MitoTALEN reduces mutant mtDNA load and restores tRNA Ala levels in a mouse model of heteroplasmic mtDNA mutation

Mutations in the mitochondrial DNA (mtDNA) are responsible for several metabolic disorders, commonly involving muscle and the central nervous system 1 . Because of the critical role of mtDNA in oxidative phosphorylation, the majority of pathogenic mtDNA mutations are heteroplasmic, co-existing with wild-type molecules 1 . Using a mouse model with a heteroplasmic mtDNA mutation 2 , we tested whether mitochondrial-targeted TALENs (mitoTALENs) 3 , 4 could reduce the mutant mtDNA load in muscle and heart. AAV9-mitoTALEN was administered via intramuscular, intravenous, and intraperitoneal injections. Muscle and heart were efficiently transduced and showed a robust reduction in mutant mtDNA, which was stable over time. The molecular defect, namely a decrease in transfer RNA Ala levels, was restored by the treatment. These results showed that mitoTALENs, when expressed in affected tissues, could revert disease-related phenotypes in mice.