REGULATION OF KIDNEY DEVELOPMENT

肾脏调节体液的体积和成分。在.期间 胚胎发育的肾单位，肾脏的功能单位，形成 在诱导分化后从中间中胚层分化出来 输尿管芽接触(71例)。该项目的目标是确定 Wnt基因在肾脏发生中的作用及其引导输尿管芽生长的机制 形成和生长。 Wnt基因家族的成员与发育有关 调节和WNT-1在胚胎脊髓中表达，一种有效的 体外肾单位形成诱导剂(55，79)。我们证明了 表达外源性Wnt-1的成纤维细胞触发分离的中间体 中胚层分化为肾单位(32)。WNT的几名成员 基因家族在肾脏中表达，我们将测试其中是否有 基因赋予培养的成纤维细胞诱导肾单位的活性(32，79，83)。 WNT基因产物是分泌的基质结合糖蛋白，它是 可能是输尿管芽分泌的肾单位诱导蛋白(S) 是否与矩阵关联(5，71)。无成纤维细胞WNT+细胞外基质 将被制备并在体外测试肾单位的诱导活性。 所有描述输尿管芽形成的模型都是基于 描述了调节肾管生长的机制(58)。世俗的 WNT-11mRNA的空间分布增加了它的可能性 在肾管形态发生中起一定作用。我们将确定是否 持续的Wnt-11表达扰乱了这一过程。使用逆转录病毒 介导性基因转移我们将测试鸟类肾管和 输尿管芽完全通过导管上皮的生长形成，或者通过 导管的生长和从后部诱导的细胞募集 中间中胚层(48个)。后一种机制调节肾管 非洲爪蛙发育过程中的伸长，以及最近在我们的 实验室增加了大鼠输尿管芽/肾 收集系统也以类似的方式发展(12)。谱系分析 测试分离的中间中胚层的分化命运将是 使用额外的组织化学标记物加强了对 输尿管芽/肾收集系统和一种独立的标记方法 带有基因组标签的细胞。此外，我们还将测试RET、SD或LD 突变的中间中胚层，像野生型一样，能够形成 与均相标记共培养时的肾脏收集系统 输尿管芽肿40例，45例，74例。这些实验的结果将检验 肾收集系统在体内形态发生依赖的假说 关于中间中胚层细胞的募集。

The kidney regulates the volume and composition of body fluids. During embryonic development nephrons, the functional units of the kidney, form from intermediate mesoderm after it is induced to differentiate by ureteric bud contact (71). The goal of this project is to determine the role of Wnt genes in nephrogenesis and the mechanisms guiding ureteric bud formation and growth. Members of the Wnt gene family have been implicated in developmental regulation and Wnt-1 is expressed in embryonic spinal cord, a potent inducer of nephron formation in vitro (55,79). We demonstrate that fibroblasts expressing exogenous Wnt-1 trigger isolated intermediate mesoderm to differentiate into nephrons (32). Several members of the Wnt gene family are expressed in kidney and we will test whether any of these genes confer nephron-inducing activity to cultured fibroblasts (32,79,83). Wnt gene-products are secreted matrix-binding glycoproteins and it is likely that the nephron inducing protein(s) secreted by the ureteric bud are matrix associated (5,71). Fibroblast-free Wnt + extracellular matrices will be prepared and tested for nephron inducing activity in vitro. All models describing ureteric bud formation are based on the poorly characterized mechanisms mediating nephric duct growth (58). The temporal and spatial distribution of Wnt-11 mRNA raises the possibility that it plays a role in nephric duct morphogenesis. We will determine if persistent Wnt-11 expression perturbs this process. Using retroviral mediate gene transfer we will test whether the avian nephric duct and ureteric bud form exclusively by growth of the duct epithelium, or by growth of the duct and induced recruitment of cells from posterior intermediate mesoderm (48). This latter mechanism mediates nephric duct elongation during Xenopus development, and recent lineage analyses in our laboratory raise the possibility that the rat ureteric bud/renal collecting system grows in an similar manner (12). Lineage analyses testing the differentiated fate of isolated intermediate mesoderm will be strengthened using an additional histochemical marker to identify the ureteric bud/renal collecting system and an independent method of marking cells with a genomic tag. In addition, we will test whether RET, Sd, or Ld mutant intermediate mesoderm, like wild type, is competent to form the renal collecting system when co-cultured with homogeneously marked ureteric buds (40,45,74). Results of these experiments will test the hypothesis that renal collecting system morphogenesis in vivo is dependent on recruitment of cells from intermediate mesoderm.