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Intellectual disability syndromic and non-syndromic v0.6062 CRNKL1 Mark Cleghorn gene: CRNKL1 was added
gene: CRNKL1 was added to Intellectual disability syndromic and non-syndromic. Sources: Other
Mode of inheritance for gene: CRNKL1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Phenotypes for gene: CRNKL1 were set to complex neurodevelopmental disorder MONDO:0100038
Penetrance for gene: CRNKL1 were set to Complete
Review for gene: CRNKL1 was set to GREEN
Added comment: Unpublished, presented at ESHG June 2024 - Louise Bicknell, University of Otago NZ
8 unrelated families via gene matcher with rare, de novo, missense variants in CRNKL1
severe microcephaly (all, -8 to -11 SD)
ID/epilepsy
pontocerebellar hypoplasia (6/8)
simplified gyration (8/8)
7 variants are missense at p.Arg267 residue
1 variant missense at p.Arg301
RNA-seq on patient fibroblasts - no alteration in gene expression
Zebrafish homolog of Arg267 and Arg301 - mimics observed phenotype (reduced brain development), increased in embryo apoptosis
RNQ seq on affected zebrafish embryos - transcriptome strongly disrupted
Splicing analysis in progress

CRKNL1 supports U6 structure in spliceosome
Sources: Other
Intellectual disability syndromic and non-syndromic v0.6022 FAM177A1 Chirag Patel gene: FAM177A1 was added
gene: FAM177A1 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: FAM177A1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: FAM177A1 were set to PMID: 38767059, 25558065
Phenotypes for gene: FAM177A1 were set to Neurodevelopmental disorder, MONDO_0100500
Review for gene: FAM177A1 was set to GREEN
gene: FAM177A1 was marked as current diagnostic
Added comment: PMID: 38767059
5 individuals from 3 unrelated families reported with with biallelic loss of function variants in FAM177A1. Clinical features included: global developmental delay, intellectual disability, seizures, behavioural abnormalities, hypotonia, gait disturbance, and macrocephaly.

They showed that FAM177A1 localizes to the Golgi complex in mammalian and zebrafish cells. Intersection of the RNA-seq and metabolomic datasets from FAM177A1-deficient human fibroblasts and whole zebrafish larvae demonstrated dysregulation of pathways associated with apoptosis, inflammation, and negative regulation of cell proliferation.

PMID: 25558065
A study of 143 multiplex consanguineous families identified a homozygous frameshift variant in FAM177A1 in 1 family with 4 affected siblings with intellectual disability, dolicocephaly, obesity, and macrocephaly. The variant segregated with all 4 affected siblings and parents were confirmed heterozygous carriers.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5756 GTF3C5 Bryony Thompson gene: GTF3C5 was added
gene: GTF3C5 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: GTF3C5 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: GTF3C5 were set to 38520561; 35503477
Phenotypes for gene: GTF3C5 were set to neurodevelopmental disorder MONDO:0700092, GTF3C5-related
Review for gene: GTF3C5 was set to GREEN
gene: GTF3C5 was marked as current diagnostic
Added comment: 4 families/probands with syndromic ID. Loss of function is the expected
PMID: 38520561 - Biallelic variants identified (3 missense & 1 stopgain) in 4 individuals from 3 families presenting with multisystem developmental syndrome including the features: growth retardation, developmental delay, intellectual disability, dental anomalies, cerebellar malformations, delayed bone age, skeletal anomalies, and facial dysmorphism. Gene-disease relationship supported by: reduced protein expression in patient cells, yeast assays, and a zebrafish model
PMID: 35503477 - 1 proband with biallelic missense variants and hypomelanosis of Ito, seizures, growth retardation, abnormal brain MRI, developmental delay, and facial dysmorphism
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5717 CELSR3 Crystle Lee gene: CELSR3 was added
gene: CELSR3 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: CELSR3 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: CELSR3 were set to PMID: 38429302
Phenotypes for gene: CELSR3 were set to Neurodevelopmental disorder (MONDO#0700092), CELSR3-related
Review for gene: CELSR3 was set to GREEN
Added comment: PMID: 38429302:12 affected individuals from 11 families reported with bi-allelic variants. Phenotype ranged from CNS anomalies (7/12), CNS and CAKUT (3/12) and CAKUT only (2/12). 8/12 has ID/DD. Only missense variants reported and 1 inframe variant. Functional studies done in zebrafish demonstrate similar structural anomalies of the developing pronephros and neuronal abnormalities to affected individuals
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5712 SNF8 Chern Lim gene: SNF8 was added
gene: SNF8 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: SNF8 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: SNF8 were set to 38423010
Phenotypes for gene: SNF8 were set to Severe developmental delay, epileptic encephalopathy, brain MRI abnormality; intellectual disability, childhood-onset optic atrophy, ataxia
Review for gene: SNF8 was set to GREEN
gene: SNF8 was marked as current diagnostic
Added comment: PMID: 38423010
- Nine individuals from six families presenting with a spectrum of neurodevelopmental/neurodegenerative features caused by bi-allelic variants in SNF8. In total, three putative LoF variants and four missense variants were identified.
- The phenotypic spectrum included four individuals with severe developmental and epileptic encephalopathy, massive reduction of white matter, hypo-/aplasia of the corpus callosum, neurodevelopmental arrest, and early death. A second cohort shows a milder phenotype with intellectual disability, childhood-onset optic atrophy, or ataxia. All mildly affected individuals shared the same hypomorphic variant, c.304G>A (p.Val102Ile) as compound heterozygous.
- Functional studies using fibroblasts derived from patients and zebrafish model showed LoF is the disease mech.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5706 ZFX Sarah Leigh gene: ZFX was added
gene: ZFX was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: ZFX 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: ZFX were set to 26350204; 26740508; 38325380
Phenotypes for gene: ZFX were set to X-linked neurodevelopmental disorder with recurrent facial gestalt
Review for gene: ZFX was set to GREEN
Added comment: To date, germline variants in ZFX have not been associated with a phenotype in OMIM or Gen2Phen.
A single ZFX variant has been associated with a neurodevelopmental disorder, that has a Rett syndrome-like phenotype disorder, in a 14 year old male. The ZFX variant was allelic with another X-linked variant in SHROOM4. These variants were inherited from the mother, who had random X inactivation pattern (PMID: 26740508).
PMID: 38325380 reports 11 ZFX variants in 18 subjects from 16 unrelated families (14 males and 4 females) with an X-linked neurodevelopmental disorder with recurrent facial gestalt. Seven variants were truncating and the remaining were missense variants within the Zinc finger array. In the pedigree of family 6 (figure 3, PMID: 38325380), it was apparent that there were female carriers of the ZFX variant (GRCh38 chrX: 24229396A>G, c.2438A>G, p.Tyr774Cys) with hyperparathyroidism and two affected males and one affected female, with the neurodevelopmental disorder. It appeared that skewed X-inactivation in the female carriers was responsible for the different phenotypic features. The association between ZFX variants and a novel neurodevelopmental disorder, was further supported by functional studies showing altered transcriptional activity in missense variants and altered behavior in a zebrafish loss-of-function model.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5687 WDR44 Zornitza Stark gene: WDR44 was added
gene: WDR44 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: WDR44 was set to X-LINKED: hemizygous mutation in males, biallelic mutations in females
Publications for gene: WDR44 were set to 38191484
Phenotypes for gene: WDR44 were set to Ciliopathy, MONDO:0005308, WDR44-related
Review for gene: WDR44 was set to GREEN
Added comment: 11 male patients with 6 missense and 1 nonsense variant in WDR44 displaying a wide range of cognitive impairment and variable congenital anomalies associated with primary cilium dysfunction. All patients had learning difficulties with 8 labelled as intellectually disabled (mild-moderate). Other clinical features included anomalies of craniofacial, musculoskeletal, brain, renal and cardiac development.
WDR44 is a negative regulator of ciliogenesis. Increased binding is hypothesised to underlie the pathogenicity of WDR44 variants identified in this cohort. Functional data supported impaired ciliogenesis initiation in patient fibroblasts and a zebrafish model. A zebrafish model recapitulated the human phenotype when morphants expressed WDR44 L668S, D669N, S764F, G782C, H839R, and R733* variants. Of note, D648G or N840S did not recapitulate the phenotype in the zebrafish model.
The studies supported a GoF mechanism, but the authors could not rule out that LoF of WDR44 contributes to the ciliopathy-like phenotype observed, because protein expression data was only available for a limited number of patients.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5660 BORCS8 Lauren Rogers changed review comment from: 3 unrelated families with five affected children with homozygous or compound heterozygous loss of function missense and PTC variants.

