Section of Pediatric Nephrology, Department of Pediatrics, Tulane University Health Sciences Center, New Orleans, Louisiana, United States of America.
PLoS One. 2012;7(9):e44869. doi: 10.1371/journal.pone.0044869. Epub 2012 Sep 12.
Congenital reduction in nephron number (renal hypoplasia) is a predisposing factor for chronic kidney disease and hypertension. Despite identification of specific genes and pathways in nephrogenesis, determinants of final nephron endowment are poorly understood. Here, we report that mice with germ-line p53 deletion (p53(-/-)) manifest renal hypoplasia; the phenotype can be recapitulated by conditional deletion of p53 from renal progenitors in the cap mesenchyme (CM(p53-/-)). Mice or humans with germ-line heterozygous mutations in Pax2 exhibit renal hypoplasia. Since both transcription factors are developmentally expressed in the metanephros, we tested the hypothesis that p53 and Pax2 cooperate in nephrogenesis. In this study, we provide evidence for the presence of genetic epistasis between p53 and Pax2: a) p53(-/-) and CM(p53-/-)embryos express lower Pax2 mRNA and protein in nephron progenitors than their wild-type littermates; b) ChIP-Seq identified peaks of p53 occupancy in chromatin regions of the Pax2 promoter and gene in embryonic kidneys; c) p53 binding to Pax2 gene is significantly more enriched in Pax2 -expressing than non-expressing metanephric mesenchyme cells; d) in transient transfection assays, Pax2 promoter activity is stimulated by wild-type p53 and inhibited by a dominant negative mutant p53; e) p53 knockdown in cultured metanephric mesenchyme cells down-regulates endogenous Pax2 expression; f) reduction of p53 gene dosage worsens the renal hypoplasia in Pax2(+/-) mice. Bioinformatics identified a set of developmental renal genes likely to be co-regulated by p53 and Pax2. We propose that the cross-talk between p53 and Pax2 provides a transcriptional platform that promotes nephrogenesis, thus contributing to nephron endowment.
先天性肾单位数量减少（肾发育不全）是慢性肾脏病和高血压的一个易感因素。尽管已经确定了肾发生过程中的特定基因和途径，但终末肾单位数量的决定因素仍知之甚少。在这里，我们报道了具有种系 p53 缺失（p53(-/-)）的小鼠表现出肾发育不全；该表型可以通过条件性删除帽间充质（CM(p53-/-)）中的肾祖细胞中的 p53 来重现。种系中存在 Pax2 杂合突变的小鼠或人类表现出肾发育不全。由于这两种转录因子在后肾中均有发育表达，因此我们测试了 p53 和 Pax2 在肾发生中合作的假设。在这项研究中，我们提供了 p53 和 Pax2 之间存在遗传上位性的证据：a）p53(-/-)和 CM(p53-/-)胚胎中的肾祖细胞中 Pax2 mRNA 和蛋白的表达低于其野生型同窝仔；b）ChIP-Seq 鉴定了胚胎肾脏中 p53 结合在 Pax2 启动子和基因染色质区域的峰；c）p53 与 Pax2 基因的结合在表达 Pax2 的后肾间充质细胞中明显更丰富，而非表达的后肾间充质细胞；d）在瞬时转染实验中，野生型 p53 刺激 Pax2 启动子活性，而显性负突变 p53 抑制 Pax2 启动子活性；e）在培养的后肾间充质细胞中敲低 p53 可下调内源性 Pax2 表达；f）降低 p53 基因剂量会加重 Pax2(+/-)小鼠的肾发育不全。生物信息学鉴定了一组可能由 p53 和 Pax2 共同调控的发育性肾基因。我们提出，p53 和 Pax2 之间的串扰提供了一个促进肾发生的转录平台，从而有助于终末肾单位的数量。
