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12 Mar 2026	Intellectual disability v9.300	HCN2	Ida Ertmanska gene: HCN2 was added gene: HCN2 was added to Intellectual disability. Sources: Literature Q1_26_promote_green tags were added to gene: HCN2. Mode of inheritance for gene: HCN2 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: HCN2 were set to 40468825 Phenotypes for gene: HCN2 were set to Generalized epilepsy with febrile seizures plus, type 11, OMIM:602477; neurodevelopmental disorder, MONDO:0700092 Review for gene: HCN2 was set to GREEN Added comment: PMID: 40468825 Houdayer et al., 2025 21 individuals with HCN2 variants from 15 unrelated families - 13 monoallelic cases and 8 biallelic. The phenotypic spectrum included developmental delay/intellectual disability (DD/ID, 17/21), epilepsy (10/21), language disorders (16/21), movement disorders (12/21), and axial hypotonia (10/21). Movement disorders included dystonia, tremor, cerebellar signs, stereotypies. Muscle tone abnormalities included axial hypotonia, hypertonia, pyramidal signs and spasticity. Biallelic LOF cases uniformly presented with severe intellectual disability, while monoallelic cases showed mild to moderate ID (IQ 40-60) with evidence of skill regression. Heterozygous GOF variants resulted in borderline ID and milder epilepsy phenotype. Thirteen pathogenic HCN2 variants (12 new and 1 already described) were identified: 11 missense, 1 recurrent inframe deletion, and 1 frameshift. Functional evidence: electrophysiology with Xenopus laevis oocytes and membrane trafficking investigated in HEK cells - p.(Arg324His) variant showed a strong increase of HCN2 conductance; p.(Ala363Val) and p.(Met374Leu) exhibited dominant negative effects. The p.(Leu377His), p.(Pro493Leu), and p.(Gly587Asp) variants rendered HCN2 electrophysiologically silent and impaired membrane trafficking. Structural 3D-analysis revealed that, except for p.(Arg324His), all variants altered HCN2 stability. HCN2 is associated with several AD phenotypes in OMIM: Generalized epilepsy with febrile seizures plus, type 11 602477; Febrile seizures, familial, 2 602477; {Epilepsy, idiopathic generalized, susceptibility to, 17} 602477 - all same MIM number (accessed 12th Mar 2026). Not yet added to ClinGen or Gene2Phenotype. Sources: Literature
23 Feb 2026	Intellectual disability v9.278	ATOH1	Ida Ertmanska changed review comment from: Comment on list classification: There are 4 individuals from 3 unrelated families reported in literature with biallelic ATOH1 variants and an associated neurodevelopmental syndrome. All patients presented with severe GDD/ID. Based on available evidence, this gene should be promoted to Green for Intellectual disability.; to: Comment on list classification: There are 4 individuals from 3 unrelated families reported in literature with biallelic ATOH1 variants and an associated neurodevelopmental syndrome. All patients presented with severe GDD/ID. Individuals with heterozygous ATOH1 variants present with hearing loss and mild cerebellar signs, without intellectual disability. Hene, based on available evidence, this gene should be promoted to Green for Intellectual disability with MOI set to BIALLELIC, autosomal or pseudoautosomal.
23 Feb 2026	Intellectual disability v9.277	ATOH1	Ida Ertmanska gene: ATOH1 was added gene: ATOH1 was added to Intellectual disability. Sources: Literature Q1_26_promote_green tags were added to gene: ATOH1. Mode of inheritance for gene: ATOH1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ATOH1 were set to 9367153; 21146598; 33111345; 35518571; 41592563 Phenotypes for gene: ATOH1 were set to ?Deafness, autosomal dominant 89 , OMIM:620284; hearing loss, autosomal dominant 89, MONDO:0859528; pontocerebellar hypoplasia, MONDO:0020135 Review for gene: ATOH1 was set to GREEN Added comment: PMID: 41592563 Bertola et al., 2026 Report of 5 unrelated families with heterozygous frameshift variants in ATOH1 associated with hearing loss (7/7, mild to severe), cerebellar symptoms (4/6), and a pattern of brainstem malformations (7/7). Cerebellar symptoms are noted to be subtle: motor delay, balance issues, mild ataxia, tremor, and other cerebellar signs. Intellectual disability ascertained in 1/7 individuals - this patient also carried a RNU4-2 variant, thought to be responsible for ID in this case. Authors also report a homozygous early-truncating variant c.102dup, (p.Pro35AlafsTer18), causing a distinct neurodevelopmental syndrome with severe pontocerebellar hypoplasia, severe ID, and profound hearing loss. Heterozygous parents were asymptomatic. PMID: 35518571 Višnjar et al., 2022 A homozygous missense variant NM_005172.1:c.481C>G, p.(Arg161Gly) in the ATOH1 gene was identified in the proband and his affected sister, segregating with apparently recessive pontocerebellar hypoplasia (PCH), severe global developmental delay, intellectual disability, and hearing loss. Brain MRI findings were: posteriorly thin corpus callosum, small posterior fossa with the upward displacement of the tentorium, small cerebellum with more severely hypoplastic vermis than hemispheres, and small brainstem. PMID: 33111345 Brownstein et al., 2020 Family HL263: Mizrahi Jewish family, affected individuals heterozygous for ATOH1 c.1030delC, p.His344fs17Ter (affects C-terminus). Variant co-segregated over five generations with progressive non-syndromic hearing loss, with onset at birth or early childhood. Method: WES. Western analysis revealed a significantly slower rate of degradation for mutant ATOH1 protein compared to wild-type ATOH1. Increased protein stability = untimely expression leading to hearing loss. PMID: 27431290 Anazi et al., 2017 Cohort of ID patients. Patient 15DG1898 was homozygous for ATOH1: c.212del, p.(Gly71Alafs*36); clinical presentation: ID, generalised hypotonia, nystagmus, pontocerebellar hypoplasia, brain atrophy (frontal lobe). No mention of hearing loss (not assessed?). Functional evidence: Loss of Atoh1 in mice causes hearing impairment, cerebellar and cochlear malformations, and death (PMID: 9367153, Ben-Arie et al., 1997. ATOH1 previously known as MATH1). Conditional deletion of Atoh1 leads to lack of differentiated inner ear hair cells (PMID: 21146598 Pan et al., 2010). ATOH1 is putatively linked to ?Deafness, autosomal dominant 89, MIM:620284 in OMIM (accessed 23rd Feb 2026). Sources: Literature
20 Feb 2026	Intellectual disability v9.273	CCT8	Ida Ertmanska gene: CCT8 was added gene: CCT8 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CCT8 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CCT8 were set to 39480921 Phenotypes for gene: CCT8 were set to CCT8-related neurodevelopmental disorder with brain abnormalities Review for gene: CCT8 was set to AMBER Added comment: PMID: 39480921 Kraft et al., 2024 Report of 2 individuals (20yo male and 79yo male) with heterozygous CCT7 variants: c.925_929del p.(Asn309Hisfs16) - de novo & c.1166_1169delAAAG, p.(Glu389Glyfs3) - inheritance not known. Patients presented with DD/ID (2/2), cerebral/pyramidal signs (1), seizures (2/2) and MRI abnormalities: Polymicrogyria (2/2). CCT8 is not yet associated with a disease entity in OMIM (accessed 20th Feb 2026). Sources: Literature
20 Feb 2026	Intellectual disability v9.272	CCT7	Ida Ertmanska gene: CCT7 was added gene: CCT7 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CCT7 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CCT7 were set to 39480921 Phenotypes for gene: CCT7 were set to CCT7-related neurodevelopmental disorder with brain abnormalities Review for gene: CCT7 was set to RED Added comment: PMID: 39480921 Kraft et al., 2024 Report of 1 individual (5yo male) with a de novo heterozygous CCT7 variant: c.1135G>A, p.(Glu379Lys), presenting with DD/ID, cerebral/pyramidal signs, and MRI abnormalities:Inferior vermis hypoplasia, corpus callosum hypoplasia. CCT7 is not yet associated with a disease entity in OMIM (accessed 20th Feb 2026). Sources: Literature
20 Feb 2026	Intellectual disability v9.269	CCT3	Ida Ertmanska gene: CCT3 was added gene: CCT3 was added to Intellectual disability. Sources: Literature Q1_26_promote_green tags were added to gene: CCT3. Mode of inheritance for gene: CCT3 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CCT3 were set to 39480921 Phenotypes for gene: CCT3 were set to Neurodevelopmental disorder with speech or visual impairment and brain hypomyelination, OMIM:621034; neurodevelopmental disorder with speech or visual impairment and brain hypomyelination, MONDO:0976125 Review for gene: CCT3 was set to GREEN Added comment: PMID: 39480921 Kraft et al., 2024 4 individuals aged 2-8 yo, reported with heterozygous CCT3 variants (frameshift, missense, stop gain - all 4 confirmed de novo). Patients presented with ID, seizures, visual impairment and brain malformations. Phenotype spectrum: DD/ID (4/4, severe), seizures (2/4), visual impairment (3/4), pyramidal/cerebellar signs (4/4), brain MRI abnormalities (3/3). MRI findings included cerebellar atrophy, hypomyelination of white matter, hypoplasia of corpus callosum, and atrophy of optic tract, chiasm and optic nerves. CCT3 is associated with Neurodevelopmental disorder with speech or visual impairment and brain hypomyelination, OMIM:621034 (OMIM accessed 20th Feb 2026). Sources: Literature
