Fig. 2. Clonal analysis of the effect of VEGF during primitive erythropoiesis. (A) VEGF increases the number of Ery^P per single EB. On day 7 of culture either with or without VEGF (5 ng ml^–1), 25 EBs were picked at random and assayed individually into hematopoiesis. Histograms represent the frequency of EBs giving rise to the indicated number of Ery^P. (B) Gene-expression analysis of day-7 EBs treated with VEGF. Individual EBs (10) were dissociated as above and analyzed for hematopoietic-marker expression. No reverse transcriptase (RT) served as a control for genomic DNA contamination. Membranes were hybridized sequentially with the probes as shown. L32 is a loading control. (C) Plots illustrate the level of gene expression in a single EB compared to L32. Horizontal bars represent median values. *P<0.05 compared to untreated cells.