Ligand for multiple Notch receptors and involved in the mediation of Notch signaling. May be involved in cell-fate decisions during hematopoiesis. Enhances fibroblast growth factor-induced angiogenesis (in vitro). Seems to be involved in early and late stages of mammalian cardiovascular development. Inhibits myoblast differentiation. May regulate fibroblast growth factor-induced angiogenesis.