Enforced expression of SCL does not prevent mast-cell formation from SCL^−/Δ cells. (A) Western blot of SCL^+/Δ bone marrow cells infected with either an MSCV-GFP retrovirus (GFP) or MSCV-SCLiresGFP retrovirus (SCL). Cells were harvested 3 weeks after sorting for GFP expression and growth in IL-3 and SCF. (B) Wright-Giemsa stain of SCL^−/Δ bone marrow cells infected with the GFP or SCL retrovirus and cultured for 6 days in erythroid media containing SCF, Epo, IGF-1, and dexamethasone. (C) Numbers of erythroblasts (Erys) and granulocyte-macrophage cells (G/Ms) generated from 10⁵ infected SCL^+/Δ or SCL^−/Δ bone marrow cells cultured in erythroid media for 6 days. Data are representative of 3 independent experiments.