Deciphering enhancers of hearing loss genes for efficient and targeted gene therapy of hereditary deafness.

Hereditary hearing loss accounts for about 60% of congenital deafness. Although adeno-associated virus (AAV)-mediated gene therapy shows substantial potential for treating genetic hearing impairments, there remain significant concerns regarding the specificity and safety of AAV vectors. The sophisticated nature of the cochlea further complicates the challenge of precisely targeting gene delivery. Here, we introduced an AAV-reporter-based in vivo transcriptional enhancer reconstruction (ARBITER) workflow, enabling efficient and reliable dissection of enhancers. With ARBITER, we successfully demonstrated that the conserved non-coding elements (CNEs) within the gene locus collaboratively regulate the expression of Slc26a5, which was further validated using knockout mouse models. We also assessed the potential of identified enhancers to treat hereditary hearing loss by conducting gene therapy in Slc26a5 mutant mice. Based on the original Slc26a5 enhancer with limited efficiency, we engineered a highly efficient and outer hair cell (OHC)-specific enhancer, B8, which successfully restored hearing of Slc26a5 knockout mice.