Gene editing in a Myo6 semi-dominant mouse model rescues auditory function

Myosin VI(MYO6) is an unconventional myosin that is vital for auditory and vestibular function. Pathogenic variants in the human MYO6 gene cause autosomal-dominant or-recessive forms of hearing loss. Effective treatments for Myo6 mutation causing hearing loss are limited. We studied whether adenoassociated virus (AAV)-PHP.eB vector-mediated in vivo delivery of Staphylococcus aureus Cas9 (SaCas9-KKH)-single-guide RNA (sgRNA) complexes could ameliorate hearing loss in a Myo6(WT/C442Y) mouse model that recapitulated the phenotypes of human patients. The in vivo editing efficiency of the AAVSaCas9-KKH-Myo6-g2 system on Myo6(C442Y) is 4.05% on average in Myo6(WT/C442Y) mice, which was similar to 17-fold greater than editing efficiency of Myo6(WT) alleles. Rescue of auditory function was observed up to 5 months post AAV-SaCas9-KKH-Myo6-g2 injection in Myo6(WT/C442Y) mice. Meanwhile, shorter latencies of auditory brainstem response (ABR) wave I, lower distortion product otoacoustic emission (DPOAE) thresholds, increased cell survival rates, more regular hair bundle morphology, and recovery of inward calcium levels were also observed in the AAV-SaCas9-KKH-Myo6-g2-treated ears compared to untreated ears. These findings provide further reference for in vivo genome editing as a therapeutic treatment for various semi-dominant forms of hearing loss and other semi-dominant diseases.