Inducible Dysplastic Nephropathy in B2-Deficient Mice

描述(申请人提供)：肾脏和尿路发育异常是儿童慢性肾功能衰竭最常见的原因。虽然单基因肾发育不全综合征仍在继续被揭示，但相当大比例的病例是散发性的，被认为是多基因或基因-环境相互作用的结果。在之前的资助期间，我们开发了一种独特的小鼠肾脏发育不全模型，该模型是由明确的基因-环境相互作用产生的。该动物模型表明，在胎儿应激条件下，缓激肽B2受体(B2R)是正常肾脏发育所必需的。作为对妊娠盐负荷的反应，B2R缺失型胎儿获得了一种发育不良的肾脏表型，其特征是细胞过度凋亡、间质扩张和分化基因表达受抑。两条独立的证据支持异常的P53激活在调节肾脏发育不全中的中心作用。首先，发育不良的肾脏过度表达促凋亡形式的P53，即P-Ser46-P53。第二，导致胚系P53单倍体功能不全的遗传杂交挽救了盐胁迫下B2R缺失突变体的肾脏发育。这项建议的长期目标是阐明在发育中的肾脏中导致P53异常激活和终末上皮分化中断的途径。具体目的1将验证这样一种假设，即在B2R缺失的胚胎中诱导P53是受肾脏限制的，并伴随着上游P53应激诱导激酶的激活/表达。具体目的2将使用两种互补的遗传方法来确定P-Ser46-P53在肾发育不全发病机制中的直接作用。第一个涉及减少B2R基因缺失小鼠胚系中的p53基因剂量；第二个是携带突变的Ser46-Ala p53等位基因的B2R基因缺失小鼠。我们推测，在这两种情况下，B2R缺失的后代都将受到保护，免受肾脏发育不全的影响。具体目标3将验证P-Ser46-P53通过将组蛋白脱乙酰酶(HDAC)募集到末端分化基因的启动子区域来抑制分化基因表达的假设。此外，我们还将探讨HDAC抑制剂在恢复终末分化和阻止肾发育不全进展方面的潜在治疗益处。我们预计，我们的研究将出现新的发病模式和治疗策略，有望应用于肾发育不全的治疗。

DESCRIPTION (provided by applicant): Abnormalities of kidney and urinary tract development are the most common cause of chronic renal failure in children. While monogenetic renal dysgenesis syndromes continue to be unraveled, a sizable proportion of cases are sporadic and considered polygenic or a result of gene-environment interactions. During the previous funding period, we developed and characterized a unique mouse model of renal dysgenesis that is produced by defined gene-environment interactions. This animal model demonstrated that the bradykinin B2 receptor (B2R) is required for normal renal development under conditions of fetal stress. In response to gestational salt loading, B2R-null fetuses acquire a dysplastic renal phenotype characterized by excessive apoptosis, stromal expansion, and suppressed differentiated gene expression. Two independent lines of evidence support a central role for aberrant p53 activation in mediating the renal dysgenesis. First, the dysplastic kidneys overexpress a pro-apoptotic form of p53, P-Ser46-p53. Second, genetic crosses resulting in germline p53 haploinsufficiency rescue kidney development in salt-stressed B2R-null mutants. The long-term objective of this proposal is to elucidate the pathways leading to aberrant p53 activation and disruption of terminal epithelial differentiation in the developing kidney. Specific Aim 1 will test the hypothesis that induction of p53 in B2R-null embryos is kidney-restricted and is accompanied by activation/expression of upstream p53 stress-induced kinases. Specific Aim 2 will determine the direct role of P-Ser46-p53 in the pathogenesis of the renal dysgenesis using two complementary genetic approaches. The first involves p53 gene dosage reduction in the germline of B2R-null mice; the second, generation of B2R null mice harboring a mutant Ser46-to-Ala p53 allele. We postulate that, in both cases, the B2R-null progeny will be protected from the renal dysgenesis. Specific Aim 3 will test the hypothesis that P-Ser46-p53 suppresses differentiated gene expression through recruitment of histone deacetylases (HDAC) to the promoter regions of terminal differentiation genes. In addition, we will explore the potential therapeutic benefit of HDAC inhibitors in the restoration of terminal differentiation and halting progression of the renal dysgenesis. We anticipate that new pathogenetic paradigms and therapeutic strategies will emerge from our studies that can hopefully be applied for the treatment of renal dysgenesis.