Cdx in GI Differentiation and Transdifferentiation

描述（申请人摘要）：多个基因的复杂相互作用 在内胚层和中胚层中表达是分化所必需的， 胃肠道的发育。专业化和独特的 食道、胃、肠和结肠的上皮细胞来自于 在胚胎发生期间的内胚层。这些器官的独特特征是 然而，通常在整个生命过程中维持，转分化或肠 化生可发生在食管中出现的膀胱型粘膜，或 胃这一重要的人类癌前病变的起源尚不清楚， 具有明确的临床意义。CDX1和CDX2，肠特异性同源框 转录因子，是指导发育的候选基因， 分化和维持肠表型。此外，CDX1 和CDX2，虽然在正常胃或食管中不表达， 在胃和食管粘膜的肠上皮化生中表达。的 研究者假设CDX1和CDX2指导转分化 发生在肠上皮化生中的程序。这一假设将得到解决 通过相互关联的特定目标，采用转基因小鼠模型来探索 Cdx1和Cdx2在发育中的胃和成年胃中的作用， 食管上皮细胞通过这两种基因的错误表达。具体目标1 研究了Cdx表达在早期胚胎发生中的生物学后果。 Cdxl和Cdx2的编码区将被置于 Hnf3 γ顺式调节元件，其将指导Cdxl的异位表达 或Cdx2在转基因小鼠发育中的胃内胚层中的表达。的 申请人已经通过该方法成功地表达了Cdx2， 肠型细胞的证据。具体目标2利用第二转基因 小鼠模型，以确定Cdx表达对分化的 通过将Cdx1或Cdx2的编码区 在四环素诱导型启动子的控制下。两者的表型 将检查转基因模型的形态学和基因表达的变化。 表情将测定肠特异性基因的表达， 随后分析将包括消减杂交以详细研究 在表达转基因的组织中差异表达的基因。在 此外，由于肠上皮化生是人类的癌前病变， 评估动物对癌症的易感性增加。总的来说， 该项目的总体目标是阐明Cdxl的生物学作用， 和Cdx2在肠上皮化生中的作用及其分子机制 由Cdxl和Cdx2诱导的转分化程序。

DESCRIPTION (Applicant's Abstract): Complex interactions of multiple genes expressed in the endoderm and mesoderm are necessary for differentiation and development of the gastrointestinal tract. The specialized and distinct epithelia of the esophagus, stomach, intestine and colon arise from the endoderm during embryogenesis. The unique characteristics of these organs are usually maintained throughout life, however, transdifferentiation or intestinal metaplasia can occur in which intestinal-type mucosa arises in the esophagus or stomach. The origin of this important human premalignant lesion is unknown but of clear clinical relevance. CDX1 and CDX2, intestine specific homeobox transcription factors, are candidate genes for directing development, differentiation and the maintenance of the intestinal phenotype. Moreover, CDX1 and CDX2, although not expressed in the normal stomach or esophagus, are expressed in intestinal metaplasia of the gastric and esophageal mucosa. The investigator hypothesizes that CDX1 and CDX2 direct the transdifferentiation program that occurs in intestinal metaplasia. This hypothesis will be addressed by interrelated specific aims, which employ transgenic mouse models to explore the effects of Cdxl and Cdx2 in the developing stomach and adult gastric and esophageal epithelia through misexpression of both genes. Specific aim 1 examines the biological consequences of Cdx expression in early embryogenesis. The coding regions of Cdxl and Cdx2 will be placed under the control of Hnf3gamma cis-regulatory elements, which will direct ectopic expression of Cdxl or Cdx2 in the endoderm of the developing stomach of transgenic mice. The applicant has already successfully expressed Cdx2 by this method and has evidence of intestinal type cells. Specific aim 2 utilizes a second transgenic mouse model to define the effect of Cdx expression on the differentiated esophageal and gastric mucosa by placing the coding regions of Cdxl or Cdx2 under the control of a tetracycline inducible promoter. The phenotype of both transgenic models will be examined for changes in morphology and gene expression. The expression of intestine specific genes will be determined and subsequent analysis will include subtractive hybridization to study in detail genes that are differentially expressed in tissue expressing the transgene. In addition, as intestinal metaplasia is a premalignant condition in humans, the animals will be assessed for increased susceptibility to cancer. In summary, the overall goal of this project is to elucidate the biological roles of Cdxl and Cdx2 in intestinal metaplasia and the molecular mechanisms of the transdifferentiation program induced by Cdxl and Cdx2.