title: High aggregate burden of somatic mtDNA point mutations in aging and Alzheimer's disease brain.
abstract: The mitochondrial theory of aging proposes that mitochondrial DNA (mtDNA) accumulates mutations with age, and that these mutations contribute to physiological decline in aging and degenerative diseases. Although a great deal of indirect evidence supports this hypothesis, the aggregate burden of mtDNA mutations, particularly point mutations, has not been systematically quantified in aging or neurodegenerative disorders. Therefore, we directly assessed the aggregate burden of brain mtDNA point mutations in 17 subjects with Alzheimer's disease (AD), 10 elderly control subjects and 14 younger control subjects, using a PCR-cloning-sequencing strategy. We found that brain mtDNA from elderly subjects had a higher aggregate burden of mutations than brain mtDNA from younger subjects. The average aggregate mutational burden in elderly subjects was 2 x 10(-4) mutations/bp. The bulk of these mutations were individually rare point mutations, 60% of which changed an amino acid. Control experiments ensure that these results were not due to artifacts arising from PCR error, mistaken identification of nuclear pseudogenes or ex vivo oxidation. Cytochrome oxidase activity correlated negatively with increasing mutational burden. These findings significantly bolster the mitochondrial theory of aging.
authors.affiliation: Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA. mtl2002@med.cornell.edu
authors.forename: Michael T
authors.initials: MT
authors.lastname: Lin
authors.forename: David K
authors.initials: DK
authors.lastname: Simon
authors.forename: Colette H
authors.initials: CH
authors.lastname: Ahn
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Kim
authors.forename: M Flint
authors.initials: MF
authors.lastname: Beal
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics*; D000544:Alzheimer Disease / Q000201:enzymology / Q000235:genetics*; D001921:Brain / Q000378:metabolism; D002648:Child; D003001:Cloning, Molecular; D004272:DNA, Mitochondrial / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000378:metabolism; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011544:Pseudogenes; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV