Can mediate aggregation most likely through a homophilic molecular interaction. Interacts with MAGI1. Highly expressed in the heart and lung. Weakly expressed in the kidney and skin. Expression is restricted to the vascular endothelial cells. Expressed in the kidney, heart and tongue (at protein level). Also expressed on megakaryocytes and activated platelets. Expression in 8.5 dpc-9.5 dpc embryos is observed in embryonic blood vessels including the dorsal aorta, intersomitic arteries and the forming vascular plexus in the head as well as the cardiac outflow tract. By 10.5 dpc-11.5 dpc embryos expression is found in association with the all recognizable blood vessels and in association with cells lining the heart chambers. At 10.5-days embryos expression is associated with syncytiotrophoblasts and cytotrophoblasts as well as endothelial cells associated with blood vessels in the decidua. Expression decreased after mid-gestation from 15.5-day embryos. Up-regulated on the surface of platelets upon activation.