Related Experiment Video
Updated: Aug 19, 2026
Implementing Patch Clamp and Live Fluorescence Microscopy to Monitor Functional Properties of Freshly Isolated PKD Epithelium
Published on: September 1, 2015
Differential expression of Cux-1 and p21 in polycystic kidneys from Pkd1 null and cpk mice
Madhulika Sharma1, Jennifer G Brantley, Neal I Alcalay
1Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Background:
Cux-1 is a murine homeodomain protein that functions as a cell cycle-dependent transcriptional repressor in proliferating cells. Targets of Cux-1 repression include the cyclin kinase inhibitors p21 and p27. In the kidney, Cux-1 is spatially and temporally regulated, and ectopic expression of Cux-1 in transgenic mice results in renal hyperplasia. Previously, we observed that Cux-1 is deregulated in cystic kidneys from cpk mice. Recent studies have suggested a role for the cyclin kinase inhibitor p21 in the development of polycystic kidney disease (PKD) in mice lacking PKD1.
Methods:
Since p21 is a target of transcriptional repression by Cux-1, we compared the expression of Cux-1 and p21 in kidneys from Pkd1 null and cpk mice by immunohistochemistry and Western blotting. We also evaluated apoptosis and the expression of the cyclin kinase inhibitor p27 in Pkd1 null and cpk mice by terminal deoxynucleotidal transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) staining, immunohistochemistry, and Western blotting.
Results:
In both early and late embryonic kidneys from Pkd1 null mice, Cux-1 was highly and ectopically expressed in normal-appearing tubule epithelium, interstitial cells, and in the epithelial cells lining the cysts, where it colocalized with proliferating cell nuclear antigen (PCNA). Increased Cux-1 expression in Pkd1 null kidneys was also associated with a decrease in p27 expression at late stages of cystogenesis. In cpk kidneys, Cux-1 was not up-regulated until late stages of cyst development. Moreover, in contrast to Pkd1 null kidneys, p21 and p27 were highly expressed in cpk kidneys. In late stages of cystogenesis, Cux-1 and p21 colocalized in cyst lining cells, which also showed a high incidence of apoptosis.
Conclusion:
These results suggest that cyst development in Pkd1 null mice and cpk mice proceeds through different mechanisms. In Pkd1 null mice, ectopic expression of Cux-1 is associated with increased cell proliferation. In contrast, in cpk mice, ectopic expression of Cux-1 is associated with apoptosis.
Insights
Cux-1 protein deregulation in polycystic kidney disease (PKD) models suggests distinct cyst development pathways. Pkd1 null mice show increased proliferation, while cpk mice exhibit apoptosis, both involving Cux-1.
Area of Science:
- Molecular Biology
- Genetics
- Nephrology
Background:
- Cux-1 is a transcriptional repressor regulating cell cycle genes like p21 and p27.
- Ectopic Cux-1 expression in mice causes renal hyperplasia.
- Cux-1 deregulation was previously observed in cystic kidneys of cpk mice.
Purpose of the Study:
- To investigate the role and expression patterns of Cux-1 in different mouse models of polycystic kidney disease (PKD).
- To compare the mechanisms of cyst development in Pkd1 null and cpk mice concerning Cux-1, p21, and p27 expression.
Main Methods:
- Immunohistochemistry and Western blotting were used to compare Cux-1 and p21 expression in Pkd1 null and cpk kidneys.
- Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) staining, immunohistochemistry, and Western blotting assessed apoptosis and p27 expression.
Main Results:
- In Pkd1 null kidneys, Cux-1 was ectopically expressed and colocalized with PCNA, associated with decreased p27.
- In cpk kidneys, Cux-1 upregulation occurred late, and p21 and p27 were highly expressed.
- In late-stage cpk cystogenesis, Cux-1 and p21 colocalized with high apoptosis incidence.
Conclusions:
- Cyst development in Pkd1 null mice involves increased cell proliferation linked to ectopic Cux-1.
- Cyst development in cpk mice is associated with apoptosis, also involving ectopic Cux-1, suggesting divergent pathogenic mechanisms.
