Mouse Notch1 is a 300 kDa type I transmembrane glycoprotein and it functions as a receptor for membrane-bound ligands Jagged1, Jagged2 and Delta1 to regulate cell-fate determination. Mouse Notch1 is synthesized as a 2531 amino acid (aa) precursor that contains an 18 aa signal sequence, a 1707 aa extracellular domain (ECD) with 36 EGFlike repeats and three Lin12/notch repeats, a 21 aa transmembrane segment and a 785 aa cytoplasmic domain that contains six ankyrin repeats, a glutamine-rich domain and a PEST sequence. Notch1 may play an essential role in postimplantation development, probably in some aspect of cell specification and/or differentiation and may be involved in mesoderm development, somite formation and neurogenesis.