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Intellectual disability syndromic and non-syndromic v0.6203 TTL Bryony Thompson Marked gene: TTL as ready
Intellectual disability syndromic and non-syndromic v0.6203 TTL Bryony Thompson Gene: ttl has been classified as Amber List (Moderate Evidence).
Intellectual disability syndromic and non-syndromic v0.6203 TTL Bryony Thompson Classified gene: TTL as Amber List (moderate evidence)
Intellectual disability syndromic and non-syndromic v0.6203 TTL Bryony Thompson Gene: ttl has been classified as Amber List (Moderate Evidence).
Intellectual disability syndromic and non-syndromic v0.6123 TTL Mark Cleghorn gene: TTL was added
gene: TTL was added to Intellectual disability syndromic and non-syndromic. Sources: Other
Mode of inheritance for gene: TTL was set to BIALLELIC, autosomal or pseudoautosomal
Phenotypes for gene: TTL were set to complex neurodevelopmental disorder MONDO:0100038
Review for gene: TTL was set to AMBER
Added comment: TTL
Valentina Serpieri, University of Pavia
ESHG talk 1/6/24

FAM1 (Italy)
2 affected sisters born to consanguineous Pakistani parents
GDD, spastic tetraparesis, optic atrophy, brain anomalies resembling tubulinopathies (dysplasia of corpus callosum, basal ganglia, brainstem)
WES: homozygous TTL:c.1013G>A; p.Cys338Tyr in both affected sisters

Via genematcher
5 more families (9 individuals) w similar phenotypes and biallelic variants in TTL

FAM2 (Egypt): homozygous p.Arg46Pro
FAM3 (Egypt): homozygous p.Arg46Pro
FAM4 (Australia): homozygous p.Gln183Arg
FAM5 (France): homozygous p.Trp147*
FAM6 (Saudi Arabia): homozygous p.His243Tyr

TTL KO mice: death soon after birth, no overt malformations, but defects in organisation of cerebral layers

Functional work on patient fibroblasts
FAM1 – reduced quantity of TTL protein compared to control on Western blot, decreased function of TTL protein (increase in detyrosinated tubulin) compared to controls – infer LoF as mechanism
FAM3 – mentioned but no details
FAM4– mentioned but no details
Sources: Other
Intellectual disability syndromic and non-syndromic v0.4959 FOSL2 Krithika Murali gene: FOSL2 was added
gene: FOSL2 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: FOSL2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Publications for gene: FOSL2 were set to 36197437
Phenotypes for gene: FOSL2 were set to Neurodevelopmental disorder, MONDO:0700092, FOSL2-related
Review for gene: FOSL2 was set to GREEN
Added comment: PMID 36197437 Cospain et al 2022 report 11 individuals from 10 families with heterozygous PTC variants in exon 4/4 of the FOSL2 gene. All variants were predicted to escape NMD resulting in a truncated protein, with the truncation occurring proximal to the C-terminal domain (supportive functional studies).

In 10/11 families the variant occurred de novo in a single affected proband. In one family with 2 affected siblings, the variant was present in the siblings but absent in the unaffected parent likely due to gonadal mosaicism.

Clinical features included:
- Cutis aplasia congenital of the scalp (10/11)
- Tooth enamel hypoplasia and discolouration (8/9)
- Multiple other ectodermal features also noted e.g. small brittle nails, hypotrichosis/hypertrichosis, lichen sclerosis
- 5 individuals had cataracts (mostly bilateral, congenital/early childhood onset)
- 6/9 IUGR
- 5/9 postnatal growth restriction
- 7/9 developmental delay/ID (mild to severe)
- 5/7 ADHD/ASD
- 2/9 seizures
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4928 UBAP2L Konstantinos Varvagiannis gene: UBAP2L was added
gene: UBAP2L was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: UBAP2L was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Publications for gene: UBAP2L were set to 35977029
Phenotypes for gene: UBAP2L were set to Delayed speech and language development; Motor delay; Intellectual disability; Autistic behavior; Seizures; Microcephaly; Abnormality of head or neck; Short stature; Abnormality of the skeletal system
Penetrance for gene: UBAP2L were set to unknown
Review for gene: UBAP2L was set to GREEN
Added comment: Based on Jia et al (2022 - PMID: 35977029) speech, motor delay as well as ID are observed in individuals harboring de novo pLoF variants in UBAP2L. The gene encodes a regulator of the stress granule (SG) assembly. Extensive evidence is provided on the effect of variants as well as the role of UBAP2L and other genes for components and/or regulation of SG in pathogenesis of NDDs. Among others a Ubap2l htz deletion mouse model (behavioral and cognitive impairment, abnormal cortical development due to impaired SG assembly, etc). Data from 26 previous studies, aggregating 40,853 probands with NDDs (mostly DD/ID, also ASD) suggest enrichment for DNMs in UBAP2L or other genes previously known and further shown to be important for SG formation (incl. G3BP1/G3BP2, CAPRIN1).

