Polaris, a protein involved in left-right axis patterning, localizes to basal bodies and cilia

Mutations in Tg737 cause a wide spectrum of phenotypes, including random le ft-right axis specification, polycystic kidney disease, liver and pancreati c defects, hydrocephalus, and skeletal patterning abnormalities. To further assess the biological function of Tg737 and its role in the mutant patholo gy, we identified the cell population expressing Tg737 and determined the s ubcellular localization of its protein product called Polaris. Tg737 expres sion is associated with cells possessing either motile or immotile cilia an d sperm. Similarly, Polaris concentrated just below the apical membrane in the region of the basal bodies and within the cilia or flagellar axoneme. T he data suggest that Polaris functions in a ciliogenic pathway or in cilia maintenance, a role supported by the loss of cilia on the ependymal cell la yer in ventricles of Tg7370(orpk) brains and by the lack of node cilia in T g737(Delta2-3 beta Gal) mutants.