Blast colony potential and hematopoietic and smooth muscle/endothelial potential of blast colonies generated from HAT^+/+, HAT^+/−, and HAT^−/− ES cell lines. (A) Number of blast colonies generated by HAT^+/+, HAT^+/−, and HAT^−/− ES cell lines. Bars represent standard error of the mean number of colonies from at least 3 cultures. P values indicating that the differences between the number of colonies generated by the HAT^+/+ and the HAT^−/− are statistically significant are indicated. (B) Comparative size of HAT^+/+ and HAT^−/− individual blast colonies generated from day 3.5 EBs (magnification ×200). (C) Individual HAT^+/+, HAT^+/−, and HAT^−/− blast colonies were analyzed for their ability to generate hematopoietic and endothelial cells. Thirty-two blast colonies from each cell line were grown in liquid culture. The ability of each individual blast colony to expand and generate or not hematopoietic (H⁺ or H⁻) and/or endothelial (E⁺ or E⁻) cells was scored 4 days later. (D) Generation by individual blast colonies of nonadherent hematopoietic (white arrowhead) and adherent endothelial cells (black arrowhead). Note the limited proliferation of hematopoietic cells from HAT^−/− blast colonies.