20 Feb 2026	Intellectual disability v9.266	TCP1	Ida Ertmanska gene: TCP1 was added gene: TCP1 was added to Intellectual disability. Sources: Literature Q1_26_promote_green tags were added to gene: TCP1. Mode of inheritance for gene: TCP1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: TCP1 were set to 39480921 Phenotypes for gene: TCP1 were set to Intellectual developmental disorder with polymicrogyria and seizures, OMIM:621021 Review for gene: TCP1 was set to GREEN Added comment: PMID: 39480921 Kraft et al., 2024 8 individuals reported with heterozygous TCP1 (CCT1) variants (frameshift, missense, stop gain - 5 confirmed de novo). Patients presented with ID, seizures, and brain malformations. Phenotype spectrum: DD/ID of variable severity (6/6 assessed), seizures (6/7), visual impairment (2/7), pyramidal signs (4 individuals), brain MRI abnormalities (7/8). MRI findings included polymicrogyria, heterotopia, ventriculomegaly and white matter hyperintensities, hypoplasia of corpus callosum. TCP1 is associated with Intellectual developmental disorder with polymicrogyria and seizures, OMIM:621021 (OMIM accessed 20th Feb 2026). Sources: Literature
21 Oct 2025	Intellectual disability v9.144	MED12L	Eleanor Williams changed review comment from: Since the last review additional cases have been reported. In OMIM this gene is associated with Nizon-Isidor syndrome, OMIM:618872 (AD) - accessed 21st October 2025 In ClinGen the gene has a definitive rating with Nizon-Isidor syndrome, MONDO:0030030 There are now 3 more reports of plausable pathogenic variants in this gene in patients with an intellectual disability phenotype. 2 cases with de novo variants and 1 with a maternally inherited variant. PMID: 36212160 - Park et al 2022 - WES to analyse 1,180 Korean patients with neurological symptoms. 1 individual with a de novo variant c.1895C>T; p.Ser632Leu in MED12L and a phenotype of global developmental delay and facial dysmorphism. PMID: 35920825 - Ferraz et al 2022 - a male proband with a confirmed de novo germline frameshift variant in MED12L (NM_053002.6 (MED12L_v001):c.971del;p.(pro324Glnfs∗18)) identified by WES. The clinical phenotype included mild motor and speech delay, oligodontia, and dysmorphic signs. Of note the patient also carried 2 de novo chromosomal balanced reciprocal translocations: 46,XY,t(1;2)(p33;p22),t(5;9)(p15;q21) and the authors note that Nizon et al. 2019 report a patient with a balanced reciprocal translocation suggesting that the MED12L loss-of-function variant may contribute to chromosomal instability. PMID: 40957966 - Dutta et al 2025 - report a proband with likely pathogenic MED12L nonsense variant (p.Arg1210Ter) which is maternally inherited (father also sequenced). At 2.5 yo the proband was diagnosed with global developmental delay, absent speech, ASD, hyperactivity, exophoria and myopia. Developmental regression began between 18 - 24 months. She has frequent respiratory infections. The 19 yo mother has a clinical history which includes speech delay and learning disability, but features are much milder than the proband. The proband also has inherited a pathogenic GAMT variant from her mother and a pathogenic TNFRSF13B variant from her father but these are not thought to contribute to the ID phenotype.; to: Since the last review additional cases have been reported. In OMIM this gene is associated with Nizon-Isidor syndrome, OMIM:618872 (AD) - accessed 21st October 2025 In ClinGen the gene has a definitive rating with Nizon-Isidor syndrome, MONDO:0030030 (last curated November 19th, 2024) There are now 3 more reports of plausable pathogenic variants in this gene in patients with an intellectual disability phenotype. 2 cases with de novo variants and 1 with a maternally inherited variant. PMID: 36212160 - Park et al 2022 - WES to analyse 1,180 Korean patients with neurological symptoms. 1 individual with a de novo variant c.1895C>T; p.Ser632Leu in MED12L and a phenotype of global developmental delay and facial dysmorphism. PMID: 35920825 - Ferraz et al 2022 - a male proband with a confirmed de novo germline frameshift variant in MED12L (NM_053002.6 (MED12L_v001):c.971del;p.(pro324Glnfs∗18)) identified by WES. The clinical phenotype included mild motor and speech delay, oligodontia, and dysmorphic signs. Of note the patient also carried 2 de novo chromosomal balanced reciprocal translocations: 46,XY,t(1;2)(p33;p22),t(5;9)(p15;q21) and the authors note that Nizon et al. 2019 report a patient with a balanced reciprocal translocation suggesting that the MED12L loss-of-function variant may contribute to chromosomal instability. PMID: 40957966 - Dutta et al 2025 - report a proband with likely pathogenic MED12L nonsense variant (p.Arg1210Ter) which is maternally inherited (father also sequenced). At 2.5 yo the proband was diagnosed with global developmental delay, absent speech, ASD, hyperactivity, exophoria and myopia. Developmental regression began between 18 - 24 months. She has frequent respiratory infections. The 19 yo mother has a clinical history which includes speech delay and learning disability, but features are much milder than the proband. The proband also has inherited a pathogenic GAMT variant from her mother and a pathogenic TNFRSF13B variant from her father but these are not thought to contribute to the ID phenotype.
