USH2A and retinitis pigmentosa: This study was designed to demonstrate that the adenine and cytosine base editors (ABEs and CBEs) can be efficiently tested and applied to correct mutations in a large disease gene, USH2A. Mutations in USH2A cause retinitis pigmentosa (RP), and in cases where hearing loss is also present, the syndrome is termed Usher syndrome type 2 (USH2).29