Effect of Tpo on embryo or yolk sac EryP, BFU-E, MIX, colony-forming unit–granulocyte-macrophage (GM), CFU-Meg, and burst-forming unit–megakaryocyte (BFU-Meg) CFC formation.

E7.5 whole embryo (A), E8.25 whole embryo (B), E8.5 yolk sac (C), and E9.5 yolk sac (D) cells were plated in the primitive erythroid colony assay or progenitor assay or megakaryocyte assays (as described in “Materials and methods”) in the presence or absence of 50 ng/mL Tpo. *P < .05, −Tpo compared with +Tpo. Data represent the mean values of triplicate samples from 4 experiments; error bars represent SEM.