Ccbe1^lacZ/lacZ embryos develop severe edema associated with a complete lack of lymphatic vessels. (A,B) E12.5 Ccbe1^lacZ/lacZ embryos appear indistinguishable from wild-type littermates. (C,D) Severe cutaneous edema (“e”) is present in E16.5 Ccbe1^lacZ/lacZ embryos. (E,F) Edema is revealed by H&E staining of skin from the E16.5 Ccbe1^lacZ/lacZ and control embryos shown in panels C and D. (G-P) Ccbe1^lacZ/lacZ embryos lack lymphatic vessels. (G,H) H&E staining of sagittal sections reveals a typical cluster of subcostal vessels including an artery (“A”), vein (“V”), and lymphatic (“L”) in an E16.5 wild-type embryo but the subcostal lymphatic is absent in a Ccbe1^lacZ/lacZ littermate. (I,J) Anti-LYVE1 immunostaining confirms the absence of subcostal lymphatic vessels in an E16.5 Ccbe1^lacZ/lacZ embryo. (K,L) Anti-LYVE1 immunostaining reveals a well-developed network of large lymphatic vessels adjacent to the carotid artery (“A”) and cardinal vein (“V”) in a transverse section from an E15.5 wild-type embryo, but none are present in a Ccbe1^lacZ/lacZ littermate. (M-P) Immunostaining for LYVE1, PROX1, and PODOPLANIN identifies lymphatic vessels in the skin of an E16.5 wild-type embryo but not in a Ccbe1^lacZ/lacZ littermate. Note the presence of LYVE1⁺;PROX1⁻ cells that are likely to be tissue macrophages. (Q,R) CCBE1-deficient embryos have normal blood vessel growth. Platelet endothelial cell adhesion molecule staining of E16.5 wild-type and Ccbe1^lacZ/lacZ littermate embryo skin is shown. The reduced number of total vessels in the Ccbe1^lacZ/lacZ skin sample reflects the loss of lymphatic vessels. Scale bars indicate 20 μm. PECAM1, platelet endothelial cell adhesion molecule.