Morphogenesis of mammalian gut endoderm

在这个项目中，我们将使用最先进的技术来解决哺乳动物细胞谱系承诺、分离和形态发生的基本问题，以小鼠为模型。这一建议侧重于肠道内胚层，这是一种胚胎组织，它产生了许多内部器官的主要细胞类型，包括甲状腺、胸腺、肺、胃、肝、胰腺、肠和膀胱。对正常肠道内胚层形态发生的严格理解，包括对产生肠道内胚层及其衍生组织的细胞的起源、承诺、规范和分化的了解，应该支持理解疾病进展的逻辑努力，并为这些重要器官系统设计新的治疗策略。关于哺乳动物胚胎胚层形成的普遍观点是，肠道内胚层、外胚层和中胚层完全是在原肠胚形成过程中由多能外胚层形成的。此外，虽然胚外组织与外胚层相互作用以建立体轴，但它们仅对胚外结构起作用，如卵黄囊和胎盘。我们的研究挑战了这一观点，并为本项目的具体目标所测试的假设提供了信息。本项目的主要目的是结合分子、胚胎学和实时成像技术来确定内脏内胚层的命运，并研究其在哺乳动物肠道内胚层形态发生中的作用。在特异性目标1中，我们将确定胎儿和成年小鼠的内脏内胚层和肠道内胚层组织之间是否存在谱系关系。在特异性目标2中，我们将阐明驱动肠道内胚层形态发生的机制。具体目标3，研究导致胚胎外（内脏）内胚层细胞在中线信号中心周围组织的事件序列，并验证这种排列对中线形成和/或功能至关重要的假设。我们的研究结果也与基于细胞的治疗和疾病建模的干细胞分化有关，因为目前肝、肺、胰腺和其他内胚层细胞类型的体外分化方案假设只有外胚层起源，并特别选择在原肠胚形成之前形成的胚胎外内胚层。

DESCRIPTION (provided by applicant): In this project we will use state-of-the-art technologies to address fundamental questions of cell lineage commitment, segregation and morphogenesis in mammals, using the mouse as a model. This proposal focuses on the gut endoderm, an embryonic tissue that gives rise to the major cell types of many internal organs, including the thyroid, thymus, lung, stomach, liver, pancreas, intestine and bladder. A rigorous understanding of normal gut endoderm morphogenesis, including knowledge of the origin, commitment, specification and differentiation of cells generating gut endoderm and its derivative tissues, should underpin logical efforts to understand disease progression and design new therapeutic strategies for these vital organ systems. The prevailing view of germ layer formation in mammalian embryos is that the gut endoderm, along with the ectoderm and mesoderm, derives solely from the pluripotent epiblast during the process of gastrulation. Moreover, while extra-embryonic tissues interact with the epiblast to establish the body axes, they contribute solely to extra-embryonic structures, such as the yolk sac and placenta. Our studies challenge this view, and inform the hypotheses being tested in the Specific Aims of this project. The broad aim of this project is to use a combination of molecular, embryological and live imaging techniques to determine the fate of the visceral endoderm a presumed extra-embryonic tissue, and investigate its role(s) in the morphogenesis of the mammalian gut endoderm. In Specific Aim 1, we will determine if a lineage relationship exists between the visceral endoderm and the gut endoderm tissues of the fetus and adult mouse. In Specific Aim 2, we will elucidate the mechanisms that drive gut endoderm morphogenesis. Specific Aim 3, investigates the sequence of events leading to the organization of extra-embryonic (visceral) endoderm cells around midline signaling centers, and test the hypothesis that this arrangement is central to midline formation and/or function. Our findings are also relevant to stem cell differentiation for cell-based therapies and disease modeling because, current protocols for the in vitro differentiation of liver lung, pancreas and other endodermal cell types assume an epiblast-only origin and specifically select against the extra-embryonic endoderm that forms prior to gastrulation.