Polycystic kidney disease: new understanding in the pathogenesis.

Polycystic kidney disease (PKD) is a disease of the nephron, characterized by the formation of multiple renal tubular cysts, leading to endstage renal failure. The most common form is autosomal dominant PKD (ADPKD) and is caused by mutations in the PKD1 gene in 85% of cases or in PKD2 in 10-15%. Rarer forms include autosomal recessive PKD (ARPKD) and nephronophthisis with high mortality and morbidity in children. Recent advances suggest that the PKD1-encoded protein, polycystin-1, is a renal epithelial cell membrane mechanoreceptor, sensing morphogenetic cues in the extracellular environment at the basal surface in focal adhesion complexes; at the lateral surface in cell adherens junctions; and in the lumen at the apical primary cilium. Activation via multiprotein complex formation, intracellular signal transduction cascades and regulation of fetal gene transcription leads to appropriate renal tubule epithelial cell division and differentiation in normal kidneys, but is disrupted in PKD resulting in cyst formation.