SLP-76 is required in platelets for normal lymphatic vascular development. (A-B) PF4-Cre;Slp-76^fl/− embryos exhibit blood-filled cutaneous lymphatics. (C-D) PF4-Cre;Slp-76^fl/− neonates exhibit blood-filled mesenteric and intestinal lymphatic vessels. A indicates artery; V, vein; and L, lymphatic. (E-H) Twelve-week-old PF4-Cre;Slp-76^fl/− animals exhibit vascular mixing phenotypes that range in severity from blood-filled Peyer patches (PP, left) to disruption of the normal vascular pattern of the intestine wall and blood-filled mesenteric lymphatic vessels (L, right).