for subunits of the mediator complex (eg. MED12 or MED13L) or from individuals with Cockayne syndrome. Therefore haploinsufficiency is suggested to underly the transcriptional defect. (MED12L also appears to be intolerant to LoF variation with a pLI score of 1). Some features appear to be common among the disorders caused by pathogenic variants in MED12L or other subunits of the kinase module (MED12, MED13, MED13L) eg. ID, abnormal behaviour or autistic features. Animal models are not discussed / (probably not) available (MGI for Med12l : http://www.informatics.jax.org/marker/MGI:2139916). MED12L is not associated with any phenotype in OMIM or G2P. The gene is not commonly included in gene panels for ID offered by diagnostic laboratories. As a result, this gene can be considered for inclusion in the ID panel, probably as amber (4 variants affecting only MED12L, segregation studies performed for 2, degree of ID reported mild on 2 occasions) pending further reports. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.800 | SNAP25 |
Konstantinos Varvagiannis gene: SNAP25 was added gene: SNAP25 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: SNAP25 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: SNAP25 were set to 29491473; 28135719; 29100083; 25381298; 25003006 Phenotypes for gene: SNAP25 were set to ?Myasthenic syndrome, congenital 18, 616330 Penetrance for gene: SNAP25 were set to Complete Review for gene: SNAP25 was set to GREEN gene: SNAP25 was marked as current diagnostic Added comment: Probably 9 individuals with heterozygous SNAP25 pathogenic variants have been reported to date, most summarized in the first reference (NM_130811.2 used as reference for all variants below): - Fukuda et al. (2018 - PMID: 29491473) 2 sibs (~11 and 2.5 y.o) with seizures and cerebellar ataxia but not ID. harboring c.176G>C (p.Arg59Pro) variant which was inherited from a mosaic unaffected parent. - DDD study (2017 - PMID: 28135719) [also in Heyne et al. 2018 - PMID: 29942082] 3 inividuals (11 m - 7 y of age) with DD and seizures due to c.118A>G (p.Lys40Glu), c.127G>C (p.Gly43Arg) and c.520C>T (p.Gln174*) de novo variants. - Hamdan et al. (2017 - PMID: 29100083) a 23 y.o. male with epilepsy and ID and c.496G>T (p.Asp166Tyr) de novo variant - Shen et al. (2014 - PMID: 25381298) a 11 y.o. female with epilepsy and ID and c.200T>A (p.Ile67Asn) de novo variant - Rohena et al. (2013 - PMID: 25003006) a 15 y.o. female with epilepsy and ID and c.142G>T (p.Val48Phe) de novo variant - Decipher patient 292139, a male with c.212T>C (p.Met71Thr) with hypotonia, DD, poor coordination and additional features (epilepsy not reported). Seizures of variable type [absence seizures, generalized tonic-clonic (most), focal clonic, myoclonic, etc] have been reported for most (8/9) of these individuals. DD was a feature in several subjects and intellectual outcome has been specifically commented on for 5 (2 without and 3 with ID - moderate/severe/not further specified). SNAP25 encodes a (t-)SNARE protein essential for synaptic vesicle exocytosis. Mutations in genes for other components of the SNARE complex (eg. STXBP1) have been associated with epilepsy and/or ID. SNAP25a and SNAP25b are the 2 major protein isoforms [corresponding transcripts: ENST00000304886 (NM_003081) and ENST00000254976 (NM_130811) respectively]. These isoforms are produced by utilization of alternative exons 5 (5a or 5b) though the amino-acid sequence encoded by these exons appears to be identical except for 9 residues. Most variants reported to date affect both transcripts (and protein isoforms) although 2 were specific for ENST00000254976 (or SNAP25b isoform - Fukuda et al. and Shen et al.). Mouse Snap25 has also 2 isoforms. Both are predominantly localized in embryonic and adult mouse brains. Snap25a is produced before Snap25b though the latter becomes the major isoform early postnatally (by the second week) [PMIDs cited: 7878010, 21526988]. Based on the phenotype of some individuals with chromosome 20 deletions in Decipher (note: only 3 deletions spanning SNAP25 however appear currently, the phenotype is not specified and 2 of them are >4.5Mb) or the pLI of 0.96 in gnomAD, haploinsufficiency has been proposed as a likely mechanism. A dominant-negative effect was however suggested for the Ile67Asn studied by Shen et al. Functional studies have not been performed for other variants. Animal models discussed: - Snap25 null drosophila show complete loss of synaptic transmission upon electroretinogram recordings (PMID cited: 12242238). - In mice, elimination of Snap25b expression resulted in developmental defects, seizures and impaired short-term synaptic plasticity (PMID cited: 19043548). - Mice with a 4.6 Mb deletion encompassing 12 genes (incl. Snap25) display seizure predisposition (PMID cited: 23064108). - Heterozygosity for Ile67Thr in (blind-drunk mutant) mice results in impaired vesicle trafficking, impaired sensorimotor gating and ataxia (PMID cited:17283335). In OMIM, heterozygous SNAP25 mutations are associated with ?Myasthenic syndrome, congenital, 18 (with intellectual disability and ataxia). SNAP25 is part of the DD panel, associated with "Epilepsy and intellectual disability" (disease confidence: probable). This gene is included in gene panels for ID offered by some diagnostic laboratories (incl. Radboudumc). SNAP25 is among the genes discussed by Erger et al. (PMID: 30914295) as associated with ID in OMIM/HPO/G2P/SysID but not included in the current panel. As a result SNAP25 can be considered for inclusion in the ID panel probably as green (3 individuals with ID, role of SNARES in "synaptopathies", supportive animal models) or amber (if functional studies for individual variants would be required). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.800 | CACNA1B |
