Body composition of surGasp1 mice. Proportion of body fat and lean mass in surGasp1-20, wild-type FVB or Bl6/FVB, myostastin deficient (Gdf8-/-) mice at 10 weeks was calculated as the percentage of their respective body weights. Since the Gdf8-/- mice were maintained on the Bl6/FVB background, we used wild-type Bl6/FVB as control. Data are presented as means ± SEM. * : p < 0.05.