title: Mechanisms of formation and accumulation of mitochondrial DNA deletions in aging neurons.
abstract: 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.
authors.affiliation: Neuroscience Program, University of Miami School of Medicine, Miami, FL 33136, USA.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Fukui
authors.forename: Carlos T
authors.initials: CT
authors.lastname: Moraes
mesh_terms: D000375:Aging / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D004272:DNA, Mitochondrial / Q000378:metabolism*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D004318:Doxycycline / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009928:Organ Specificity / Q000187:drug effects; D017384:Sequence Deletion / Q000187:drug effects; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D004272:DNA, Mitochondrial; C024388:CTGCAG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific; D013752:Tetracycline; D004318:Doxycycline