Department of Neurology, University of Miami, Miller School of Medicine, Miami, Florida, United States of America.
PLoS Genet. 2013;9(12):e1003990. doi: 10.1371/journal.pgen.1003990. Epub 2013 Dec 5.
The accumulation of heteroplasmic mitochondrial DNA (mtDNA) deletions and single nucleotide variants (SNVs) is a well-accepted facet of the biology of aging, yet comprehensive mutation spectra have not been described. To address this, we have used next generation sequencing of mtDNA-enriched libraries (Mito-Seq) to investigate mtDNA mutation spectra of putamen from young and aged donors. Frequencies of the "common" deletion and other "major arc" deletions were significantly increased in the aged cohort with the fold increase in the frequency of the common deletion exceeding that of major arc deletions. SNVs also increased with age with the highest rate of accumulation in the non-coding control region which contains elements necessary for translation and replication. Examination of predicted amino acid changes revealed a skew towards pathogenic SNVs in the coding region driven by mutation bias. Levels of the pathogenic m.3243A>G tRNA mutation were also found to increase with age. Novel multimeric tandem duplications that resemble murine control region multimers and yeast ρ(-) mtDNAs, were identified in both young and aged specimens. Clonal ∼50 bp deletions in the control region were found at high frequencies in aged specimens. Our results reveal the complex manner in which the mitochondrial genome alters with age and provides a foundation for studies of other tissues and disease states.
异质体线粒体 DNA（mtDNA）缺失和单核苷酸变异（SNV）的积累是衰老生物学中公认的一个方面，但尚未描述全面的突变谱。为了解决这个问题，我们使用下一代测序技术对富含 mtDNA 的文库（Mito-Seq）进行了研究，以调查年轻和老年供体纹状体中的 mtDNA 突变谱。随着常见缺失的频率增加，其折叠倍数超过了主要弧缺失，老年组中“常见”缺失和其他“主要弧”缺失的频率显著增加。SNV 也随年龄增长而增加，在含有翻译和复制所需元件的非编码控制区积累速度最快。对预测的氨基酸变化的检查显示，由于突变偏向，编码区中的致病性 SNV 呈倾斜趋势。编码区 m.3243A>G tRNA 突变的水平也随着年龄的增长而增加。在年轻和老年标本中均发现了类似鼠类控制区多联体和酵母 ρ(-) mtDNA 的新型串联重复多联体。在控制区发现了高频率的克隆性约 50 bp 缺失，这些缺失在老年标本中发现。我们的结果揭示了线粒体基因组随年龄变化的复杂方式，并为其他组织和疾病状态的研究提供了基础。
