Origins of the Vertebrate Erythro/Megakaryocytic System

Figure 4

Nonmammalian and mammalian model of erythropoiesis and thrombopoiesis. According to the integrated model of hematopoiesis, mammalian erythrocytes and megakaryocytes have likely evolved from their nonmammalian erythroid and thrombocytic homologs as an evolutionary improvement. Nonmammalian erythrocytes and thrombocytes are phenotypically similar (nucleated, diploid oval-shaped cells), whereas mammalian megakaryocytes and erythrocytes are very different from each other. Numbers indicate the proliferation potential of particular progenitors. TEP: thrombocyte-erythroid progenitor; CFU-T: colony-forming unit-thrombocyte. Modified from Bartunek et al. [16] and Svoboda et al. [17].