ΔE9-10 HSPCs show a growth advantage in the myeloid compartment. (A) Strategy for competitive repopulating assays using BM cells from ΔE9-10 mice. CD45.2 BM cells (2 × 10⁶) from WT and ΔE9-10 mice were transplanted into lethally irradiated CD45.1 recipient mice along with the same number of CD45.1 WT BM cells. Bcor exon 4 and exons 9 and 10 were deleted by injecting tamoxifen at 4 weeks posttransplantation. (B) The chimerism of CD45.2 donor cells in PB after the tamoxifen injection (n = 5). (C) The chimerism of CD45.2 donor cells in BM (n = 5) 5 months after the tamoxifen injection (n = 5). (D) Growth of WT and ΔE9-10 LSK HSPCs and GMPs in culture. HSCs and HSPCs were cultured in triplicate under myeloid cell culture conditions (stem cell factor [SCF] + thrombopoietin (TPO) + interleukin-3 [IL-3] + granulocyte-macrophage colony-stimulating factor [GM-CSF]). Data are shown as the mean ± standard error of the mean (SEM). *P < .05; **P < .01; ***P < .001 by the Student t test.