Konstantinos Varvagiannis gene: CACNA1B was added gene: CACNA1B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CACNA1B was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: CACNA1B were set to Global developmental delay; Developmental regression; Seizures; Intellectual disability; Abnormality of movement Penetrance for gene: CACNA1B were set to Complete Review for gene: CACNA1B was set to GREEN Added comment: Gorman et al. (2019 - doi.org/10.1016/j.ajhg.2019.03.005) report on 6 individuals from 3 unrelated families, with biallelic LoF CACNA1B variants. The phenotype corresponds to a developmental epilepic encephalopathy with hyperkinetic movement disorder (ID was a universal feature, DD and/or regression occurred prior to the onset of seizures in several individuals) . CACNA1B encodes calcium channel, voltage-dependent N type, α-1B subunit (Ca v2.2). As commented by the authors, Ca v2.1 and v2.2 are important for SNARE-mediated release of neurotransmitters through modulation of Ca+2 levels. In addition, Ca v2.2 has been postulated to have a role in synaptic plasticity, synaptogenesis, migration of immature neurons, etc. It is thought to have a crucial role in neurotransmission in the early postnatal period (Ca v2.2 channels are subsequently replaced by Ca v2.1 in mature synapses within the thalamus, cerebellum and auditory brainstem). Knockout mice display neurodevelopmental abnormalities including impaired locomotor activity and memory impairment (all ref. cited within the article). 3 sibs, born to 1st cousin parents, harbored p.Leu1222Argfs*29 (NM_000718.4:c.3665del) in the homozygous state. One additional individual was homozygous for p.Arg383*. Compound heterozygosity for a frameshift and a splicing variant (p,Gly1192Cysfs* and c.4857+1G>C) was identified in 2 sibs from a 3rd family. Expression/functional studies have not been performed for any of the variants reported. In OMIM, monoallelic CACNA1B pathogenic variants are associated with ?Dystonia 23 (MIM 614860) based on the identification of a heterozygous missense (R1389H) mutation in members of a Dutch with myoclonus-dystonia syndrome (Groen et al. 2015 - PMID: 25296916). As a result, this gene can be considered for inclusion in the epilepsy and ID panels as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.798 | VAMP2 |
Konstantinos Varvagiannis gene: VAMP2 was added gene: VAMP2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: VAMP2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: VAMP2 were set to 30929742 Phenotypes for gene: VAMP2 were set to Generalized hypotonia; Global developmental delay; Intellectual disability; Autistic behavior; Stereotypic behavior; Seizures; Abnormality of movement; Cortical visual impairment Penetrance for gene: VAMP2 were set to unknown Review for gene: VAMP2 was set to GREEN gene: VAMP2 was marked as current diagnostic Added comment: Salpietro et al. (2019 - PMID: 30929742 - DDD study among the co-authors) report on 5 individuals each with private heterozygous de novo variants in VAMP2. The overlapping phenotype consisted among others of hypotonia with DD, moderate/severe ID and ASD (all in 5/5). Other features included the presence of clinical seizures (3/5 - EEG anomalies observed in all individuals), variable Rett-like stereotypies, hyperkinetic movements, central visual impairment. OFC was normal in all subjects. VAMP2 encodes the vesicular SNARE protein synaptobrevin-2 which - along with its partners (syntaxin-1A and synaptosomal-associated protein 25) - mediates fusion of synaptic vesicles for the release of neurotransmitters. A number of synaptic proteins involved in Ca+2-regulated neurotransmitter release (eg. Munc18 encoded by STXBP1) regulate the fusion of synaptic vesicles, although SNAREs alone are sufficient for this process. All variants localized in the v-SNARE domain (aa 31-91 - of 116 total residues - NP_0055047.2) with some phenotypic differences between variants localizing in the C-terminal end of the v-SNARE domain compared to those localizing in its proximal part. The following 3 missense variants and 2 in-frame deletions were reported (using NM_014232 as reference): c.223T>C or p.Ser75Pro - c.233A>C or p.Glu78Ala - c.230T>C or p.Phe77Ser - c.128_130delTGG or p.Val43del and c.135_137delCAT or p.Ile45del. Functional studies were performed for 2 missense variants and were suggestive of impairment in vesicle fusion for the Ser75Pro variant. The fusion profile for Glu78Ala was however similar to wt. Upon Munc18-activated conditions, wt vesicle fusion was 2-fold increased, in contrast to a >90% loss-of-function effect which was observed for the Ser75Pro variant. Munc18 was however able to activate vesicle fusion mediated by the Glu78Ala variant. When using mixed v-liposomes (50:50 Wildtype:Ser75Pro mutant) the fusion profile was identical to the profile of homogeneous samples containing only the mutant protein which was suggestive of dominant interference of the mutant with wildtype. In gnomAD, VAMP2 has a (low) Z-score and pLI of 1.41 and 0.89 respectively. The authors comment that mutations in other genes encoding presynaptic proteins involved in Ca+2-regulated neurotransmitter release (eg SNAP25, STXBP1, etc) have been identified in other neurological disorders (with ID as a feature). VAMP2 is not associated with any phenotype in OMIM or G2P. This gene is included in gene panels for ID offered by some diagnostic laboratories. As a result, VAMP2 can be considered for inclusion in the ID panel probably as green (5 individuals, degree of ID relevant) or amber. