Fig. 1.

Schematic diagram of a primary cilium and associated processes. Polycystic kidney disease (PKD) is controlled by a defined network of different genes/proteins discussed in this review. Cilia are small antennae that detect a variety of different extracellular stimuli and orchestrate multiple signaling pathways with nuclear trafficking of some molecules [e.g., C-termini of polycystin-1 (PC1) and fibrocystin/polyductin (FPC)]. The inner ciliary structure is defined by the axoneme that is composed of nine microtubule doublets derived from the basal body and mother centriole of the centrosome. Along this microtubule core, the transport of proteins in the anterograde direction toward the tip of the cilium and in the retrograde direction towards the cell body is organized by an elaborate process called intraflagellar transport