Studies in the worm C. elegans have contributed extensively to the finding that cystic kidney diseases can be considered ciliopathies; osm-5 is orthologous to the murine polycystic kidney disease gene Tg737, which encodes the protein Polaris and human IFT88; both polaris and OSM-5 have the tetratricopeptide repeat (TPT), a motif that mediates protein-protein interactions; the association of pathologies in mice mutant for Tg737 with ciliary defects in the kidney cells and studies in elegans that demonstrate that osm-5 is expressed and migrates within cilia, substantiate a ciliogenic role for polaris and osm-5, possibly as components of the intraflagellar transport (IFT) system; osm-5 is also required for correct ciliary targeting of lov-1 and pkd-2, genes that are orthologous to human PKD1 and PKD2, which are mutated in human autosomal dominant polycystic kidney disease.