Fig. 7. Enhanced cell proliferation in the mid- and rostral hindbrain of Sp8-deficient embryos. (A-D) BrdU-labeled cells with a pulse of 30 minutes are shown in frontal sections, at the level of the posterior midbrain (A,B) and in sagittal hindbrain sections (C,D) of 10.5 wild-type and mutant embryos. In mutant embryos, a remarkable increase in the number of proliferating cells was evident, thus suggesting that Sp8 negatively regulates cell proliferation. All images are at the same magnification. A and B are 5 µm sections; C and D are 10 µm sections.