• Embryonic stem cells;
  • Erythroid progenitors


The temporal pattern of embryonic, fetal, and adult globin expression in the α (ζ [RIGHTWARDS ARROW] α) and β (ε [RIGHTWARDS ARROW] γ and γ [RIGHTWARDS ARROW] β) clusters were quantitatively analyzed at the transcriptional and translational levels in erythrocytes induced from primate embryonic stem cells in vitro. When vascular endothelial growth factor receptor-2high CD34+ cells were harvested and reseeded onto OP9 stromal cells, two-wave erythropoiesis occurred sequentially. Immunostaining and real-time reverse transcription-polymerase chain reaction analyses of floating mature erythrocytes revealed that globin switches occurred in parallel with the erythropoietic transition. Colony-forming assays showed replacement of primitive clonogenic progenitor cells with definitive cells during culturing. A decline in embryonic ζ- and ε-globin expression at the translational level occurred in individual definitive erythroid progenitors. Expression of β-globin in individual definitive erythroid progenitors was upregulated in the presence of OP9 stromal cells. Thus, this system reproduces early hematopoietic development in vitro and can serve as a model for analyzing the mechanisms of the globin switch in humans.