Cell-Cell Interactions during intestinal development

描述（由申请人提供）：肠道令人印象深刻的大吸收表面积主要是由于它的长度以及数以百万计的指状绒毛突起提供的广泛的表面放大。先天性或后天的疾病会导致肠道表面积的严重损失，严重损害肠道吸收营养的能力，并可能危及生命。在过去的项目期间的工作已经开始确定一些细胞和分子机制，控制绒毛的形成在子宫内的小鼠模型。胚胎日(E) 14.5和E15.5（小鼠）之间的这段时间尤为重要，因为在这段时间内，上皮和下层间质的可控形态重塑导致绒毛的出现。这些研究的工作假设是：在E14.5之前，绒毛的发育受到Bmp信号的积极抑制。在E14.5时，上皮Hh信号通过促进间质团簇的形成来启动绒毛发育。集束图案通过图灵系统进行，血管与这些集束的耦合是绒毛出现所必需的。重要的是，由于所有这些事件的形态学特征也存在于人类肠道中，因此在小鼠模型中发现的大多数信号范式很可能适用于人类肠道。本研究利用遗传小鼠模型和一种新的肠道外植体培养系统，从机制上剖析这些表面生成过程中涉及的相互关联的信号和模式事件。此外，一种新的软件工具可以高效识别基因组DNA中的Hh应答信号增强子，这将有助于识别Hh靶基因。具体目标旨在1)确定Bmp信号如何控制绒毛形成的能力，并确定哪个组织（上皮或间质）施加这种控制；2)确定间充质细胞簇形成过程中的Hh靶基因；3)确定维管元素之间的关系，形成集群和集群模式。通过对这些相关过程的详细分析，这些研究的目标是对肠道吸收面的形成有新的认识。要想从细胞成分中制造出生物工程器官，不仅需要我们阐明对形态发生和细胞命运决定很重要的分子信号，还需要我们理解构成器官的功能单位的模式的规则。本研究对新生绒毛单位（上皮、间质、脉管系统）信号串扰的独特关注，将对我们理解肠绒毛在胚胎中最初是如何形成的产生重大影响。

DESCRIPTION (provided by applicant): The impressively large absorptive surface area of the intestine is largely contributed by its length as well as the extensive surface amplification provided by millions of fingerlike villus projections. Congenital or acquired pathologies that result in significant loss of this intestinal surface area seriously compromise the ability of the intestine to absorb nutrients and can be life threatening. Work in the past project period has begun to identify some of the cellular and molecular mechanisms that control the formation of villi in utero in the murine model. The period between embryonic day (E) 14.5 and E15.5 (in the mouse) is particularly important since during this time, controlled morphogenic remodeling in both the epithelium and the underlying mesenchyme results in the emergence of villi. The Working Hypothesis underlying these studies is that: Villus development is actively inhibited by Bmp signaling prior to E14.5. At E14.5, epithelial Hh signals initiate villus development by promoting the formation of mesenchymal clusters. Cluster patterning proceeds via a Turing system and vascular coupling to these clusters precedes and is required for villus emergence. Importantly, since the morphological hallmarks of all of these events are also present in the human intestine, it is likely that the majority of the signaling paradigms uncovered in the mouse model will be applicable to the human intestine. This proposal makes use of genetic mouse models as well as a novel intestinal explant culture system to mechanistically dissect the interconnected signaling and patterning events involved in these surface- generating processes. Additionally, a new software tool that can recognize Hh-responsive signaling enhancers in genomic DNA with high efficiency will aid in the recognition of Hh target genes. The Specific Aims are designed to 1) Determine how Bmp signaling controls competence to form villi and establish which tissue (epithelium or mesenchyme) exerts this control; 2) Identify Hh target genes during the formation of mesenchymal clusters; and 3) Determine the relationship between vascular elements, forming clusters and cluster pattern. Through detailed analysis of these linked processes, the goal of these studies is to gain new insight into the formation of the intestinal absorptive surface. The ability to bioengineer organs from their cellular components will require not only that we elucidate the molecular signals that are important for morphogenesis and cell fate determination, but also that we understand the rules that govern the patterning of the functional units that comprise the organ. The unique focus of this investigation on signaling crosstalk in the nascent villus unit (epithelium, mesenchyme, vasculature) will have a major impact on our understanding of how intestinal villi are first formed in the embryo. PUBLIC HEALTH RELEVANCE: The surface of the small intestine is highly convoluted by finger-like projections called villi; this extended surface area is critical for efficient nutrient absorption. Loss of intestinal surface area either by congenital intestinal defects or by pathological or surgical events, can be life threatening. The ability to bioengineer the intestine from its cellular components will require not only that we elucidate the molecular signals that are important for morphogenesis and cell fate determination, but also that we understand the rules that govern the patterning of the functional units that comprise the organ. Currently, little is known about how villi are generated in utero. Through the study of mouse models with perturbed villus formation and through the analysis of a novel intestinal explant culture system, we propose to dissect the molecular processes responsible for villus emergence. The unique focus of this investigation on signaling crosstalk in the nascent villus unit (epithelium, mesenchyme, vasculature) will have a major impact on our understanding of how intestinal villi are first formed in the embryo.