CRISPR-free RNA Base Editing Mediated PTC-readthrough Restores Hearing in Humanized Mice with Otof Nonsense Mutation [RNA-seq]

Today, the gene editing for hereditary deafness is becoming a promising field with global interest. Among them, AAV-mediated otoferlin overexpression is undoubtedly the most successful representative of deaf-related gene therapy. However, it remains challenging to realize physiological, endogenous pattern of otoferlin expression. Here, we firstly generated a humanized homology Otof c.1315C>T (p.R439X), equivalent to OTOF c.1273C>T (p.R425X) identified in human with profound hearing loss, nonsense mutation-caused deaf mice model. We then delivered the 'RESTART v3' system, which is a CRISPR-free RNA base editor for nonsense mutation suppression, into the cochlea of the mice model. We accomplished a physiological manner of otoferlin expression; moreover, the edited premature termination codon is precisely reversed back to the original amino acid. Using multiple assays to estimate hearing restoration, we identified a significant reduced thresholds of auditory brain response (ABR) and statistical enhanced amplitudes of behavioral auditory startle reflex (ASR) in the treated mice with the RNA editing system. Thus, our study presented a successful CRISPR-free RNA editing approach to significantly restore hereditary deafness carrying humanized Otof c.1315C>T (p.R439X) non-sense mutation, providing a great promise for future clinical translation. Overall design: we examined the global modification level of cochlear tissues with or without RESTART treatment to evaluate the off-target events.