Fig. 5. Rspo3 is required for mouse vascular development. (A-C) External morphology of wild-type and Rspo3^-/- embryos (A), yolk sacs (B) and placentas (C) (E10.5). Enlarged pericardial sac with hemorrhage is marked by arrowhead in A. Note pale Rspo3^-/- yolk sac in B and pale Rspo3^-/- chorionic plate in C (arrowheads). (D,E) Yolk sac morphology in Rspo3^-/- embryos (E9.5). (D) PECAM antibody staining of yolk sac vasculature at E9.5. (E) Histological section of the PECAM stained yolk sacs shown in D, counterstaining with Eosin. (F) PECAM staining of the trunk region of wild-type and Rspo3^-/- embryos E9.5. (G,H) Placental defects in Rspo3^-/- embryos. (G) Hematoxylin and Eosin staining of histological section. Note reduced embryonic vessels in Rspo3^-/- labyrinth. (H) PECAM staining of placentas shown in C. Representative samples from 20 wild-type and 20 knockout embryos are shown.