Epithelial polarisation plays an important role in tissue morphogenesis and perturbations in this process can lead to developmental defects and cause cancer. My group has recently identified a novel vertebrate- and epithelialspecific SNARE, STX19, that is required for the delivery of biosynthetic and endocytic material to the cell surface. Using proteomics and yeast-two-hybrid screening we have identified several novel, STX19 interacting partners that are important players in establishing and maintaining epithelial polarity. It is our hypothesis that STX19 plays a role in the delivery of cell polarity proteins to the cell surface and is required for epithelial polarisation. To test this hypothesis shRNA will be used to knock down STX19 and its interacting partners in 2 and 3D cell cultures models and epithelial polarisation visualized using structured illumination microscopy. To asses the physiological role of STX19, CRISPR/Cas9 will be also used to generate a STX19 knockout zebrafish and organ development monitored using light sheet microscopy. Using both SIM and light sheet microscopy will allow the processes which drive tissue development to be visualised at an unprecedented spatiotemporal resolution.