Fig. 5. Smad1 phosphorylation induced by BMP addition to hES cells. Undifferentiated hES cells were deprived of fetal calf serum for 4 hours then used as controls (A-D) or treated with BMP2 (50 ng/ml) for 1.5 hours (E-H). After fixing and permeabilization, cells were stained with GCTM2 (green, A and E) and anti-PSmad1 (red, F). Comparison of B and F and the overlays of control and treated cells in C and G indicate that BMP treatment leads to nuclear translocation of Smad1. (I) Nuclear fluorescent intensity quantified as pixel density in ten serial z-sections in a confocal laser scanning microscope.