The response to BMP signals decreases during late differentiation stages. (A-H) Myoblasts were cultured for 9 days under differentiation conditions and double immunolabeled for p-Smad (B,F) and MHC (C,G). Nuclei were counterstained with DAPI (A,E). Boxed areas in the overlay images (D,H) are enlarged in (D',H'). p-Smad phosphorylation is strongly reduced in fused myotubes (white arrows in H') but is clearly present in mononucleated myoblasts (white arrows in d'). Magnification is 100×.
Friedrichs et al. BMC Cell Biology 2011 12:26 doi:10.1186/1471-2121-12-26