Fig. 5

Expression of both Myomaker and Myomerger in myofibers results in combinatorial effects. A Western blots for Myomaker and Myomerger expression in the soleus, EDL, and rectus femoris after 3 days of dox treatment. B Serum CK levels after 3 days of induction in myofibers. C Quantification of the proportion of IgM⁺ myofibers in the soleus, EDL, TA, and rectus femoris after 3 days of induction reveals an elevated proportion of IgM⁺ myofibers compared to the control in all four muscles. D Myofiber stiffness assessed by atomic force microscopy is reduced after 3 days of concurrent Myomaker and Myomerger expression. Each bar represents the average stiffness of three myofibers from a given mouse. E Quantification of myofibers with centrally localized nuclei in the soleus, TA, and rectus femoris. F Muscle mass to tibia length ratios of the TA and rectus femoris. G Myofiber size in the soleus, TA, and rectus femoris, quantified by minimum Feret’s diameter. H Picrosirius red staining revealed elevated fibrosis when both Myomaker and Myomerger are expressed in myofibers. Scale bar = 100 μm. Fibrosis is quantified as the percentage of total area staining positive for Picrosirius red. Statistical analyses and presentation: Data are presented as mean ± SEM; B–G Two-tailed Student’s t-test, identical muscles were compared in C and E–G; stiffness values were compared between the two groups using average values from each mouse for D; *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. H one-way ANOVA with a Tukey’s post hoc test; **P < 0.01, ***P < 0.001