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.766 | STAG2 | Rebecca Foulger commented on gene: STAG2: PMID:29263825 (Soardi et al., 2017) report 5 individuals from a pedigree with a STAG2 p.Ser327Asn (c.980 G > A) variant that perfectly cosegregates with a phenotype of syndromic mental retardation in a characteristic X-linked recessive pattern- heterozygous female carriers of the variant (aunt and mother of the proband) were healthy. Other healthy relatives did not have the c.980 G>A variant. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.654 | CUX1 |
Konstantinos Varvagiannis gene: CUX1 was added gene: CUX1 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: CUX1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CUX1 were set to 30014507; 20510857; 25059644 Phenotypes for gene: CUX1 were set to Global developmental delay with or without impaired intellectual development, 618330 Penetrance for gene: CUX1 were set to unknown Review for gene: CUX1 was set to GREEN gene: CUX1 was marked as current diagnostic Added comment: Heterozygous pathogenic variants in CUX1 cause Global developmental delay with or without impaired intellectual development (MIM 618330). Platzer et al. (2018 - PMID: 30014507) report on 9 individuals from 7 families with heterozygous null-allele variants in CUX1. All individuals displayed DD (speech delay 9/9 - motor delay 7/9 - hypotonia 3/7 for whom this information was available). Mild/moderate ID was a feature in 5/8. Catch up was observed in 3/8 individuals who - despite a history of previous significant DD - displayed a normal age-related intelligence. For 1/9 individual (Decipher 338131) information on eventual ID was unavailable. Overall the phenotype was compatible with non-syndromic DD with possible ID. CUX1 encodes Cut homebox-1 transcription factor. 5 LoF variants (Gln21*, Gln800Argfs*19, Gln873*, Ala1067Cysfs*3, Leu1262Argfs*10) and 2 intragenic deletions (deletion of exons 9-24 in one subject and 3-24 in another) are reported. In 6/9 individuals the variant (SNV/CNV) had occurred as a de novo event. Mosaic de novo intragenic deletion was reported for the subject from Decipher. In one family 2 sibs with mild ID had inherited a LoF variant from their affected mother with moderate ID (origin of the variant unknown in her case). Leu1262Argfs*10 lies in the penultimate exon (NM_001202543.1 used as ref.) and is presumed to escape NMD. Expression studies (or functional studies) are not performed for any of the variants. As Gln800Argfs*19, found in one subject with mild ID in the present study, has been reported once in gnomAD, and given the presence of 12 individuals overall with LoF variants in the specific database, plausible explanations are discussed (among others : mild phenotype, incomplete penetrance, somatic mosaicism, exclusion of individuals with severe early-onset disorders in gnomAD, etc). Given the reported variants, the probability of LoF intolerance (pLI:1.00), and the haploinsufficiency score (% HI) of 7.19, haploinsufficiency is thought to be the underlying mechanism. CUX1 however appears to be intolerant also to missense SNVs (z-score : 5.05). Mouse models suggest a role for Cux1 in brain development and signaling. As the authors note, Cux1 (similar to its paralog, Cux2) is selectively expressed in layer II to IV cortical neurons. In Cux1-deficient mice, dendrites display a simpler morphology with decrease in dendritic length and number of branches (PMIDs cited: 20510857, 25059644). (MGI db for Cux1 - http://www.informatics.jax.org/marker/MGI:88568 : "Homozygotes for a targeted null mutation exhibit delayed lung development and neonatal mortality. Survivors show growth retardation and hair defects. Homozygotes for a partially deleted protein have curly hair, and females tend to lose their litters"). Finally, heterozygous mutations in CUX2, encoding cut-like homeobox-2 transcription factor, cause Epileptic encephalopathy, early infantile, 67 (MIM 618141 - in all cases reported to date due to a recurrent missense variant. Gene rated green in the current panel). ------- CUX1 is not associated with any phenotype in G2P. This gene is included in panels for ID offered by diagnostic laboratories (incl. Radboudumc). ------- As a result, CUX1 can be considered for inclusion in the ID panel as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| 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 | ZNF462 |
