Mechanisms of endoderm specification along the A-P axis.

描述（由申请人提供）：尽管包括肺、肝、胰腺和肠在内的内胚层来源器官的先天性缺陷普遍存在，但令人惊讶的是，关于决定内胚层器官原基沿前后（A-P）轴形成的机制知之甚少，这是本研究的长期目标。我们发表的和初步的研究表明，在脊椎动物物种中，内胚层模式是高度保守的，我们假设一种生长因子FGF4在体内建立这些肠管结构域中起着核心作用。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的命运和抑制前内胚层细胞的命运来影响肠管。本建议旨在确定这种情况发生的机制。我们发现FGF4可以直接调节A-P内胚层细胞的命运，并改变体内内胚层细胞沿A-P轴的正常迁移路径，这表明两者都对发育中的肠管起作用。此外，调节内胚层模式和肠管发育的fgf4靶基因在很大程度上是未知的。我们已经鉴定出一个内胚层特异性的fgf4应答基因，该基因编码FGF结合蛋白1 （FGFbp1）。我们的研究已经确定FGFbp1是分泌的，与FGF4结合，阻止FGF4附着在细胞外基质（ECM）上，并增强其活性。这些数据支持了我们的假设，即FGFbpl在内胚层和肠管形成过程中作为内胚层特异性FGF4激动剂。我们将研究fgf4信号沿A-P轴调控肠管发育的分子机制，目的如下：确定FGF4在体内建立肠管结构域的细胞生物学机制。目标2。研究进化保守的fgf4靶基因在内胚层模式中的作用。目标3。探讨FGFbp1在肠管发育过程中的作用及机制。概要描述：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，这一信息将使我们能够诱导胚胎干细胞成为重要的内胚层可移植衍生物，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.