Polycystic kidney disease (PKD) includes a group of disorders that are 
characterized by the presence of cysts in the kidney and other organs, including 
the pancreas. Here we show that in orpk mice, a model system for PKD that 
harbors a mutation in the gene that encodes the polaris protein, pancreatic 
defects start to occur at the end of gestation, with an initial expansion of the 
developing pancreatic ducts. Ductal dilation continues rapidly after birth and 
results in the formation of large, interconnected cysts. Expansion of pancreatic 
ducts is accompanied by apoptosis of neighboring acinar cells, whereas endocrine 
cell differentiation and islet formation appears to be unaffected. Polaris has 
been shown to co-localize with primary cilia, and these structures have been 
implicated in the formation of renal cysts. In the orpk pancreas, cilia numbers 
are reduced and cilia length is decreased. Expression of polycystin-2, a protein 
involved in PKD, is mislocalized in orpk mice. Furthermore, the cellular 
localization of beta-catenin, a protein involved in cell adhesion and Wnt 
signaling, is altered. Thus, polaris and primary cilia function are required for 
the maturation and maintenance of proper tissue organization in the pancreas.