Editor’s summary
Mutations in MIR96, a microRNA expressed in inner hair cells, result in autosomal dominant deafness-50 (DFNA50), a form of nonsyndromic hearing loss. Here, Zhu et al. optimized a CRISPR-Cas9 system to specifically erase mutations in MIR96 and show that adeno-associated virus (AAV) delivery of this editing system to the cochleae of presymptomatic and symptomatic mice carrying one of the human mutations (the 14C>A mutation) promoted hair cell survival and improved hearing long term. These results suggest that microRNA editing might be a promising strategy to preserve auditory function in patients with DFNA50. —Daniela Neuhofer
Abstract
Mutations in microRNA-96 (MIR96) cause autosomal dominant deafness-50 (DFNA50), a form of delayed-onset hearing loss. Genome editing has shown efficacy in hearing recovery through intervention in neonatal mice, yet editing in the adult inner ear is necessary for clinical applications, which has not been done. Here, we developed a genome editing therapy for the MIR96 mutation 14C>A by screening different CRISPR systems and optimizing Cas9 expression and the sgRNA scaffold for efficient and specific mutation editing. AAV delivery of the KKH variant of Staphylococcus aureus Cas9 (SaCas9-KKH) and sgRNA to the cochleae of presymptomatic (3-week-old) and symptomatic (6-week-old) adult Mir9614C>A/+ mutant mice improved hearing long term, with efficacy increased by injection at a younger age. Adult inner ear delivery resulted in transient Cas9 expression without evidence of AAV genomic integration, indicating the good safety profile of our in vivo genome editing strategy. We developed a dual-AAV system, including an AAV-sgmiR96-master carrying sgRNAs against all known human MIR96 mutations. Because mouse and human MIR96 sequences share 100% homology, our approach and sgRNA selection for efficient and specific hair cell editing for long-term hearing recovery lay the foundation for the development of treatment for patients with DFNA50 caused by MIR96 mutations.