HEK293T cells show the missense variants are expressed at normal levels but exhibit reduced assembly with other BORC subunits and reduced ability to drive lysosome distribution. The BORCS8 PTC frameshift variant is expressed at lower levels and is completely incapable of assembling with other BORC subunits and promoting lysosome distribution. Zebrafish KO of the orthologous brocs8 causes decreased brain and eye size, neuromuscular anomalies and impaired locomotion, recapitulating some of the key traits of the human disease.
Sources: Literature; to: 3 unrelated families with five affected children with homozygous or compound heterozygous loss of function missense and PTC variants. 5/5 hypotonia, failure to thrive, global developmental delay, profound intellectual disability, muscle weakness and atrophy, dysmorphic features. 3/5 with microcephaly, 3/5 with seizures, 4/5 with spasticity, 3/5 with scoliosis, 4/4 with optic atrophy.

HEK293T cells show the missense variants are expressed at normal levels but exhibit reduced assembly with other BORC subunits and reduced ability to drive lysosome distribution. The BORCS8 PTC frameshift variant is expressed at lower levels and is completely incapable of assembling with other BORC subunits and promoting lysosome distribution. Zebrafish KO of the orthologous brocs8 causes decreased brain and eye size, neuromuscular anomalies and impaired locomotion, recapitulating some of the key traits of the human disease.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5660 BORCS8 Lauren Rogers gene: BORCS8 was added
gene: BORCS8 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: BORCS8 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: BORCS8 were set to 38128568
Phenotypes for gene: BORCS8 were set to Neurodevelopmental disorder (MONDO#0700092), BORCS8-related
Review for gene: BORCS8 was set to GREEN
Added comment: 3 unrelated families with five affected children with homozygous or compound heterozygous loss of function missense and PTC variants.

HEK293T cells show the missense variants are expressed at normal levels but exhibit reduced assembly with other BORC subunits and reduced ability to drive lysosome distribution. The BORCS8 PTC frameshift variant is expressed at lower levels and is completely incapable of assembling with other BORC subunits and promoting lysosome distribution. Zebrafish KO of the orthologous brocs8 causes decreased brain and eye size, neuromuscular anomalies and impaired locomotion, recapitulating some of the key traits of the human disease.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5567 BRAF Zornitza Stark Marked gene: BRAF as ready
Intellectual disability syndromic and non-syndromic v0.5567 BRAF Zornitza Stark Gene: braf has been classified as Green List (High Evidence).
Intellectual disability syndromic and non-syndromic v0.5567 BRAF Zornitza Stark Phenotypes for gene: BRAF were changed from to Cardiofaciocutaneous syndrome (MIM# 115150); Noonan syndrome (MIM# 613706); LEOPARD syndrome (MIM# 613707)
Intellectual disability syndromic and non-syndromic v0.5566 BRAF Zornitza Stark Publications for gene: BRAF were set to
Intellectual disability syndromic and non-syndromic v0.5565 BRAF Zornitza Stark Mode of pathogenicity for gene: BRAF was changed from to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments
Intellectual disability syndromic and non-syndromic v0.5564 BRAF Zornitza Stark Mode of inheritance for gene: BRAF was changed from Unknown to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Intellectual disability syndromic and non-syndromic v0.5549 BRAF Claire Fryer-Smith reviewed gene: BRAF: Rating: GREEN; Mode of pathogenicity: Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments; Publications: 10610177, 16474404, 19206169; Phenotypes: Cardiofaciocutaneous syndrome (MIM# 115150), Noonan syndrome (MIM# 613706), LEOPARD syndrome (MIM# 613707); Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Intellectual disability syndromic and non-syndromic v0.5273 DCAF15 Chirag Patel gene: DCAF15 was added
gene: DCAF15 was added to Intellectual disability syndromic and non-syndromic. Sources: Other
Mode of inheritance for gene: DCAF15 was set to BIALLELIC, autosomal or pseudoautosomal
Phenotypes for gene: DCAF15 were set to Cornelia de Lange syndrome
Review for gene: DCAF15 was set to AMBER
Added comment: ESHG 2023:
3 unrelated cases with CdLS (1 x TOP with MCA, 1 x death @20mths, 1 x living child)
Features suggestive of CdLS - DD, microcephaly, CHD, dysmorphism, visual/hearing impairment.

WES identified recurrent de novo variant (p.Ser470Phe) in DCAF15 gene. This mediates ubiquitination and degradation of target proteins, and interacts with cohesin complex members (SMC1/SMC3).

Protein analysis from individuals showed increased accumulation of ubiquitination-modified proteins and SM3 (GOF mechanism). EpiSign analysis showed same DNA methylation pattern as other CdLS cases/genes. Zebrafish model showed reduced body length, reduced head size, reduced oligodendrocytes, heart defect, aberrant motor neurons, and abnormal response to visual/auditory stimuli.
Sources: Other
Intellectual disability syndromic and non-syndromic v0.5271 CYHR1 Chirag Patel gene: CYHR1 was added
gene: CYHR1 was added to Intellectual disability syndromic and non-syndromic. Sources: Other
Mode of inheritance for gene: CYHR1 was set to BIALLELIC, autosomal or pseudoautosomal
Phenotypes for gene: CYHR1 were set to Neurodevelopmental disorder and microcephaly
Review for gene: CYHR1 was set to AMBER
gene: CYHR1 was marked as current diagnostic
Added comment: ESHG 2023:
5 individuals from 3 families with biallelic LOF variants in CYHR1 (aka ZTRAF1). Presentation with microcephaly, hypotonia, DD, and ID. Expression studies showed mislocalisation of CYHR1. Mutant fibroblasts showed increased lysosomal markers and upregulated lysosomal proteins, leading to impaired autophagy. Zebrafish KO however did not show a phenotype.
Sources: Other
Intellectual disability syndromic and non-syndromic v0.5182 CTR9 Achchuthan Shanmugasundram changed review comment from: PMID:35717577 reported two additional unrelated cases with non-synonymous heterozygous CTR9 variants (p.Glu15Asp and p.Pro25Arg) and they presented with macrocephaly, motor delay, and intellectual disability. In addition, functional studies in also showed that knockout/ over-expression of CTR9 variants caused motor defects and enlargement of telencephalon (homologous to the mammalian cerebrum).; to: PMID:35717577 reported two additional unrelated cases with non-synonymous heterozygous CTR9 variants (p.Glu15Asp and p.Pro25Arg) and they presented with macrocephaly, motor delay, and intellectual disability. In addition, functional studies in zebrafish also showed that knockout/ over-expression of CTR9 variants caused motor defects and enlargement of telencephalon (homologous to the mammalian cerebrum).
Intellectual disability syndromic and non-syndromic v0.5182 DPYSL2 Achchuthan Shanmugasundram gene: DPYSL2 was added
gene: DPYSL2 was added to Intellectual disability syndromic and non-syndromic. 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.

