The Notch (N) pathway is a highly conserved and ubiquitous signalling system involved in determining cell fate. There is a medical relevance to understand the molecular mechanisms involved in N signalling as N dysfunction is linked to cancer, stroke and Alzheimer’s disease. N is activated by its ligands (Delta/Serrate/LAG2;DSL) expressed on adjacent cells and there is a clear correlation between ubiquitination and endocytosis for effective ligand signalling. Although several models for DSL ligand endocytosis have been identified, the behaviour of DSL ligands during these events remains unclear. Attempts to address this issue have lacked the ability to follow spatial and temporal movement of DSL ligands accurately. The current project will therefore address these issues by using live fluorescent imaging techniques to follow movement of Delta (Dl) ligand, fused to a fluorescent reporter, in the wing imaginal disc of Drosophila Melagonaster. This will be achieved by examining Dl molecules present in large intracellular vesicles throughout the wing disc where the ubiquitin ligases Neuralized and Mindbomb1 are expressed. To establish whether Dl activity is dynamic in these particles, we will utilise the FRAP imaging technique. We will follow the movement of Dl molecules from these particles, using a photoswitchable reporter to address the model of “recycling”, where DSL ligands are processed into an active state within these vesicles before being trafficked back to the cell surface to activate N. The effects of impairing endocytosis upon Dl movement from these particles will also be addressed. The project will also address the importance of endocytosis/recycling for effective Dl/N signalling via utilisation of a fluorescent N reporter. These studies will advance our understanding about the dynamic nature of Dl molecules and further assist in elucidating the mechanisms involved in endocytic regulation of N signalling during development.