Roles of hedgehog signaling in foregut development

描述（由首席研究员提供）：胚胎前肠衍生物的正确发育对于哺乳动物出生时的生存至关重要。头侧内胚层前肠管分为腹侧呼吸管（喉和气管）和背侧消化管（食道和胃）。尽管其具有务实的重要性，但人们对其基本机制知之甚少。例如，前肠分隔缺陷导致常见的出生缺陷，涉及这些系统之间的异常通讯，临床上称为气管食管瘘（TEF）和喉食管裂。声波刺猬 (Shh) 对于形成不同的喉/气管和食管至关重要，因为 Shh 无效的小鼠前肠是无区室化的。我们的初步数据表明，发育中的气管和食管中的后期Shh表达对于前肠上皮的分层和专门的前肠中胚层的发育至关重要。我们的总体假设是，shh 信号传导作为前肠发育的主要调节因子，最初控制对从共同前体形成食道、气管和喉所必需的组织重塑，随后形成这些新生器官的内胚层和中胚层组织的模式。我们提出了一系列对小鼠胚胎中Shh表达和接收的组织特异性和时间遗传操作，结合组织学和分子分析，以研究Shh信号在前肠发育中的作用。目标 1 确定 Shh 信号传导在气管与食管正常分离中的作用、发生这种情况的形态发生过程，以及 Shh 信号传导的破坏如何导致 TEF。目标 2 反过来解决了喉与食道的分离问题，特别关注神经嵴衍生的喉软骨在此过程中的作用。目标 3 阐明了 Shh 在内胚层不同分层和分化模式中的作用。在目标 4 中，我们确定了 Shh 信号在特化前肠中胚层（包括气管软骨环、气管平滑肌和食管平滑肌）分化中的时空功能。总而言之，这些研究将为了解 Shh 信号在气管、食道和喉的正常发育和先天性缺陷中的作用提供重要的见解。 公共卫生相关性：胚胎前肠衍生物的正常发育对于哺乳动物出生时的生存至关重要。头侧内胚层前肠管分为腹侧呼吸管（喉和气管）和背侧消化管（食道和胃）。然后这些必须发育成有功能的器官。尽管其务实重要性，但人们对其基本机制知之甚少。该提案是针对一个研究项目，旨在剖析 Sonic Hedgehog 细胞间信号通路在小鼠前肠发育中的作用。我们阐明了在共同前肠管的初始区室化以及内胚层和中胚层的器官特异性分化中的关键作用。我们的结果与人类前肠出生缺陷的机制直接相关，并可能与食管癌的发病机制相关。

DESCRIPTION (provided by Principal Investigator): Proper development of embryonic foregut derivatives is essential for mammalian survival at birth. The rostral endodermal foregut tube divides into ventral respiratory (larynx and trachea) and dorsal alimentary (esophagus and stomach) components. Remarkably little is known about the underlying mechanisms, despite their pragmatic importance. For example, defects in foregut compartmentalization result in common birth defects involving abnormal communications between these systems, known clinically as tracheoesophageal fistulas (TEF) and laryngo-esophageal clefts. Sonic hedgehog (Shh) is essential for generation of distinct laryngeal/tracheal and esophageal tubes, as the Shh-null mouse foregut is uncompartmentalized. Our preliminary data indicate that later Shh expression in the developing trachea and esophagus is critical for the stratification of foregut epithelia and development of specialized foregut mesoderm. Our overall hypothesis is that shh signaling acts as a master regulator of foregut development, initially to control tissue remodeling essential for formation of esophagus, trachea and larynx from a common precursor, and subsequently to pattern the endodermal and mesodermal tissues of these nascent organs. We propose a series of tissue-specific and temporal genetic manipulations of Shh expression and reception in the mouse embryo, coupled with histological and molecular analyses, to investigate the roles of Shh signaling in foregut development. Aim 1 determines the role of Shh signaling in normal separation of trachea from esophagus, the morphogenic process by which this occurs, and how the disruption of Shh signaling results in TEF. Aim 2 in turn addresses the separation of larynx from esophagus, with special attention to the role of neural crest-derived laryngeal cartilages in this process. Aim 3 elucidates the role of Shh in the different patterns of stratification and differentiation within the endoderm. In Aim 4, we determine the spatiotemporal functions of Shh signaling in differentiation of specialized foregut mesoderm, including the tracheal cartilage rings, trachealis smooth muscle, and esophageal smooth muscle. Altogether, these studies will provide important insight into the roles of Shh signaling in normal development and congenital defects of the trachea, esophagus, and larynx. PUBLIC HEALTH RELEVANCE: Proper development of embryonic foregut derivatives is essential for mammalian survival at birth. The rostral endodermal foregut tube divides into ventral respiratory (larynx and trachea) and dorsal alimentary (esophagus and stomach) components. These must then develop into functional organs. Little is known about the underlying mechanisms, despite their pragmatic importance. This proposal is for a research project to dissect the roles of the Sonic hedgehog intercellular signaling pathway in mouse foregut development. We elucidate critical roles in the initial compartmentalization of the common foregut tube, and in the organ-specific differentiation of endoderm and mesoderm. Our results are of direct relevance to the mechanisms of human foregut birth defects and potentially to the pathogenesis of esophageal cancer.