Deletion of Tmod1 shifts muscle fiber types toward a faster distribution. (A) The distribution of fiber sizes in the TA was shifted rightward in Tmod1^−/−Tg+ muscle. Graph shows the size distribution of n = 560 Tmod1^+/+ fibers and n = 479 Tmod1^−/−Tg+ fibers measured from n = 2 mice/genotype. (B) The mean fiber cross-sectional area was significantly elevated in both the TA and soleus, suggesting a faster fiber type. (C) The proportion of type 2A/X/B fibers was elevated in the TA and soleus of Tmod1^−/−Tg+ mice at the expense of type 1 fibers. (D) Although there were no significant differences in the size of type 1 fibers, type 2A/X/B fibers were significantly larger in Tmod1^−/−Tg+ TA and soleus. (E) TA and soleus tissue lysates were separated on 8% SDS-PAGE gels. In both TA and soleus, a shift toward faster MHC isoforms was evident in Tmod1^−/−Tg+ mice. Molecular mass is indicated in kilodaltons. (F) No significant differences in centralized nuclei were observed between Tmod1^+/+ and Tmod1^−/−Tg+ muscle. *, P < 0.05; **, P < 0.01; ***, P < 0.001. n = 4 (in C and D) or n = 8 (in B, E, and F) muscles/genotype. Data are mean ± SEM.