Figure 4.

Lineage relationships among myeloid progenitors. (A) Flow cytometric analysis for cells with the MKP phenotype in the culture of CMPs and MEPs. Note more MKPs present in the CMP culture. (B) Two models for the MKP development. The first model suggests that commitment to the megakaryocytic lineage occurs at the level of MEP where the progenitor has to make a choice to become either MKP or erythrocyte progenitor (ErP; yet to be prospectively identified). In the second model, the commitment occurs earlier, at the stage of CMP. Although MEPs are bipotent, they differentiate mainly into the erythroid lineage. The majority of MKPs are the direct descendants of CMPs.