Konstantinos Varvagiannis gene: ZNF462 was added gene: ZNF462 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: ZNF462 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZNF462 were set to 28513610; 29427787; 14564155; 12825074 Phenotypes for gene: ZNF462 were set to Ptosis; Prominent metopic ridge; Craniosynostosis; Global developmental delay; Intellectual disability; Autistic behavior Penetrance for gene: ZNF462 were set to unknown Review for gene: ZNF462 was set to AMBER gene: ZNF462 was marked as current diagnostic Added comment: Weiss et al. (PMID: 28513610) report on 8 individuals (from 6 unrelated families) with heterozygous pathogenic variants affecting ZNF462. Frequent features included ptosis metopic ridging, craniosynostosis, dysgenesis of corpus callosum. DD (with or without ASD) was a feature in 4 (4/8), one of whom was reported to present mild ID. 4 LoF mutations as well as 2 9q31.2 deletions spanning also other genes are reported [NM_021224.4]: Fam. 1 - c.3787C>T p.(Arg1263*) (familial) - Normal development in all 3 family members Fam. 2 - c.2979_2980delinsA p.(Val994Trpfs*147) (de novo) - DD Fam. 3 - c.4263delA p.(Glu1422Serfs*6) (de novo) - DD Fam. 4 - Chr9:g.(108940763-110561397)del (hg19) (de novo) - Normal development Fam. 5- Chr9:g(108464368-110362345)del (hg19) (de novo) - DD with mild ID Fam. 6 - c.5145delC p.(Tyr1716Thrfs*28) (de novo) - DD There were no expression/functional studies performed although haploinsufficiency can be presumed based on these variants (ZNF462 has a pLI of 1 in ExAC). ----------- Cosemans et al. (PMID: 29427787) report on an individual investigated - among others - for mild ID and ASD. This individual harbored a de novo (complex) translocation disrupting ZNF462 and KLF12. As this subject presented similar features to those reported by Weiss et al. (eg. craniofacial anomalies, abn. development, ASD) and given that KLF12 is not associated with any disorder, the phenotype of this individual was thought to be secondary to disruption of ZNF462. Details on this patient - before delineation of the translocation breakpoints - were provided previously by Fryns and Hendrickx ( PMID:9297446). ----------- Cited by the previous article, a further case of ZNF462 disruption due to translocation was previously published in the literature (same individual - Talisetti et al. PMID: 14564155 / Ramocki et al. PMID: 12825074). Profound ID was among the features of this individual although the translocation disrupted also a further ID gene (ASXL2). ----------- In ClinVar 8 variants have been submitted as pathogenic/likely pathogenic although a phenotype is provided only for 3 variants published by Weiss et al.(submitting lab participating in PMID: 28513610 / SCV000494060.1 corresp. to Fam.1 / SCV000494061.1 - Fam.2 / SCV000494062.1 - Fam. 3). ----------- Several individuals with de novo coding variants in ZNF462 have been reported in the context of larger cohorts (some with ID as a principal feature). http://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=ZNF462 ----------- In Decipher apart from the DDD study participants DDD4K.03663 and DDD4K.03792 (appearing in the denovo-db) with LoF and abnormality of the nervous system, several further individuals have been submitted. 2 of these subjects, harbored a de novo LoF (submitted as pathogenic) and had ID as a feature. ---------- ZNF462 is included in the DD panel of G2P, associated with Craniofacial anomalies, corpus callosum dysgenesis, ptosis, and developmental delay [Disease confidence: probable / Global DD (but not ID) among the phenotypes assigned to this entry]. This gene is not associated with any phenotype in OMIM. ---------- ZNF462 is included in gene panels for ID offered by diagnostic laboratories (incl. Radboudumc). ---------- As a result this gene can be considered for inclusion in the ID panel probably as amber (or green if the current evidence is thought to be sufficient). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.588 | TBC1D20 |
Konstantinos Varvagiannis gene: TBC1D20 was added gene: TBC1D20 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: TBC1D20 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TBC1D20 were set to 24239381; 26063829 Phenotypes for gene: TBC1D20 were set to Warburg Micro syndrome 4 (MIM 615663) Penetrance for gene: TBC1D20 were set to Complete Review for gene: TBC1D20 was set to GREEN gene: TBC1D20 was marked as current diagnostic Added comment: Biallelic pathogenic variants in TBC1D20 cause Warburg Micro syndrome 4 (MIM 615663). --------- Liegel et al. (PMID: 24239381) report on 7 individuals from 5 unrelated families. ID was a universal feature along with opthalmological, endocrine and other neurological features of the disorder. Seizures were noted in 4 individuals from 2 families. Table S4 of this article provides clinical details on each subject. All affected individuals were homozygous for LoF variants, private to each family. 3 nonsense variants, 1 frameshift one as well as an intragenic deletion (exons 2-8) were identified. These subjects belonged to a cohort of 77 individuals with suspected Warburg Micro syndrome (WMS) or disorders of the same spectrum (eg. Martsof syndrome). Screening for TBC1D20 mutations in these individuals was performed after identification of a homozygous LoF Tbc1d20 mutation in blind sterile mice, presenting a phenotype somewhat similar to WMS (congenital cataracts and testicular anomalies). Alternative causes of WM (eg. pathogenic variants in RAB3GAP1, RAB3GAP2 and RAB18) had previously been excluded in this cohort. The authors demonstrated aberrant lipid droplet formation in embryonic fibroblasts from blind sterile mice as well as in fibroblasts from individuals with a diagnosis of WMS due to mutations in either of TBC1D20, RAB18 and RAB3GAP1. --------- TBC1D20 is included in the DD panel of G2P, associated with Warburg micro syndrome 4 (Disease confidence: probable / ID among the phenotypes assigned to this entry). This gene is included in gene panels for ID offered by different diagnostic laboratories (incl. Radboudumc). --------- As a result, TBC1D20 can be considered for inclusion in the ID panel as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.588 | SLC35A3 |
