Genetic evidence is quite strong that ciliary dysfunction is an important determinant of renal epithelial cell biology and cystogenesis: 1) The gene products of PKD1 and PKD2 (polycystin 1 and polycystin 2) [8], Tg737 (polaris) [19], and cpk (cystin) [20] localize to the cilium [21] and mutations in these genes result in the transformation of a tubular, absorbing epithelium into a cystic, fluid secreting epithelium with clinical symptoms of polycystic kidney disease [8], [22]. This evidence concerns the gene PKD1 and polycystic kidney disease.