MitoTALEN: A General Approach to Reduce Mutant mtDNA Loads and Restore Oxidative Phosphorylation Function in Mitochondrial Diseases

Mol Ther. 2015 Oct;23(10):1592-9. doi: 10.1038/mt.2015.126. Epub 2015 Jul 10.


We have designed mitochondrially targeted transcription activator-like effector nucleases or mitoTALENs to cleave specific sequences in the mitochondrial DNA (mtDNA) with the goal of eliminating mtDNA carrying pathogenic point mutations. To test the generality of the approach, we designed mitoTALENs to target two relatively common pathogenic mtDNA point mutations associated with mitochondrial diseases: the m.8344A>G tRNA(Lys) gene mutation associated with myoclonic epilepsy with ragged red fibers (MERRF) and the m.13513G>A ND5 mutation associated with MELAS/Leigh syndrome. Transmitochondrial cybrid cells harbouring the respective heteroplasmic mtDNA mutations were transfected with the respective mitoTALEN and analyzed after different time periods. MitoTALENs efficiently reduced the levels of the targeted pathogenic mtDNAs in the respective cell lines. Functional assays showed that cells with heteroplasmic mutant mtDNA were able to recover respiratory capacity and oxidative phosphorylation enzymes activity after transfection with the mitoTALEN. To improve the design in the context of the low complexity of mtDNA, we designed shorter versions of the mitoTALEN specific for the MERRF m.8344A>G mutation. These shorter mitoTALENs also eliminated the mutant mtDNA. These reductions in size will improve our ability to package these large sequences into viral vectors, bringing the use of these genetic tools closer to clinical trials.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / metabolism
  • Deoxyribonucleases / metabolism
  • Electron Transport Complex I / genetics
  • Electron Transport Complex I / metabolism
  • Gene Dosage
  • Gene Expression
  • Gene Order
  • Genetic Therapy
  • Genetic Vectors* / genetics
  • Humans
  • Hydrolysis
  • Mitochondria / genetics
  • Mitochondria / metabolism
  • Mitochondrial Diseases / genetics
  • Mitochondrial Diseases / metabolism
  • Mitochondrial Diseases / therapy
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism
  • Mutation*
  • Oxidative Phosphorylation*
  • Point Mutation
  • Protein Transport
  • Transcription Factors / metabolism


  • DNA, Mitochondrial
  • Mitochondrial Proteins
  • Transcription Factors
  • MT-ND5 protein, human
  • Deoxyribonucleases
  • Electron Transport Complex I