Treatment of autosomal dominant hearing loss by in vivo delivery of genome editing agents

Although genetic factors contribute to almost half of all deafness cases, treatment options for genetic deafness are limited(1–5). We developed a genome editing approach to target a dominantly inherited form of genetic deafness. Here we show that cationic lipid-mediated in vivo delivery of Cas9:guide RNA complexes can ameliorate hearing loss in a mouse model of human genetic deafness. We designed and validated in vitro and in primary fibroblasts genome editing agents that preferentially disrupt the dominant deafness-associated allele in the Tmc1 (transmembrane channel-like 1) Beethoven (Bth) mouse model, even though the mutant Bth allele differs from the wild-type allele at only a single base pair. Injection of Cas9:guide RNA:lipid complexes targeting the Bth allele into the cochlea of neonatal Bth/+ mice substantially reduced progressive hearing loss. We observed higher hair cell survival rates and lower auditory brainstem response (ABR) thresholds in injected ears compared with uninjected ears or ears injected with complexes that target an unrelated gene. Enhanced acoustic reflex responses were observed among injected compared to uninjected Bth/+ animals. These findings suggest protein:RNA complex delivery of target gene-disrupting agents in vivo as a potential strategy for the treatment of some autosomal dominant hearing loss diseases.