Expression of Utx in HSPCs, analysis of repopulating activity of Utx^Δ/ΔHSPCs, and homing ability of Utx^Δ/ΔHSPCs. (A) Relative expression levels of Utx in hematopoietic stem and progenitor subfractions. The results are shown relative to levels in LT-HSCs. (B) Experimental procedure for serial competitive repopulation experiments (top). Percentages of donor-derived cells in the PB of recipients of Utx^+/+ or Utx^Δ/Δ cell transplants at first and second BMTs. Percentages of lineage-committed, donor-derived cells in the PB of recipients at first BMT (bottom). *P < .05; **P < .01; ***P < .001. (C) Engraftment of Utx^+/++EV, Utx^Δ/Δ+EV, and Utx^Δ/Δ+Utx cells at 3 months after transplantation. The percentages of donor-derived cells in the PB are shown relative to that of Utx^+/++EV. *P < .05. (D) Homing ability (left) and expression (right) of Cxcr4 in Utx^+/+ and Utx^Δ/Δ cells. ***P < .001.