A decisive technical leap forward for personalized medicine to treat mitochondrial diseases

Mitochondrial diseases, arising from mutations in mitochondrial DNA (mtDNA), are a diverse group of disorders that lead to severe conditions. Expression of mtDNA is a prerequisite for ATP production by oxidative phosphorylation. Individual cells contain many hundred copies of mtDNA and mutated mtDNA coexist with wild type genomes, a phenomenon termed heteroplasmy, rendering the diagnosis and treatment of mtDNA-caused diseases challenging. In this issue of EMBO Molecular Medicine, Nash et al report an effective method to decrease heteroplasmy levels of disease-linked mtDNA in cardiac and skeletal muscles of a mouse model. For this, the team developed a novel strategy relying on a tandem mitochondrial-targeted zinc finger nuclease (tandem mtZFN) delivered via adeno-associated virus (AAV) particle to tissues. This approach significantly reduced the mtDNA mutation load, thereby shifting heteroplasmy levels and alleviating molecular phenotypes associated with the mutation. This breakthrough provides a promising new avenue for therapeutic interventions to treat mitochondrial diseases.