Details provided below.

Not associated with any phenotype in OMIM, G2P or SysNDD.

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Jia et al (2022 - PMID: 35977029) describe 12 affected individuals with heterozygous de novo pLoF variants in UBAP2L.

Phenotype: Features included hypotonia, speech (11/11) and motor delay (8/12), ID (8/10 with formal evaluation), variable behavioral concerns (ADHD 5/11, ASD in 4/10, etc). Seizures were reported in 7/12 with 3/10 having a formal diagnosis of epilepsy. Few had microcephaly (3/10). Facial dysmorphisms were common (9/9) and included abnormal palpebral fissures, deep prominent concha, high broad forehead, hypertelorism, thin upper lip and mild synophrys (each in 4 or less individuals). Short stature or skeletal alterations were described in some (4/10 each).

Role of the gene: UBAP2L encodes an essential regulator of stress granule assembly. Stress granules are membraneless cytoplasmic compartments in eukaryotic cells, induced upon a variety of stressors and playing a role in regulation of gene expression.

Variants identified : 9 nonsense/frameshift UBAP2L variants and 3 splicing ones were reported, in all cases as de novo events, upon trio/quad exome sequencing. All were absent from gnomAD. There were no other causative variants.

Variant effect/studies (NM_014847.4 / NP_055662.3) :
- Minigene assays revealed that the 3 splice variants all resulted in out-of-frame exon skipping.
- In patient fibroblasts one of these splice variants was demonstrated to result to reduced protein levels.
- 8 of the 9 nonsense/frameshift variants were predicted to result to NMD.
- 1 nonsense variant (c.88C>T/p.Q30*) was shown to result to decreased protein expression in patient fibroblasts, with detection of the protein using an antibody for the C terminus but not the N terminus. Protein N-terminal sequencing confirmed that the protein lacked the N terminus, with utilization of an alternative start site (11 codons downstream).
- Generation of HeLa UBAP2L KO cell lines resulted in significant reduction of SG numbers which was also the case for 4 variants studied, under stress conditions.
- The protein has a DUF domain (aa 495-526) known to mediate interaction of UBAP2L with G3BP1 (a stress granule marker) with deletions of this domain leading to shuttling of UBAP2L from the cytoplasm to the nucleus. Truncating variants upstream of the DUF domain were shown to result in nuclear localization.

Mouse model :
- The authors generated Ubap2l KO model with hmz deletion of Ubap2l resulting in a lethal phenotype (2.6% survived) and htz deletion leading to behavioral issues (low preference for social novelty, anxious-like behaviors) and cognitive impairment.
- Ubap2l haploinsufficiency resulted in abnormal cortical development and lamination with reduction of neural progenitor proliferation.
- Ubap2l deficiency was shown to impair SG assembly during cortical development both under physiological stress conditions or upon utilization of an oxidative stress inducer.