This gene has not yet been associated with relevant phenotypes either in OMIM or in Gene2Phenotype.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5040 EXOSC3 Michelle Dang changed review comment from: Association with global developmental delay, hypotonia, hyperreflexia, cerebellar (+/- pontine) atrophy with variable severity. Assessment of cognitive function/IQ limited by motor and speech impairments. Severe forms associated with early deaths during infancy periods. Intellectual impairment/psychomotor retardation (to varying degrees) reported in all cases across varying degrees of severity (23284067). Zanni et al (23975261) identified 2 individuals with compound heterozygous mutations resulting in intellectual impairment and early onset spasticity. Wan et al (22544365) described global developmental delay in addition to cerebellar features and spinal motor degeneration.; to: Association with global developmental delay, hypotonia, hyperreflexia, cerebellar (+/- pontine) atrophy with variable severity. Assessment of cognitive function/IQ limited by motor and speech impairments. Severe forms associated with early deaths during infancy periods.
Intellectual impairment/psychomotor retardation (to varying degrees) reported in all cases across varying degrees of severity (23284067). Zanni et al (23975261) identified 2 individuals with compound heterozygous mutations resulting in intellectual impairment and early onset spasticity. Wan et al (22544365) described global developmental delay in addition to cerebellar features and spinal motor degeneration, with functional effects of the mutation reproduced with knocked down endogenous expression of exosc3 in zebrafish embryos and subsequent rescue of the phenotype by co-injection with wild-type zebrafish exosc3 mRNA.
Intellectual disability syndromic and non-syndromic v0.5023 SMC5 Zornitza Stark gene: SMC5 was added
gene: SMC5 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: SMC5 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: SMC5 were set to 36333305
Phenotypes for gene: SMC5 were set to Multiple congenital anomalies/dysmorphic syndrome, MONDO:0019042, SLF2-related; Atelis syndrome; microcephaly; short stature; ID
Review for gene: SMC5 was set to GREEN
Added comment: Four individuals from three families with a chromosome breakage disorder and bi-allelic variants in this gene. However, three of the individuals had the same homozygous missense variant. Evidence for functional impact of the variant was limited. However, zebrafish model recapitulated the phenotype and was not rescued by the introduction of this variant, arguing for functional effect. Borderline Amber/Green.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.5021 SLF2 Zornitza Stark gene: SLF2 was added
gene: SLF2 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: SLF2 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: SLF2 were set to 36333305
Phenotypes for gene: SLF2 were set to Multiple congenital anomalies/dysmorphic syndrome, MONDO:0019042, SLF2-related; Atelis syndrome; microcephaly; short stature; ID
Review for gene: SLF2 was set to GREEN
Added comment: Seven individuals from 6 families with a chromosome breakage disorder and bi-allelic variants in this gene (LoF). Functional data including zebrafish model.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4973 MED11 Ain Roesley gene: MED11 was added
gene: MED11 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: MED11 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: MED11 were set to 36001086
Phenotypes for gene: MED11 were set to neurodevelopmental disorder MONDO#0700092, MED11-related
Review for gene: MED11 was set to GREEN
gene: MED11 was marked as current diagnostic
Added comment: 7 affected from 5 families (3x consang) with the same recurrent variant of p.(Arg109*).

Protein truncating, NOT NMD as proven by RT-PCR and western blot. Zebrafish knockout model recapitulates key clinical phenotypes

NO evidence of founder effect from haplotype analysis

7/7 cerebral dysgyria, cortical atrophy
5/7 limb contracture
4/7 epilepsy
3/7 families with IUGR
3/7 GDD
3/7 hearing loss
3/7 undescended testis
2/7 nystagmus
1/7 congenital cataract
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4973 MED11 Ain Roesley gene: MED11 was added
gene: MED11 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: MED11 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: MED11 were set to 36001086
Phenotypes for gene: MED11 were set to neurodevelopmental disorder MONDO#0700092, MED11-related
Review for gene: MED11 was set to GREEN
gene: MED11 was marked as current diagnostic
Added comment: 7 affected from 5 families (3x consang) with the same recurrent variant of p.(Arg109*).

Protein truncating, NOT NMD as proven by RT-PCR and western blot. Zebrafish knockout model recapitulates key clinical phenotypes

