T8993G Mutation Research Articles

Oligomycin Induces a Decrease in the Cellular Content of a Pathogenic Mutation in the Human Mitochondrial ATPase 6 Gene

A T --> 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 F0 portion of the mitochondrial ATP synthase complex. Fibroblasts harboring high levels of the T8993G mutation have decreased ATP synthesis activity, but do not display any growth defect under standard culture conditions. Combining the notions that cells with respiratory chain defects grow poorly in medium containing galactose as the major carbon source, and that resistance to oligomycin, a mitochondrial inhibitor, is associated with mutations in the ATPase 6 gene in the same transmembrane domain where the T8993G amino acid substitution is located, we created selective culture conditions using galactose and oligomycin that elicited a pathological phenotype in T8993G cells and that allowed for the rapid selection of wild-type over T8993G mutant cells. We then generated cytoplasmic hybrid clones containing heteroplasmic levels of the T8993G mutation, and showed that selection in galactose-oligomycin caused a significant increase in the fraction of wild-type molecules (from 16 to 28%) in these cells.

Mitochondrial disease associated with the T8993G mutation of the mitochondrial ATPase 6 gene: a clinical, biochemical, and molecular study in six families

AIMTo contribute to the establishment of a rational clinical, neuroradiological, and molecular approach to neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP) and maternally inherited Leigh’s syndrome (MILS).METHODS AND RESULTSThe...

Inheritance and expression of mitochondrial DNA point mutations

An important feature of the mitochondrial genom is the occurrence of heteroplasmy and the possibility for transmission to the offspring of various proportions of wild-type and mutated mtDNA. We have investigated the proportion of the tRNALys A8344G mutation, the tRNALeu(UUR) A3243G mutation, and the ATPase 6 T8993G mutation in patients with MERRF, MELAS, and Leigh's syndrome and their maternal relatives. The level of mutated mtDNA in the offspring of carriers of the tRNALys mutation is correlated to the level in lymphocytes in the mother and seems to be transmitted by an essentially random mechanism where only a few mtDNA copies are founders of the mitochondrial genom in the offspring and the probability that the mutation is not transmitted to the offspring is high when the mothers carriers predominantly wild-type mtDNA. However, we found age-related differences in the distribution of mutated mtDNA in carriers of the tRNALys and tRNALeu mutations, which have to be considered before levels of mutated mtDNA are used for prediction of prognosis and transmission of a disorder.