Differential Effect of Calsequestrin Ablation on Structure and Function of Fast and Slow Skeletal Muscle Fibers

Figure 4

In dCASQ-null animals (4–6 months of age) ~30% of Soleus fibers presented severe structural damage. (a), (c), and (e): histology; (b), (d), and (f): EM. (a) and (b) WT Soleus fibers from adult mice (4–6 months of age) always showed a well-defined cross-striation and well-organized EC coupling (not shown) and mitochondrial apparatus. (c)–(f) At 4–6 months of age, ~30% of Soleus fibers (see Table 1) from dCASQ-null mice were affected by severe structural alterations, which were clearly visible both at the histological examination (e) and in EM (f). In (e) arrowheads point to three contracture cores within the same severely damaged fiber (asterisk), while in (f) is shown a small portion of a fiber presenting degeneration of the contractile elements and initial Z line streaming (arrow). Fibers with similar alterations are very rare in CASQ1-null fibers ((c) and (d)) and never seen in WT. See Table 1 for quantitative analysis.