Expression of mitochondria-targeted SOD1 in skeletal muscle of normal mice.

<p>(<b>A</b>) Normal muscle fibers transfected with mt-SOD1-Dendra or mt-SOD1<sup>G93A</sup>-Dendra. Both proteins preferentially target to mitochondria. 90% of fibers expressing mt-SOD1<sup>G93A</sup>-Dendra show aggregated fluorescent proteins inside mitochondria (n=73), while not a single fiber expressing wild type mt-SOD1-Dendra has protein aggregates (n=36). (<b>B</b>) Enlarged boxes (<b>a1</b> and <b>a2</b>) taken from the mt-SOD1<sup>G93A</sup>-Dendra fiber show that fiber regions (1, 2 and 3) with fluorescent protein aggregates have reduced TMRE staining (<b>a1.1</b> and <b>a2.2</b>). (<b>C</b>) Fluorescence profiles of Dendra (<b>F<sub>Dendra</sub></b>, green) and TMRE (<b>F<sub>TMRE</sub></b>, red) at those three regions indicate that depolarized mitochondria are at the site of protein aggregates. (<b>D</b>). Representative images of normal muscle fibers expressing mt-SOD1-Dendra or mt-SOD1<sup>G93A</sup>-Dendra. 63% of mt-SOD1<sup>G93A</sup>-Dendra fibers show fragmented mitochondria comparing to only 11% of mt-SOD1-Dendra fibers. Bar: 10 µm. </p>