Cbfβ-SMMHC and Nras^G12D expand preleukemic stem and progenitor cells. Quantification of BM cells from Mx1Cre (control, white), Nras^+/LSL-G12D/Mx1Cre (Nras, gray), Cbfb^+/56M/Mx1Cre (CM, black), and Nras^+/LSL-G12D/Cbfb^+/56M/Mx1Cre (Nras/CM, diagonal) mice by flow cytometry, 20 days after Cre activation. (A-C) n = 8-14 mice per group: (A) BM cell numbers (per mouse) in each group; (B) lineage-negative (Lin^–) BM cell numbers in each group; (C) Lineage-positive (Lin⁺) BM cell numbers in each group. (D-E) n = 4-8 mice per group: (D) LSK⁺ cell numbers in BM; (E) long-term (LT-HSCs, LSK⁺CD34^–FLT3^–), short-term (ST-HSCs, LSK⁺CD34⁺FLT3^–) hematopoietic stem, and multipotential progenitor (MPPs, LSK⁺CD34⁺FLT3⁺) cell numbers in each group. (F-G) n = 5-12 mice per group: (F) LSK^– cell numbers; (G) common myeloid progenitor (CMP, LSK^–CD34⁺FcγRII/III^–), megakaryocyte-erythroid progenitor (MEP, LSK^–CD34^–FcγRII/III^–), and granulocyte-monocyte progenitor (GMP, LSK^–CD34⁺FcγRII/III⁺) cell numbers in each group. *P < .05, **P < .01.