Regulation of Cell Turnover During Epithelial Tissue Homeostasis

项目总结摘要 上皮组织内的细胞不断被细胞凋亡消除，取而代之的是细胞增殖， 然而，协调细胞移除和细胞分裂以保持恒定细胞数量的机制仍然存在 未知。未能协调细胞的出生和死亡可导致种群数量的失调和 屏障功能受损，或相反，组织增生和癌症形成。因此，一个彻底的 对引导上皮组织细胞周转的遗传基础的理解将为深入了解 分子途径，可以通过加强去除和增强对不同人类病理的利用 更换有缺陷的电池。这项提议的目标是定义细胞和分子机制 它调节上皮组织中的细胞周转，以维持适当的总体种群数量。我的 最近的结果表明，清除过多或有缺陷的细胞是影响相邻细胞是否 细胞会分裂、挤压或死亡。重要的是，这项研究还表明，能力的变化迅速 上皮组织中明显的凋亡细胞可能会导致几种上皮病变，包括 肠上皮的屏障功能或危险细胞的积聚促进癌症 队形。然而，一直缺乏一个模型系统来研究凋亡细胞清除的变化如何影响 活体上皮细胞的细胞周转和组织维持。为了研究活的上皮组织中的细胞周转， 我们已经开发了一个工具包来扰乱基因功能，并对 斑马鱼发育中的上皮细胞，为实时分析细胞周转提供了无与伦比的途径。vbl.使用 发育中的斑马鱼来研究上皮双层中的细胞周转，我们已经发现了 基底上皮细胞亚群的损伤促使活细胞邻居充当吞噬细胞，迅速清除 细胞的凋亡性碎片。然后，基础干细胞进行分裂，以补偿细胞的损失 保持组织的完整性和功能。我们的初步数据表明，抑制细胞死亡或WNT 信号转导消除了细胞凋亡诱导的分裂，导致再生失败。此外，基因 WNT信号在损伤反应中的过度表达导致细胞总数的增加。 在下面的提案中，我们将检验这样一种假设，即清除含有WNT的凋亡细胞 邻近的干细胞直接影响它们的增殖，从而驱动上皮细胞的更新。在AIM 1，我们将确定去除濒临死亡的细胞如何刺激干细胞介导的替代。在目标2中，我们将 明确引导细胞凋亡诱导增殖以维持细胞总数的分子机制。在……里面 目的3，我们将确定凋亡小体和微粒是否能促进干细胞的增殖。一起， 这些研究将有助于揭示调节上皮组织动态平衡的细胞和分子事件以及如何 变化会导致人类的致病条件。

PROJECT SUMMARY ABSTRACT Cells within epithelial tissues are continually being eliminated by apoptosis and replaced by cell proliferation, however the mechanisms that coordinate cell removal with cell division to retain constant cell numbers remain unknown. Failure to coordinate the birth and death of cells can lead to dysregulation of population numbers and compromised barrier function, or conversely, tissue hyperplasia and carcinoma formation. Thus, a thorough understanding of the genetic underpinnings guiding cellular turnover in epithelial tissues will provide insight into molecular pathways that can be leveraged against diverse human pathologies by enhancing the removal and replacement of defective cells. The goal of this proposal is to define the cell and molecular mechanisms that regulate cell turnover in epithelial tissues to maintain appropriate overall population numbers. My recent results suggest that clearance of excess or defective cells was a major influence in whether neighboring cells would divide, extrude or die. Importantly, this work also suggested that alterations in the ability to rapidly clear apoptotic cells from the epithelial tissues may lead to several epithelial pathologies, including decreased barrier function in the intestinal epithelium or the accumulation of dangerous cells to promote carcinoma formation. Yet, a model system has been lacking to study how changes in apoptotic cell clearance could impact cell turnover and tissue maintenance in living epithelia. To investigate cell turnover in a living epithelial tissue, we have developed a toolset to perturb gene function and perform live imaging of division and death in the epithelia of the developing zebrafish, providing unparalleled access to analyze cell turnover in real time. Using the developing zebrafish to study cellular turnover in an epithelial bilayer, we have uncovered that induction of damage in a subset of basal epithelial cells promotes live cell neighbors to act as phagocytes that rapidly clear the apoptotic cellular debris. The basal stem cells then undergo division to compensate for the cell loss and maintain tissue integrity and function. Our preliminary data suggests that inhibition of either cell death or WNT signaling eliminates the apoptosis-induced division and results in failed regeneration. Further, genetic overexpression of WNT signaling in the context of a damage response led to an increase in overall cell numbers. In the following proposal, we will test the hypothesis that clearance of WNT-containing apoptotic cells by neighboring stem cells directly influences their proliferation to drive cell turnover in epithelia. In Aim 1, we will determine how removal of dying cells stimulates stem cell-mediated replacement. In Aim 2, we will define the molecular mechanisms guiding apoptosis-induced proliferation to maintain overall cell numbers. In Aim 3, we will determine if apoptotic bodies and microparticles can promote stem cell proliferation. Together, these studies will help reveal the cell and molecular events regulating epithelial tissue homeostasis and how alterations lead to human pathogenic conditions.