21 Oct 2025	Intellectual disability v9.141	MED12L	Eleanor Williams edited their review of gene: MED12L: Added comment: Since the last review additional cases have been reported. In OMIM this gene is associated with Nizon-Isidor syndrome, OMIM:618872 (AD) - accessed 21st October 2025 In ClinGen the gene has a definitive rating with Nizon-Isidor syndrome, MONDO:0030030 There are now 3 more reports of plausable pathogenic variants in this gene in patients with an intellectual disability phenotype. 2 cases with de novo variants and 1 with a maternally inherited variant. PMID: 36212160 - Park et al 2022 - WES to analyse 1,180 Korean patients with neurological symptoms. 1 individual with a de novo variant c.1895C>T; p.Ser632Leu in MED12L and a phenotype of global developmental delay and facial dysmorphism. PMID: 35920825 - Ferraz et al 2022 - a male proband with a confirmed de novo germline frameshift variant in MED12L (NM_053002.6 (MED12L_v001):c.971del;p.(pro324Glnfs∗18)) identified by WES. The clinical phenotype included mild motor and speech delay, oligodontia, and dysmorphic signs. Of note the patient also carried 2 de novo chromosomal balanced reciprocal translocations: 46,XY,t(1;2)(p33;p22),t(5;9)(p15;q21) and the authors note that Nizon et al. 2019 report a patient with a balanced reciprocal translocation suggesting that the MED12L loss-of-function variant may contribute to chromosomal instability. PMID: 40957966 - Dutta et al 2025 - report a proband with likely pathogenic MED12L nonsense variant (p.Arg1210Ter) which is maternally inherited (father also sequenced). At 2.5 yo the proband was diagnosed with global developmental delay, absent speech, ASD, hyperactivity, exophoria and myopia. Developmental regression began between 18 - 24 months. She has frequent respiratory infections. The 19 yo mother has a clinical history which includes speech delay and learning disability, but features are much milder than the proband. The proband also has inherited a pathogenic GAMT variant from her mother and a pathogenic TNFRSF13B variant from her father but these are not thought to contribute to the ID phenotype.; Changed rating: GREEN; Changed publications to: 31155615, 36212160, 35920825, 40957966; Changed phenotypes to: Nizon-Isidor syndrome, OMIM:618872, Nizon-Isidor syndrome, MONDO:0030030; Changed mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
23 Sep 2025	Intellectual disability v9.98	CCT6A	Arina Puzriakova gene: CCT6A was added gene: CCT6A was added to Intellectual disability. Sources: Literature Q3_25_promote_green tags were added to gene: CCT6A. Mode of inheritance for gene: CCT6A was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CCT6A were set to 39480921 Phenotypes for gene: CCT6A were set to Neurodevelopmental disorder, MONDO:0700092 Review for gene: CCT6A was set to GREEN Added comment: PMID: 39480921 (2024) - 5 unrelated individuals with variants in the CCT6A gene, including 4 de novo (4 LoF, 2 missense), presenting with neurodevelopmental disorders. Main clinical features include DD/ID (4/5), pyramidal/cerebellar signs (3/4), variable brain abnormalities (3/5), microcephaly (2/5 - severe only in one) seizures (2/4), visual impairment (2/5). Sources: Literature
01 Sep 2025	Intellectual disability v9.66	GNS	Arina Puzriakova Phenotypes for gene: GNS were changed from Mucopolysaccharidosis type IIID, OMIM:252940 to Mucopolysaccharidosis type IIID, OMIM:252940
01 Sep 2025	Intellectual disability v9.65	GNS	Arina Puzriakova Phenotypes for gene: GNS were changed from Mucopolysaccharidosis type IIID, 252940; MUCOPOLYSACCHARIDOSIS TYPE 3D (MPS3D) to Mucopolysaccharidosis type IIID, OMIM:252940
25 Oct 2024	Intellectual disability v7.64	TRMT5	Arina Puzriakova changed review comment from: Comment on list classification: New gene added to the panel by Alexander Rossor (UCL Institute of Neurology). There is sufficient evidence to promote this gene to Green at the next GMS panel update. Associated with relevant phenotype in OMIM, but not associated with phenotype in G2P. At least 3 variants reported in at least three cases, together with supportive functional studies. Phenotype is characterised as a highly variable multisystemic disorder, ranging from hypotonia and GDD in infancy to exercise intolerance and muscle weakness in early adulthood. Peripheral neuropathy is a universal feature in all cases. Various other neurological features such as spasticity, cerebellar signs and seizures, and involvement of other organ systems, including the heart, pancreas, and kidney may also be observed.; to: Comment on list classification: There is sufficient evidence to promote this gene to Green at the next GMS panel update. Associated with relevant phenotype in OMIM, but not associated with phenotype in G2P. At least 3 variants reported in at least three cases, together with supportive functional studies. Phenotype is characterised as a highly variable multisystemic disorder, ranging from hypotonia and GDD in infancy to exercise intolerance and muscle weakness in early adulthood. Peripheral neuropathy is a universal feature in all cases. Various other neurological features such as spasticity, cerebellar signs and seizures, and involvement of other organ systems, including the heart, pancreas, and kidney may also be observed.
