The Δ3 and Δ34 regions are necessary for the synergistic effect of PEG-rhuMGDF on the VEG-dependent growth of blast cell colonies.

EBs3 derived from mpl^+/+, mpl^−/−, mpl^−/− flmpl, mpl^−/− Δ3mpl, or mpl^−/− Δ34mpl ES cells were dissociated and replated for blast cell colony assay with VEGF or VEGF+PEG-rhuMGDF. Values represent the ratio of the number of blast cell colonies generated with VEGF+PEG-rhuMGDF to the number of those with VEGF (mean of duplicate dishes in 3 independent experiments; *P < .05, comparison with mpl^−/−).