Notch signalling in Drosophila: three ways to use a pathway

Cell-cell interactions mediated by Notch are critical at multiple stages of development. Our current understanding of the Notch signalling pathway sug gests a comparatively simple transduction mechanism. However, this core pat hway can be deployed in three different types of developmental process: lat eral inhibition, lineage decisions and boundary formation. These illustrate how the activity of the pathway can be modulated both at the cell surface, through availability and effectiveness of ligand interactions, and inside the cell, through effects on the transduction pathway and the responsivenes s of target genes.