NO evidence of founder effect from haplotype analysis

7/7 cerebral dysgyria, cortical atrophy
5/7 limb contracture
4/7 epilepsy
3/7 families with IUGR
3/7 GDD
3/7 hearing loss
3/7 undescended testis
2/7 nystagmus
1/7 congenital cataract
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4687 GLRA2 Zornitza Stark gene: GLRA2 was added
gene: GLRA2 was added to Intellectual disability syndromic and non-syndromic. Sources: Expert list
Mode of inheritance for gene: GLRA2 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: GLRA2 were set to 26370147; 20479760; 35294868
Phenotypes for gene: GLRA2 were set to Intellectual developmental disorder, X-linked, syndromic, Pilorge type, MIM# 301076
Review for gene: GLRA2 was set to GREEN
Added comment: More than 10 unrelated families reported. Both males and females affected, though some mothers are asymptomatic or mild. Zebrafish model.
Sources: Expert list
Intellectual disability syndromic and non-syndromic v0.4524 HIST1H4D Paul De Fazio changed review comment from: Single individual described with a de novo missense variant Arg41His (Arg40 in H4 nomenclature). Apart from langauge delay and moderate ID, phenotypes included facial dysmorphisms and cochlear abnormalities and arhinencephaly on MRI. Hearing was normal. Birth length, OFC, weight were all reduced (-2 to -2.5SD).
A zebrafish model has developmental defects.
Sources: Literature; to: HGNC recognised gene name: H4C4
Single individual described with a de novo missense variant Arg41His (Arg40 in H4 nomenclature). Apart from langauge delay and moderate ID, phenotypes included facial dysmorphisms and cochlear abnormalities and arhinencephaly on MRI. Hearing was normal. Birth length, OFC, weight were all reduced (-2 to -2.5SD).
A zebrafish model has developmental defects.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4519 HIST1H4E Paul De Fazio changed review comment from: 17 patients identified with de novo missense variants affecting Lys31, Pro32, Arg35, Leu37, Arg40 (recurrent), Arg45 (recurrent), Tyr98 (recurrent). All individuals had ID/dev delay. Additional phenotypes in some but not all individuals included epilepsy, hypotonia, facial dysmorphism. Most had reduced birth length, OFC, weight (-1 to -3SD).
A zebrafish model has developmental defects.
Sources: Literature; to: HGNC recognised gene: H4C5
17 patients identified with de novo missense variants affecting Lys31, Pro32, Arg35, Leu37, Arg40 (recurrent), Arg45 (recurrent), Tyr98 (recurrent). All individuals had ID/dev delay. Additional phenotypes in some but not all individuals included epilepsy, hypotonia, facial dysmorphism. Most had reduced birth length, OFC, weight (-1 to -3SD).
A zebrafish model has developmental defects.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4519 HIST1H4C Paul De Fazio changed review comment from: 6 additional individuals with ID and dev delay. All variants were de novo. Lys92 (Lys91 in H4 nomenclature) and Pro33 (Pro32) were the only variants identified. Additional phenotypes in some but not all patients included hypotonia, facial dysmorphisms, conductive hearing loss. Most had reduced birth length, OFC, weight (-1 to -2.5SD).
A zebrafish model has developmental defects.; to: HGNC recognised gene name: H4C3
6 additional individuals with ID and dev delay. All variants were de novo. Lys92 (Lys91 in H4 nomenclature) and Pro33 (Pro32) were the only variants identified. Additional phenotypes in some but not all patients included hypotonia, facial dysmorphisms, conductive hearing loss. Most had reduced birth length, OFC, weight (-1 to -2.5SD).
A zebrafish model has developmental defects.
Intellectual disability syndromic and non-syndromic v0.4519 HIST1H4E Paul De Fazio gene: HIST1H4E was added
gene: HIST1H4E was added to Intellectual disability syndromic and non-syndromic. 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 Neurodevelopmental disorder, HIST1H4E-related MONDO:0700092
Review for gene: HIST1H4E was set to GREEN
gene: HIST1H4E was marked as current diagnostic
Added comment: 17 patients identified with de novo missense variants affecting Lys31, Pro32, Arg35, Leu37, Arg40 (recurrent), Arg45 (recurrent), Tyr98 (recurrent). All individuals had ID/dev delay. Additional phenotypes in some but not all individuals included epilepsy, hypotonia, facial dysmorphism. Most had reduced birth length, OFC, weight (-1 to -3SD).
A zebrafish model has developmental defects.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4519 NRCAM Ee Ming Wong gene: NRCAM was added
gene: NRCAM was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: NRCAM was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: NRCAM were set to PMID: 35108495
Phenotypes for gene: NRCAM were set to neurodevelopmental disorder, MONDO:0700092
Penetrance for gene: NRCAM were set to unknown
Review for gene: NRCAM was set to GREEN
gene: NRCAM was marked as current diagnostic
Added comment: -Ten individuals from 8 families with developmental delay/intellectual disability, hypotonia, peripheral neuropathy, and/or spasticity
- Affected individuals are biallelic for missense and/or LoF variants which are mainly in the fibronectin type III (Fn-III) domain
- Zebrafish mutants lacking the third Fn-III domain displayed significantly altered swimming behavior compared to wild-type larvae (p < 0.03) and a trend toward increased amounts of alpha-tubulin fibers in the dorsal telencephalon, demonstrating an alteration in white matter tracts and projections
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4519 HIST1H4D Paul De Fazio gene: HIST1H4D was added
gene: HIST1H4D was added to Intellectual disability syndromic and non-syndromic. 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 Neurodevelopmental disorder, HIST1H4D-related MONDO:0700092
Review for gene: HIST1H4D was set to AMBER
gene: HIST1H4D was marked as current diagnostic
Added comment: Single individual described with a de novo missense variant Arg41His (Arg40 in H4 nomenclature). Apart from langauge delay and moderate ID, phenotypes included facial dysmorphisms and cochlear abnormalities and arhinencephaly on MRI. Hearing was normal. Birth length, OFC, weight were all reduced (-2 to -2.5SD).
A zebrafish model has developmental defects.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4517 HIST1H4F Elena Savva edited their review of gene: HIST1H4F: Added comment: PMID: 35202563 - single de novo missense in a patient with neurodevelopmental features of intellectual disability and motor and/or gross developmental delay.
- zebrafish studies show a significant increase in all of mild dev delay, necrosis, defective organogenesis and pre-gastrulation failure
Sources: Literature; Changed rating: AMBER
Intellectual disability syndromic and non-syndromic v0.4517 HIST1H4F Elena Savva gene: HIST1H4F was added
gene: HIST1H4F was added to Intellectual disability syndromic and non-syndromic. 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 PMID: 35202563
Phenotypes for gene: HIST1H4F were set to Neurodevelopmental disorders
Review for gene: HIST1H4F was set to GREEN
Added comment: PMID: 35202563 - single de novo missense in a patient with neurodevelopmental features of intellectual disability and motor and/or gross developmental delay.
- zebrafish studies show a significant increase in all of mild dev delay, necrosis, defective organogenesis and pre-gastrulation failure
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4515 HIST1H4I Elena Savva gene: HIST1H4I was added
gene: HIST1H4I was added to Intellectual disability syndromic and non-syndromic. 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 PMID: 35202563
Phenotypes for gene: HIST1H4I were set to Neurodevelopmental syndrome
Review for gene: HIST1H4I was set to GREEN
Added comment: PMID: 35202563
- 3 unrelated de novo patients, p.His75Arg was recurring and observed in 2/3 probands.
- Zebrafish study shows both variants resulted in a significant increases in developmental issues such as in mild dev delay, necrosis and defective organogenesis.
- All patients had intellectual disability and motor and/or gross developmental delay and dysmorphisms.
- 2/3 patients showed bilateral conductive hearing loss
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4184 PLXNA1 Chirag Patel gene: PLXNA1 was added
gene: PLXNA1 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: PLXNA1 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Publications for gene: PLXNA1 were set to PMID: 34054129
Phenotypes for gene: PLXNA1 were set to Neurodevelopmental disorder with cerebral and eye anomalies
Review for gene: PLXNA1 was set to GREEN
Added comment: Dworschak et al. (2021) via WES reported 10 patients from 7 families with biallelic (n=7) or de novo (n=3) PLXNA1 variants. Shared phenotypic features include global developmental delay (9/10), brain anomalies (6/10), and eye anomalies (7/10). Seizures were predominantly reported in patients with monoallelic variants. Zebrafish studies showed an embryonic role of plxna1a in the development of the central nervous system and the eye. Biallelic variants in the extracellular Plexin-A1 domains lead to impaired dimerization or lack of receptor molecules, whereas monoallelic variants in the intracellular Plexin-A1 domains might impair downstream signaling through a dominant-negative effect.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4051 VPS50 Konstantinos Varvagiannis gene: VPS50 was added
gene: VPS50 was added to Intellectual disability syndromic and non-syndromic. 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
Intellectual disability syndromic and non-syndromic v0.4023 AP1G1 Zornitza Stark changed review comment from: Two bi-allelic homozygous missense variants were found in two distinct families with Italian and Pakistani origins; homozygous missense variants.

