ALK-1 gain-of-function stimulates hematopoiesis. iALK-1 ES cells were differentiated as EBs in the presence or absence of Dox for 4.25 and 6.25 days, and assayed for primitive erythroid (A) and definitive CFCs (B), respectively. Error bars indicate SEs of 3 independent experiments performed in duplicate. Gene expression analyses for embryonic globin (C) and β major globin (D) at days 4.25 and 6.25 of EB differentiation. Transcripts are normalized to Gapdh. Error bars indicate SE from 2 independent experiments performed in duplicate. (E-F) Relative levels of Flk-1, Gata1, Gata2, Lmo2, and SCL in 4.25 and 6.25 EBs, respectively. Transcripts are normalized to Gapdh. (G) A representative FACS profile for CD41 and c-Kit in induced and noninduced iALK-1 cells at EB day 6.25. Fluorescence intensity for c-Kit is indicated on the y axis and CD41 on the x axis. *P < .05, ***P < .001