Cbfb is required for the development of Flt3⁺ progenitor cells in BM. (A-B) BM cells from 6- to 8-week-old Vav1-iCre⁺Cbfb^F/+ (Het) and Vav1-iCre⁺Cbfb^F/F (CKO) mice were analyzed for expression of lineage markers (B220, CD11b, MHC-II, CD16/32), c-kit, Sca1, CD150, CD105, CD115, and CD135 (Flt3). Frequencies of LSK HSCs/MPPs (A), and Flt3⁺ LSK LMPPs (B) are shown with rectangular gates. (C) CD150 and CD16/32 expression in Lin^–c-kit⁺Sca1^– progenitors. CD16/32⁺CD150⁺ and CD16/32^–CD150⁺ populations are shown with rectangular gates with percentages. (D) c-kit and CD135 or CD115 expression in Lin^–Sca1^– BM progenitors. Flt3⁺c-kit⁺ (MDP/CLP), Flt3⁺Lin^–Sca1^–c-kit^lo/– (CDP), and c-kit⁺CD115⁺ populations are shown with rectangular gates with percentages. (E) Statistical analysis of CD16/32^– LSK, LMPP, and MDP cells at 6 to 8 (shown as 7 weeks) and 12 to 16 weeks (14 weeks) of age. (F) Expression of CD105 and CD16/32 in B220^–CD11b^–Sca1^– BM cells in Vav1-iCre⁺Cbfb^F/+ (het) and Vav1-iCre⁺Cbfb^F/F (CKO) mice. CD105⁺ erythroid progenitor cells are shown with rectangular gates and frequencies (mean and standard deviation). *P < .05; ***P < .005. n.s., not significant. Flow cytometry data represent analysis of 3 to 6 mice.