Altered proportion of quiescent primitive cells in GATA-2^+/– bone marrow. Bone marrow cells were stained with stem-cell markers (Sca-1 and c-kit) and lineage antibodies to separate stem-cells. Simultaneous staining with the DNA dye Hoechst 33 342 (Hst) was used to determine the percentage of S/G₂/M in the Lin^– c-kit⁺Sca-1⁺ compartment. Data from multiple experiments are summarized in panel A (P = .931; n = 6). To determine the fraction of G₀ cells in the stem-cell compartment, the RNA dye Pyronin Y (PY) and Hst were used to stain Lin^–c-kit⁺Sca-1⁺ cells and flow cytometry performed to determine the percentage of G₀ (PY^lo) in the G₀/G₁ fraction (Hst^low). Representative flow cytometry plots are shown (B) and data from multiple experiments are summarized in panel C (P = .004; n = 7). To functionally corroborate altered quiescence from GATA-2^+/– animals, mice from GATA-2^+/– and GATA-2^+/+ groups were treated with 5-FU in vivo. One day after a single intraperitoneal injection of 5-FU at a dose of 150 mg/kg, nucleated cells were obtained and plated in limiting dilution long-term culture and CAFCs were scored at week 5 (D) (P = .048; n = 5). Error bars depict the standard error of the mean. All statistical analyses were performed using the Student t test.