[5] Human JAG1 is one of five ligands for receptors in the NOTCH signaling pathway which helps to determine cellular fate and is active during many developmental stages.

[8][9][10][11] In situ hybridization and conditional gene knockout studies have helped to demonstrate the role JAG1 plays in development and its effects on different organ systems.

In humans, JAG1 has broad expression in many tissue types including the pancreas, heart, placenta, prostate, lung, kidney, thymus, testis, and leucocytes in the adult.

[15] Conditional gene knockout mouse models with Jag1 mutations targeted to the portal vein mesenchyme, endothelium, and cranial neural crest all exhibit features classic to those in individuals with ALGS, highlighting the role of this tissue type in disease origins[16][17][18][19][20] ALGS is an autosomal dominant multi-system disorder affecting several body systems including the liver, heart, skeleton, eye, facial structure, kidneys and vascular system.

[21][22] JAG1 mutation types include protein truncating (splice site, frameshift, and nonsense), missense, and whole gene deletions accounting for 80%, 7%, and 12% respectively.

Specifically, 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.