Report of the first patient with a homozygous OTUD7A variant responsible for epileptic encephalopathy and related proteasome dysfunction.

Fiche publication

Date publication

janvier 2020

Journal

Clinical genetics

Auteurs

Membres identifiés du Cancéropôle Est :
Pr FAIVRE Laurence , Pr THAUVIN-ROBINET Christel , Dr DUPLOMB-JEGO Laurence

Tous les auteurs :
Garret P, Ebstein F, Delplancq G, Dozieres-Puyravel B, Boughalem A, Auvin S, Duffourd Y, Klafack S, Zieba BA, Mahmoudi S, Singh KK, Duplomb L, Thauvin-Robinet C, Costa JM, Krüger E, Trost D, Verloes A, Faivre L, Vitobello A

Lien Pubmed

https://www.ncbi.nlm.nih.gov/pubmed/31997314

Résumé

Heterozygous microdeletions of chromosome 15q13.3 (MIM: 612001) show incomplete penetrance and are associated with a highly variable phenotype that may include intellectual disability, epilepsy, facial dysmorphism and digit anomalies. Rare patients carrying homozygous deletions show more severe phenotypes including epileptic encephalopathy, hypotonia and poor growth. For years, CHRNA7 (MIM: 118511), was considered the candidate gene that could account for this syndrome. However, recent studies in mouse models have shown that OTUD7A/CEZANNE2 (MIM: 612024), which encodes for an ovarian tumor (OTU) deubiquitinase, should be considered the critical gene responsible for brain dysfunction. In this study, a patient presenting with severe global developmental delay, language impairment and epileptic encephalopathy was referred to our genetics center. Trio exome sequencing (tES) analysis identified a homozygous OTUD7A missense variant (NM_130901.2:c.697C > T), predicted to alter an ultra-conserved amino acid, p.(Leu233Phe), lying within the OTU catalytic domain. Its subsequent segregation analysis revealed that the parents, presenting with learning disability, and brother were heterozygous carriers. Biochemical assays demonstrated that proteasome complex formation and function were significantly reduced in patient-derived fibroblasts and in OTUD7A knockout HAP1 cell line. We provide evidence that biallelic pathogenic OTUD7A variation is linked to early-onset epileptic encephalopathy and proteasome dysfunction. This article is protected by copyright. All rights reserved.