title: The 8993 mtDNA mutation: heteroplasmy and clinical presentation in three families.
abstract: The point mutation at bp 8993 of human mtDNA in the ATPase 6 gene is associated with neurogenic weakness, ataxia and retinitis pigmentosa, and with subacute necrotizing encephalomyelopathy (Leigh disease) when present at high copy number. In this study we describe three new multiplex families with the ATPase 8993 mtDNA mutation and demonstrate a correlation between the percentage heteroplasmy of this mutation and the clinical phenotype. By combining this study with previous data we produce a graph of age of onset of symptoms versus percentage heteroplasmy of the mutation. Finally, we determine that ATP synthesis with NAD-linked substrates in cultured lymphoblast mitochondria from three patients with Leigh disease who had a high percentage heteroplasmy was on average 66% of the rate seen in control lymphoblast mitochondria. Similar rates are observed in lymphoblast mitochondria isolated from patients with Leigh disease due to complex I deficiency. This percentage appears to be independent of the rate of electron transport in mitochondria from patient cell lines with the mtDNA 8993 mutation.
authors.affiliation: Department of Biochemistry, University of Toronto, Ont., Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Tatuch
authors.forename: R A
authors.initials: RA
authors.lastname: Pagon
authors.forename: B
authors.initials: B
authors.lastname: Vlcek
authors.forename: R
authors.initials: R
authors.lastname: Roberts
authors.forename: M
authors.initials: M
authors.lastname: Korson
authors.forename: B H
authors.initials: BH
authors.lastname: Robinson
mesh_terms: D000251:Adenosine Triphosphatases / Q000172:deficiency / Q000235:genetics; D000255:Adenosine Triphosphate / Q000096:biosynthesis; D017668:Age of Onset; D001483:Base Sequence; D017931:DNA Primers; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism; D004579:Electron Transport; D015870:Gene Expression; D014644:Genetic Variation; D006801:Humans; D007223:Infant; D007888:Leigh Disease / Q000235:genetics* / Q000378:metabolism; D008214:Lymphocytes; D008297:Male; D017237:Mitochondrial Encephalomyopathies / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D010085:Oxidative Phosphorylation; D010375:Pedigree; D017354:Point Mutation; D012174:Retinitis Pigmentosa / Q000235:genetics
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases