Homozygous Knockout of Cep250 Leads to a Relatively Late-Onset Retinal Degeneration and Sensorineural Hearing Loss in Mice

Abstract

Purpose Usher syndrome (USH) is the most common syndromic inherited retinal disease, causing retinitis pigmentosa and sensorineural hearing loss. We reported previously that a nonsense mutation in the centrosome-associated protein CEP250 gene (encoding C-Nap1) causes atypical USH in patients of Iranian Jewish origin. To better characterize CEP250 , we aimed to generate and study a knockout (KO) mouse model for Cep250 . Methods Mice heterozygous for a “knockout-first” Cep250 construct were generated and bred with Cre recombinase mice to generate the null allele and produce homozygous Cep250 KO mice. Retinal function was evaluated by full-field electroretinography (ffERG) at variable ages, and retinal structure changes were examined using histological analysis. Hearing thresholds were detected using auditory brainstem response (ABR) at the age of 20 months. Results The Cep250 KO mouse model was generated by activating a construct harboring a deletion of exons 6 and 7. At 6 months, the ffERG was normal, but it decreased gradually with age. For both photopic and scotopic ffERG responses, very low amplitudes were evident at 20 months. Histological analysis confirmed late-onset retinal degeneration. ABR tests illustrated that hearing threshold significantly increased at the age of 20 months. Conclusions Although most USH animal models have normal retinal function and structure, the Cep250 KO mouse model shows both retinal degeneration and hearing loss with a relatively late age of onset. This model may shed more light on CEP250 -associated retinal and hearing deficits and represents an efficient platform for the development of treatment modalities for USH. Translational Relevance Our study demonstrates better understanding of Cep250 -associated retinal and hearing disease in a mouse model and may help in developing more efficient gene therapy modalities.

RNA-Seq Analysis Reveals an Essential Role of the cGMP-PKG-MAPK Pathways in Retinal Degeneration Caused by Cep250 Deficiency

“…ERG also suggests the loss of retinal function in Cep250 knockout mice to some extent, although not markedly. Abu-Diab et al describe another homozygous knockout of Cep250 with a relatively late onset of retinal degeneration in which P180 did not reveal a reduced ONL thickness and ERG response; meanwhile, in P360, these parameters were diminished [8]. We suppose that the two reasons below may account for the differences between our studies.…”

“…The Cep250 gene encodes the C-Nap1 protein, an essential member of the centrosome activating element CEP family and a critical protein that regulates the adhesion of centrosomes during intermitosis [8,9]. Two members, CEP290 and CEP164, have been shown to have mutations that cause symptoms of RP [10,11].…”

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

“…Nevertheless, we cannot exclude the possibility that retinal degeneration begins at a later age. According to the literature, Cep250 knockout mice do not show visual phenotype at the ages of 3 and 6 months while their visual responses decrease at 12 and 20 months [ 33 , 34 ]. These findings support that visual phenotype may be age-dependent, and long-term follow-up is necessary.…”

“…In the present study, we did not perform the test of visual response in the knockout mice. Two reports on Cep250 knockout mice used the same knockout allele, which was generated by the deletion of exon 6 and 7, resulting in the early truncation of the 178 amino acid protein [ 33 , 34 ]. In our mice, we deleted exons 3–12 resulting in the early truncation of the 77 amino acid protein.…”