A Schematic overview of the generation of a murine model of MLL-AF9 myeloid leukemia using Usp15−/− and Usp15+/+ BM cells. BM cells were transduced with retrovirus encoding MLL-AF9 (MA9) and GFP. After the selection of GFP-expressing cells, lethally-irradiated mice were engrafted with the AML cells and then monitored for engraftment and overall survival. B Representative analysis of the leukemic cell burden in the BM of mice four weeks after engraftment with MLL-AF9;Usp15+/+ and MLL-AF9;Usp15−/− AML cells. C Summary of the leukemic cell burden in the BM of mice four weeks after engraftment with MLL-AF9;Usp15+/+ (n = 7 mice per group) and MLL-AF9;Usp15−/− (n = 6 mice per group) AML cells. *P < 0.05. D Kaplan-Meier analysis of overall survival of mice engrafted with MLL-AF9;Usp15+/+ (n = 7) and MLL-AF9;Usp15−/− (n = 6) AML cells. *P = 0.04. E Summary of the leukemic cell burden in the BM of mice at the time of death (“sick”) at ~10 weeks after engraftment with MLL-AF9;Usp15+/+ and MLL-AF9;Usp15−/− AML cells and remaining mice (“non-sick”) at 10 weeks. F Schematic overview of the generation of BM engraftment of Usp15−/− and Usp15+/+ BM cells into lethally-irradiated recipient mice. BM cells (CD45.2) from Usp15−/− and Usp15+/+ mice were engrafted into lethally-irradiated mice (CD45.1) and then BM and PB were analyzed by immunophenotyping. G Representative flow plots of the gating strategy for hematopoietic progenitor populations in the BM of recipient mice, including Lineage-negative (Lin−), Lineage-c-Kit+ (LK), Lineage-c-Kit+Sca1+ (LSK), granulocyte-monocyte progenitors (GMP), megakaryocyte-erythroid progenitors (MEP), and common myeloid progenitors (CMP), and lymphoid progenitors (CLP). H–J Frequency of LK, LSK, CMP, GMP, and MEPs populations from the BM of recipient mice transplanted with Usp15+/+ and Usp15−/− BM cells. (n = 5 mice per group). K Schematic overview of the generation of competitive BM chimeras using Usp15−/− and Usp15+/+ BM cells. BM cells (CD45.2) from Usp15−/− and Usp15+/+ mice and wild-type (WT) BM cells (CD45.1) were mixed at equal proportions and then engrafted into lethally-irradiated mice (CD45.1). Percent of CD45.2+ cells in the PB and BM was measured at the indicated time points. L Peripheral blood chimerism of cBMT recipients at 1, 4, and 7 months post-transplant (n = 10 mice per group). M Frequency of Usp1+/+ and Usp15−/− lineage-committed B-cell (B220), T-cell (CD3e), and myeloid (CD11b) progenitors in the bone marrow at 7-months post-cBMT (n = 10 mice per group).