RNA-seq analysis for the Fluo-4 abnormal myofibers in aged mice

In a rapidly aging society, the age-related decline in muscle mass and force, sarcopenia, is an urgent medical and economic issue. However, the molecular mechanisms of sarcopenia are still largely unknown. Using Ca2+ indicator Fluo-4, we identified the presence of the Fluo-4 abnormal muscle fibers only in aged mice. The Fluo-4 abnormal muscle fibers had a tubular aggregate-like structure and morphologically abnormal mitochondria. Furthermore, a cluster of mitochondria-related genes, including mitochondrially-encoded genes, were downregulated in Ca2+-abnormal muscle fibers. These results indicate that the Fluo-4 abnormal muscle fibers are accumulated in aged mice, and that age-related mitochondrial abnormalities are more prominent in these fibers.