An important component of the kidney are the tubes that make urine. These tubes, as the name implies, are usually long channels through which the urine flows. In polycystic kidney disease (PKD), these tubes start to dilate and can become large balls (cysts) filled with fluid. Sometimes they are disconnected from the other tubes and are no longer capable of making urine. This results in the kidney not working properly. We study the mechanisms responsible for the tubes becoming cystic using genetically engineered mice that have a form of and cell lines that mimic some of the characteristics of PKD.