31 May 2023	Intellectual disability 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
31 May 2023	Intellectual disability 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
23 Mar 2023	Intellectual disability 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
17 Sep 2022	Intellectual disability v3.1720	PTPA	Konstantinos Varvagiannis gene: PTPA was added gene: PTPA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PTPA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PTPA were set to 36073231 Phenotypes for gene: PTPA were set to Intellectual disability; Parkinsonism Penetrance for gene: PTPA were set to Complete Review for gene: PTPA was set to AMBER Added comment: Biallelic PTPA pathogenic variants lead to a form of ID with later-onset parkinsonism based on 4 individuals from 2 families in the literature. Affected individuals were homozygous for missense variants demonstrated to result to reduced mRNA and protein levels as well as PP2A complex activation. Drosophila studies support an age-dependent locomotor dysfunction. Variants in other PP2A-complex-related genes also lead to NDDs. Summary provided below. There is currently no associated phenotype in OMIM, G2P, PanelApp Australia or SysNDD. Consider inclusion in relevant panels (ID, Parkinsonism/movement disorders, etc) with amber rating pending further reports. ------ Fevga, Tesson et al (2022 - PMID: 36073231) describe the features of 4 individuals, from 2 unrelated families, with biallelic pathogenic PTPA variants. These presented with normal or delayed early milestones, learning disability and ID (mild to moderate) followed by progressive signs of parkinsonism (at the age of 11 yrs in 2 sibs, 15 yrs in another individual). Motor symptoms were responsive to levodopa and later to deep brain stimulation. Linkage analysis in one consanguineous family followed by exome revealed homozygosity for a missense PTPA variant (NM_178001:c.893T>G/p.Met298Arg). Exome sequencing in affected subjects from the 2nd family revealed homozygosity for a further missense variant (c.512C>A/p.Ala171Asp). There were no other candidate variants for the phenotype following parental / segregation studies. Role of the gene: As the authors discuss, PTPA (or PPP2R4) is ubiquitously expressed in all tissues incl. brain and encodes a phosphotyrosyl phosphatase activator of the dimeric form of protein phosphatase-2A (PP2A). PP2A in turn, is the major Ser/Thr phosphatase in brain targeting a large number of proteins involved in diverse functions. Activation of PP2A is dependent on its methylation, which is negatively regulated by the PP2A-specific methylesterase (PME-1). By binding to PME-1, PTPA counteracts the negative influence of the former on PP2A. Pathogenic variants in genes encoding subunits/regulators of the PP2A complex (e.g. PPP2R1A or PPP2CA) are associated with neurodevelopmental disorders. Variant studies: Upon overexpression of wt and both variants in a HEK-293 cell line the authors demonstrated that both variants resulted in significantly reduced mRNA and protein levels (which for Ala171Asp were attributed to increased proteasomal degradation). Both variants were shown to result in impaired PP2A complex activation compared to wt. Drosophila / animal models: Pan-neuronal RNAi-mediated knockdown of ptpa in Drosophila resulted in an age-dependent locomotor dysfunction, reversible with L-DOPA treatment. Previous studies in mice suggest cognitive/electrophysiological impairments upon downregulation of PP2A activity in transgenic mice. Sources: Literature
04 Dec 2021	Intellectual disability v3.1478	SPRED2	Zornitza Stark gene: SPRED2 was added gene: SPRED2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SPRED2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SPRED2 were set to 34626534 Phenotypes for gene: SPRED2 were set to developmental delay; intellectual disability; cardiac defects; short stature; skeletal anomalies; a typical facial gestalt Review for gene: SPRED2 was set to GREEN gene: SPRED2 was marked as current diagnostic Added comment: PMID: 34626534 Homozygosity for three different variants c.187C>T (p.Arg63∗), c.299T>C (p.Leu100Pro), and c.1142_1143delTT (p.Leu381Hisfs∗95) were identified in four subjects from three families. All variants severely affected protein stability, causing accelerated degradation, and variably perturbed SPRED2 functional behaviour. The clinical phenotype of the four affected individuals included developmental delay, intellectual disability, cardiac defects, short stature, skeletal anomalies, and a typical facial gestalt as major features, without the occurrence of the distinctive skin signs characterizing Legius syndrome. Sources: Literature
22 Sep 2021	Intellectual disability v3.1300	IMPDH2	Arina Puzriakova Added comment: Comment on list classification: New gene added by Zornitza Stark. This gene is not yet associated with a relevant phenotype in OMIM or G2P, but sufficient unrelated cases with relevant phenotype to rate Green at the next GMS review. Neurodevelopmental delay is an early feature that may be evident prior to other manifestations (plausible that other cases may develop dystonic signs later in life) and so inclusion on this panel is warranted.
