EE372 mediates hEGF-dependent megakaryocyte colony formation. Bone marrow cells from adult nontransgenic control (wt, wild-type) and EE372 transgenic mice were used to test the ability of hEGF and EE372 to support CFU-meg colony formation. (A) Cultures were exposed to either hEGF (EGF, solid histograms, 20 ng/mL) or Tpo (open histograms, 50 ng/mL) in the presence of IL-3 (10 mg/mL). At day 7, acetylcholinesterase-positive CFU-meg colonies were scored (mean values ± standard error for n = 4 replicate assays). In this experiment, numbers of Tpo-induced colonies appear to be greater for the EE372 mouse. However, this effect was not observed in repeated independent analyses. (B) Shown are the similar morphologies of acetylcholinesterase-positive (brown) CFU-meg colonies propagated from EE372 mice in the presence of Tpo (top panel) or hEGF (lower panel).