Hearing loss and pathological changes in a mouse model harboring Gjb2 p.D50N variant

Abstract

The GJB2 gene, which encodes Connexin26 (Cx26), is the gene most strongly associated with hearing loss. However, the mechanism underlying the phenotypic heterogeneity of hearing loss caused by GJB2 variants remains unclear. Most existing studies have focused on conditional knockout mouse models, which typically exhibit severe to profound hearing loss and thus cannot explain the etiology of mild to moderate hearing loss. In this study, Gjb2^D50N/- mouse model carrying the Gjb2 p.D50N variant were established by combining CRISPR-Cas9 technology with crossbreeding with conditional knockout mice. Auditory Brainstem Response (ABR) testing showed that these model mice developed a mild to moderate progressive increase in hearing thresholds. Pathological analysis revealed fragmentation of gap junction plaques (GJPs) between supporting cells and a reduction in the uptake capacity of the glucose analog 2-NBDG by outer hair cells (OHCs) in Gjb2^D50N/- mice. However, no significant loss of hair cells (HCs) or spiral ganglion neurons (SGNs) was observed in the early stages. The study hypothesizes that early mild to moderate hearing loss associated with D50N variant may not result from cochlear structural abnormalities, but rather from insufficient energy supply to OHCs due to GJP dysfunction. This model provides a tool for understanding the hearing heterogeneity caused by different GJB2 variants and lays a foundation for the development of effective therapeutic strategies for mild to moderate hearing loss.

Keywords: CRISPR-Cas9; GJB2; Hearing loss; Metabolic product transport impairment.