21 Apr 2021	Intellectual disability v3.1034	NEUROD2	Arina Puzriakova gene: NEUROD2 was added gene: NEUROD2 was added to Intellectual disability. Sources: Literature Q2_21_rating tags were added to gene: NEUROD2. Mode of inheritance for gene: NEUROD2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: NEUROD2 were set to 16504944; 30323019; 33438828 Phenotypes for gene: NEUROD2 were set to Developmental and epileptic encephalopathy 72, OMIM:618374 Review for gene: NEUROD2 was set to GREEN Added comment: NEUROD2 is associated with a relevant phenotype in OMIM (MIM# 618374), but is not yet listed in Gene2Phenotype. - PMID: 30323019 (2019) - Two unrelated children with refractory early-infantile epileptic encephalopathy. Developmental delay (DD) preceded onset of seizures in both cases, with signs of DD becoming evident at 2-4 months and seizures arising at 5 months of age. Patient 1 became seizure-free after introducing a ketogenic diet at 16 months; however, an EEG at 22 months remained abnormal and she continues to have severe GDD with no independent sitting, walking or speaking at the chronological age of 3 years and 2 months. Patient 2 became seizure-free when a vagal nerve stimulator (VNS) was placed at 16 months of age. He displayed significant improvement on EEG and subsequently began regaining neurodevelopmental milestones. WES revealed different de novo variants in the NEUROD2 gene (P1: c.388G>C, p.E130Q; P2: c.401T>C, p.M134T, respectively). Knockdown of the neurod2 in Xenopus tropicalis tadpoles resulted in abnormal swimming behaviour and progressive seizures followed by periods of immobility. Overexpression of wild-type human NEUROD2 in tadpoles induced non-neuronal cells to differentiate into neurons - on the other hand, overexpression of the mutant alleles failed to to cause any (p.E130Q) or a comparable degree (p.M134T) of ectopic neuronal induction as seen with the wild-type protein. - Conference poster (Genomics of Rare Disease 2021) - 'Neuronal Differentiation Factor 2 (NEUROD2) Pathogenic Variant as a Molecular Aetiology of Infantile Spasm ' by Sakpichaisakul et al, QSNICH, Thailand - In a 15 month-old female with infantile spasm, trio exome sequencing revealed a de novo variant in NEUROD2 (c.388G>C, p.E130Q). She was born of non-consanguineous healthy parents with no family history of epilepsy. Poor eye contact and no social smile were noted in the first few months, followed by the first infantile spasm at 5 months of age. This was initially controlled by combined vigabatrin and prednisolone therapy - however relapsing seizures were detected at 15 months. Sequential treatment with vigabatrin following prednisolone resulted in cessation of seizures, and subsequently regaining of neurodevelopmental milestones (sitting without support, grabbing objects without pincer grasp and speaking one single word) ----- Cases without seizures - - PMID: 33438828 (2021) - Adolescent (14 yrs old) with GDD but without seizures who was found to have a novel de novo NEUROD2 missense variant (c.488 T > C, p.L163P). An additional individual (12 yrs) with DD and a different missense NEUROD2 (c.703G>A, p.A235T) was also identified, but lacking parental samples for segregation analysis. Functional analysis in Xenopus laevis revealed that injection of the p.L163P mRNA variant resulted in a defective ability to induce ectopic neurons in tadpoles as compared with wild-type NEUROD2 mRNA, while the p.A235T variant functioned similarly to wild-type. Sources: Literature
08 Dec 2020	Intellectual disability v3.639	MORC2	Arina Puzriakova Added comment: Comment on list classification: Though signs suggestive of neuropathy were observed in the cohort presented by Sacoto et al (PMID:32693025), these were not the predominant feature of the disease presentation or the primary indication for diagnostic testing. Inclusion on this panel would be of value for detecting such cases, and so this gene should be promoted to Green at the next GMS panel update (added 'for-review' tag)
02 Oct 2020	Intellectual disability v3.369	PRKD1	Arina Puzriakova changed review comment from: Gene included previously in context of publication by Sifrim et al. (2016) (PMID: 27479907). However, re-evaluation of this paper showed that only two of the three patients had ID, which may possibly be associated with microcephaly. The two individuals carried a c.1774G>A and c.896T>G variant, respectively; however, a third patient also harbouring the c.1774G>A variant did not display any neuropsychological signs (or microcephaly) at 4.86 years (see supplementary table 12). A recent report (PMID: 32817298, 2020) describes two additional unrelated cases with de novo variants, c.1774G>C and c.1808G>A, respectively. These patients shared cardiac and ectodermal abnormalities, as with the previously described patients; however, mental development was normal in both individuals.; to: Gene included previously in context of publication by Sifrim et al. (2016) (PMID: 27479907). However, re-evaluation of this paper showed that only two of the three patients had ID, which may possibly be associated with microcephaly. The two individuals carried a c.1774G>A and c.896T>G variant, respectively; however, a third patient also harbouring the c.1774G>A variant did not display any neuropsychological signs (or microcephaly) at 4.86 years (see supplementary table 12, and figure 3). A recent report (PMID: 32817298, 2020) describes two additional unrelated cases with de novo variants, c.1774G>C and c.1808G>A, respectively. These patients shared cardiac and ectodermal abnormalities, as with the previously described patients; however, mental development was normal in both individuals.
