Project Summary/Abstract Chronic kidney disease (CKD) poses an important global disease burden with limited therapeutic options. Novel therapeutic strategies to improve renal function include implanting patient-derived kidney organoids onto the native kidneys. However, an inability to connect organoid tubules with the host’s kidney tubules presents a major problem that remains to be solved. Currently, the molecular mechanisms driving interconnection between tubules and their lumens are poorly understood. Filling this gap in knowledge is critical to advance work with implantable renal replacement tissues. Our previous studies have shown that mice lacking afadin, a cytoskeletal scaffolding protein, from renal epithelial tubules, have a defect in lumen continuity. The goal of this project is to determine how lumen connection/fusion occurs within tubules and determine the molecular mechanism by which afadin promotes lumen fusion and maintenance in renal epithelia. We hypothesize that lumen fusion requires cellular rearrangements and that these are facilitated by afadin-mediated regulation of cell-cell contacts. Here, I propose to use well-defined in vitro and in vivo models to: (1) Determine the mechanism of lumen fusion after the onset of de novo lumenogenesis, (2) Identify the afadin domains required for lumen fusion, and (3) Determine the role of afadin in lumen maintenance in vitro and in an in vivo inducible knockout mouse model. The knowledge obtained from these studies will enable a better design of epithelial structures that have the ability to form and maintain a continuous lumen for future use as implantable therapeutics.