Konstantinos Varvagiannis gene: SLC35A3 was added gene: SLC35A3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC35A3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC35A3 were set to 24031089; 28328131; 28777481; 16344554 Phenotypes for gene: SLC35A3 were set to ?Arthrogryposis, mental retardation, and seizures (MIM 615553) Penetrance for gene: SLC35A3 were set to Complete Review for gene: SLC35A3 was set to GREEN gene: SLC35A3 was marked as current diagnostic Added comment: Biallelic pathogenic variants in SLC35A3 cause Arthrogryposis, mental retardation, and seizures (MIM 615553). -------- Edvardson et al. (PMID: 24031089) report on 8 affected individuals from 3 nuclear Ashkenazi Jewish families. All harbored a nonsense [NM_012243.1:c.514C>T / p.(Gln172*)] as well as a missense variant [NM_012243.1:c.886A>G / p.(Ser296Gly)] in the compound heterozygous state. Most of the parents, who were heterozygous for the one or the other variant, were distantly related. Common features included ASD (8/8), arthrogryposis (8/8), seizures (6/8) and intellectual disability (6/8 - variable degrees). Upon cDNA studies, the (predicted) missense variant led to skipping of exon 8 and there was no normal size transcript (as would be expected for a variant of this type). Introduction of a premature stop codon due to this variant as well instability of the mRNA from the Gln172Ter allele was presumed to lead to absence of functional SLC35A3 protein. Testing of 2045 Ashkenazi Jewish individuals revealed a carrier frequency of 1/205 for the missense variant in this community (with no occurrence of the nonsense variant). SLC35A3 is a nucleotide sugar transporter that transports (uniquely) UDP-N-acetylglucosamine (UDP-GlcNAc) from the cytoplasm where it is synthesized to its site of use in the Golgi. Proper function of such transporters is essential for biosynthesis of glycoproteins, glycolipids and proteoglycans. Although the transport of UDP-GlcNAc is mediated also by other less specific transporters, members of the SLC35 family, reduced transport was shown in patient fibroblasts compared to controls. In addition an abnormal N-glycan profile was shown in patient fibroblasts (but was not the case in serum). Biallelic SLC35A3 mutations in cattle were previously shown to cause a Complex Vertebral Malformation (CVM) syndrome characterized by abnormal growth, vertebral and heart malformations as well as arthrogryposis (Thomsen et al. - PMID: 16344554). Arthrogryposis as well as some skeletal features observed in patients were similar to those of the animal model. -------- Marini et al. (PMID: 28328131) report on 2 sibs compound heterozygous for a missense and a frameshift variant [NM_012243.2:c.73C>T or p.(Arg25Cys) and c.899_900delTTinsA or p.(Leu300Glnfs*6)]. Hypotonia, DD with ID, early-onset seizures and arthrogryposis were features in both. Severe scoliosis was also noted in the younger sib. --------- Edmondson et al. (PMID: 28777481) report on a neonate (follow-up till the 21st day of life) with extensive vertebral anomalies (butterfly vertebrae, hemibertebrae, sagittal clefts, scoliosis), heart defects (PFO, PDA) and arthrogryposis. Presence of hypotonia or other neurologic features (eg. seizures) is not commented on. Conventional caryotype and SNP-array analysis were normal apart from the presence of ROH regions due to parental consanguinity. Exome sequencing revealed only a homozygous missense SNV [c.74G>T or p.(Arg25Leu) - NP_036375.1] which was supported by an abnormal N-glycan profile. As proposed for the bovine model (PMID: 16344554) and discussed in this article, similarity of the skeletal/congenital heart defects with those observed in Alagille syndrome might be due to some of the Notch functions being dependent upon N-acetylglucosamine modification. --------- In ClinVar : There is a further submission of p.Ser296Gly as pathogenic (SCV000699337.1 - 2016) apart from the submission by OMIM (SCV000108589.2 - 2013). The associated condition is Arthrogryposis, mental retardation, and seizures. A frameshift variant [NM_012243.2(SLC35A3):c.680dup (p.Asp227Glufs)- SCV000826704.1 - April 2018] as well as an intragenic deletion [NC_000001.10:g.(?_100472570)_(100477109_?)del (GRCh37) - SCV000837123.1 - June 2018] have both been submitted as pathogenic, associated with Arthrogryposis, mental retardation, and seizures. (Note: due to the different submission dates, one can presume that these variants were found in different individuals). --------- SLC35A3 is not associated with any phenotype in OMIM. It is included in gene panels for ID offered by some diagnostic laboratories. --------- As a result, this gene can be considered for inclusion in the ID panel probably as green (or amber) [Consider upgrade of this gene to green in other panels (eg. CDGs, arthrogryposis, IEMs) and/or inclusion in other possibly relevant panels.] Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.587 | FRRS1L |
