Col4a1 heterozygosity does not lead to myopathy. (A) Representative H&E-stained muscle sections from 6-mo-old mice. Both R26^Flpe;Col4a1^+/+ and Col4a1^+/− muscles appeared normal with occasional myofibers with non-peripheral nuclei (NPN, arrows) observed at low frequency. Scale bar = 100 μm. (B) Quantification of myofibers with NPN. Sample sizes in parentheses. Data are presented as mean ± SEM. NS, not significant (P = 0.115), unpaired Student’s t test.