Cbfβ-SMMHC repression of early B-cell program is cell-autonomous. (A) Flow chart depicting the noncompetitive repopulation assay used in this study. BM cells from Cbfb^+/56M/Mx1Cre floxed or control mice were transplanted into lethally irradiated wild-type recipients, and treated with pIpC 2 weeks later. Contribution of donor cells to peripheral blood was analyzed biweekly up to 14 weeks. BM progenitor populations were analyzed at 16 weeks. (B) Time course of control- (♦) or restored- (■) derived B220⁺ B cells in the peripheral blood shown as mean plus or minus SD (n = 5; **P < .01; ***P < .001). (C) Contribution of control- (▩) and Cbfβ-SMMHC restored- (■) cells in various progenitor populations, including CLP, pre–pro-B, pro-B, and pre-B cells in the BM 16 weeks after induction. Shown are mean plus or minus SD (n = 5; *P < .05; **P < .01; ***P < .001).