Dll4, a novel Notch ligand expressed in arterial endothelium

We report the cloning and characterization of a new member of the Delta fam ily of Notch ligands, which we have named Dll4. Like other Delta genes, Dll 4 is predicted to encode a membrane-bound ligand, characterized by an extra cellular region containing several EGF-like domains and a DSL domain requir ed for receptor binding. In situ analysis reveals a highly selective expres sion pattern of Dll4 within the vascular endothelium. The activity and expr ession of Dll4 and the known actions of other members of this family sugges t a role for Dll4 in the control of endothelial cell biology.