Fig. 2

Muscle DRP1-chronic inhibition alters mitochondrial morphology, RCS organization and complex-I- and complex-II-dependent respiration. a Representative EM cross-sectional images of mitochondrial distribution and morphology in gastrocnemius from WT and Drp1^−/− mice. In cross-sections, the different morphology of mitochondria in Drp1^−/− from WT is often evident: in Drp1^−/− fibers mitochondria are more often larger in size (scale bar: 1 μm). b Mitochondrial DNA copy number quantification. mtDNA was amplified by RT-PCR from the total DNA of gastrocnemius muscles of the indicated genotype. The data are normalized to control and represent average ± SEM of five independent experiments. c Representative immunoblots of four independent experiments of muscle homogenates showing no difference of porin/GAPDH ratio. d RT-PCR analysis of mitochondria dynamics transcripts of muscles of WT and Drp1^−/−. DRP1 deletion induces PGC1α, OPA1, and Mfn1 transcript levels. The data represent average ± SEM (n = 8) and are normalized for GAPDH and expressed as fold increase of controls. e Succinate dehydrogenase (SDH) staining of Drp1^fl/fl and Drp1^−/− muscles show a different distribution of mitochondrial network in KO mice. f Respiratory control ratio (RCR) of muscle-isolated mitochondria energized with 5 mM/2.5 mM GLU/MAL or 10 mM SUCC. The data represent average ± SEM of three independent experiments. g DRP1 deficiency leads to a significant reduction of CIII and CIV assembly in respiratory chain supercomplexes (RCS). Representative Blue Native PAGE analysis showing RCS developed and normalized for individual respiratory chain complexes. Left panel: CI subunit NDUFB8, middle panel: CIII-Core2 protein 2 and right panel: CIV subunit COXI. h Representative immunoblot analysis of OPA1 different isoforms show an increase in OPA1 cleavage in Drp1-null muscles (n = 4). Two-tailed unpaired Student’s t test was used. Statistical significance: *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001