FIG. 6.

Increased responsiveness of p107-deficient progenitors to FGF2. E14.5 neural progenitors were cultured under neurosphere-promoting conditions with increasing concentrations of FGF2 (A), and the average numbers (Ave. #) of neurospheres from six replicate wells were counted after 7 days (B). p107 deficiency results in an increased number of spheres at each concentration, and the appearance of spheres is observed at lower FGF2 concentrations (0.2 ng/ml) relative to the control (0.6 ng/ml). Bars represent means ± standard errors of the means (SEM) (three control and four p107^−/− embryos from a minimum of two litters). Significance was determined using paired two-tailed t tests. *, P < 0.05. Bar = 500 μm.