Expression of Hex in mesoderm and the hematopoietic and vascular lineages. The 3′ cDNA prepared by RT-PCR from the different populations and lineages was run on a 1.5% agarose gel, blotted, and probed separately with 3′ probes from the indicated genes. L32 was included as an internal control. Bry^-Flk-1^-, Bry⁺Flk-1^-, and Bry⁺Flk-1⁺ representing premesoderm and mesodermal populations were isolated from day-3 serum-stimulated EBs. LiqTR (-) and LiqTR (+) represent pools of transitional colonies generated from day-2.5 EBs in the absence or presence of VEGF, respectively. Blast indicates pools of blast colonies from day-3 EBs, whereas Ep and Mac represent pools of primitive erythroid and macrophage colonies from day-6 EBs. D14FL is uncultured day-14 fetal liver cells, and d14FL/Epo (erythropoietin) and d14Fl/Mix represent fetal liver cells cultured for 7 days in erythropoietin or a mix of cytokines. D4T is an EB-derived endothelial cell line.