Eight de novo heterozygous variants were identified in nine isolated affected individuals from nine families; including five missense, two frameshift, and one intronic variant that disrupts the canonical splice acceptor site.

Knocking out AP1G1 Zebrafish model resulted in severe developmental abnormalities and increased lethality.

All individuals had neurodevelopmental disorder (NDD) including global developmental delay and ID, which varied in severity from mild to severe.
Sources: Literature; to: Two bi-allelic homozygous missense variants were found in two distinct families with Italian and Pakistani origins; homozygous missense variants.

Eight de novo heterozygous variants were identified in nine isolated affected individuals from nine families; including five missense, two frameshift, and one intronic variant that disrupts the canonical splice acceptor site.

Knocking out AP1G1 Zebrafish model resulted in severe developmental abnormalities and increased lethality.

All individuals had neurodevelopmental disorder (NDD) including global developmental delay and ID, which varied in severity from mild to severe.

GREEN for mono-allelic, AMBER for bi-allelic.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4023 AP1G1 Zornitza Stark gene: AP1G1 was added
gene: AP1G1 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: AP1G1 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Publications for gene: AP1G1 were set to 34102099
Phenotypes for gene: AP1G1 were set to Neurodevelopmental disorder (NDD); Intellectual Disability; Epilepsy
Review for gene: AP1G1 was set to GREEN
Added comment: Two bi-allelic homozygous missense variants were found in two distinct families with Italian and Pakistani origins; homozygous missense variants.

Eight de novo heterozygous variants were identified in nine isolated affected individuals from nine families; including five missense, two frameshift, and one intronic variant that disrupts the canonical splice acceptor site.

Knocking out AP1G1 Zebrafish model resulted in severe developmental abnormalities and increased lethality.

All individuals had neurodevelopmental disorder (NDD) including global developmental delay and ID, which varied in severity from mild to severe.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.3975 C2orf69 Zornitza Stark gene: C2orf69 was added
gene: C2orf69 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: C2orf69 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: C2orf69 were set to 34038740; 33945503
Phenotypes for gene: C2orf69 were set to Combined oxidative phosphorylation deficiency-53 (COXPD53), MIM#619423
Review for gene: C2orf69 was set to GREEN
Added comment: PMID 34038740: 20 affected children from 8 unrelated families reported, presenting with fatal syndrome consisting of severe autoinflammation and progredient leukoencephalopathy with recurrent seizures; 12 of these subjects, whose DNA was available, segregated homozygous loss-of-function C2orf69 variants. Endogenous C2ORF69 was found to be (1) loosely bound to mitochondria, (2) affects mitochondrial membrane potential and oxidative respiration in cultured neurons, and (3) controls the levels of the glycogen branching enzyme 1 (GBE1) consistent with a glycogen-storage-associated mitochondriopathy. Zebrafish model.

PMID 33945503: 8 individuals from 5 families reported with muscle hypotonia, developmental delay, progressive microcephaly, and brain MRI abnormalities. Age at onset ranged from birth to 6 months of age. Six patients had vision impairment, liver abnormalities, inflammation/inflammatory arthritis, and 5 patients had seizures.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.3875 IFT74 Zornitza Stark gene: IFT74 was added
gene: IFT74 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: IFT74 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: IFT74 were set to 27486776; 32144365; 33531668
Phenotypes for gene: IFT74 were set to Bardet-Biedl syndrome 20, MIM# 617119; Joubert syndrome
Review for gene: IFT74 was set to GREEN
Added comment: Two individuals reported with BBS phenotype.

PMID 33531668: Identified IFT74 as a JBTS-associated gene in 3 unrelated families through WES. All the affected individuals carried truncated variants and shared one missense variant (p.Q179E) found only in East Asians. The expression of the human p.Q179E-IFT74 variant displayed compromised rescue effects in zebrafish ift74 morphants. Attenuated ciliogenesis; altered distribution of IFT proteins and ciliary membrane proteins, including ARL13B, INPP5E, and GPR161; and disrupted hedgehog signaling were observed in patient fibroblasts with IFT74 variants.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.3847 LTBP1 Chern Lim changed review comment from: PMID:33991472
- Premature truncating variants in multiple affected individuals from 4 unrelated consanguineous families.
- Affected individuals present with connective tissue features (cutis laxa and inguinal hernia), craniofacial dysmorphology, variable heart defects, and prominent skeletal features (craniosynostosis, short stature, brachydactyly, and syndactyly).
- Most of the affected individuals have developmental delay and other neurological features.
- Functional studies done on patient fibroblasts and zebrafish models.
Sources: Literature; to: PMID:33991472
- Premature truncating variants in multiple affected individuals from 4 unrelated consanguineous families.
- Affected individuals present with connective tissue features (cutis laxa and inguinal hernia), craniofacial dysmorphology, variable heart defects, and prominent skeletal features (craniosynostosis, short stature, brachydactyly, and syndactyly).
- Most of the affected individuals have developmental delay and other neurological features.
- Functional studies done on patient fibroblasts and zebrafish models.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.3847 LTBP1 Chern Lim gene: LTBP1 was added
gene: LTBP1 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: LTBP1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: LTBP1 were set to 33991472
Phenotypes for gene: LTBP1 were set to cutis laxa syndrome
Review for gene: LTBP1 was set to GREEN
gene: LTBP1 was marked as current diagnostic
Added comment: PMID:33991472
- Premature truncating variants in multiple affected individuals from 4 unrelated consanguineous families.
- Affected individuals present with connective tissue features (cutis laxa and inguinal hernia), craniofacial dysmorphology, variable heart defects, and prominent skeletal features (craniosynostosis, short stature, brachydactyly, and syndactyly).
- Most of the affected individuals have developmental delay and other neurological features.
- Functional studies done on patient fibroblasts and zebrafish models.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.3401 CBY1 Bryony Thompson gene: CBY1 was added
gene: CBY1 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: CBY1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: CBY1 were set to 33131181; 25103236; 25220153
Phenotypes for gene: CBY1 were set to intellectual disability; cerebellar ataxia; molar tooth sign; polydactyly; Joubert syndrome
Review for gene: CBY1 was set to GREEN
Added comment: Three cases in two unrelated consanguineous families with homozygous loss of function variants, with ID as a feature of the phenotype. Multiple null model organisms recapitulate the human phenotype: Null mouse model had cystic kidneys, a phenotype common to ciliopathies. Reducing Cby levels in Xenopus laevis model reduced the density of multiciliated cells, the number of basal bodies per multiciliated cell, and the numbers of neural tube primary cilia; it also led to abnormal development of the neural crest, central nervous system, and pronephros. Depletion of cby1 in zebrafish results in ciliopathy‐related phenotypes.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.3383 ZNF526 Zornitza Stark gene: ZNF526 was added
gene: ZNF526 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: ZNF526 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: ZNF526 were set to 21937992; 25558065; 33397746
Phenotypes for gene: ZNF526 were set to Intellectual disability; Microcephaly; Cataracts; Epilepsy; Hypertonia; Dystonia
Review for gene: ZNF526 was set to GREEN
Added comment: Currently not associated with any phenotype in OMIM (last updated on 09/12/2011), but has a 'possible' disease confidence rating for 'Autosomal Recessive Mental Retardation' in Gene2Phenotype.

