Identification of Ery/Ps within wild-type and Smad5^−/− EBs.

(A) EBs were dissociated at day 4 to 6 and replated into cultures containing Epo favoring the growth of primitive erythroid colonies. (B) The inhibitory effect of TGF-β1 added to Ery/P colony assays at final concentrations of 0.3 and 2 ng/mL. Numbers of Ery/P colonies were scored after 5 to 7 days of culture. Results shown (means ± SEMs) are from 3 independent experiments. Significance was determined using the Student t test. *represents data found to be significantly different from wild-type control values (P < .05).