Notch 1 is a 270-300 kDa transmembrane heterodimeric protein with multiple extracellular growth factor-like repeats, and with an intracellular domain consisting of multiple different domain types. It serves as a receptor for membrane ligands, such as Delta 1, Jagged1 (CD339), and Jagged2, and regulates cell fate decisions. Upon ligand binding the transmembrane form of Notch 1 is repeatedly cleaved to provide approximately 120 kDa Notch intracellular fragment (NICD), which translocates to the nucleus and acts as a part of transcriptional complexes that alter differentiation, proliferation, and apoptosis. The highest level of Notch 1 expression is in brain, lung and thymus.