SMAD1 and Miyoshi myopathy: Although the mechanism whereby TGF-β inhibits OB differentiation still remains unclear, we found at least in our experimental conditions that TGF-β inhibition markedly enhances the phosphorylation of Smad1 to potentiate BMP-2 signaling without affecting the canonical Wnt pathway in OB precursor cells suppressed by MM cells (Figures 3C-D).