- PMID: 21937992 (2011) - Two unrelated families (with 4 affected individuals in each) with non-syndromic ID (mild or moderate, respectively) identified harbouring different biallelic missense variants in the ZNF526 gene.

- PMID: 25558065 (2015) - One family with ID, Noonan-like facies, pulmonary stenosis and a homozygous missense variant in this gene. No further details provided.

- PMID: 33397746 (2021) - Five individuals from four unrelated families with homozygous ZNF526 variants. Four harboured truncating variants, and were all affected by profound DD and severe ID, microcephaly (ranging from -4 SD to -8 SD), bilateral progressive cataracts, hypertonic-dystonic movements, epilepsy and brain MRI anomalies. The fifth patient had a homozygous missense variant and a slightly less severe disorder, with postnatal microcephaly (-2 SD), progressive bilateral cataracts, severe ID, and normal brain MRI. Zebrafish model demonstrated brain and eye malformations resembling findings seen in the human holoprosencephaly spectrum
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.3248 BICRA Elena Savva Added comment: Comment when marking as ready: 12 individuals reported, 11 de novo (1 not resolved), "with neurodevelopmental phenotypes—developmental delay (HP:0001263), intellectual disability (HP:0001249), autism spectrum disorder (HP:0000729), and/or behavioral phenotypes (HP:0000708)—and variable structural birth defects and dysmorphic features". Mostly LoF or gene deletions, but 2 missense reported. Zebrafish model supports the gene-disease association.
Intellectual disability syndromic and non-syndromic v0.3248 BICRA Paul De Fazio gene: BICRA was added
gene: BICRA was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: BICRA was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Publications for gene: BICRA were set to 33232675
Phenotypes for gene: BICRA were set to Developmental delay, intellectual disability, autism spectrum disorder,behavioral abnormalities, dysmorphic features
Review for gene: BICRA was set to GREEN
gene: BICRA was marked as current diagnostic
Added comment: 12 individuals reported, 11 de novo (1 not resolved), "with neurodevelopmental phenotypes—developmental delay (HP:0001263), intellectual disability (HP:0001249), autism spectrum disorder (HP:0000729), and/or behavioral phenotypes (HP:0000708)—and variable structural birth defects and dysmorphic features". Mostly LoF or gene deletions, but 2 missense reported. Zebrafish model supports the gene-disease association.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2833 FAM50A Konstantinos Varvagiannis gene: FAM50A was added
gene: FAM50A was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: FAM50A 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: FAM50A were set to 32703943
Phenotypes for gene: FAM50A were set to Mental retardation syndrome, X-linked, Armfield type (MIM #300261)
Penetrance for gene: FAM50A were set to unknown
Review for gene: FAM50A was set to GREEN
Added comment: Lee et al (2020 - PMID: 32703943) provide evidence that Armfield X-Linked intellectual disability syndrome is caused by monoallelic FAM50A pathogenic variants. The current review is based only on this reference.

The authors provide clinical details on 6 affected individuals from 5 families.

Features included postnatal growth delay, DD and ID (6/6 - also evident for those without formal IQ assesment), seizures (3/6 from 2 families), prominent forehead with presence of other facial features and variable head circumference (5th to >97th %le), ocular anomalies (5/6 - strabismus/nystagmus/Axenfeld-Rieger), cardiac (3/6 - ASD/Fallot) and genitourinary anomalies (3/6).

In the first of these families (Armfield et al 1999 - PMID: 10398235), linkage analysis followed by additional studies (Sanger, NGS of 718 genes on chrX, X-exome NGS - several refs provided) allowed the identification of a FAM50A variant. Variants in other families were identified by singleton (1 fam) or trio-ES (3 fam).

In affected individuals from 3 families, the variant had occurred de novo. Carrier females in the other families were unaffected (based on pedigrees and/or the original publication). XCI was rather biased in most obligate carrier females from the 1st family (although this ranged from 95:5 to 60:40).

Missense variants were reported in all affected subjects incl. Trp206Gly, Asp255Gly, Asp255Asn (dn), Glu254Gly (dn), Arg273Trp (dn) (NM_004699.3).

Previous studies have demonstrated that FAM50A has ubiquitous expression in human fetal and adult tissues (incl. brain in fetal ones).

Immunostaining suggests a nuclear localization for the protein (NIH/3T3 cells). Comparison of protein levels in LCLs from affected males and controls did not demonstrate significant differences. Protein localization for 3 variants (transfection of COS-7 cells) was shown to be similar to wt.

Complementation studies in zebrafish provided evidence that the identified variants confer partial loss of function (rescue of the morpholino phenotype with co-injection of wt but not mt mRNA). The zebrafish ko model seemed to recapitulate the abnormal development of cephalic structures and was indicative of diminished/defective neurogenesis. Transcriptional dysregulation was demonstrated in zebrafish (altered levels and mis-splicing). Upregulation of spliceosome effectors was demonstrated in ko zebrafish.

Similarly, mRNA expression and splicing defects were demonstrated in LCLs from affected individuals. FAM50A pulldown followed by mass spectrometry in transfected HEK293T cells demonstrated enrichment of binding proteins involved in RNA processing and co-immunoprecipitation assays (transfected U-87 cells) suggested that FAM50A interacts with spliceosome U5 and C-complex proteins.

Overall aberrant spliceosome C-complex function is suggested as the underlying pathogenetic mechanism.

Several other neurodevelopmental syndromes are caused by variants in genes encoding C-complex affiliated proteins (incl. EFTUD2, EIF4A3, THOC2, etc.).

Please consider inclusion in the ID panel with green rating and epilepsy panel with amber (seizures in individuals from 2 families).
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2805 NARS Konstantinos Varvagiannis changed review comment from: [Please note that HGNC Approved Gene Symbol for this gene is NARS1]

Manole et al (2020 - PMID: 32738225) provide evidence that both biallelic and monoallelic (de novo) pathogenic NARS1 variants cause a neurodevelopmental disorder. In total 32 individuals from 21 families are reported, with biallelic variants identified in individuals from 13 families and de novo in 8 families.

Similar features were reported for AR/AD occurrences of the disorder and included of microcephaly (90% - most often primary), epilepsy (23/32 or 74% - variable semiology incl. partial/myoclonic/generalized tonic-clonic seizures), DD and ID (as a universal feature), abnormal tone in several (hypotonia/spasticity), ataxia, demyelinating peripheral neuropathy (in 3 or more for each inheritance mode - or a total of 25%). Some individuals had dysmorphic features.

NARS1 encodes an aminoacyl-tRNA synthetase (ARS) [asparaginyl-tRNA synthetase 1]. Aminoacyl-tRNA synthetases constitute a family of enzymes catalyzing attachment of amino-acids to their cognate tRNAs. As the authors comment, mutations in genes encoding several other ARSs result in neurological disorders ranging from peripheral neuropathy to severe multi-systemic NDD. Dominant, recessive or both modes for inheritance for mutations in the same gene (e.g. AARS1, YARS1, MARS1, etc) have been reported.

