How do migrating epithelia change direction?

摘要：动物在其一生中都在建立和维持各种功能器官。为了形成一个器官，胚胎发育过程中要经历多个步骤，既要制造出该器官所需的所有不同类型的细胞，又要组织这些不同的细胞，使它们能够协同工作，发挥器官的功能。组织细胞的一个共同策略是通过协调的细胞运动和形状变化。该项目旨在了解每种不同类型的细胞如何获得所需的信息，以便移动到正确的位置并获得所需的形状。这个过程需要细胞相互识别，评估它们在发育组织中的当前位置，最后，利用它们的环境和/或DNA蓝图中的信息，在组织中导航到需要它们的位置。为了了解细胞如何管理这种复杂的舞蹈，研究人员将研究一个例子，在这个例子中，细胞组织形成一个类似器官的结构，并发育成果蝇卵。蛋壳的形成需要一系列精确的细胞运动来保护发育中的胚胎。果蝇卵巢将被培养，细胞运动将通过显微镜成像，使用遗传和抗体测定来识别细胞相互作用的特定蛋白质。这些研究将能够区分细胞运动的主要信息来源是来自内部程序还是来自外部环境线索。所鉴定的蛋白质和机制将扩展细胞库的知识，可用于在动物门中观察到的许多不同类型的器官中创建有组织的结构。这项研究将为内华达大学拉斯维加斯分校的本科生和研究生提供必要的科学训练。他们将获得团队合作、批判性思维、数据管理以及进行实验室研究所需的技能等重要技能。技术摘要：本提案的实验将研究细胞迁移片改变其迁移方向的机制。这项工作将集中在果蝇黑腹果蝇的卵发生上，利用先进的遗传操作工具和新技术对卵巢外植体中的细胞运动进行实时延时成像。在前人研究的基础上，对比了两种诱导方向变化机制的模型；这些模式并不相互排斥。一种模型认为，每个细胞通过调节基因表达的内在程序来独立地决定改变其方向，以响应骨形态发生蛋白（BMP）形态发生梯度。实验将测试特定的候选转录调节因子在新迁移的特定阶段开始时的需求。第二个模型是细胞对外部信号做出反应，从而改变它们的方向或改变它们的迁移行为。该项目的这一方面跟进了已发表的报告，即BMP反应系统可能使用非转录机制来诱导细胞形状的变化，以及这些细胞中另一种信号系统被调节的初步数据。研究者预测，内在的基因调控启动了迁移反应的能力，而外在的信号引导细胞的迁移行为。这项工作将确定发育基因调控网络和细胞效应器之间的分子联系，这些效应器在多细胞生物的组织中创造了多种功能结构。除了这些研究活动，研究者还合作组织了一个每月一次的科学咖啡馆（www.sciencecafes.org），为当地和区域的科学家提供一个互动的场所，与拉斯维加斯的普通社区讨论当前的科学话题。

LAY ABSTRACT:Animals build and maintain functional organs throughout their lives. To build an organ, multiple steps occur as the embryo develops, both to make all the different types of cells needed for that organ, and to organize these different cells so that they can work together to perform the organ's function. A common strategy for organizing cells is through coordinated cellular movements and shape changes. This project aims to understand how each different kind of cell obtains the information it needs to move into the correct places and acquire the needed shape. This process requires that cells recognize each other, assess their current location in the developing tissue, and finally, use information from their environment and/or in their DNA blueprint to navigate through the tissue to the location where they are needed. To understand how cells manage this intricate dance, the investigator will study an example where cells organize to create an organlike structure that develops into a fruit fly egg. A series of precise cellular movements is needed to build the eggshell, which protects the developing embryo. Fly ovaries will be cultured and cell movements will be imaged through the microscope, using genetic and antibody assays to identify the specific proteins that cells use to interact with each other. These studies will be able to distinguish whether the major source of information for a cell's movements come from an internal program or from external environmental cues. The proteins and mechanisms identified will expand the knowledge of the cellular repertoire available to create organized structure in the many different types of organs observed across animal phyla. This research will provide essential scientific training for undergraduate and graduate students at the University of Nevada, Las Vegas. They will acquire important skills in teamwork, critical thinking, data management,as well as the needed skills to perform laboratory research.TECHNICAL ABSTRACT:The experiments of this proposal will examine the mechanisms by which a migrating sheet of cells can change its direction of migration. The work will focus on oogenesis of the fruit fly Drosophila melanogaster, to take advantage of sophisticated tools for genetic manipulations and new technologies for real-time, time-lapse imaging of cellular movements in ovary explants. Based on previous research, two models for the mechanisms that induce the change in direction will be contrasted; these models are not mutually exclusive. One model is that each cell decides independently to change its direction, through an intrinsic program of regulated gene expression in response to a bone morphogenetic protein (BMP) morphogen gradient. Experiments will test specific candidate transcriptional regulators for their requirements in the onset of specific phases of the new migration. The second model is that the cells respond to an extrinsic signal that reorients their direction or otherwise changes their migration behavior. This aspect of the project follows up on published reports that the BMP response system may use non-transcriptional mechanisms to induce changes in cell shape, as well as preliminary data that another signaling system is modulated in these cells. The investigator predicts that intrinsic gene regulation initiates the competence for a migration response, and that extrinsic signals orient the cells' migratory behaviors. This work will identify the molecular links between developmental gene regulatory networks and the cellular effectors that create the diverse array of functional architecture seen in tissues of multicellular organisms. In addition to these research activities, the investigator is collaboratively organizing a monthly Science Cafe (www.sciencecafes.org) to provide an interactive venue for local and regional scientists to discuss current scientific topics with the general Las Vegas community.