Among the hallmark characteristics associated with aging, POLG-mutant mice acquire severe and accelerated onset of sarcopenia, hearing loss, osteoporosis, graying of fur and alopecia, thymic involution, testicular atrophy, enlarged heart, loss of red blood cells, weight loss, as well as a marked reduction in lifespan (Trifunovic et al. 2004, Kujoth et al. 2005). This evidence concerns the gene POLG and sarcopenia.