Mpl^−/− flmpl ES cell–derived blast cell colonies develop in the presence of PEG-rhuMGDF.

The Δ3 region is dispensable for this effect. EBs3 derived from mpl^−/−, mpl^−/− flmpl, mpl^−/−Δ3mpl, or mpl^−/− Δ34mpl ES cells were dissociated and plated for blast cell colony assay in the absence of VEGF and in the presence of PEG-rhuMGDF. Values represent the mean of duplicate dishes in 3 independent experiments.