Abstract

Mutations in mitochondrial DNA and their role in sarcopenia is suspected, but not yet fully understood. We hypothesized that mitochondrial DNA deletions accumulate by clonal expansion in certain muscle fibers and contribute to a cytochrome c oxidase negative phenotype and subsequently, these abnormal fibers factor in the development of myopathy. We examined muscle sections from wild type and mitochondrial mutator mice, which express a defective proofreading version of polymerase gamma. The polymerase gamma mutator mice develop a premature aging phenotype and their muscles show electron transport chain abnormalities by 13-15 months. Serial muscle sections were stained for cytochrome oxidase activity and succinate dehydrogenase. Abnormal fibers were identified as cytochrome c oxidase negative fibers with increased succinate dehydrogenase staining, as this indicated respiratory chain deficiency. Fibers identified in multiple sections were collected by laser capture microdissection and prepared for PCR amplification. We are currently working on whole mitochondrial genome amplification of single cells captured by laser capture microdissection using overlapping primers.