Oligomycin induces a decrease in the cellular content of a pathogenic mutation in the human mitochondrial ATPase 6 gene

AT --> G mutation at position 8993 in human mitochondrial DNA is associated with the syndrome neuropathy, ataxia, and retinitis pigmentosa and with a maternally inherited form of Leigh's syndrome. The mutation substitutes an arginine for a leucine at amino acid position 156 in ATPase 6, a component of the F-0 portion of the mitochondrial ATP synthase complex Fibroblasts ha rboring high levels of the T8993G mutation have decreased ATP synthesis act ivity, hut do not display any growth defect under standard culture conditio ns, Combining the notions that cells with respiratory chain defects grow po orly in medium containing galactose as the major carbon source, and that re sistance to oligomycin, a mitochondrial inhibitor, is associated with mutat ions in the ATPase 6 gene in the same transmembrane domain where the T8993G amino acid substitution is located, we created selective culture condition s using galactose and oligomycin that elicited a pathological phenotype in T8993G: cells and that allowed for the rapid selection of wild-type over T8 993G mutant cells. We then generated cytoplasmic hybrid clones containing h eteroplasmic levels of the T8993G mutation, and showed that selection in ga lactose-oligomycin caused a significant increase in the fraction of wild-ty pe molecules (from 16 to 28%) in these cells.