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

Abstract

Leber congenital amaurosis (LCA), an inherited retinal degen-eration, causes severe visual dysfunction in children and adoles-cents. In patients with LCA, pathogenic variants, such as RPE65, are evident in specific genes, related to the functions of retinal pigment epithelium and photoreceptors. In contrast to the orig-inal Cas9, base editing tools can correct pathogenic substitu-tions without generation of DNA double-stranded breaks (DSBs). In this study, dual adeno-associated virus (AAV) vec-tors containing split adenine base editors (ABEs) with trans- splicing intein were prepared for in vivo base editing in retinal degeneration of 12 (rd12) mice, an animal model of LCA, pos-sessing a nonsense mutation of C to T transition in the Rpe65 gene (p.R44X). Subretinal injection of AAV-ABE in retinal pigment epithelial cells of rd12 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 thera-peutic 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.