Figure 7

Regeneration may be enhanced in the MRL background. Embryonic myosin heavy chain (eMHC) staining was increased in Sgcg^MRL/D2 compared to Sgcg muscle, and eMHC fibers were seen in areas where dye uptake was seen. However, phosphorylated histone 3 (PH3), a marker of mitotic index, was not increased in Sgcg^MRL/D2 compared to Sgcg muscle. Skeletal muscle central nucleation and fiber size variability are enhanced by the MRL background. Sgcg^MRL/D2 muscle demonstrated an increase in centrally nucleated fibers compared to Sgcg^D2 mice. Fiber size variability was reflected in the coefficient of variability of fiber diameter measurements. The solid line indicates significance (p < 0.05). These data support that the MRL exerts its effect in skeletal muscle, at least in part, by promoting regeneration.