Additional evidence of UBAP2L and SG overall in pathogenesis of NDDs:
- Based on DNMs from 40,853 individuals with NDDs from 26 studies (9,228 with ASD, 31,625 with DD/ID) the authors demonstrate significant excess of DNM in 31 genes encoding SG components, regulators or both, the latter being the case for UBAP2L and 2 further genes (G3BP1 and G3BP2 - both with crucial roles in SG assembly).
- Excess dn splice-site (N=3) and missense (N=5) variants in G3BP1 were observed in the above cohort [c.95+1G>A, c.353+1G>T, c.539+1G>A / p.S208C, R320C, V366M].
- Excess dn missense (N=7) variants in G3BP2 were observed in the above cohort [p.R13W, D151N, E158K, L209P, E399D, K408E, R438C].
- Generation of G3BP1 or G3BP2 KO HeLa cell lines and immunofluorescence upon use of oxidative stress inducer revealed significant reduction of stress granules.
- Generation of HeLa cell lines for 5 G3BP1 mutants (R78C*, R132I*, S208C*, R320C*, V366M) and 7 G3BP2 mutants (p.R13W*, D151N*, E158K, L209P*, E399D, K408E, R438C) revealed that several (those in asterisk) resulted in significantly fewer SG formation under oxidative stress compared to WT while the subcellular distribution of the proteins under stress was identical to WT.
- Among the identified genes for SG enriched for DNMs, CAPRIN1 was implicated in previous publications as a NDD risk gene with 3 dn missense SNVs reported (p.I373K, p.Q446H, p.L484P). CAPRIN1 binding to G3BP1/2 has been shown to promote SG formation. Significant reduction of SG was observed in CAPRIN1 KO HeLa lines. p.I373K abolished interaction with G3BP1/2 and disrupted SG formation.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.4163 ABHD16A Lucy Spencer gene: ABHD16A was added
gene: ABHD16A was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: ABHD16A was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: ABHD16A were set to PMID: 34587489
Phenotypes for gene: ABHD16A were set to Spastic paraplegia
Added comment: 11 individuals from 6 families with a complicated form of hereditary spastic paraplegia who carry bi-allelic deleterious variants in ABHD16A. Affected individuals present with a similar phenotype consisting of global developmental delay/intellectual disability, progressive spasticity affecting the upper and lower limbs, and corpus callosum and white matter anomalies. Immunoblot analysis on extracts from fibroblasts from four affected individuals demonstrated little to no ABHD16A protein levels compared to controls.
In 5 of the families the affected members were homozygous, 3 of these families were consanguineous. 2 families have the same variant- both families are French-Canadian.
4 missense variants, 1 frameshift, 1 nonsense.
From PMID: 34587489
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.1607 CARS Alison Yeung gene: CARS was added
gene: CARS was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: CARS was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: CARS were set to PMID: 30824121
Phenotypes for gene: CARS were set to Intellectual disability; microcephaly; brittle hair and nails
Review for gene: CARS was set to GREEN
gene: CARS was marked as current diagnostic
Added comment: Three reported unrelated families
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.1568 METTL5 Zornitza Stark Marked gene: METTL5 as ready
Intellectual disability syndromic and non-syndromic v0.1568 METTL5 Zornitza Stark Gene: mettl5 has been classified as Green List (High Evidence).
Intellectual disability syndromic and non-syndromic v0.1494 METTL5 Zornitza Stark Classified gene: METTL5 as Green List (high evidence)
Intellectual disability syndromic and non-syndromic v0.1494 METTL5 Zornitza Stark Gene: mettl5 has been classified as Green List (High Evidence).
Intellectual disability syndromic and non-syndromic v0.1493 METTL5 Zornitza Stark gene: METTL5 was added
gene: METTL5 was added to Intellectual disability, syndromic and non-syndromic_GHQ_VCGS. Sources: Expert list
Mode of inheritance for gene: METTL5 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: METTL5 were set to 29302074; 31564433
Phenotypes for gene: METTL5 were set to Intellectual developmental disorder, autosomal recessive 72, MIM# 618665
Review for gene: METTL5 was set to GREEN
Added comment: Three unrelated families and animal model.
Sources: Expert list
Intellectual disability syndromic and non-syndromic v0.1255 METTL23 Zornitza Stark Marked gene: METTL23 as ready
Intellectual disability syndromic and non-syndromic v0.1255 METTL23 Zornitza Stark Gene: mettl23 has been classified as Green List (High Evidence).
Intellectual disability syndromic and non-syndromic v0.419 METTL23 Chirag Patel Source Genetic Health Queensland was removed from METTL23.
Source Expert list was added to METTL23.
Mode of inheritance for gene METTL23 was changed from Unknown to BIALLELIC, autosomal or pseudoautosomal
Phenotypes for gene: METTL23 were changed from to Mental retardation, autosomal recessive 44; OMIM#615942
Publications for gene METTL23 were changed from PubMed: 24501276; 24626631 to PubMed: 24501276; 24626631
Intellectual disability syndromic and non-syndromic v0.418 METTL23 Chirag Patel reviewed gene: METTL23: Rating: GREEN; Mode of pathogenicity: None; Publications: PubMed: 24501276, 24626631; Phenotypes: Mental retardation, autosomal recessive 44, OMIM#615942; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
Intellectual disability syndromic and non-syndromic v0.0 METTL23 Zornitza Stark gene: METTL23 was added
gene: METTL23 was added to Intellectual disability, syndromic and non-syndromic_GHQ. Sources: Expert Review Green,Genetic Health Queensland
Mode of inheritance for gene: METTL23 was set to Unknown