Prospective isolation and global gene expression analysis of the erythrocyte colony-forming unit (CFU-E)

The erythrocyte colony-forming unit (CFU-E) is a rare bone marrow (BM) progenitor that generates erythrocyte colonies in 48 hours. The existence of CFU-Es is based on these colonies, but CFU-Es have not been purified prospectively by phenotype. We have separated the “nonstem,” “nonlymphoid” compartment (lineage marker [lin] – c-Kit + Sca-1 – IL-7Rα – ) into interleukin 3 receptor α negative (IL-3Rα – ) and IL-3Rα + subsets. Within IL-3Rα – but not IL-3Rα + cells we have identified TER119 – CD41 – CD71 + erythrocyte-committed progenitors (EPs). EPs generate CFU-E colonies at about 70% efficiency and generate reticulocytes in vivo. Depletion of EPs from BM strongly reduces CFU-E frequencies. EPs lack potential for erythrocyte burst-forming unit, megakaryocyte, granulocyte (G), and monocyte (M) colonies, and for spleen colony-forming units. Chronically suppressed erythropoiesis in interferon consensus sequence-binding protein (ICSBP)–deficient BM is associated with reduced frequencies of both the EP population and CFU-E colonies. During phenylhydrazine-induced acute anemia, numbers of both the EP population and CFU-E colonies increase. Collectively, EPs (lin – c-Kit + Sca-1 – IL-7Rα – IL-3Rα – CD41 – CD71 + ) account for most, if not all, CFU-E activity in BM. As a first molecular characterization, we have compared global gene expression in EPs and nonerythroid GM progenitors. These analyses define an erythroid progenitor-specific gene expression pattern. The prospective isolation of EPs is an important step to analyze physiologic and pathologic erythropoiesis.