Conclusions
These results support a functional role for beta-catenin during proliferation of hIPCs and suggest that activated beta-catenin signalling may also be important during hIPC derivation from islets.
Methods
Localization of beta-catenin was performed using confocal microscopy. Expression levels of beta-catenin target genes were measured by quantitative real-time polymerase chain reaction. Loss-of-function studies were performed using specific short interfering RNAs.
Results
Immunostaining of islet outgrowths revealed translocation of beta-catenin from plasma membranes in intact islets to the nucleus in cells migrating out. There were no nuclear beta-catenin-positive cells in intact islets whereas between 35% and 70% of cells in established hIPC cultures exhibited nuclear beta-catenin. Transcripts for beta-catenin target genes were increased in hIPCs compared to those in islets. Beta-catenin translocated to the cell membrane when hIPCs formed epithelial cell clusters. In proliferating hIPCs, there was a strong correlation between markers of proliferation and nuclear beta-catenin. Treatment of hIPCs with the glycogen synthase kinase-3beta inhibitor (2'Z,3'E)-6-Bromoindirubin-3'-oxime increased intracellular beta-catenin but reduced nuclear beta-catenin, and was associated with reduced cell proliferation. Finally, knockdown of beta-catenin decreased beta-catenin target gene expression and hIPC proliferation. Conclusions: These results support a functional role for beta-catenin during proliferation of hIPCs and suggest that activated beta-catenin signalling may also be important during hIPC derivation from islets.