Expression of MR SCF improves runting associated withSl/Sl^d mice. Shown in the left panel are pictures of 12-week-old mutant mice that either express the MR form of SCF or overexpress the soluble form. The right panel shows the weights of these mice and their comparison with wt littermates. Weight comparison between Sl/Sl^d (n = 16),Sl/Sl^d-S (n = 10),Sl/Sl^d-MR (n = 14), and wt (n = 20) mice. All black-eyed white mice and wt mice at 12 weeks of age were weighed. The results show mean ± SEM (bars). (*) P = .01,Sl/Sl^d-MR versus Sl/Sl^dand Sl/Sl^d-S.