Cd53^−/− HSCs are less quiescent upon inflammatory stress. Cell cycling in mobilized HSCs was measured in WT and Cd53^−/− mice over the course of G-CSF treatment, as outlined in Figure 1D. The percentages of cells in the (A) G₀ and (B) S/G₂/M phases at the indicated time points are shown. (n = 3-6 mice per group per time point). (C) Representative flow plot of cell cycling analysis by Ki-67 and DAPI staining after 3 days of G-CSF treatment. (D) Survival of WT and Cd53^−/− mice treated with serial 5-FU doses (arrows; n = 14-15 mice per group). (E) BM cellularity in WT and Cd53^−/− mice at the time of death after serial 5-FU treatments. (n = 5-6 mice per group). (F) Frequency of HSPCs (lineage-, c-Kit+ cells) in WT and Cd53^−/− BM at 7 days after a single dose of 5-FU. (G) Percentage of HSPCs in the G₀ and (H) S/G₂/M phases in the BM 7 days after a single dose of 5-FU. Error bars represent mean ± SEM. ∗P < .05; and ∗∗P < .01 by an unpaired Student t test. DAPI, 4',6-diamidino-2-phenylindole.