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

Abstract

Although genetic factors contribute to almost half of all deafness cases, treatment options for genetic deafness are limited1–5. 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.

Identification of four TMC1 variations in different Chinese families with hereditary hearing loss

“…By injection of Cas9:guide RNA:lipid complexes targeting the Bth allele into the cochlea of neonatal Bth mice, Gao et al. () reduced the progressive hearing loss of Bth mice, providing a possible strategy to rescue auditory function of human patients with TMC1 variants.…”

“…This dominant variant can cause progressive and profound hearing loss in humans. Recently, gene therapy in the Bth mouse model by delivery of genome editing agents was shown to be effective (Xue Gao et al., ). The successful treatment of the Bth mouse suggests possible strategies to correct TMC1 variants and potentially rescue hearing in human patients.…”

Debugging the genetic code: Non-viral in vivo delivery of therapeutic genome editing technologies

“…Gao et al used the Cas9 system for the treatment of autosomal dominant hearing loss using cationic lipids. The deafness associated allele in Tmc1 was targeted in a Beethoven mouse model by injection of lipid-RNP complexes into the cochlea of neonatal pups with a reported ~2% disruption of the dysfunctional Tmc1 allele [31]. …”

An ode to gene edits that prevent deafness

“…Excitons comprise an electron and a hole (the absence of an electron), and have two possible states: singlet and triplet. Triplet states were thought to be poor emitters of light, but, on page 189, Becker et al 1 report that semiconductors known as lead halide perovskites have bright triplet excitons. The results could signify a breakthrough in optoelectronics because triplet states are three times more abundant than singlet states 2 and currently limit the efficiency of organic light-emitting diodes 3 .…”