Intravitreal adenine base editing of RS1 improves vision in a preclinical mouse model of retinoschisis

Base editing offers high potential for treating genetic diseases, particularly those with limited treatment options. Retinoschisis, an X-linked retinal disease causing progressive vision loss, currently lacks effective therapies. We identified the c.422G>A (p.Arg141His) variant of the RS1 gene in six male patients with retinoschisis and generated a humanized mouse model harboring this variant, which mimicked the disease phenotype. By testing adenine base editors and single-guide RNAs, we identified an optimal combination of high editing efficiency and low bystander editing. Intravitreal injection of adeno-associated viral vectors encoding this adenine base editor achieved ∼40% editing efficiency in all retinal cells, restored retinal layer integrity, and preserved visual functions in 2-week-old male hemizygous mice. These mice exhibited retinal layer splitting at baseline, further validating the model. This study demonstrates a strategy for identifying effective base editing tools for clinical use through the preclinical evaluation of humanized mouse lines with patient-derived mutations and highlights their applicability in treating genetic diseases.