JAM-2, a novel immunoglobulin superfamily molecule, expressed by endothelial and lymphatic cells

Cell-cell contacts are essential for morphogenesis and tissue function and play a vital role in mediating endothelial cohesion within the vascular sys tem during vessel growth and organization. We identified a never junctional adhesion molecule, named JAM-2, by a selective RNA display method, which a llowed identification of transcripts encoding immunoglobulin superfamily mo lecules regulated during coculture of endothelial cells with tumor cells. T he JAM-2 transcript is highly expressed during embryogenesis and is detecte d in lymph node and Peyer's patches RNA of adult mice. Accordingly, antibod ies specific for JAM-a stain high endothelial venules and lymphatic vessels in lymphoid organs, and vascular structures in the kidney. Using real time video microscopy, we show that JAM-2 is localized within minutes to the ne wly formed cell-cell contact, The role of the protein in the sealing of cel l-cell contact is further suggested by the reduced paracellular permeabilit y of cell monolayer transfected with JAM-2 cDNA, and by the localization of JAM-2 to tight junctional complexes of polarized cells. Taken together, ou r results suggest that JAM-2 is a novel vascular molecule, which participat es in interendothelial junctional complexes.