Role of the cdx homeobox genes in the regulation of wt1 and nephron development

cdx 同源盒基因在 wt1 和肾单位发育调节中的作用

• 批准号: 7579971
• 负责人: Alan J Davidson
• 金额: $ 35.25万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-03 至 2012-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7579971
• 关键词: Affect; Animals; Apoptosis; C.I. Solvent Yellow 56; Cell Proliferation; Cells; Characteristics; Chemicals; Child; Chronic; Chronic Kidney Failure; Code; Congenital Abnormality; Data; Defect; Development; Distal; Electron Microscopy; Embryo; Enzymes; Exhibits; Filtration; Fishes; Gene Expression; Genes; Homeobox; Homeobox Genes; Infant; Intermediate Mesoderm; Kidney; Kidney Diseases; Knowledge; Lead; Light; Link; Mammals; Metanephric structure; Modeling; Molecular; Nephrons; Paraxial Mesoderm; Pathway interactions; Pattern; Play; Positioning Attribute; Pronephric structure; Proteins; Regulation; Reporter; Role; Side; Signal Transduction; Staging; Stream; Testing; Transcription factor genes; Transgenic Organisms; Tretinoin; Vitamin A; Wilms' tumor suppressor 1a; Work; Zebrafish; base; design; functional genomics; in vivo; insight; knock-down; malformation; mutant; nephrogenesis; new therapeutic target; podocyte; prevent; promoter; research study; small molecule; solute; spatiotemporal; transcription factor

DESCRIPTION (provided by applicant): Congenital kidney malformations are the leading cause of chronic renal failure in children. At present, we have a poor understanding of the developmental pathways that control the formation of the nephron, the key functional unit of the kidney. We are using zebrafish to elucidate the embryonic pathways that govern the subdivision of the nephron into functionally distinct segments. The zebrafish embryo is ideal for these studies as the intermediate mesoderm on either side of the trunk forms two simple linear nephrons. From a functional genomics approach we have isolated a number of renal transcription factor and solute transporter genes. The expression patterns of these genes subdivide the zebrafish nephron into distinct proximal and distal segments much like the mammalian nephron. Combinations of transcription factors define each segment suggesting a `renal transcription factor code' determines segment identity. This code is disrupted in embryos deficient in the homeobox transcription factor genes cdx1a and cdx4, which act as master regulators of the hox genes. Doubly-deficient embryos display abnormal hox expression patterns, a posterior shift in the position of the kidney, and a loss of distal tubules. In addition, cdx mutants exhibit expanded expression of Wilms' tumor suppressor-1a (wt1a), a transcription factor implicated in metanephros development and podocyte differentiation in mammals. The cdx genes are expressed in the trunk (paraxial mesoderm) adjacent to the intermediate mesoderm. Expression of raldh2, encoding an enzyme involved in retinoic acid (RA) synthesis, is expanded in the paraxial mesoderm of cdx-deficient embryos. Knock-down of Raldh2 in cdx4 mutants is able to rescue the kidney positioning defect, whereas in wild-types it down-regulates wt1a expression. These results suggest that aberrant RA signaling is responsible for the renal defects in cdx mutants and led us to examine the role of RA in nephron segmentation. Using DEAB, a chemical antagonist of Raldh2, we found that RA is required at multiple stages of nephrogenesis to induce podocytes and the proximal tubules, and to suppress distal tubule fates. Based on these data we hypothesize that the cdx-hox pathway acts upstream of raldh2 to restrict RA synthesis and that RA induces podocytes and proximal tubule fates by up-regulating genes such as wt1a. The aims of this proposal are designed to test this hypothesis. We will characterize the cellular and molecular nephron defects in cdx- and RA-deficient animals and use rescue experiments and knock-down studies to determine the epistatic relationships between the cdx, hox, and raldh2 genes. Using chemical and molecular antagonists of RA, as well as a RA-responsive transgenic reporter line, we will determine where and when RA signaling is required to induce proximal nephron fates. These studies will establish a link between the cdx-hox and RA pathways in the control of nephron segmentation, shed new light on renal birth defects, and will be useful for developing new therapies to treat, or prevent, chronic renal failure.Birth defects that affect the kidneys are the leading cause of chronic renal failure in infants and children, however at present, we have a poor understanding of the genes that control kidney formation. We have found that retinoic acid, a derivative of Vitamin A, plays a central role in regulating normal renal development. This work advances our understanding of how kidneys arise in the embryo and may be lead to new therapeutic targets to treat or prevent chronic renal failure.

描述（由申请人提供）： 先天性肾脏畸形是儿童慢性肾衰竭的主要原因。目前，我们对控制肾脏的关键功能单元的形成的发育途径有糟糕的理解。我们正在使用斑马鱼来阐明控制肾单位分为功能截然不同的段的胚胎途径。斑马鱼的胚胎是这些研究的理想选择，因为中间的中间中胚层都形成了两个简单的线性肾脏。从功能基因组学方法中，我们分离了许多肾转录因子和溶质转运蛋白基因。这些基因的表达模式将斑马鱼肾脏细分为不同的近端和远端段，就像哺乳动物肾单位一样。转录因子的组合定义了每个段表明“肾脏转录因子代码”决定了段的身份。该代码在缺乏同型转录因子基因CDX1A和CDX4的胚胎中被破坏，后者充当HOX基因的主要调节剂。缺陷型胚胎表现出异常的HOX表达模式，肾脏位置的后偏移以及远端小管的损失。此外，CDX突变体表现出Wilms肿瘤1A（WT1A）的扩展表达，这是一种涉及哺乳动物跨虫发育和足细胞分化的转录因子。 CDX基因在中间中胚层附近的躯干（近期中胚层）中表达。 RALDH2的表达，编码与视黄酸合成的酶（RA）合成的酶的表达在CDX缺陷型胚胎的近期中胚层中扩展。 CDX4突变体中RALDH2的敲除可以挽救肾脏定位缺陷，而在野生型中，它下调了WT1A的表达。这些结果表明，异常的RA信号传导负责CDX突变体的肾脏缺陷，并使我们检查了RA在肾单位分割中的作用。使用DEAB（raldh2的化学拮抗剂），我们发现在多个肾脏发生阶段需要RA来诱导足细胞和近端小管，并抑制远端小管命运。基于这些数据，我们假设CDX-Hox途径在RALDH2上游起作用以限制RA合成，并且RA通过上调的基因（例如WT1A）诱导了足细胞和近端小管命运。该提案的目的旨在检验该假设。我们将表征CDX和RA缺陷动物中的细胞和分子肾脏缺损，并使用救援实验并进行敲门研究来确定CDX，HOX和RALDH2基因之间的同志关系。使用RA的化学和分子拮抗剂，以及RA反应性转基因报告基因，我们将确定需要在何处以及何时何时何地诱导近端肾单位命运。这些研究将建立CDX-HOX和RA途径之间的联系，以控制肾单位分割，对肾脏先天缺陷进行新的启示，对于开发治疗或预防的新疗法将很有用。但是，影响肾脏的慢性肾衰竭缺陷，影响肾脏的主要原因是婴儿和儿童的慢性肾衰竭的主要原因，但是目前，我们的培训是不良的培训。我们发现，维生素A的衍生物视黄酸在调节正常肾脏发育中起着核心作用。这项工作提高了我们对肾脏如何在胚胎中出现的理解，并可能导致新的治疗靶标，以治疗或预防慢性肾衰竭。