Ligand for multiple Notch receptors and involved in the mediation of Notch signaling (PubMed:18660822, PubMed:20437614). May be involved in cell-fate decisions during hematopoiesis (PubMed:9462510). Seems to be involved in early and late stages of mammalian cardiovascular development. Inhibits myoblast differentiation (By similarity). Enhances fibroblast growth factor-induced angiogenesis (in vitro). {ECO:0000250, ECO:0000269|PubMed:18660822, ECO:0000269|PubMed:20437614, ECO:0000269|PubMed:9462510}. This is the function of JAG1 (jagged canonical Notch ligand 1, ENSG00000101384).