Konstantinos Varvagiannis gene: FRRS1L was added gene: FRRS1L was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: FRRS1L was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: FRRS1L were set to 27236917; 27239025; 21147040; 29276473 Phenotypes for gene: FRRS1L were set to Epileptic encephalopathy, early infantile, 37 (MIM 616981) Penetrance for gene: FRRS1L were set to Complete Review for gene: FRRS1L was set to GREEN gene: FRRS1L was marked as current diagnostic Added comment: Biallelic pathogenic variants in FRRS1L cause Epileptic encephalopathy, early infantile, 37 (EIEE37 - MIM 616981). Several individuals homozygous for LoF variants have been reported by Madeo et al. (PMID:27236917) and Shaheen et al. (PMID:27239025 - 2 individuals of this family previously published in 21147040). DD and choreoathetotic movement disorder may precede onset of seizures and subsequent regression. Intellectual disability was a universal feature. Both articles and the respective phenotype are summarized in OMIM. Extensive functional studies have been performed in the article by Madeo et al. as well as in PMID: 29276473 (Han et al.) and suggest a role in glutamatergic transmission. FRRS1L is included in the DD panel of G2P, associated with Epileptic encephalopathy with continuous spike-and-wave during sleep. This gene is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboudumc). As a result, this gene can be considered for inclusion in the ID panel as green, if the phenotype of EIEE is thought to be relevant. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.587 | TCF20 | Konstantinos Varvagiannis edited their review of gene: TCF20: Added comment: One further individual investigated for mild ID and focal epilepsy was found to harbor a de novo frameshift variant [NM_005650.3:c.5430dup or p.(Ala1811Serfs*4)] in PMID: 30525188.; Changed publications: 27436265, 25228304, 28135719, 27479843, 28333917, 28554332, 30525188 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.584 | ZBTB11 |
Konstantinos Varvagiannis gene: ZBTB11 was added gene: ZBTB11 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZBTB11 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ZBTB11 were set to 29893856; 28382966 Phenotypes for gene: ZBTB11 were set to Intellectual disability Penetrance for gene: ZBTB11 were set to Complete Review for gene: ZBTB11 was set to AMBER Added comment: Fattahi et al. (PMID: 29893856) report on 9 individuals from 2 broader consanguineous pedigrees with biallelic ZBTB11 mutations. Features in the first family (from Iran) consisted of moderate ID, microcephaly, ataxic gait, and spasticity with MRI findings of cerebellar atrophy and ventriculomegaly. Individuals from the second family (from Pakistan) presented with moderate ID and variable features. Homozygosity for missense ZBTB11 variants, private to each family was shown (NM_014415.3:c.2185C>T / p.H729Y and c.2640T>G / p.H880Q for the first and second family respectively). As the authors note, ZBTB11 is predicted to be a zinc finger transcriptional regulator and one of the hypotheses emitted suggests possible disruption of DNA binding. Functional studies performed demonstrated that the mutant proteins were excluded from the nucleolus where the (wt) protein localizes. Previous zebrafish models (PMID: 28382966) suggested CNS degeneration among other phenotypes in Zbtb11 mutants. Knockdown of the drosophila ZBTB11-ortholog (CkIIα-i1) resulted in recognizable shrinking of the mushroom body with significant reduction in the number of neurons compared to controls. Other Zinc Finger and BTB Domain-Containing proteins cause disorders with ID as a prominent feature (eg. ZBTB16, ZBTB20, etc.). ZBTB11 is not associated with any phenotype in OMIM nor in G2P. As a result, this gene can be considered for inclusion in this panel probably as amber (2 pedigrees only) or green (given the supportive functional studies). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.584 | PITRM1 |
Konstantinos Varvagiannis gene: PITRM1 was added gene: PITRM1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PITRM1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PITRM1 were set to 26697887; 29764912; 29383861 Phenotypes for gene: PITRM1 were set to Intellectual disability; Ataxia Penetrance for gene: PITRM1 were set to Complete Review for gene: PITRM1 was set to GREEN gene: PITRM1 was marked as current diagnostic Added comment: Biallelic pathogenic variants in PITRM1 seem to be associated with a phenotype of DD/ID and spinocerebellar ataxia. 6 individuals from 3 unrelated families have been reported. PMID: 26697887 reports on 2 individuals from a consanguineous Norwegian family homozygous for a missense variant (NM_014889.2:c.548G> or p.Arg183Gln). PMID: 29764912 reports on 2 consanguineous Palestinian families each with 2 affected boys. All affected individuals for both families were homozygous for a further missense variant (p.Thr931Met). The boys from one Palestinian family appeared to be more severely affected - compared to the sibs from the other family with the same variant - due to a concurrent X-chromosome rearrangement. Pathogenicity is supported by extensive functional studies performed in both articles as well as an additional one (PMID: 29383861) on Arg183Gln. PITRM1 is included in gene panels for ID offered by (few) diagnostic laboratories. The gene is not associated with any phenotype in OMIM nor in G2P. As a result, PITRM1 can be considered for inclusion in the ID panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.584 | LINGO1 |
