Therapeutic adenine base editing corrects nonsense mutation and improves visual function in a mouse model of Leber congenital amaurosis

Leber congenital amaurosis (LCA) is an inherited retinal degeneration that causes severe visual dysfunction in children and adolescents. In patients with LCA, pathogenic variants are evident in specific genes, such as RPE65, which are related to the functions of retinal pigment epithelium and photoreceptors. Base editing confers a way to correct pathogenic substitutions without double-stranded breaks in contrast to the original Cas9. In this study, we prepared dual adeno-associated virus vectors containing the split adenine base editors with trans-splicing intein (AAV-ABE) for in vivo adenine base editing in retinal degeneration 12 (rd12) mice, an animal model of LCA, which possess a nonsense mutation of C to T transition in the Rpe65 gene (p.R44X). AAV-ABE induced an A to G transition in retinal pigment epithelial cells of rd12 mice when injected into the subretinal space. The on-target editing was sufficient to recover wild-type mRNA, RPE65 protein, and light-induced electrical responses of retinal tissues. We suggest adenine base editing to correct pathogenic variants in the treatment of LCA.