Fig. 6. Regeneration is present in gxi muscle. The percentage of centrally placed nuclei is increased in gxi and gsg^–/– muscle reflecting enhanced regeneration. Centrally placed nuclei develop after myoblasts fuse to regenerate muscle. Quadriceps muscle was studied. There is no significant increase in number of centrally nucleated myofibers in integrin 7 mutant (Itg7^–/–) muscle (P>0.05). -sarcoglycan mutant (gsg^–/–) and double-mutant gxi muscle both have significantly increased centrally nucleated myofibers compared to the wild type and Itg7^–/– (P<0.001 for all comparisons). No difference was detected between the number of centrally nucleated fibers between gsg^–/– and gxi mice (P>0.05).