A novel base editor SpRY-ABE8e^F148A mediates efficient A-to-G base editing with a reduced off-target effect

Adenine base editors (ABEs) can mediate two transition mutations, A-to-G and T-to-C, which are suitable for repairing G·C-to-T·A pathogenic variants, the most significant human pathogenic variant. By combining the protospacer adjacent motif (PAM)less SpRY nuclease with F148A-mutated TadA∗8e deaminase, we developed a new editor, SpRY-ABE8e^F148A, in this study, which has narrowed the editing range and enhanced A-to-G editing efficiency in most sites with NR/YN PAMs. Furthermore, compared with SpRY-ABE8e, SpRY-ABE8e^F148A significantly decreased the RNA off-target effect. Therefore, this engineered base editor, SpRY-ABE8e^F148A, expanded the editing scope and improved the editing precision for G·C-to-T·A pathogenic variants. Besides, we established a bioinformatics tool, adenine base-repairing sgRNA database of pathogenic variant (ARDPM), to facilitate the development of precise editors.