Increased repopulating activity of HSPCs from Mll^PTD/WT mice is not restricted to phenotypically identified HSCs but also comes from ST-HSCs and myeloid progenitors. The fractions of WT or Mll^PTD/WT (CD45.2⁺) BM cells were transplanted into lethally irradiated CD45.1⁺/CD45.2⁺ WT recipient mice along with 1 × 10⁵ WT (CD45.1⁺) helper cells. Engraftment was assessed 16 weeks after transplantation. Shown is the mean ± SD percentage of donor-derived WT or Mll^PTD/WT cells (CD45.2⁺) in recipient PB. (A) Equal number of LSK/SLAM⁺ (3.5 × 10²) or LSK/SLAM⁻ (3.5 × 10³) fractions from WT or Mll^PTD/WT BM cells were transplanted into CD45.1⁺/CD45.2⁺ WT recipient mice (2 experiments, n = 8). (B) WT or Mll^PTD/WT (CD45.2⁺) LT-HSCs (8 × 10²) or ST-HSCs (1.2 × 10³) or MPP (3.5 × 10³) were transplanted into CD45.1⁺/CD45.2⁺ WT recipient mice (2 experiments, n = 8). (C) WT or Mll^PTD/WT (CD45.2⁺) GMP population cells (3.5 × 10³) were transplanted into CD45.1⁺/CD45.2⁺ WT recipient mice (2 experiments, n = 8). (D) Frequency of lineage-repopulation myeloid (CD45.2⁺CD11b⁺) or B (CD45.2⁺B220⁺) or T (CD45.2⁺CD5⁺) cells compared with competitor (CD45.1) derived lineage-repopulation present in CD45.1⁺/CD45.2⁺ WT recipient mice. *P < .05. **P < .01. (E) Mll^PTD/WT (CD45.2⁺) GMP population cells in serial diluted dose (1.5 × 10³, 5 × 10³, 1 × 10⁴, and 5 × 10⁴) were transplanted into CD45.1⁺/CD45.2⁺ WT recipient mice (n = 4). Engraftment was assessed at 6, 12, and 20 weeks after transplantation (n = 4). (F) Frequency of donor-derived lineage-repopulation myeloid or B or T cells compared with competitor (CD45.1) derived lineage-repopulation present in CD45.1⁺/CD45.2⁺ WT recipient mice. Data are shown at 12 weeks after transplantation.