Normal mast-cell progenitors arise from GMPs rather than MEPs. (A) Proportion of progenitor cell types generated from 10-day liquid cultures of GMPs, CMPs, or MEPs from SCL^+/Δ or SCL^−/Δ mice. Wells containing only single colonies were analyzed by morphology and flow cytometry. At least 20 colonies were analyzed for each cell type. (B) Wright-Giemsa stain of a single colony from SCL^+/Δ GMP culture. (C) Flow cytometric analysis of a single colony from SCL^+/Δ GMP culture. (D) Wright-Giemsa stain of a single colony from a SCL^+/Δ CMP culture.