Loss of 1 allele of c-Myc leads to a decrease in HSC quiescence and an increase in HSC apoptosis. (A-B) Flow cytometric analysis of the S phase of HSCs and HPCs from WT and HET mice 4 months after pIpC injection. Cells were stained with BrdU and Hoechst to indicate the S phase (BrdU-FITC⁺ population). Gating strategy is shown in (A) and summary data of S phase in HSCs and HPCs are presented in (B). (C-D) Flow cytometric analysis of the cell cycle of HSCs from WT and HET mice 4 months after pIpC injection. Cells were stained with Hoechst DNA Dye and pyroninY RNA Dye to indicate the different cell cycle stages. G₀ phase (Hoechst⁻ pyroninY⁻), G₁ phase (Hoechst⁻ pyroninY⁺), and G₂-S-M phase (Hoechst⁺ pyroninY⁺) cell percentage in the HSC population. Gating strategy (C); summary data (D). (E-F) Flow cytometric analysis of the apoptotic cell ratio (annexin V⁺) in HSCs and HPCs from WT and HET mice 4 months after pIpC injection (n = 7-14). Gating strategy (E); summary data (F). *P < .05; **P < .01; ***P < .001, by Student t test.