Regulation of the intestinal colonization niche by epithelial cell death

项目摘要 肠道微生物群由生活在胃肠道中的数万亿个微生物组成。 微生物产生的代谢物到达肠外组织，并可以在血液中找到，以及 因此能够影响身体的几乎所有组织。有趣的是，一些基因的表达 胃肠道的生长依赖于微生物群的定植。在这个项目中，我们将探索 肠道微生物群控制肠上皮细胞(IECS)基因调控的机制 通过对参与IEC细胞死亡的微生物组调控基因的研究。肠沙门氏菌血清型 小鼠伤寒沙门氏菌(STM)是一种擅长克服宿主防御而致病的病原体。扫描隧道显微镜 通过利用宿主的反应，触发有利于病原体生长的炎症反应 与感染有关。我们的初步发现表明，STM能够从动态平衡的微生物群中受益- 介导的细胞死亡途径尚未被描述。在稳态条件下，代谢物产生 由微生物引起的IECS下垂，有助于维持正常的上皮性周转。然而，一旦 STM感染，病原体利用这一途径引起IEC下垂增加，导致STM增加 胃肠道中的数字。我们的早期结果表明IEC下垂途径的成分丢失。 导致STM腔外生长和扩散到肠外器官，但目前尚不清楚STM是如何 激活IEC下垂，以及这一途径是否确实导致肠下垂的增加 感染过程中的上皮细胞。因此，我推测在胃肠道感染期间，STM会 微生物组控制的动态平衡IEC特异性细胞死亡途径的优势使其大量繁殖。 为了阐明微生物群和STM是如何激活IEC下垂的，以及这种激活如何导致 胃肠道内和肠外部位的细胞死亡和下游病原体扩张， 我们提出了两个具体目标。在目标1中，我们将评估肠道微生物群在诱导IEC中的作用 通过测序和使用常规和诺和菌素的体内小鼠模型相结合的方法，焦虑症 老鼠。在AIM 2中，我们将使用小鼠感染模型来确定STM在感染过程中如何引起IEC下垂， 并定义了上游激活途径。我们的机械论方法将提供一个因果联系 微生物组，宿主细胞死亡途径，和病原体扩张。成功完成这项提案将 确定在稳定状态和感染性状态下起关键作用的先前未定义的IEC细胞死亡途径 条件。这个项目还将扩展我的培训，将IEC生物学中的关键方法和概念包括在内 在微生物组的研究中。总之，建议的研究和培训计划将有助于更好地 了解IECS及其在宿主免疫中的作用，同时为我未来的独立职业生涯做好准备 宿主-微生物相互作用领域的研究人员。

Project Summary The intestinal microbiome is made up of trillions of microorganisms that inhabit the gastrointestinal tract. Metabolites produced by the microbiome reach extraintestinal tissues, and can be found in the bloodstream, and are thereby able to influence almost all tissues of the body. Interestingly, the expression of a number of genes of the gastrointestinal tract is dependent on colonization by the microbiome. In this project, we will explore the mechanisms through which the gut microbiome controls gene regulation of intestinal epithelial cells (IECs), through the study of a microbiome-modulated gene involved in IEC cell death. Salmonella enterica serovar Typhimurium (STm) is a pathogen that is adept at overcoming host defenses in order to cause disease. STm triggers an inflammatory response that benefits growth of the pathogen by taking advantage of the host response to infection. Our preliminary findings suggest that STm is able to benefit from a homeostatic microbiome- mediated cell death pathway that has yet to be described. Under steady state conditions, metabolites produced by the microbiome lead to pyroptosis of IECs, which helps maintain normal epithelial turnover. However, upon STm infection, the pathogen harnesses this pathway to elicit increased IEC pyroptosis, leading to increased STm numbers in the gastrointestinal tract. Our early results indicate loss of components of the IEC pyroptosis pathway led to lower STm luminal outgrowth and dissemination to extraintestinal organs, yet, it is unclear how STm activates IEC pyroptosis, and whether this pathway indeed leads to an increase in pyroptosis of intestinal epithelial cells during infection. Thus, I hypothesize that during infection of the gastrointestinal tract, STm takes advantage of a microbiome-controlled homeostatic IEC-specific cell death pathway to bloom to high numbers. In order to elucidate how the microbiome and STm activate IEC pyroptosis, and how this activation leads to cell death and downstream pathogen expansion within the gastrointestinal tract and in extraintestinal sites, we propose two specific aims. In AIM 1 we will assess the contribution of the gut microbiome to induction of IEC pyroptosis, by using a combination of sequencing and in vivo mouse models using conventional and gnotobiotic mice. In AIM 2 we will use mouse infection models to determine how STm elicits IEC pyroptosis during infection, and define the upstream activation pathway. Our mechanistic approach will provide a causal link between the microbiome, a host cell death pathway, and pathogen expansion. Successful completion of this proposal will identify a previously undefined IEC cell death pathway that plays a crucial role under steady state and infectious conditions. This project will additionally expand my training to include key methods and concepts in IEC biology and in the study of the microbiome. Altogether, the research and training plan proposed will facilitate a better understanding of IECs and their role in host immunity, while preparing me for a future career as an independent investigator in the field of host-microbe interactions.