Mitochondrial adenine base editing of mouse somatic tissues via adeno-associated viral delivery

The development of adenine base editing in mitochondria, alongside cytidine base editing, has significantly expanded the genome engineering capabilities of the mitochondrial DNA. We tested the recent advancements in adenine base editing technology using optimised TALEs targeting genes Mt-Cytb, Mt-CoII and Mt-Atp6 in mouse cells, and observed successful A:T to G:C conversions within the target windows of each gene. We then used the best-performing Mt-Atp6 pairs for systemic AAV9 delivery to neonatal mice and quantified editing in somatic tissues after 4 weeks and 6 months. Adenine editing was low at 4 weeks and increased only modestly after 6 months, indicating that prolonged exposure alone is insufficient to overcome the limited activity of the editor architectures tested here in vivo. These findings establish the feasibility of AAV-delivered mitochondrial A-to-G editing while defining important limitations that require further optimisation.