Vasculature and hematopoiesis of yolk sacs from wild-type and VEGFR-3–deficient mice at E9.5.

(A) Wild-type embryo shows a well-developed vasculature at E9.5. The arrowhead in panel A indicates the vitelline artery. (B) A yolk sac from VEGFR-3–deficient mutant shows severe anemia and defective large vessels. Yolk sacs from wild-type (C) and VEGFR-3–deficient mutant (D) at E9.5 stained in whole-mount with anti-CD31 antibody. Note the abnormality of vascular network formation and the lack of large vessels in the VEGFR-3–deficient yolk sac. Section of the yolk sac from wild-type (E) and VEGFR-3–deficient (F) embryo at E9.5. Note the smaller numbers of hematopoietic cells in the yolk sac derived from VEGFR-3–deficient embryos. (G) Number of hematopoietic cells present in the yolk sac from embryos at E9.5. Error bars indicate SEM (n = 4). E9.5 yolk sac stained with May-Grünwald-Giemsa from wild-type (H) and VEGFR-3–deficient (I) embryos. Staining blood cells from a wild-type (J) and VEGFR-3–deficient mutant (K) yolk sac were stained with antiembryonic hemoglobin polyclonal antibody. Hemoglobin expression is visualized as a red reaction product. The nucleus was counterstained with hematoxylin. Scale bars indicate 200 μm (C,D), 100 μm (E,F), and 10 μm (H-K).