PEG-rhuMGDF–induced ERK activation in mpl^−/− ES cells transfected with the full-length

c-mpl or the mutants Δ34 and Δ3. EBs6 cells were sorted for double Flag and CD41 expression. Whole-cell extracts were then analyzed by SDS-PAGE and Western blot analysis with phospho-specific anti-ERK1/2 or anti-ERK1/2 antibody. Images were made with Adobe Photoshop 5.0. (MGDF: PEGrhu MGDF).