TY - JOUR T1 - Single AAV-mediated mutation replacement genome editing in limited number of photoreceptors mediate marked visual restoration JF - bioRxiv DO - 10.1101/552653 SP - 552653 AU - Koji M Nishiguchi AU - Kosuke Fujita AU - Fuyuki Miya AU - Shota Katayama AU - Toru Nakazawa Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/12/01/552653.abstract N2 - Supplementing wildtype copies of functionally defective genes (gene supplementation) with adeno-associated virus (AAV) is a strategy being explored clinically for various retinal dystrophies. However, the low cargo limit of this vector (∼5,000 bps) allows its use in only a fraction of patients with mutations in relatively small pathogenic genes. To overcome this issue, we developed a single AAV platform that allows local replacement of a mutated sequence with its wildtype counterpart, based on combined CRISPR-Cas9 and micro-homology-mediated end-joining (MMEJ). In blind mice, the mutation replacement rescued ∼10% of photoreceptors, resulting in an incredible ∼10,000-fold improvement in light sensitivity and increasing visual acuity to ∼60% of the controls. Surprisingly, these effects were comparable to restoration mediated by gene supplementation, which targets ∼70% of photoreceptors. This strategy paves the way for treatment of inherited disorders caused by mutations in larger genes, for which conventional gene supplementation therapy is not currently feasible. ER -