Konstantinos Varvagiannis gene: LINGO1 was added gene: LINGO1 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: LINGO1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: LINGO1 were set to 28837161 Phenotypes for gene: LINGO1 were set to Mental retardation, autosomal recessive 64 (MIM 618103) Penetrance for gene: LINGO1 were set to Complete Review for gene: LINGO1 was set to AMBER gene: LINGO1 was marked as current diagnostic Added comment: Biallelic pathogenic variants in LINGO1 cause Mental retardation, autosomal recessive 64 (MIM 618103). Ansar et al. (PMID: 28837161) report on 5 individuals from 2 consanguineous Pakistani families. Affected individuals from both families presented with similar phenotype consisting of global developmental delay (5/5), intellectual disability (5/5), microcephaly (4/5) as well as abnormal behavior (5/5). Subjects from both families were homozygous for missense variants (private to each family) affecting proximal residues (290 and 288) of the protein (NM_032808.6:c.869G>A or p.Arg290His and c.863A>G or p.Tyr288Cys). All variants were absent in an ethnically matched control cohort (201 individuals) as well as the relevant subpopulation in gnomAD. Functional studies were not performed. LINGO1 is a transmembrane protein predominantly expressed in the CNS. Previous studies suggest that this protein has an important role in myelination, neuronal survival and CNS repair. LINGO1 is rather intolerant to both missense and LoF variants (Z-score of 4 and pLI of 0.95). According to the authors these variants may be hypomorphic, which might in turn suggest that monoallelic heterozygous LoF mutations could cause ID (although this remains an assumption). This gene is not associated with any phenotype in G2P but is included in panels for ID offered by diagnostic laboratories (incl. Radboudumc). As a result, LINGO1 can be considered for inclusion in this panel probably as amber (2 families, no functional studies). 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 v2.564 | 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 v2.562 | RALA |
Konstantinos Varvagiannis gene: RALA was added gene: RALA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: RALA was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for gene: RALA were set to Global developmental delay; Intellectual disability; Seizures; Abnormality of nervous system morphology Penetrance for gene: RALA were set to unknown Mode of pathogenicity for gene: RALA 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: RALA was set to GREEN Added comment: Hiatt et al. (doi.org/10.1371/journal.pgen.1007671) report on 11 individuals (incl. a pair of monozygotic twins) from 10 unrelated families, most (10/11) with de novo mutations in RALA. DD/ID was a prominent feature (the authors note that ID was specifically noted in 8 but could not be excluded in 3 further individuals who appear to be very young in the table). Structural brain anomalies (9/11), seizures (6/11) and common facial features were also noted. RALA belongs to the RAS superfamily of small GTPases. 5 different de novo missense variants and 1 in-frame deletion, all within a GTP/GDP binding region of RALA (although appart in the protein primary structure) were observed. 7 occurrences of missense variants concerned Val25 and Lys128 (V25M, V25L, K128R), one Asp130 (D130G) and a further one Ser157 (S157A). The in-frame deletion concerned Ala158. Missense variants in corresponding positions of RAS proteins (HRAS/KRAS/NRAS) have been reported in RASopathies, while the authors observed some phenotypic overlap with the latter group of disorders (DD/ID, growth delay, macrocephaly, high forehead and position of ears). Functional studies demonstrated reduction in GTPase activity (for all variants) and altered RALA effector binding (for most reduction - in the case of S157A, increase). Several lines of evidence are provided to show that alteration of the GTP/GTP-binding rather than a dosage effect is considered the likely mechanism. RALA is depleted in missense mutations in its GTP/GDP binding domain. For these reasons and others (segregation studies not possible, variant observed 2x in Bravo database, phenotypic differences compared to the rest of the cohort, ROH suggesting parental consanguinity in the specific individual) the single nonsense variant (R176X) reported in the study is considered a VUS. 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 v2.561 | 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 v2.556 | 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 | TELO2 |
