Delta-like protein 3 (DLL3) is a transmembrane protein that belongs to the Delta/Serrate/Lag-2 (DSL) family of Notch ligands.May be required to divert neurons along a specific differentiation pathway. Plays a role in the formation of somite boundaries during segmentation of the paraxial mesoderm. DLL3 protein is expressed on the surface of tumor cells but not in normal adult tissues.