31 Dec 2019	Intellectual disability 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 ]
10 Dec 2019	Intellectual disability v2.1143	AFF3	Konstantinos Varvagiannis changed review comment from: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- Shimizu et al. (8/2019 - PMID: 31388108) describe an additional individual with de novo AFF3 missense variant. The phenotype overlaps with that summarized by Voisin et al. incl. mesomelic dysplasia with additional skeletal anomalies, bilateral kidney hypoplasia and severe DD at the age of 2.5 years. Seizures and pulmonary problems were not observed. Although a different RefSeq is used the variant is among those also reported by Voisin et al. [NM_002285.2:c.697G>A (p.Ala233Thr) corresponding to NM_001025108.1:c.772G>A (p.Ala258Thr)]. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article). [Review modified to add additional reference/case report]; to: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb deletion affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- Shimizu et al. (8/2019 - PMID: 31388108) describe an additional individual with de novo AFF3 missense variant. The phenotype overlaps with that summarized by Voisin et al. incl. mesomelic dysplasia with additional skeletal anomalies, bilateral kidney hypoplasia and severe DD at the age of 2.5 years. Seizures and pulmonary problems were not observed. Although a different RefSeq is used the variant is among those also reported by Voisin et al. [NM_002285.2:c.697G>A (p.Ala233Thr) corresponding to NM_001025108.1:c.772G>A (p.Ala258Thr)]. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article). [Review modified to add additional reference/case report]
26 Nov 2019	Intellectual disability v2.1122	TMX2	Konstantinos Varvagiannis edited their review of gene: TMX2: Added comment: A recent report by Vandervore, Schot et al. following the previous review (Am J Hum Genet. 2019 Nov 12 - PMID: 31735293), provides further evidence that biallelic TMX2 mutations cause malformations of cortical development, microcephaly, DD and ID and epilepsy. As a result this gene should probably be considered for inclusion in the ID/epilepsy panels with green rating. Overall, 14 affected subjects from 10 unrelated families are reported in the aforementioned study. The majority had severe DD/ID (failure to achieve milestones, absent speech/ambulation and signs of cerebral palsy) with few having a somewhat milder impairment. 12 (of the 14) presented with epilepsy (spasms, myoclonic seizures, focal seizures with/without generalization or generalized tonic-clonic seizures) with onset most often in early infancy. Upon brain MRI (in 12 individuals), 5 presented polymicrogyria, 2 others pachygyria, 4 with brain atrophy, etc. All individuals were found to harbor biallelic TMX2 mutations by exome sequencing while previous investigations in several had ruled out alternative causes (infections, metabolic or chromosomal anomalies). Missense variants, an in-frame deletion as well as pLoF (stopgain/frameshift) variants were reported. [NM_015959.3 used as ref below]. The effect of variants was supported by mRNA studies, eg. RT-qPCR/allele specific RT-qPCR. The latter proved reduced expression for a frameshift variant (c.391dup / p.Leu131Profs6) most likely due to NMD. Total mRNA levels were also 23% lower in an individual compound htz for a missense variant and a stopgain one localized in the last exon (c.757C>T / p.Arg253). As for the previously reported c.614G>A (p.Arg205Gln), affecting the last nucleotide of exon 6, total mRNA in skin fibroblasts from a homozygous individual was not significantly decreased. RNA-Seq however demonstrated the presence of 4 different transcripts (roughly 25% each), one representing the regular mRNA, one with intron 6 retention (also present at low levels in healthy individuals), one with loss of 11 nucleotides within exon 6 and a fourth one due to in-frame skipping of exon 6. *To the best of my understanding : Thioredoxin (TRX)-related transmembrane proteins (TMX) belong to the broader family of oxidoreductases of protein disulfide isomerase (PDI) having an important role in protein folding. Study of the data from the Allen Human Brain Atlas suggest relevant fetal expression also increasing during postnatal life. As RNA-seq was carried out for 2 individuals, GO analysis suggested that the most deregulated clusters of genes are implicated in post-translational protein modifications (as would be expected for PDIs), membranes and synapse while pathway analysis suggested that relevant categories were inhibited eg. nervous system development/function and cell growth/proliferation/survival. Upon transfection of HEK293T cells, exogenous TMX2 was shown to co-localize with calnexin (CNX) to the (ER) mitochondria-associated-membrane. Mass-spectrometry based analysis of co-immunoprecipitated proteins confirmed interaction with CNX but also other regulators of calcium homeostasis, mitochondrial membrane components and respiratory chain NADH dehydrogenase. Study of the mitochondrial activity of TMX2-deficient fibroblasts suggested reduced respiratory reserve capacity, compensated by increased glycolytic activity. TMX2 occurs in both reduced and oxidized monomeric form. It also forms (homo)dimers with the ratio of dimers/monomers increasing under conditions of oxidative stress. Variant TMX2 increased propensity to form dimers, thus mimicking increased oxidative state. This was observed under stress but also under native conditions. ---------; Changed rating: GREEN
