Abstract: During the past years, we have identified several factors that have contributed to the understanding of how lipidated Wnt proteins are produced and secreted. Specifically, we identified the multi-pass transmembrane protein Evi/Wls as a cargo-receptor for Wnt proteins. Evi/Wls shuttles from the Golgi to the plasma membrane and is recycled through the endocytic compartment back to the Golgi. Furthermore, we found that p24-proteins are required for sorting of Wnts into COPII-vesicles. However, it remains unknown how and where in the cell Wnt proteins are unloaded from the cargo-receptor complex and whether compartment-specific unloading leads to Wnt protein association with specific extracellular carriers or vesicles. As part of the SFB1324, we are interested in understanding how Wnt proteins are released from the cargo-receptor, how the Wnt proteins are secreted in polarized tissues in vivo and how these mechanisms contribute to overall Wnt activity. To address these questions, we will combine novel genome engineering tools with well-established cell biology methods and novel imaging techniques such as super-resolution microscopy to study the process of Wnt secretion and the physiological consequences of perturbed secretion routes in cells and in vivo in Drosophila.