Notch signalling

Cell-cell interactions mediated by Notch play critical roles at multiple st ages of development in both invertebrate and vertebrate species. Three type s of Notch-dependent processes are illustrated in this review: lateral inhi bition, binary fate decision following asymmetric cell division and formati on of organization centers at compartmental boundaries. These last two proc esses illustrate how Notch activity can be modulated both at the cell surfa ce and inside the cell. Notch signaling involves the interaction of the rec eptor with its ligand on an adjacent cell. This interaction appears to trig ger an intracellular proteolytic cleavage that releases intracellular domai n of Notch. The activated form of the receptor is believed to enter the nuc leus and promote transcription by interacting with the Suppressor of Hairle ss DNA-binding protein. The direct read-out of this signaling event is the transcriptional activation of Notch target-genes.