Cell-specific delivery of GJB2 restores auditory function in mouse models of DFNB1 deafness and mediates appropriate expression in NHP cochlea

Abstract Mutations in the GJB2 gene cause the most common form of human hereditary hearing loss, known as DFNB1. GJB2 is expressed in two cell groups of the cochlea—epithelial cells of the organ of Corti and fibrocytes of the inner sulcus and lateral wall—but not by sensory hair cells or neurons. Attempts to treat mouse models of DFNB1 with AAV vectors mediating nonspecific Gjb2 expression have not substantially restored function, perhaps because inappropriate expression in hair cells and neurons could compromise their electrical activity. Here, we used genomic chromatin accessibility profiling to identify candidate gene regulatory elements (GREs) that could drive cell-type-specific expression of Gjb2 in the cochlea. HA-tagged GJB2, delivered to a conditional knockout model in an AAV vector with GRE control of expression, was localized to the appropriate cell types, prevented the cochlear degeneration observed in untreated knockout mice, and partially rescued hearing sensitivity. In a Gjb2 partial knockdown mouse model, such exogenous GJB2 prevented degeneration and completely restored hearing sensitivity. We tested control of expression by these GREs in nonhuman primate cochleas and found that vector-delivered human GJB2.HA was located in the appropriate cell types and caused little or no reduction in hearing sensitivity. Together, these findings suggest that GRE-mediated expression of GJB2 could prevent hearing loss in DFNB1 patients. Competing Interest Statement M.V.I. is a consultant to and holds equity in Skylark Bio. K.D.K. is an employee and holds equity in Skylark Bio. Y.L. is a consultant to Skylark Bio. D.P.C. holds equity in Skylark Bio. M.V.I., K.T.B., S.H., M.A.N., C.W.P., E.C.G., M.E.G., and D.P.C. are inventors on patent application US20230340038A1, Recombinant adeno associated virus (raav) encoding gjb2 and uses thereof. The inventors and Harvard Medical School may benefit from the potential commercialization of the technology described in this manuscript.