Coculture of human H1 hES cells with the OP9 stromal cell line results in simultaneous generation of mature erythroid and megakaryocytic cells. (A) Kinetics of erythroid maturation studied by flow cytometry. Embryonic (top panel) and adult (bottom panel) erythroid cells, obtained from the differentiation of mobilized CD34⁺ cells, cultured in the presence of SCF, EPO, and IL-3, were analyzed for the expression of GPA, CD36, and CD71 erythroid differentiation markers. The cells were also incubated with isotype-matched irrelevant antibodies as negative controls. 7-AAD–positive cells were excluded from the analyses by appropriate gating. Figure shows representative diagrams of 3 repeated determinations derived from H1 ES cell line. Values in each quadrant are the mean ± SD of 3 independent experiments. (B) Globin chains expression in hES-derived erythrocytic cells. On the left, histograms show mRNA expression of globin chains obtained using the quantitative PCR assay performed in triplicate. The error bars represent SD. The level of globin chain expression is illustrated. On the right, results are presented with respect to their gene locus. Bars represent expression levels of indicated transcripts relative to the overall expression of the α- or the β-gene locus.