Globin expression in the 14-day cocultures. (A) HPLC chromatograms illustrating globin expression in erythroblasts obtained after 14 days (left panel) or 24 days (right panel) of liquid culture of CD34⁺ cells that had been obtained after coculture of hESCs with FH-B-hTERT for 2 weeks. Cells in the left panel, which were mostly pro- and basophilic erythroblasts, expressed predominantly ζ- and ϵ-globin. Cells in the right panel, which were mostly poly- and orthochromatic erythroblasts, expressed predominantly α- and ϵ-globin. (B,C) Histograms summarizing the quantification of globin expression by HPLC (B) or real-time PCR (C) in the cells described in panel A. Results demonstrated that the globin expressed in these cells was of the embryonic type and that at least part of the regulation occurred at the transcriptional level. Percent α-globin was calculated as 100 × α-globin/(α-globin + ζ-globin). Percent γ-globin was calculated as 100 × γ-globin/(γ-globin + ϵ-globin). Error bars represent SD.