Some variants were recurrent, e.g. the c.1600C>T / p.Arg534* which occurred in 6 families as a de novo event or c.1633C>T p.Arg545Cys (homozygous in 6 families). 3 different variants were reported to have occured de novo (c.965G>T - p.Arg322Leu, c.1525G>A - p.Gly509Ser, p.Arg534*) with several other variants identified in hmz/compound htz individuals. A single SNV (c.1067A>C - p.Asp356Ala) was suggested to be acting as modifier and pathogenic only when in trans with a severe variant. [NM_004539.4 used as RefSeq for all].

The authors provide several lines of evidence for a partial loss-of-function effect (e.g. reduction in mRNA expression, enzyme levels and activity in fibroblasts or iNPCs) underlying pathogenicity of the variants identified in individuals with biallelic variants. A gain-of-function (dominant-negative) effect is proposed for de novo variants (such effect also demonstrated for the p.Arg534* in a zebrafish model).

As also Manole et al suggest, NARS1 can be considered for inclusion in gene panels for DD/ID, epilepsy and/or demyelinating neuropathy.
Sources: Literature; to: [Please note that HGNC Approved Gene Symbol for this gene is NARS1]

Manole et al (2020 - PMID: 32738225) provide evidence that both biallelic and monoallelic (de novo) pathogenic NARS1 variants cause a neurodevelopmental disorder. In total 32 individuals from 21 families are reported, with biallelic variants identified in individuals from 13 families and de novo in 8 families.

Similar features were reported for AR/AD occurrences of the disorder and included microcephaly (90% - most often primary), epilepsy (23/32 or 74% - variable semiology incl. partial/myoclonic/generalized tonic-clonic seizures), DD and ID (as a universal feature), abnormal tone in several (hypotonia/spasticity), ataxia, demyelinating peripheral neuropathy (in 3 or more for each inheritance mode - or a total of 25%). Some individuals had dysmorphic features.

NARS1 encodes an aminoacyl-tRNA synthetase (ARS) [asparaginyl-tRNA synthetase 1]. Aminoacyl-tRNA synthetases constitute a family of enzymes catalyzing attachment of amino-acids to their cognate tRNAs. As the authors comment, mutations in genes encoding several other ARSs result in neurological disorders ranging from peripheral neuropathy to severe multi-systemic NDD. Dominant, recessive or both modes for inheritance for mutations in the same gene (e.g. AARS1, YARS1, MARS1, etc) have been reported.

Some variants were recurrent, e.g. the c.1600C>T / p.Arg534* which occurred in 6 families as a de novo event or c.1633C>T p.Arg545Cys (homozygous in 6 families). 3 different variants were reported to have occured de novo (c.965G>T - p.Arg322Leu, c.1525G>A - p.Gly509Ser, p.Arg534*) with several other variants identified in hmz/compound htz individuals. A single SNV (c.1067A>C - p.Asp356Ala) was suggested to be acting as modifier and pathogenic only when in trans with a severe variant. [NM_004539.4 used as RefSeq for all].

The authors provide several lines of evidence for a partial loss-of-function effect (e.g. reduction in mRNA expression, enzyme levels and activity in fibroblasts or iNPCs) underlying pathogenicity of the variants identified in individuals with biallelic variants. A gain-of-function (dominant-negative) effect is proposed for de novo variants (such effect also demonstrated for the p.Arg534* in a zebrafish model).

As also Manole et al suggest, NARS1 can be considered for inclusion in gene panels for DD/ID, epilepsy and/or demyelinating neuropathy.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2805 NARS Konstantinos Varvagiannis gene: NARS was added
gene: NARS was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: NARS was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Publications for gene: NARS were set to 32738225
Phenotypes for gene: NARS were set to Abnormal muscle tone; Microcephaly; Global developmental delay; Intellectual disability; Seizures; Ataxia; Abnormality of the face; Demyelinating peripheral neuropathy
Penetrance for gene: NARS were set to Complete
Review for gene: NARS was set to GREEN
Added comment: [Please note that HGNC Approved Gene Symbol for this gene is NARS1]

Manole et al (2020 - PMID: 32738225) provide evidence that both biallelic and monoallelic (de novo) pathogenic NARS1 variants cause a neurodevelopmental disorder. In total 32 individuals from 21 families are reported, with biallelic variants identified in individuals from 13 families and de novo in 8 families.

Similar features were reported for AR/AD occurrences of the disorder and included of microcephaly (90% - most often primary), epilepsy (23/32 or 74% - variable semiology incl. partial/myoclonic/generalized tonic-clonic seizures), DD and ID (as a universal feature), abnormal tone in several (hypotonia/spasticity), ataxia, demyelinating peripheral neuropathy (in 3 or more for each inheritance mode - or a total of 25%). Some individuals had dysmorphic features.

NARS1 encodes an aminoacyl-tRNA synthetase (ARS) [asparaginyl-tRNA synthetase 1]. Aminoacyl-tRNA synthetases constitute a family of enzymes catalyzing attachment of amino-acids to their cognate tRNAs. As the authors comment, mutations in genes encoding several other ARSs result in neurological disorders ranging from peripheral neuropathy to severe multi-systemic NDD. Dominant, recessive or both modes for inheritance for mutations in the same gene (e.g. AARS1, YARS1, MARS1, etc) have been reported.

Some variants were recurrent, e.g. the c.1600C>T / p.Arg534* which occurred in 6 families as a de novo event or c.1633C>T p.Arg545Cys (homozygous in 6 families). 3 different variants were reported to have occured de novo (c.965G>T - p.Arg322Leu, c.1525G>A - p.Gly509Ser, p.Arg534*) with several other variants identified in hmz/compound htz individuals. A single SNV (c.1067A>C - p.Asp356Ala) was suggested to be acting as modifier and pathogenic only when in trans with a severe variant. [NM_004539.4 used as RefSeq for all].

The authors provide several lines of evidence for a partial loss-of-function effect (e.g. reduction in mRNA expression, enzyme levels and activity in fibroblasts or iNPCs) underlying pathogenicity of the variants identified in individuals with biallelic variants. A gain-of-function (dominant-negative) effect is proposed for de novo variants (such effect also demonstrated for the p.Arg534* in a zebrafish model).

As also Manole et al suggest, NARS1 can be considered for inclusion in gene panels for DD/ID, epilepsy and/or demyelinating neuropathy.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2722 EXOC7 Chirag Patel gene: EXOC7 was added
gene: EXOC7 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: EXOC7 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: EXOC7 were set to PMID: 32103185
Phenotypes for gene: EXOC7 were set to brain atrophy; seizures; developmental delay; microcephaly
Review for gene: EXOC7 was set to GREEN
Added comment: 4 families with 8 affected individuals with brain atrophy, seizures, and developmental delay, and in more severe cases microcephaly and infantile death. Four novel homozygous or comp.heterozygous variants found in EXOC7, which segregated with disease in the families. They showed that EXOC7, a member of the mammalian exocyst complex, is highly expressed in developing human cortex. In addition, a zebrafish model of Exoc7 deficiency recapitulates the human disorder with increased apoptosis and decreased progenitor cells during telencephalon development, suggesting that the brain atrophy in human cases reflects neuronal degeneration.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2719 PDCD6IP Chirag Patel gene: PDCD6IP was added
gene: PDCD6IP was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: PDCD6IP was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: PDCD6IP were set to PMID: 32286682
Phenotypes for gene: PDCD6IP were set to Primary microcephaly
Review for gene: PDCD6IP was set to RED
Added comment: One consanguineous family with 2 affected sibs with primary microcephaly (-4SD), intellectual disability and short stature (-5/6SD), and homozygous frameshift variant in PDCD6IP. The homozygous variant was confirmed in both affected sibs, while the four healthy siblings and parents were heterozygous. The clinical features observed in the patients were similar to the phenotypes observed in mouse and zebrafish models of PDCD6IP mutations in previous studies.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2703 GOLGA2 Elena Savva gene: GOLGA2 was added
gene: GOLGA2 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: GOLGA2 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: GOLGA2 were set to PMID: 30237576; 26742501
Phenotypes for gene: GOLGA2 were set to Neuromuscular disorder
Review for gene: GOLGA2 was set to AMBER
Added comment: PMID: 30237576 - One 11 year old patient with a homozygous PTC.
Patient had global dev delay, microcephaly, distal muscle weakness with joint contractures and elevated CK levels. Muscle biopsy showed dystrophin changes. MRI at 2 years old showed brain atrophy with thin corpus callosum and hypomyelination. No seizures or regression.

