Altering the balance between healthy and mutated mitochondrial DNA.

Pathogenic mutations of the mitochondrial genome are frequently found to co-exist with wild-type mtDNA molecules, a state known as heteroplasmy. In most disease cases, the mutation is recessive with manifestation of a clinical phenotype occurring when the proportion of mutated mtDNA exceeds a high threshold. The concept of increasing the ratio of healthy to mutated mtDNA as a means to correcting the biochemical defect has received much attention. A number of strategies are highlighted in this article, including manipulation of the mitochondrial genome by antigenomic drugs or restriction endonucleases, zinc finger peptide-targeted nucleases and exercise-induced gene shifting. The feasibility of these approaches has been demonstrated in a number of models, however more work is necessary before use in human patients.