REGULATION OF KIDNEY DEVELOPMENT

肾调节体液的体积和组成。 期间 胚胎发育肾单位，肾脏的功能单位，形成 从中间中胚层分化， 输尿管芽接触71例。该项目的目标是确定 Wnt基因在肾发生中的作用及输尿管芽的调控机制 形成和生长。 Wnt基因家族的成员已经被牵连在发育中。 调节和Wnt-1在胚胎脊髓中表达，这是一种有效的 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的几位成员 基因家族在肾脏中表达，我们将测试这些基因家族中的任何一个 基因赋予培养的成纤维细胞肾单位诱导活性（32，79，83）。 Wnt基因产物是分泌的基质结合糖蛋白， 可能是输尿管芽分泌的肾单位诱导蛋白 矩阵相关（5，71）。无成纤维细胞Wnt +细胞外基质 制备并测试体外肾单位诱导活性。 所有描述输尿管芽形成的模型都是基于 介导肾小管生长的特征性机制（58）。时间 Wnt-11 mRNA的空间分布提高了它可能 在肾小管形态发生中起作用。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 介导的基因转移，我们将测试是否禽肾管和 输尿管芽的形成完全由导管上皮细胞的生长，或由 导管的生长和诱导的细胞从后部募集 中间中胚层（48）。后一种机制介导肾小管 在非洲爪蟾发育过程中的延伸，以及我们最近的谱系分析， 实验室提出大鼠输尿管芽/肾 收集系统以类似的方式生长（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，以识别 输尿管芽/肾集合系统和独立标记方法 带有基因标签的细胞此外，我们将测试RET、Sd或Ld是否 突变的中间中胚层，像野生型一样，能够形成 当与均匀标记的细胞共培养时， 输尿管芽（40，45，74）。这些实验的结果将测试 体内肾集合系统形态发生依赖于 从中间中胚层募集细胞。

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.