This is further supported by the observation of an overexpression of polycystin-1 in end stage ADPKD renal cystic epithelia, even though it has been suggested that this constitutes only a secondary phenomenon reflecting the differentiation stage of end-stage cystic epithelia, thus being only a consequence of the mechanisms initially triggering cyst development [176]. This evidence concerns the gene PKD1 and autosomal dominant polycystic kidney disease.