Expression data from renal primary epithelial cells

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the formation of multiple fluid-filled cysts that destroy the kidney architecture resulting in end-stage renal failure. Mutations in the ADPKD genes PKD1 and PKD2 account for nearly all the cases of ADPKD. Increased cell proliferation is one of the key features of the disease. Several studies indicated that polycystin-1, the product of PKD1, regulates cellular proliferation through various signaling pathways, but little is known about the role played by polycystin-2, the product of PKD2. Recently, it was reported that as with polycystin-1, polycystin-2 can acts as a negative regulator of cell growth by modulating the levels of the cyclin-dependent kinase inhibitor, p21 and the activity of the cyclin-dependent kinase 2, Cdk2. In this study we utilized different kidney cell lines expressing wild-type and mutant PKD2 as well as primary tubular epithelial cells isolated from a PKD transgenic rat to further explore the contribution of the p21/Cdk2 pathway in ADPKD proliferation. Surprisingly, over-expression of wild-type PKD2 in renal cell lines failed to inactivate Cdk2 activity and consequently had no effect on cell proliferation. On the other hand, expression of mutated PKD2 augmented proliferation only in the primary tubular epithelial cells of a rat model but this was independent of STAT-1/p21 pathway. Genome-wide expression analysis in these cells revealed that expression of the cyclin-dependent kinase inhibitor, p57 is downregulated, while p21 remains unchanged. This p57 reduction is accompanied by an increase in Cdk2 levels. Our results indicate the probable involvement of p57 on epithelial cell proliferation in polycystic kidney disease. In addition, it confirms that PKD2-induced proliferation is a multifactorial process. We used microarrays to study the modulation of gene expression by mutated PKD2 in the primary tubular epithelial cells of a transgenic rat mode Keywords: transgene Gene expression in the primary tubular epithelial of a transgenic rat mode with mutated PKD2 was compared with that of SD control rats