08 Aug 2019	Intellectual disability v2.996	AFF3	Konstantinos Varvagiannis changed review comment from: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article).; to: Voisin et al. (2019 - https://doi.org/10.1101/693937) report on 10 individuals with de novo missense AFF3 variants affecting a 9-amino-acid sequence (degron) important for the protein's degradation and summarize the phenotype of an additional individual previously described by Steichen-Gersdorf et al. (2008 - PMID: 18616733) with a 500 kb affecting only AFF3 (LAF4) and removing also this sequence. The phenotype of missense variants consisted of kidney anomalies, mesomelic dysplasia, seizures, hypertrichosis, intellectual disability and pulmonary problems and was overlapping with that of the deletion. [10 of 11 subjects exhibited severe developmental epileptic encephalopathy]. 9 probands harbored missense variants affecting the codon 258 while one individual had a variant affecting codon 260 [c.772G>T or p.Ala258Ser (x2), c.772G>A or p.Ala258Thr (x6), c.773C>T or p.Ala258Val (x1) and c.779T>G or p.(Val260Gly) (x1) - NM_001025108.1 / NP_001020279.1]. The deletion removed exons 4-13. AFF1-4 are ALF transcription factor paralogs, components of the transcriptional super elongation complex regulating expression of genes involved in neurogenesis and development. Using HEK293T cells expressing FLAG-tagged AFF3 (and AFF4) wt or mutants, accumulation of mutated forms was shown upon immunoblot. Aff3+/- and/or -/- mice exhibit skeletal defects. These were more pronounced in homozygous mice which demonstrated also some elements in favor of kidney dysfunction and/or metabolic deregulation and possible neurological dysfunction (signs of impaired hearing and diminished grip strength). Homozygous mice had CNS anomalies (enlarged lateral ventricles and decreased corpus callosum size) similar to some affected individuals, although these were not observed in another Aff3-/- model. Knock-in mice modeling the microdeletion and the Ala258Thr variant displayed lower mesomelic limb deformities and early lethality respectively [cited PMIDs : 21677750, 25660031, knock-in model was part of the present study]. Accumulation of the protein in zebrafish (by overexpression of the human wt AFF3 mRNA), led to morphological defects. Reanalysis of transcriptome data from previously generated HEK293T cell lines knocked down for AFF2, AFF3 and AFF4 by shRNAs (study) suggested that these transcription factors are not redundant. Finally, CHOPS syndrome (#616368) due to mutations of AFF4 also leading to increased protein stability presents a partially overlapping phenotype (incl. cognitive impairment) to that of AFF3. ---- Shimizu et al. (8/2019 - PMID: 31388108) describe an additional individual with de novo AFF3 missense variant. The phenotype overlaps with that summarized by Voisin et al. incl. mesomelic dysplasia with additional skeletal anomalies, bilateral kidney hypoplasia and severe DD at the age of 2.5 years. Seizures and pulmonary problems were not observed. Although a different RefSeq is used the variant is among those also reported by Voisin et al. [NM_002285.2:c.697G>A (p.Ala233Thr) corresponding to NM_001025108.1:c.772G>A (p.Ala258Thr)]. ---- In G2P, AFF3 is associated with Skeletal dysplasia with severe neurological disease (disease confidence : probable / ID and seizures among the assigned phenotypes). There is no associated phenotype in OMIM. Some diagnostic laboratories include AFF3 in their ID panel (eg. among the many co-authors' affiliations GeneDx and Victorian Clinical Genetics - which was already listed as source for AFF3 in the current panel). ---- As a result this gene can be considered for upgrade to green (relevant phenotype and severity, sufficient cases, evidence for accumulation similar to AFF4, animal models, etc) or amber (pending publication of the article). [Review modified to add additional reference/case report]
02 Aug 2017	Intellectual disability	GNS	BRIDGE consortium edited their review of GNS
27 Jul 2017	Intellectual disability	GNS	BRIDGE consortium edited their review of GNS
19 Jul 2017	Intellectual disability	GNS	BRIDGE consortium reviewed GNS