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Intellectual disability syndromic and non-syndromic v0.5528 TBC1D24 Zornitza Stark Marked gene: TBC1D24 as ready
Intellectual disability syndromic and non-syndromic v0.5528 TBC1D24 Zornitza Stark Gene: tbc1d24 has been classified as Green List (High Evidence).
Intellectual disability syndromic and non-syndromic v0.5528 TBC1D24 Zornitza Stark Phenotypes for gene: TBC1D24 were changed from to Developmental and epileptic encephalopathy 16, MIM# 615338; DOORS syndrome, MIM# 220500
Intellectual disability syndromic and non-syndromic v0.5527 TBC1D24 Zornitza Stark Publications for gene: TBC1D24 were set to
Intellectual disability syndromic and non-syndromic v0.5526 TBC1D24 Zornitza Stark Mode of inheritance for gene: TBC1D24 was changed from Unknown to BIALLELIC, autosomal or pseudoautosomal
Intellectual disability syndromic and non-syndromic v0.5508 TBC1D24 Kaitlyn Dianna Weldon reviewed gene: TBC1D24: Rating: GREEN; Mode of pathogenicity: None; Publications: 25719194; Phenotypes: familial infantile myoclonic epilepsy MONDO:0011506, DOORS syndrome MONDO:0009079; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
Intellectual disability syndromic and non-syndromic v0.2750 TBC1D2B Konstantinos Varvagiannis gene: TBC1D2B was added
gene: TBC1D2B was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: TBC1D2B was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: TBC1D2B were set to 32623794
Phenotypes for gene: TBC1D2B were set to Global developmental delay; Intellectual disability; Seizures; Gingival overgrowth; Behavioral abnormality; Abnormality of the mandible; Abnormality of brain morphology; Abnormality of the eye; Hearing abnormality
Penetrance for gene: TBC1D2B were set to Complete
Review for gene: TBC1D2B was set to AMBER
Added comment: Harms et al (2020 - PMID: 32623794) report on 3 unrelated individuals with biallelic pLoF TBC1D2B variants.

Features included cognitive impairment (mild ID in one case, regression at the age of 12y in another, hypotonia and delayed milestones in a third aged 8m), seizures (3/3 - variable age of onset) and/or gingival overgrowth (2/3 - prior to initiation of AEDs). Other findings included behavioral abnormalities, mandibular anomalies, abnormal brain imaging and ophthalmologic or (rarely) audiometric evaluations.

All were born to non-consanguineous couples and additional investigations were performed in some.

Variants were identified by WES or trio WGS, with Sanger confirmation/compatible segregation analyses.

In line with the pLoF variants, mRNA studies in fibroblasts from 2 unrelated affected individuals demonstrated significantly reduced (~80-90%) TBC1C2D mRNA levels compared to controls, restored following cycloheximide treatment. Protein was absent in patient fibroblasts.

TBC-domain containing GTPase activating proteins are known as key regulators of RAB GTPase activity. TBC1D2B was shown to colocalize with RAB5-positive endocytic vesicles. CRISPR/Cas9-mediated ko of TBC1D2B in HeLa cells suggested a role in EGF receptor endocytosis and decreased cell viability of TBC1D2B-deficient HeLa cells upon serum deprivation.

Genes encoding other TBC domain-containg GTPase-activating proteins, e.g. TBC1D7 and TBC1D20, TBC1D24 are associated with recessive neurodevelopmental disorders (with ID and/or seizures) and the pathophysiological defect in TBC1D2B-related disorder (deficit in vesicle trafficking and/or cell survival) is proposed to be similar to that of TBC1D24.

Overall this gene can be considered for inclusion with amber/green rating in the ID panel and green in epilepsy panel.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.0 TBC1D24 Zornitza Stark gene: TBC1D24 was added
gene: TBC1D24 was added to Intellectual disability, syndromic and non-syndromic_GHQ. Sources: Expert Review Green,Genetic Health Queensland
Mode of inheritance for gene: TBC1D24 was set to Unknown