PMID: 26742501 - One infant with a homozygous PTC.
Patient had dev delay, seizures, microcephaly and muscular dystrophy. Zebrafish null model recapitulates the human phenotype with microcephaly and skeletal muscle disorganization.

Summary: 2 patients
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2687 PSMB1 Zornitza Stark gene: PSMB1 was added
gene: PSMB1 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: PSMB1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: PSMB1 were set to 32129449
Phenotypes for gene: PSMB1 were set to Intellectual disability; microcephaly
Review for gene: PSMB1 was set to AMBER
Added comment: Two siblings reported with a homozygous missense variant in this gene; supportive experimental evidence including zebrafish model.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2657 HIST1H4J Sue White gene: HIST1H4J was added
gene: HIST1H4J was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: HIST1H4J was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Publications for gene: HIST1H4J were set to 31804630
Phenotypes for gene: HIST1H4J were set to microcephaly; intellectual disability; dysmorphic features
Penetrance for gene: HIST1H4J were set to Complete
Review for gene: HIST1H4J was set to AMBER
Added comment: single case report but with functional evidence in zebrafish and phenotypic similarity to other HIST1H4C phenotype
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2627 UGDH Konstantinos Varvagiannis gene: UGDH was added
gene: UGDH was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: UGDH was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: UGDH were set to 32001716
Phenotypes for gene: UGDH were set to Epileptic encephalopathy, early infantile, 84 - MIM #618792
Penetrance for gene: UGDH were set to Complete
Review for gene: UGDH was set to GREEN
Added comment: Hengel et al (2020 - PMID: 32001716) report on 36 individuals with biallelic UGDH pathogenic variants.

The phenotype corresponded overall to a developmental epileptic encephalopathy with hypotonia, feeding difficulties, severe global DD, moderate or commonly severe ID in all. Hypotonia and motor disorder (incl. spasticity, dystonia, ataxia, chorea, etc) often occurred prior to the onset of seizures. A single individual did not present seizures and 2 sibs had only seizures in the setting of fever.

Affected subjects were tested by exome sequencing and UGDH variants were the only/best candidates for the phenotype following also segregation studies. Many were compound heterozygous or homozygous (~6 families were consanguineous) for missense variants and few were compound heterozygous for missense and pLoF variants. There were no individuals with biallelic pLoF variants identified. Parental/sib studies were all compatible with AR inheritance mode.

UGDH encodes the enzyme UDP-glucose dehydrogenase which converts UDP-glucose to UDP-glucuronate, the latter being a critical component of the glycosaminoglycans, hyaluronan, chondroitin sulfate, and heparan sulfate [OMIM].

Patient fibroblast and biochemical assays suggested a LoF effect of variants leading to impairment of UGDH stability, oligomerization or enzymatic activity (decreased UGDH-catalyzed reduction of NAD+ to NADH / hyaluronic acid production which requires UDP-glucuronate).

Attempts to model the disorder using an already developped zebrafish model (for a hypomorphic LoF allele) were unsuccessful as fish did not exhibit seizures spontaneously or upon induction with PTZ.

Modelling of the disorder in vitro using patient-derived cerebral organoids demonstrated smaller organoids due to reduced number of proliferating neural progenitors.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.1759 FBXW11 Alison Yeung gene: FBXW11 was added
gene: FBXW11 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: FBXW11 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Publications for gene: FBXW11 were set to PMID: 31402090
Phenotypes for gene: FBXW11 were set to Intellectual disability; developmental eye anomalies; digital anomalies
Review for gene: FBXW11 was set to GREEN
gene: FBXW11 was marked as current diagnostic
Added comment: Reported in >3 unrelated individuals
Functional studies in Zebrafish
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.1602 NCAPG2 Alison Yeung gene: NCAPG2 was added
gene: NCAPG2 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: NCAPG2 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: NCAPG2 were set to 30609410
Phenotypes for gene: NCAPG2 were set to Khan-Khan-Katsanis syndrome, MIM# 618460
Review for gene: NCAPG2 was set to GREEN
Added comment: Two families and functional evidence (zebrafish model).
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.1600 RIC1 Zornitza Stark gene: RIC1 was added
gene: RIC1 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: RIC1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: RIC1 were set to 31932796
Phenotypes for gene: RIC1 were set to Cleft lip; cataract; tooth abnormality; intellectual disability; facial dysmorphism; ADHD
Review for gene: RIC1 was set to AMBER
Added comment: Zebrafish model and consanguineous families but homozygous-by-descent.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.1293 SNRPE Chirag Patel gene: SNRPE was added
gene: SNRPE was added to Intellectual disability, syndromic and non-syndromic_GHQ_VCGS. Sources: Literature
Mode of inheritance for gene: SNRPE was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Phenotypes for gene: SNRPE were set to Hypotrichosis 11; OMIM #615059
Review for gene: SNRPE was set to AMBER
Added comment: 1 patient with de novo heterozygous missense SNRPE mutation, with non-syndromic primary microcephaly and intellectual disability. SNRPE encodes SmE and they showed that the microcephaly-linked SmE variant is unable to interact with the SMN complex and as a consequence fails to assemble into U snRNPs. This results in widespread mRNA splicing alterations in fibroblast cells derived from this patient. Similar alterations were observed in HEK293 cells upon SmE depletion that could be rescued by the expression of wild type but not mutant SmE. Depletion of SmE in zebrafish causes aberrant mRNA splicing alterations and reduced brain size, reminiscent of the patient microcephaly phenotype.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.1147 TDGF1 Chirag Patel edited their review of gene: TDGF1: Added comment: No OMIM number listed.

1 patient with TDGF1 mutation with midline anomalies of the forebrain. The mutant protein is inactive in a zebrafish rescue assay, indicating a role for TDGF1 in human midline and forebrain development.; Changed publications: PMID: 12073012; Changed mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Intellectual disability syndromic and non-syndromic v0.0 BRAF Zornitza Stark gene: BRAF was added
gene: BRAF was added to Intellectual disability, syndromic and non-syndromic_GHQ. Sources: Expert Review Green,Genetic Health Queensland
Mode of inheritance for gene: BRAF was set to Unknown