Fig. 6. Neural cell proliferation and cell cycle regulation is modified in p27Kip1-null mice. A, Western blot assessment of different markers of proliferation and differentiation in the olfactory mucosa of wild-type and p27Kip1-null mice that were 3 weeks (3w), 2 months (2m), or 4 months (4m) old. B, comparison of the protein amounts in the olfactory mucosa from wild-type and p27Kip1 mice that were 3 weeks (3w), 2 months (2m), or 4 months (4m) old. C, densitometric values of PCNA signal. PCNA serves as a marker for the proliferative state of basal cells. The values are the mean of 10 independent Western blotting experiments. The differences were significant between 3 weeks and 24 months, and between 3 weeks +/+ and -/- (P < 0.01). D, Western blot assessment of cell cycle regulators in the olfactory mucosa of wild-type and p27Kip1-null mice of various ages: 3 weeks (3w); 2 months (2m), and 4 months (4m). E, immunohistochemical location of BrdUrd- positive cells, PCNA, and GAP 43 on OE sections from p27Kip1-null (right) and wild-type (left) mice. Scale bar, 100 µm. BrdUrd-positive cells are more numerous in 1-month-old p27Kip1-null mice than in wild-type mice.