Mitochondrial DNA–Deletion Mutations Accumulate Intracellularly to Detrimental Levels in Aged Human Skeletal Muscle Fibers

• Published in: American journal of human genetics Vol. 79; no. 3; pp. 469 - 480
• Main Authors: Bua, Entela, Johnson, Jody, Herbst, Allen, Delong, Bridget, McKenzie, Debbie, Salamat, Shahriar, Aiken, Judd M.
• Format: Journal Article
• Language: English
• Published: Chicago, IL Elsevier Inc 01.09.2006; University of Chicago Press; Cell Press; The American Society of Human Genetics
• Subjects: Aged; Aged, 80 and over; Aging; Aging - genetics; Biological and medical sciences; DNA, Mitochondrial - analysis; DNA, Mitochondrial - genetics; Electron Transport - genetics; Electron Transport Chain Complex Proteins - genetics; Electron Transport Complex IV - genetics; Female; General aspects. Genetic counseling; Genotype & phenotype; Humans; Male; Medical genetics; Medical sciences; Middle Aged; Mitochondria, Muscle - enzymology; Mitochondria, Muscle - genetics; Mitochondrial DNA; Muscle Fibers, Skeletal - chemistry; Muscle Fibers, Skeletal - cytology; Muscle Fibers, Skeletal - enzymology; Muscle, Skeletal - chemistry; Muscle, Skeletal - cytology; Muscle, Skeletal - enzymology; Musculoskeletal system; Mutation; Sequence Deletion; Succinate Dehydrogenase - genetics; Human; Deletion; Genetics; Mitochondrial DNA; Mutation; Striated muscle
• ISSN: 0002-9297; 1537-6605
• DOI: 10.1086/507132

Skeletal muscle–mass loss with age has severe health consequences, yet the molecular basis of the loss remains obscure. Although mitochondrial DNA (mtDNA)–deletion mutations have been shown to accumulate with age, for these aberrant genomes to be physiologically relevant, they must accumulate to high levels intracellularly and be present in a significant number of cells. We examined mtDNA-deletion mutations in vastus lateralis (VL) muscle of human subjects aged 49–93 years, using both histologic and polymerase-chain-reaction (PCR) analyses, to determine the physiological and genomic integrity of mitochondria in aging human muscle. The number of VL muscle fibers exhibiting mitochondrial electron-transport-system (ETS) abnormalities increased from an estimated 6% at age 49 years to 31% at age 92 years. We analyzed the mitochondrial genotype of 48 single ETS-abnormal, cytochrome c oxidase–negative/succinate dehydrogenase–hyperreactive (COX −/SDH ++) fibers from normal aging human subjects and identified mtDNA-deletion mutations in all abnormal fibers. Deletion mutations were clonal within a fiber and concomitant to the COX −/SDH ++ region. Quantitative PCR analysis of wild-type and deletion-containing mtDNA genomes within ETS-abnormal regions of single fibers demonstrated that these deletion mutations accumulate to detrimental levels (>90% of the total mtDNA).