PDX-1 Regulation of Intestinal Pattern Formation

描述(由申请人提供)：胚胎发育期间胃肠道的模式导致沿着小肠的前后(A-P)轴有不同的形态和功能区域。小肠上皮细胞来源于肠道内胚层细胞谱系，在消化和吸收所摄取的营养物质中起作用，其基因表达模式沿A-P轴存在空间差异。肠道畸形和上皮细胞功能缺陷常常表现为人类的致命性疾病。然而，关于调节肠道形成的基因仍有许多需要了解。这项建议的总体目标是阐明调节胃肠道模式、分化和功能的分子机制。有证据表明，HOX和ParaHox功能在胚胎中建立了重要的发育轴，包括胃肠道中的前后命运。最近对小鼠的研究表明，ParaHox成员胰腺十二指肠同源盒-1蛋白PDX-1在建立和维持发育中的胰腺分化方面发挥了作用。然而，PDX-1在小肠发育中的作用尚未完全阐明。初步研究表明，PDX-1能够诱导和抑制肠道特异基因。我们假设PDX-1通过调节肠道靶基因启动子参与建立和维持沿小肠A-P轴的上皮细胞基因表达模式。因此，研究目标旨在表征PDX-1在肠道发育中的作用，并阐明PDX-1调控肠道基因的机制。在目标1中，我们将使用条件十二指肠PDX-1失活和异位PDX-1过表达的小鼠模型来确定PDX-1在小肠发育模式中的作用。在目标2中，我们将利用微阵列技术鉴定基因表达谱并鉴定新的PDX-1肠道靶基因。在目标3中，我们将进行分子实验，以确定PDX-1对肠道靶基因启动子转录调控的机制。我们的体外和体内实验方法的结合将阐明PDX-1在胃肠道发育模式中的作用，并将增加我们对脊椎动物器官发生的理解。此外，对肠道上皮基因表达调控机制的了解可能为导致上皮功能丧失或不适当获得的胃肠道疾病提供新的诊断、治疗或预后策略。

DESCRIPTION (provided by applicant): Patterning of the gastrointestinal tract during embryogenesis results in distinct morphologic and functional regions along the anterior-posterior (A-P) axis of the small intestine. The epithelial cells of the small intestine are derived from the gut endoderm cell lineage and function in the digestion and absorption of ingested nutrients with spatial differences in gene expression patterns along the A-P axis. Intestinal malformations and defects in epithelial cell function can often manifest as lethal diseases in humans. However, much remains to be learned about the genes that regulate gut formation. The overall goal of this proposal is to elucidate molecular mechanisms regulating gastrointestinal patterning, differentiation and function. Evidence suggests that Hox and Parahox functions establish important developmental axes in the embryo, including anterior-posterior fates in the gastrointestinal tract. Studies of mice have recently demonstrated a role for the Parahox member pancreatic duodenal homeobox-1 protein, PDX-1, in establishing and maintaining differentiation of the developing pancreas. However, the role of PDX-1 in small intestinal development has not been fully elucidated. Preliminary studies have shown that PDX-1 is capable of inducing and repressing intestine-specific genes. We hypothesize that PDX-1 is involved in establishing and maintaining epithelial cell gene expression patterns along the A-P axis of the small intestine through regulation of intestinal target gene promoters. Research objectives are therefore aimed at characterizing the role of PDX-1 in intestinal development and elucidating mechanisms involved in PDX-1 regulation of intestinal genes. In Aim 1, we will define the role of PDX-1 in patterning small intestinal development using mouse models with conditional duodenal PDX-1 inactivation and ectopic PDX-1 overexpression. In Aim 2, we will characterize gene expression profiles and identify novel PDX-1 intestinal target genes by utilizing microarray technology. In Aim 3, we will perform molecular experiments aimed at characterizing mechanisms involved in PDX-1 transcriptional regulation of intestinal target gene promoters. Our combination of in vitro and in vivo experimental approaches should elucidate roles for PDX-1 in patterning gastrointestinal development and will add to our understanding of vertebrate organogenesis. In addition, knowledge of mechanisms regulating gut epithelial gene expression may provide novel diagnostic, therapeutic or prognostic strategies for gastrointestinal disorders that result in loss or inappropriate gain of epithelial function.