<p>(A). Comparison of mean number of germline mutations in wt and <i>Polg</i> mice at young and old age (n = 31 for young wt, n = 8 for young <i>Polg</i>, n = 44 for old wt and n = 14 for old <i>Polg</i>). Error bars, mean ± SEM. Asterisk indicates a significant increase in the number of mutations per tissue in old <i>Polg</i> compared to the old wt (P < 0.05, Student’s t-test). (B). Mean heteroplasmy levels of non-synonymous germline mutations with ≥2% heteroplasmy in <i>Polg</i> mice (mean ± SEM; asterisk, P < 0.05, Student’s t-test). (C) Pie charts showing gene distributions of non-synonymous germline mutations in young <i>Polg</i> mice (2 months, left) and old <i>Polg</i> mice (9 months, right). (D) Bar graphs representing the mean heteroplasmy levels of non-synonymous germline mutations in protein-coding and RNA-coding genes in <i>Polg</i> mice (asterisks, P < 0.05, Student’s t-test). (E) Pie charts showing the distribution of shared and unique mtDNA mutations detected in single skin fibroblast (SF) clones in young and old <i>Polg</i> mice. (F) Mean heteroplasmy changes for non-synonymous somatic mutations with ≥15% heteroplasmy in <i>Polg</i> mice. Error bars, mean ± SEM. Asterisk, P < 0.05, Student’s t-test. (G) Changes in number of non-synonymous somatic mutations with heteroplasmy levels ≥ 15% among different gene types with <i>Polg</i> mice aging. Error bars, mean ± SEM. Asterisks, P < 0.05, Student’s t-test.</p