Konstantinos Varvagiannis gene: TELO2 was added gene: TELO2 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: TELO2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TELO2 were set to 27132593; 28944240 Phenotypes for gene: TELO2 were set to You-Hoover-Fong syndrome, MIM 616954 Penetrance for gene: TELO2 were set to Complete Review for gene: TELO2 was set to GREEN gene: TELO2 was marked as current diagnostic Added comment: Biallelic mutations in TELO2 cause You-Hoover-Fong syndrome (MIM 616954). // PMID: 27132593 reports on 6 patients (from 4 non-consanguineous families) with biallelic TELO2 variants and a similar phenotype. Intellectual disability and microcephaly were universal features (6/6). Abnormal hearing (3/6), cortical visual impairment (3/6), abnormality of the cardiovascular system (3/6), behavioral problems (laughter outbursts in 3/6) and abnormal balance and movement disorder (6/6) were part of the phenotype. One individual had seizures. 5 missense variants and a complex allele with a stopgain variant localized in cis with a splice-site variant (NM_016111.3:c.514C>T or p.Gln172* in cis with c.2034+1G>A) are reported. As a result heterozygosity for the complex variant may be confounded with compound heterozygous state until segregation studies are performed. Functional studies support pathogenicity of the missense variants (reduced protein steady-state levels of TELO2 as well as TTI1 and TTI2 - the 2 other members of the TTT complex) suggesting loss of function. PMID: 28944240 reports on 2 sisters born to non-consanguineous parents. Both were compound heterozygous for 2 novel variants, a missense and a frameshift one. Severe microcephaly (-8.5 SD and -10.7 SD) and seizures were noted in both. The first sister passed away at the age of 2 months due to a respiratory infection. The other sister demonstrated a compatible, though much more severe phenotype (of ID, dwarfism, retinitis pigmentosa, etc) compared to previously reported patients. // Biallelic mutations in TTI2 (of the same complex) lead to similar phenotypes (gene rated green in the ID panel). // TELO2 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 | BRD4 |
Konstantinos Varvagiannis gene: BRD4 was added gene: BRD4 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: BRD4 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: BRD4 were set to 29379197; 30055032; 30302754 Phenotypes for gene: BRD4 were set to Intellectual disability; Microcephaly; Abnormal heart morphology; Abnormality of the face Penetrance for gene: BRD4 were set to unknown Review for gene: BRD4 was set to GREEN gene: BRD4 was marked as current diagnostic Added comment: PMID: 29379197 reports on 3 unrelated individuals with de novo mutations in BRD4 and a Cornelia de Lange-like phenotype. One of these individuals was a DDD study participant (DDD4K.04273). A further (fourth) individual had a 1.04 Mb deletion encompassing BRD4 (and 28 other genes) and presented with a similar phenotype. Appart from intellectual disability which was a universal feature common features included a CdLS-like appearance (3/4), microcephaly (3/4) and cardiac malformations (VSD in 2/4). Review of published patients with multigenic deletions spanning also BRD4 support a CdLS-like phenotype as well as haploinsufficiency as the underlying mechanism. As the authors note, mice heterozygous for loss-of-function mutations in BRD4 show CdLS like features. Functional studies performed demonstrated association of BRD4 with NIPBL with colocalization (/shared binding) to super-enhancers and co-regulation of gene expression. The variants reported in this study included a missense as well as 2 frameshift mutations. PMIDs: 30055032 and 30302754 report further patients with deletions spanning BRD4 and review the previously published patients. BRD4 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 v2.550 | 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 v2.535 | EIF3F |
Konstantinos Varvagiannis gene: EIF3F was added gene: EIF3F was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: EIF3F was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: EIF3F were set to 30409806 Phenotypes for gene: EIF3F were set to Intellectual disability; Seizures; Behavioral abnormality; Sensorineural hearing impairment Penetrance for gene: EIF3F were set to Complete Review for gene: EIF3F was set to GREEN Added comment: EIF3F was identified in a recent DDD publication (PMID: 30409806) as a cause of autosomal recessive intellectual disability. All 9 individuals reported were homozygous for a missense variant (Phe232Val - rs141976414) which has a frequency of 0.12% in non-Finnish Europeans. Features included intellectual disability (9/9), seizures (6/9), behavioral problems (3/9) and sensorineural hearing loss (3/9). Facial features were not specific. Extensive functional studies were performed and support pathogenicity of the variant in the homozygous state (reduced protein levels, reduced translation rate in line with the role of EIF3F encoding a subunit for eukaryotic translation initiation factor 3, as well as reduced proliferation rates). 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 v2.530 | 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 | 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 | 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 | ERF | BRIDGE consortium edited their review of ERF | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | ERF | Louise Daugherty classified ERF as amber | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | ERF | Louise Daugherty commented on ERF | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | ERF | BRIDGE consortium reviewed ERF | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||