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Early onset or syndromic epilepsy v2.208 TMEM106B Arina Puzriakova Phenotypes for gene: TMEM106B were changed from Leukodystrophy, hypomyelinating, 16 (MIM #617964) to Leukodystrophy, hypomyelinating, 16, OMIM:617964; Leukodystrophy, hypomyelinating, 16, MONDO:0054791
Early onset or syndromic epilepsy v2.207 TMEM106B Arina Puzriakova Tag missense tag was added to gene: TMEM106B.
Early onset or syndromic epilepsy v2.206 TMEM106B Arina Puzriakova Classified gene: TMEM106B as Amber List (moderate evidence)
Early onset or syndromic epilepsy v2.206 TMEM106B Arina Puzriakova Added comment: Comment on list classification: Rating Amber as only 2 individuals with seizures (both early-onset, before age 6 months) reported at present
Early onset or syndromic epilepsy v2.206 TMEM106B Arina Puzriakova Gene: tmem106b has been classified as Amber List (Moderate Evidence).
Early onset or syndromic epilepsy v2.205 TMEM106B Arina Puzriakova reviewed gene: TMEM106B: Rating: ; 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: 29186371, 29444210, 30643851, 32595021; Phenotypes: Leukodystrophy, hypomyelinating, 16 OMIM:617964; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Early onset or syndromic epilepsy v2.122 TMEM106B Konstantinos Varvagiannis gene: TMEM106B was added
gene: TMEM106B was added to Genetic epilepsy syndromes. Sources: Literature
Mode of inheritance for gene: TMEM106B was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Publications for gene: TMEM106B were set to 29186371; 29444210; 32595021
Phenotypes for gene: TMEM106B were set to Leukodystrophy, hypomyelinating, 16 (MIM #617964)
Penetrance for gene: TMEM106B were set to Complete
Mode of pathogenicity for gene: TMEM106B was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments
Review for gene: TMEM106B was set to AMBER
Added comment: 6 unrelated individuals with Leukodystrophy, hypomyelinating, 16 (MIM #617964) due to a recurrent TMEM106B variant have been reported to date in the literature (Simons et al 2017 - PMID: 29186371, Yan et al 2018 - PMID: 29444210, Ikemoto et al 2020 - PMID: 32595021).

While a 3 y.o. female described by Yan et al had DD (eg sitting at 9m, walking at 25m) with normal cognitive functioning, and a 38 y.o. female had borderline intellectual functioning (IQ 76), 4 affected individuals had ID. Among them, a 19 y.o. male with severe ID was also found to harbor a second de novo possibly damaging USP7 variant. Seizures have been reported in 2 unrelated subjects. [Clinical features are also summarized in table 1 - Ikemoto et al].

All harbored NM_001134232.2(TMEM106B):c.754G>A (p.Asp252Asn) which in almost all cases occurred as a de novo event. In a single case this variant was inherited from a mosaic parent with mild DD in infancy but normal cognition (reported by Simons et al).

As discussed by Ito et al (2018 - PMID: 30643851) the encoded protein is a structural component of the lysosomal membrane, playing a role on lysosome acidification. Acidity of the lysosome mediates multiple aspects of lysosomal function. Ito et al, using patient-derived fibroblasts assessed mRNA and protein levels. These were unaltered compared with controls. While TMEM106B had been previously shown to affect lysosome number, morphology and acidification, Ito et al demonstrated increased number of lysosomes in patient cells as well as impaired acidification compared to controls. As commented lysosomes are required for generation of myelin.

Recurrence of this missense variant, the presence of pLoF TMEM106B variants in gnomAD as well as the phenotypically normal Tmem106b null mice suggest that this variant may have a gain-of-function or dominant negative effect.

Genes for other forms of hypomyelinating lipodystrophy (incl. PLP1) have green rating in the ID panel.

Overall TMEM106B can be considered for the ID panel with green rating and the epilepsy panel with amber rating.
Sources: Literature
Early onset or syndromic epilepsy v1.100 USP7 Rebecca Foulger commented on gene: USP7: PMID:30679821: Fountain et al., 2019 report on the clinical and genetic spectrum of 16 new and 7 previously reported (by PMID:26365382) individuals with USP7 heterozygous de novo variants. The variants include 2 deletions, 3 nonsense, 3 splice site variants and 8 missense variants. Seizures are recorded in 10/22 patients. Note that Patients 18 and 20 harbor additional variants in TMEM106B and SLC2A1, Patient 19 also has a de novo heterozygous 102.5-kb mosaic loss of uncertain significance at 10q21.1.