A role for p53 in terminal epithelial cell differentiation
Zubaida Saifudeen, … , Susana Dipp, Samir S. El-Dahr
Zubaida Saifudeen, … , Susana Dipp, Samir S. El-Dahr
Published April 15, 2002
Citation Information: J Clin Invest. 2002;109(8):1021-1030. https://doi.org/10.1172/JCI13972.
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A role for p53 in terminal epithelial cell differentiation

Abstract

Terminal epithelial cell differentiation is a crucial step in development. In the kidney, failure of terminal differentiation causes dysplasia, cystogenesis, and cancer. The present study provides multiple lines of evidence implicating the tumor suppressor protein p53 in terminal differentiation of the renal epithelium. In the developing kidney, p53 is highly enriched in epithelial cells expressing renal function genes (RFGs), such as receptors for vasoactive hormones, the sodium pump, and epithelial sodium and water channels. In comparison, proliferating renal progenitors express little if any p53 or RFGs. p53 binds to and transactivates the promoters of RFGs. In contrast, expression of a dominant negative mutant form of p53 inhibits endogenous RFG expression. Moreover, binding of endogenous p53 to the promoters of RFGs coincides with the differentiation process and is attenuated once renal epithelial cells are fully differentiated. Finally, p53-null pups exhibit a previously unrecognized aberrant renal phenotype and spatial disorganization of RFGs. Interestingly, the p53-related protein p73 is unable to functionally compensate for the loss of p53 and fails to efficiently activate RFG transcription. We conclude that p53 promotes the biochemical and morphological differentiation of the renal epithelium. Aberrations in p53-mediated terminal differentiation may therefore play a role in the pathogenesis of nephron dysgenesis and dysfunction.

Authors

Zubaida Saifudeen, Susana Dipp, Samir S. El-Dahr

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DN p53 inhibits RFG expression and promoter activity. (a) IMCD3 cells we...
DN p53 inhibits RFG expression and promoter activity. (a) IMCD3 cells were cotransfected with increasing amounts (0, 100, and 500 ng) of a viral promoter–driven DN p53 plasmid and a fixed amount (1.2 μg) of B2R, AT1A, and Na,K-ATPase-α1 promoter-reporter constructs. Cell lysate was harvested 24 hours after transfection and was assayed for CAT or luciferase activity. (b) Representative RT-PCR assays of RFG mRNA expression. Transfection of IMCD3 cells with DN p53 plasmid (1.0 μg DNA) represses endogenous B2R (range 1.5- to 4-fold; n = 3), Na,K-ATPase-α1 (2.5- to 4-fold; n = 3), and AT1A (2- to 4-fold; n = 3) mRNA expression relative to that found in control pSV-lacZ–transfected cells. Transfection of pCMV-p53 (wild-type) plasmid (1.0 μg DNA) activates B2R and Na,K-ATPase-α1 mRNA expression. A full-length rat B2R cDNA template (lane labeled cDNA) was used as positive control in the PCR amplification reaction for B2R. GAPDH expression was not affected by wild-type or DN p53. (c–e) Effects of DN p53 on endogenous RFG expression evaluated by Western blot analysis using B2R (c), AT1A (d), and Na,K-ATPase-α1 (e) antibodies. Transfection efficiency in these experiments ranged between 30% and 40%. Western blotting with PAb240 shows evidence of overexpression of human DN p53. Probing for β-actin assessed equal loading of proteins on the gel. RT: reverse transcriptase; WT: wild-type; Na,K: Na,K-ATPase-α1.