DLL4: ProductsDelta-like proteins are mammalian homologs of the Drosophila protein Delta, and like Delta they serve as ligands for Notch receptors. They are type I transmembrane proteins with a common structure that includes one DSL domain and six or eight EGF-like repeats. The DSL domain mediates delta-like protein binding to Notch receptors. DLL-Notch signaling is important for tissue development and morphogenesis. A Delta-like 2 protein has been identified in Xenopus but not in mammals.