Monitoring notch/delta endosomal trafficking and signaling in Drosophila.

The Notch signaling pathway plays important roles in many organisms and developmental contexts. The activities of the Notch receptor and of its ligand Delta are known to be regulated at several steps along the endocytic pathway. However, the precise molecular mechanism of Notch activation and the role played by endosomal sorting and trafficking remain elusive. We developed an antibody uptake assay to enable live imaging of endogenous internalized Notch and Delta in Drosophila tissues. In this chapter, we describe how to perform live antibody uptake assays in the Drosophila notum. In this tissue, Notch signaling plays a crucial role in the regulation of cell fate decisions in the lineage of sensory organ precursor (SOP) cells. We describe here how to do a correlative analysis of Notch/Delta live imaging in dividing SOPs and of the lineage of these particular SOPs. Combined with the wide range of genetic and chemical tools available in Drosophila research, these two methods will provide a better understanding of the role played by endocytic proteins and endosomal trafficking in Notch regulation, in terms of botch Notch trafficking and Notch signaling output.