Mechanisms of endoderm specification along the A-P axis.

描述(申请人提供)：尽管包括肺、肝、胰腺和肠道在内的内胚层器官的先天性缺陷普遍存在，但令人惊讶的是，人们对决定内胚层器官原基将沿着前后(A-P)轴形成的机制知之甚少，这是本研究的长期目标。我们已发表的和初步的研究表明，内胚层模式在脊椎动物中高度保守，我们假设一种生长因子FGF4在体内建立这些肠管结构域中发挥核心作用。FGF4的表达模式和我们的初步数据表明，FGF4通过促进后内胚层细胞和抑制前内胚层细胞的命运来模式肠管。这项提议旨在确定实现这一目标的机制。我们发现，FGF4可以直接调节A-P内胚层细胞的命运，并且FGF4改变了内胚层细胞在体内沿着A-P轴的正常迁移路径，这表明两者都在形成发育中的肠管。此外，调控内胚层模式和肠管发育的FGF4靶基因在很大程度上还没有确定。我们已经确定了一个内胚层特异的FGF4反应基因，它编码成纤维细胞生长因子结合蛋白1(FGFbp1)。我们的研究已经确定FGFbp1是分泌的，与FGF4结合，防止它与细胞外基质(ECM)捆绑在一起，并增强其活性。这些数据支持我们的假设，即在内胚层和肠管模式形成过程中，FGFbpl作为内胚层特异性FGF4激动剂发挥作用。我们将研究FGF4信号途径沿A-P轴发育的肠管的分子机制，目的1.确定FGF4在体内建立肠管结构域的细胞生物学机制。目的2.研究进化上保守的FGF4靶基因在内胚层构型中的作用。目的3.探讨成纤维细胞生长因子bp1在肠管发育过程中的作用及其机制。描述：拟议的研究解决了一个重要的问题：一种细胞类型--内胚层是如何产生肺、肝、胰腺、胃、甲状腺和肠道的细胞的。了解这些器官的正常发育将使我们能够诊断先天性异常。此外，这些信息应该使我们能够诱使胚胎干细胞成为内胚层重要的可移植衍生品，例如用于治疗1型糖尿病患者的产生胰岛素的β细胞。

DESCRIPTION (provided by applicant): Despite the prevalence of congenital defects of endodermally derived organs including the lungs, liver, pancreas and intestines, surprisingly little is known about the mechanisms that determine where the primordia for endodermal organs will form along the anterior-posterior (A-P) axis, which is the long-term goal of this research. Our published and preliminary studies show that endoderm patterning is highly conserved across vertebrate species and we hypothesize that that one growth factor, FGF4, plays a central role in establishing these gut tube domains in vivo. The expression pattern of FGF4 and our preliminary data suggest FGF4 patterns the gut tube by promoting posterior and repressing anterior endoderm cell fate. This proposal aims to determine the mechanisms by which this occurs. We show that FGF4 can directly regulate A-P endoderm cell fate and that FGF4 alters the normal path of migration of endoderm cells along the A-P axis in vivo, suggesting that both act to pattern the developing gut tube. Moreover, the FGF4-target genes that regulate endoderm patterning and gut tube development are largely unidentified. We have identified one endoderm specific, FGF4-responsive gene that encodes FGF binding protein 1 (FGFbp1). Our studies have determined that FGFbp1 is secreted, binds to FGF4, prevents it from becoming tethered to the extracellular matrix (ECM) and enhances its activity. These data support our hypothesis that FGFbpl acts as an endoderm-specific FGF4 agonist during endoderm and gut tube patterning. We will investigate the molecular mechanisms by which FGF4-signaling patterns the developing gut tube along the A-P axis with the following aims: Aim 1. Determine the cell-biological mechanisms by which FGF4 establishes gut tube domains in vivo. Aim 2. Investigate the role of evolutionarily conserved FGF4-target genes in endoderm patterning. Aim 3. Investigate the function and mechanism of action of FGFbp1 during gut tube development. Lay Description: The proposed studies address an important question; how does one cell type, endoderm, give rise to cells of the lung, liver, pancreas, stomach, thyroid and intestine. Understanding normal development of these organs will allow us to diagnose congenital abnormalities. Additionally, this information should allow us to coax embryonic stem cells into becoming important transplantable derivatives of endoderm, such as insulin-producing beta cells to treat patients with Type 1 diabetes.