Bua Entela, Johnson Jody, Herbst Allen, Delong Bridget, McKenzie Debbie, Salamat Shahriar, Aiken Judd M
Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, WI 53706, USA.
Am J Hum Genet. 2006 Sep;79(3):469-80. doi: 10.1086/507132. Epub 2006 Jul 7.
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).
骨骼肌质量随年龄增长而流失会带来严重的健康后果，但其流失的分子基础仍不清楚。尽管已表明线粒体DNA（mtDNA）缺失突变会随年龄积累，但要使这些异常基因组具有生理相关性，它们必须在细胞内积累到高水平并存在于大量细胞中。我们使用组织学和聚合酶链反应（PCR）分析，检测了49至93岁人类受试者股外侧肌（VL）中的mtDNA缺失突变，以确定衰老人类肌肉中线粒体的生理和基因组完整性。表现出线粒体电子传递系统（ETS）异常的VL肌纤维数量从49岁时估计的6%增加到92岁时的31%。我们分析了来自正常衰老人类受试者的48根单一ETS异常、细胞色素c氧化酶阴性/琥珀酸脱氢酶高反应性（COX-/SDH++）纤维的线粒体基因型，并在所有异常纤维中鉴定出mtDNA缺失突变。缺失突变在一根纤维内是克隆性的，并且与COX-/SDH++区域相关。对单根纤维ETS异常区域内野生型和含缺失的mtDNA基因组进行定量PCR分析表明，这些缺失突变积累到了有害水平（占总mtDNA的>90%）。
