Mechanisms of formation and accumulation of mitochondrial DNA deletions in aging neurons.
Age-dependent accumulation of partially deleted mitochondrial DNA (DeltamtDNA) has been suggested to contribute to aging and the development of age-associated diseases including Parkinson's disease. However, the molecular mechanisms underlying the generation and accumulation of DeltamtDNA have not been addressed in vivo. In this study, we have developed a mouse model expressing an inducible mitochondria-targeted restriction endonuclease (PstI). Using this system, we could trigger mtDNA double-strand breaks (DSBs) in adult neurons. We found that this transient event leads to the generation of a family of DeltamtDNA with features that closely resemble naturally-occurring mtDNA deletions. The formation of these deleted species is likely to be mediated by yet uncharacterized DNA repairing machineries that participate in homologous recombination and non-homologous end-joining. Furthermore, we obtained in vivo evidence that DeltamtDNAs with larger deletions accumulate faster than those with smaller deletions, implying a replicative advantage of smaller mtDNAs. These findings identify DSB, DNA repair systems and replicative advantage as likely mechanisms underlying the generation and age-associated accumulation of DeltamtDNA in mammalian neurons.
Pubmed ID: 19095717 RIS Download
Aging | Animals | Brain | DNA Breaks, Double-Stranded | DNA, Mitochondrial | Deoxyribonucleases, Type II Site-Specific | Doxycycline | Gene Expression Regulation | HeLa Cells | Humans | Mice | Mice, Inbred C57BL | Mice, Transgenic | Neurons | Organ Specificity | Sequence Deletion | Tetracycline