Reduced number of HSPCs with impaired differentiation in Srsf2 mutant mice. (A) White blood cells (WBCs), red blood cells (RBCs), hemoglobin (Hb), hematocrit (Hct), MCV, MCH, and platelet (Plt) counts in PB from 8- to 15-week-old Vav1-Cre^+/−Srsf2^WT/WT (WT) and Vav1-Cre^+/−Srsf2^floxP95H/WT (KI) littermate male mice are plotted as dots (n = 21 per group). The mean ± standard deviation (SD) are indicated as bars. (B) Absolute numbers of nucleated BM cells in bilateral femurs and tibias from 12- to 15-week-old WT and KI male mice are shown as mean ± SD (n = 8). (C) Representative flow cytometry analysis of the BM stem and progenitor populations of WT and KI mice. (D-F) Total cell number of CD34⁻KSLs and CD34⁺KSLs (panel D); KSL cells (panel E); and LT-HSCs, MPPs, HPC-1, and HPC-2 (panel F) in the BM of 12- to 15-week-old mice (mean ± SD, n = 8). (G) Limiting-dilution analysis based on competitive repopulation 3 months after transplantation determined the frequency of multilineage repopulating cells in the BM. Data are expressed as mean and 95% confidence intervals for WT (n = 96 samples) and KI (n = 95 samples) combined from 4 independent experiments. Frequency and probability estimates were computed using the extreme limiting dilution analysis (ELDA) software (Bioinformatics). (H) Cell cycle analysis in LT-HSCs (c-Kit⁺Sca-1⁺Lin^lowCD150⁺CD48⁻) and KSL cells using Ki-67 and Hoechst 33342 staining (mean ± SD, n = 6). *P < .05; **P < .01; ***P < .001; ****P < .0001. n.s., not significant.