BM lacking Ott1 has defective recovery during hematopoietic stress and is accompanied by loss of quiescence in the HSC compartment. (A) Neutrophil counts from peripheral blood samples of Ott1^flox/null Mx1-cre (KO) or littermates possessing a WT Ott1 allele (Ctl) 6 weeks after pIpC treated with a single dose of 5-FU (150 mg/kg). Open (Ctl) and closed (KO) boxes represent the mean value, and error bars represent SD (Ctl and KO, n = 4). (B) Kaplan-Meier survival curve of KO and Ctl mice injected with weekly 5-FU (150 mg/kg). P values were calculated using Mantel-Cox test (Ctl, n = 7; KO, n = 15). (C) Cell-cycle analysis of control and KO BM LT-HSC (Lin⁻Sca-1⁺c-Kit⁺ CD34⁻) and ST-HSC (Lin⁻Sca-1⁺c-Kit⁺CD34⁺) populations using Hoechst 33342/pyronin Y from panel A at 14 days after 5-FU treatment. Representative flow panels above. (D) Absolute BM cell numbers from mice in panel A of LT-HSCs (Lin⁻Sca-1⁺c-Kit⁺CD34⁻), ST-HSCs (Lin⁻Sca-1⁺c-Kit⁺CD34⁺), progenitors (Lin⁻Sca-1⁻c-Kit⁺), and total BM (BM; A) at 14 days after 5-FU treatment. Bars represent mean values, and error bars represent SD (Ctl and KO, n = 4). (E) Cell-cycle analysis of LT- and ST-HSC populations in BM from Ott1^flox/null Mx1-cre (KO) or littermates possessing a WT Ott1 allele (control) 6 weeks after pIpC cultured in vitro in IL-3, IL-6, and SCF for 72 hours. Representative flow panels above. Graphs represent mean values, and error bars represent SD (Ctl and KO, n = 4).