Increased short-term and decreased long-term HSCs upon loss of Cxcl12. (A) Representative figures of side population (SP) analysis in Cxcl12-WT and Cxcl12-cKO mice 12 weeks (wks) after tamoxifen treatment. Bar graph on the right panel shows the percentage of SP cells in BM before and after tamoxifen treatment (mean ± SEM; *P < .05; n = 4 each time point). (B) Representative flow cytometric results of BM SP⁺LSK cells of both genotype mice 12 wks after tamoxifen treatment. Right panel shows the percentage of SP cells in LSK population in each genotype (mean ± SEM; *P < .05; n = 6 each). (C) Representative figures of flow cytometric analysis of Flt-3 and CD34 expression in LSK cells in Cxcl12-WT and Cxcl12-cKO mice 12 wks after tamoxifen treatment. Right panel is the percentage of Flt-3⁻CD34⁻, Flt-3⁻CD34⁺, and Flt-3⁺CD34⁺ cells in the LSK population from either genotype (mean ± SEM; *P < .05; n = 8 each). (D) Decreased long-term culture-initiating cell (LTC-IC) readout in BM samples (mean ± SEM; *P < .05; n = 7 each). (E) Competitive repopulation assay in which BM donor cells from Cxcl12-WT or Cxcl12-cKO mice (both CD45.2) were mixed 1:1 with CD45.1 competitor BM cells and transplanted into CD45.1 recipient mice. Twelve wks after transplantation, contribution of CD45.2 cells in recipient total BM or BM LSK population were analyzed (mean ± SEM; **P < .005, ***P < .001; n = 4).