In our group we are mainly interested in the mechanisms of cyst growth in polycystic kidneys. There is a variety of polycystic kidney diseases that are often hereditary. The most frequent form is the autosomal dominant polycystic kidney disease ADPKD. It affects one in one thousand people and leads to the development of various fluid-filled cavities (cysts) in both kidneys. Cysts then grow continuously over time which causes compression of adjacent unaffected tissue which often results in loss of renal function. Cyst expansion can mainly be attributed to secretion of chloride and fluid by the cyst epithelium into the interior of the cyst. We investigate proteins but also environmental factors that may play a role in cyst secretion. Our long-term objective is to find strategies in order to inhibit cyst growth and therefore preserve renal function.