Increased cell cycle and mobilization of multipotent progenitors in the absence of Ptch1. (A) Numbers of circulating peripheral blood and spleen myeloid colony-forming cells in Ptch1 wild-type (Ptch1^fl/fl) and null (MxPtch1^Δ/Δ) mice 4 to 6 weeks after poly(I:C). Mean plus SD calculated from 3 mice of each genotype. (B) Representative dot-plots for c-kit and Sca-1 expression on lineage-negative BM cells. Gates used to calculate proportions of LKS and LK cells are shown. (C) Proportions of LKS and LK cells expressed as a percentage of nucleated BM cells. The numbers of mice used to calculate the mean plus SD are shown in parentheses. *P < .05 by one-way ANOVA. (D) Cell-cycle analysis of FACS-isolated LKS and LK cells stained with Hoechst 33342 and Pyronin Y. The mean percentage of each stage of cell cycle calculated from 4 mice is shown. (E) Quantitative RT-PCR for cyclin D1 mRNA expression in LKS. The control samples have been normalized to 1, and the mean plus SD from 3 mice of each genotype are shown. *P < .05 by 2-tailed Mann-Whitney test.