A Novel VPS13B Mutation Identified by Whole-Exome Sequencing in Iranian Patients with Cohen Syndrome.

Cohen syndrome is caused by homozygous mutation in the vacuolar protein sorting 13 homolog B (VPS13B, also referred to as COH1) gene on chromosome 8q22.2. The VPS13B protein is involved in transmembrane transport, Golgi integrity, and neuritogenesis. Clinical manifestations of Cohen syndrome are mainly intellectual disability, developmental delay, facial abnormalities, and eye disorders. This study aimed to identify the causative variant in two unrelated families with Cohen syndrome. To this end, whole-exome sequencing (WES) was performed to identify the pathogenic variants. A homozygous nonsense variant (NM_017890:c.10369C > T; NP_060360.3: p.Q3457X) in the VPS13B gene was identified and co-segregated with all affected individuals in both families. In silico analysis highly suggested this variant as damaging for protein function. The present study increases the mutation spectrum of the VPS13B gene and could be useful in genetic diagnosis and genetic counseling in Cohen syndrome patients.