BMI1 promotes self-renewal of progenitors. (A) After transduction of CB CD34⁺ cells with either control or BMI1 vectors, the cells were sorted into HSC, CMP, MEP, and GM fractions and analyzed for CFC content. Two weeks after the primary plating, colonies were scored on the basis of morphology as CFU-GEMM, BFU-E, CFU-G, CFU-M, or CFU-GM, and secondary replating was performed in new methylcellulose assays. The cells were cultured for additional 2 weeks and colonies were scored.