Jagged1 (JAG1) is one of five cell surface proteins (ligands) that interact with four receptors in the mammalian Notch signaling pathway. The Notch Signaling Pathway is a highly conserved pathway that functions to establish and regulate cell fate decisions in many organ systems. Once the JAG1-NOTCH (receptor-ligand) interactions take place, a cascade of proteolytic cleavages is triggered resulting in activation of the transcription for downstream target genes. JAG1 gene is expressed in multiple organ systems in the body and causes the autosomal dominant disorder Alagille syndrome (ALGS) resulting from loss of function mutations within the gene. ALGS is an autosomal dominant multi-system disorder affecting several body systems including the liver, heart, skeleton, eye, facial structure, kidneys and vascular system. JAG1 expression changes have been implicated in many types of cancer. Up regulation of JAG1 has been correlated with both poor overall breast cancer survival rates and an enhancement of tumor proliferation in adrenocortical carcinoma patients.