Fig. 2: MacroD1 is relevant for myofiber size and mitochondrial quality.

A Measurement of Z line lengths in ultrastructural images of Musculus (M.) quadriceps femoris, diaphragm and myocardium in male MacroD1^−/− (KO) and wildtype (WT) mice (each n = 4). Data is shown as mean ± SD. Statistical analyses were performed using a two-tailed student t-test (*, p < 0.05; **, p < 0.005; ***, p < 0.0005). B Determination of myofiber diameter (transverse sections) in HE stained cryosections of M. quadriceps femoris, M. triceps brachii, M. gastrocnemius, and M. soleus of MacroD1^−/− (KO) and wildtype (WT) mice (each 5 males and 5 females). Median and quartiles are depicted as dashed lines. For statistical analysis, a Mann–Whitney U test was used (*, p < 0.05; **, p < 0.005; ***, p < 0.0005; ****, p < 0.0001). C Immunohistochemistry for type I myofiber-specific myosin, performed on cryosections of the M. soleus. A Chi-square test was used for statistical analysis (*, p < 0.05; **, p < 0.005; ***, p < 0.0005; ****, p < 0.0001). D Quantification of the staining (mean intensity) for the M. triceps brachii for SDH activity (mitochondrial marker). The median is depicted as straight line, whiskers indicate minimal to maximal value. Statistical analyses were performed using a two-tailed student t-test (*, p < 0.05; **, p < 0.005; ***, p < 0.0005). E Mitochondrial counts were undertaken in ultrathin sections of the myocardium from MacroD1^−/− (KO) and WT mice. F TEM images of skeletal muscle (M. triceps brachii) and myocardium in MacroD1^−/− (KO) and wildtype (WT) mice. In MacroD1^−/− mice, mitochondria are swollen and exhibit disarrangement and partial loss of cristae (cristolysis; asterisks). Bar = 500 nm. G TEM images of C2C12 cells. After the knockdown of Macrod1 (siMacroD1), mitochondria exhibit disarrangement and partial loss of cristae (cristolysis; asterisks). There is evidence of mitochondrial fission (arrow). The arrowheads highlight electron dense cytoplasmic granules present in both siMock and siMacroD1 cells. Bars = 1 µm. Source data are provided as a Source Data file.