FIG. 1.

p107 deficiency results in increased FGF2 expression. (A) In situ hybridization was performed on E14.5 and E18.5 coronal brain sections with riboprobes for FGF2. At both E14.5 and E18.5, higher levels of FGF2 mRNA were observed in p107^−/− brains specifically within the VZ. At E14.5, higher levels of FGF2 mRNA were observed for conditional (Cond.) Rb mutants; however, in contrast to the case for p107 deficiency, this increase was observed not only within the VZ but also across the developing cortex. Shown here are representative images from experiments performed in triplicate. Scale bar = 250 μm. (B) qRT-PCR displaying mRNA expression in neurospheres cultured for 6 days in vitro from E14.5 wild-type and p107 null embryos. FGF2 expression was normalized to an internal S12 control performed in the same run. Data were analyzed by two-tailed, paired Student's t test (four p107^+/+ and four p107^−/− embryos from a minimum of two litters). *, P < 0.05. Bars represent standard errors.