Visual function restoration in a mouse model of Leber congenital amaurosis via therapeutic base editing.

Leber congenital amaurosis (LCA), an inherited retinal degeneration, causes severe visual dysfunction in children and adolescents. In patients with LCA, pathogenic variants, such as , are evident in specific genes, related to the functions of retinal pigment epithelium and photoreceptors. In contrast to the original Cas9, base editing tools can correct pathogenic substitutions without generation of DNA double-stranded breaks (DSBs). In this study, dual adeno-associated virus (AAV) vectors containing split adenine base editors (ABEs) with -splicing intein were prepared for base editing in retinal degeneration of 12 () mice, an animal model of LCA, possessing a nonsense mutation of C to T transition in the gene (p.R44X). Subretinal injection of AAV-ABE in retinal pigment epithelial cells of mice resulted in an A to G transition. The on-target editing was sufficient for recovery of wild-type mRNA, RPE65 protein, and light-induced electrical responses from the retina. Compared with our previous therapeutic editing strategies using Cas9 and prime editing, or with the gene transfer strategy shown in the current study, our results suggest that, considering the editing efficacy and functional recovery, ABEs could be a strong, reliable method for correction of pathogenic variants in the treatment of LCA.