The Notch signaling pathway is a highly conserved cell signaling system present in most multicellular organisms. Mammals possess four different notch receptors, referred to as NOTCH1, NOTCH2, NOTCH3, and NOTCH4.The notch receptor is a single-pass transmembrane receptor protein.odulators of the Notch signal, e.g., the Numb protein are able to antagonize Notch effects, resulting in the halting of cell cycle and differentiation of NPCs. In this way, Notch signaling controls NPC self-renewal as well as cell fate specification.