Beta-catenin signalling in mesenchymal islet-derived precursor cells.
OBJECTIVE
Previously, we characterized human islet-derived precursor cells (hIPCs) as mesenchymal stem cells that migrate out from islets in vitro and can differentiate into functional islet-like structures following proliferative expansion. Here, we investigate the role of beta-catenin signalling in derivation and proliferation of hIPCs.


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.
Ikonomou
L
L
Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-8029, USA.
Geras-Raaka
E
E
Raaka
B M
BM
Gershengorn
M C
MC
D015415:Biomarkers / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology* / Q000378:metabolism*; D008648:Mesoderm / Q000166:cytology* / Q000378:metabolism; D021381:Protein Transport; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*; D014158:Transcription, Genetic; D051153:Wnt Proteins / Q000235:genetics; D051176:beta Catenin / Q000378:metabolism*
D015415:Biomarkers; C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D051153:Wnt Proteins; D051176:beta Catenin