Promotion of new expression of connexin gene Cx46 ( GJA3 ) in the cochlea after Cx26 ( GJB2 ) deficiency

Connexin 26 (Cx26, GJB2 ) mutations induce a high incidence of hearing loss, responsible for 70-80% of nonsyndromic hearing loss. The pathological changes mainly locate in the cochlea. However, the genetic changes in the cochlea after deficiency of Cx26 remail unclear, which hampers to fully understand the underlying deafness mechanisms to develop therapeutic interventions. In this study, we employed bulk Poly(A) RNA-Seq technique and found that Cx26 deficiency could cause many genes up-regulating and down-regulating in the cochlea. A significant change was that Cx46 ( GJA3 ), which is like Cx26 but expresses in the eye rather than the ear normally, had a remarkable upregulation and occurred in the cochlea after Cx26 deficiency. Immunofluorescent staining confirmed that Cx46 had expression in the cochlea and integrated into the gap junction networks among the cochlear supporting cells and in the cochlear lateral wall at the same location as Cx26 expression. Moreover, newly expressed Cx46 could be found in the same gap junctional plaques with Cx26. In addition, this promotion of new Cx46 expression is Cx26-specific; there was no promotion of Cx46 expression in the cochlea after deletion of Cx30 ( GJB6 ), which also predominantly co-expresses with Cx26 in the cochlea. These data demonstrated that Cx26 deficiency could promote Cx26-like Cx46 expression in the cochlea for compensation. This finding also provides a new cue for developing a genetic approach to treat this common hereditary deafness induced by GJB2 mutations.