Exhaustion of HSCs in the absence of Mysm1. (A-C) 8-week-old WT and Mysm1^−/− mice were injected with a single dose of 5-FU (75 mg/kg intraperitoneally). (A) At each indicated time, peripheral blood and BM were obtained to monitor hematopoiesis recovery. The counts of white blood cells (WBC) are shown as percentages of initial baseline values for each group of mice; n = 5 mice group. (B) Absolute number of BM (left) and LSK cells (right) of WT and Mysm1^−/− mice. (C) Distribution of LSK cells in WT and Mysm1^−/− BM. (D) Survival outcome of WT and Mysm1^−/− mice after sequential 5-FU treatment (150 mg/kg intraperitoneally) (log-rank nonparametric test) and presented as a Kaplan-Meier survival curve; n = 10 mice per group. (E) Survival outcome of WT and Mysm1^−/− mice after a lethal dose of 8 Gy of irradiation; n = 5 mice per group. (A-E) Data are representative of two independent experiments. **P < .01; ***P < .001.