Novel Variant in CEP250 Causes Protein Mislocalization and Leads to Nonsyndromic Autosomal Recessive Type of Progressive Hearing Loss

Genetic hearing loss is the most common hereditary sensorial disorder. Though more than 120 genes associated with deafness have been identified, unveiled causative genes and variants of diverse types of hearing loss remain. Herein, we identified a novel nonsense homozygous variant in CEP250 (c.3511C>T; p.Gln1171Ter) among the family members with progressive moderate sensorineural hearing loss in nonsyndromic autosomal recessive type but without retinal degeneration. CEP250 encodes C-Nap1 protein belonging to the CEP protein family, comprising 30 proteins that play roles in centrosome aggregation and cell cycle progression. The nonsense variant in CEP250 led to the early truncating protein of C-Nap1, which hindered centrosome localization; heterologous expression of CEP250 (c.3511C>T) in NIH3T3 cells within cilia expression condition revealed that the truncating C-Nap1 (p.Gln1171Ter) was not localized at the centrosome but was dispersed in the cytosol. In the murine adult cochlea, Cep250 was expressed in the inner and outer hair cells. Knockout mice of Cep250 showed significant hair cell degeneration and progressive hearing loss in auditory brainstem response. In conclusion, a nonsense variant in CEP250 results in a deficit of centrosome localization and hair cell degeneration in the cochlea, which is associated with the progression of hearing loss in humans and mice.