FIG. 3.
p27 deficiency impairs G2/M arrest in irradiated GI crypt cells. (A) Mitotic cells (arrows) are seen in both p27+/+ and p27−/− mice before treatment. Note the reduction of mitotic cells in irradiated p27+/+ but not p27−/− crypts. Increased apoptosis is seen in both p27+/+ and p27−/− crypts after irradiation (arrowheads) (magnification, ×1,000). (B) p27−/− mice have a significantly higher MI in cell positions 1 to 15 of the SI crypt than p27+/+ mice following 1.2 Gy gamma irradiation. p27+/− mice display an intermediate phenotype. (C) p27−/− mice have a significantly higher frequency of mitotic figures in positions 6 to 10 of the SI crypt than p27+/+ mice following 1.2 Gy gamma irradiation. Mean mitotic indices plus or minus the SEM are shown.