Altered fission-fusion dynamics signaling in muscle from MERKO versus Control f/f mice. (A and B) DRP1Ser637 phosphorylation (A) and DRP1 protein abundance (B) in enriched mitochondrial fractions from female Control f/f and MERKO quadriceps muscle (n = 4; representative immunoblots). Porin, control. (C) Protein-protein association between DRP1 and the phosphatase calcineurin (CnA) (above; n = 3 to 6 per genotype) in muscle from Control f/f and MERKO mice. (D and E) Calcineurin and PKA activity in quadriceps muscle from Control f/f and MERKO mice (n = 6 to 10 per genotype). (F to H) FIS1, OPA1, and MFN2 protein expression in muscle from Control f/f and MERKO mice relative to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression (control) (n = 6 per genotype). (I) Expression of Fis1, Mfn2, and Opa1 proteins in quadriceps muscle from female Control f/f and MERKO mice relative to Ppia expression (housekeeping gene control) (n = 6 per genotype). All values are expressed as means ± SEM. Mean differences detected by Student’s t test or ANOVA. *P < 0.05, difference between genotypes.