Hematopoietic colony assays from total yolk sac cells of VEGFR-3–deficient embryos and wild-type littermates at E9.5. Number of hematopoietic colonies were scored after 7 days of culture of yolk sac cells. Total cell numbers of colonies (>40 cells) per one yolk sac were obtained from 3 independent experiments and expressed as the means ± SEM (n = 3). Methylcellulose culture was performed in the presence of IL-3 (200 U/mL), stem cell factor (50 ng/mL), and EPO (2 U/mL).