Transcriptional control of collective cell migration

描述（由主要研究者提供）：关键的生理和病理过程，如伤口愈合、新生血管生成和癌症转移，依赖于定向的集体细胞迁移，由此细胞群变得极化并以有序的方式一起移动。细胞群集体迁移的能力部分由组织特异性转录输入决定，这些转录输入定义了它们表达的基因的互补，从而确定了它们迁移的能力。这个项目的长期目标是了解组织特异性转录调节因子如何控制定向集体细胞迁移的基本细胞过程。为此，简化的胚胎的脊索动物物种，海鞘玻璃海鞘，将被用来研究前心脏中胚层细胞，称为“躯干腹侧细胞”（TVC）的迁移。TVC提供了活胚胎中定向集体细胞迁移的最简单可能模型。在胚胎的每一侧，只有两个细胞一起迁移，并显示出与迁移方向一致的清晰的前导-尾随（L-T）极性：前导TVC显示出较宽的前缘和比尾随更明显的突起。先前已经确定，Mesp、成纤维细胞生长因子（FGF）信号传导和FoxF转录输入决定TVC迁移的能力。该研究的具体目标是了解转录输入如何有助于领导TVC的规范和影响其表达活性。在初步观察的基础上，将测试以下假设：（1）骨形态发生蛋白（BMP）的腹侧来源有助于下游靶基因（包括Lef/Tcf转录因子）的L-T极化表达;以及（2）这些转录输入决定Rho GTP酶RhoDF和Cdc 42的L-T极化活性，这是膜突起形成所需的。为了解决这些可能性，将首先分析TVC中Lef/Tcf的表达、顺式调节和功能，以了解L-T极化的转录输入。第二，定量成像方法将用于记录RhoDF，Cdc 42的L-T极化和在野生型条件下以及在操纵转录调节因子和其他候选Rho GTP酶之后的抑制活性，以试图表征它们对L-T极化膜突起的影响。最后，将使用TVC特异性全基因组微阵列分析，然后分别通过原位杂交和靶向过表达进行系统表达和功能分析，来鉴定集体细胞极化和增殖活性的候选调节效应物。期望通过表征转录调节因子、受调节的效应物及其对Rho GTdR信号传导和肌动蛋白丝动力学的影响来确定集体细胞迁移的转录控制机制，所述信号传导和肌动蛋白丝动力学是集体细胞极化和膜突起形成的基础。 公共卫生相关性：在包括人类在内的动物中，被称为集体细胞迁移的各种形态发生过程对于生理和病理现象如胚胎发育、伤口愈合、新生血管形成和癌症转移是必不可少的。我们建议研究的分子和细胞机制，控制定向集体细胞迁移使用最简单的可能的模型，其中包括两个细胞迁移作为一个极化对在胚胎中的海洋无脊椎动物，被囊玻璃海鞘。由于与脊椎动物的进化接近，使用这种简单模型的研究将破译驱动集体细胞迁移的基本机制，并可能应用于再生医学和预防癌症转移。

DESCRIPTION (provided by Principal Investigator): Critical physiological and pathological processes, such as wound healing, de novo vessel angiogenesis and cancer metastasis, rely on directed collective cell migrations, whereby groups of cells become polarized and move together in an orderly fashion. The ability of cell groups to migrate collectively is determined in part by the tissue-specific transcriptional inputs that define the complement of genes that they express and thus their competence to migrate. The long-term goal of this project is to understand how tissue-specific transcription regulators control the basic cellular processes underlying directed collective cell migration. To this aim, the simplified embryos of a chordate species, the ascidian Ciona intestinalis, will be used to study the migration of pre-cardiac mesoderm cells, called "trunk ventral cells" (TVCs). The TVCs provide the simplest possible model of directed collective cell migration in live embryos. On each side of the embryo, only two cells migrate together and display a clear Leader-Trailer (L-T) polarity aligned with the direction of migration: the leader TVC displays a broad leading edge and more conspicuous protrusions than the trailer. It was previously established that Mesp, Fibroblast Growth Factor (FGF) signaling and FoxF transcriptional inputs determine the ability of TVCs to migrate. The specific goal of the proposed research is to understand how transcriptional inputs contribute to the specification of the leader TVC and influence its protrusive activity. On the basis of preliminary observations, the hypotheses that (1) a ventral source of bone morphogenetic proteins (BMP) contributes to the L-T polarized expression of downstream target genes, including the Lef/Tcf transcription factor; and (2) these transcriptional inputs determine the L-T polarized activities of the Rho GTPases RhoDF and Cdc42, which are required for the formation of membrane protrusions will be tested. To address these possibilities, the expression, cis-regulation and function of Lef/Tcf in the TVCs will first be analyzed in order to understand L-T polarized transcriptional inputs. Second, quantitative imaging methods will be used to document the L-T polarization of RhoDF, Cdc42 and protrusive activities in wild-type conditions and after manipulations of transcription regulators and other candidate Rho GTPases in an attempt to characterize their effects on L-T polarized membrane protrusions. Finally, candidate regulated effectors of collective cell polarization and protrusive activity will be identified using TVC-specific whole genome microarray analysis followed by systematic expression and functional analyses by in situ hybridization and targeted over-expression, respectively. The expectation is to determine a mechanism of transcriptional control for collective cell migration by characterizing the transcription regulators, the regulated effectors and their effects on the Rho GTPase signaling and actin filament dynamics that underlie collective cell polarization and the formation of membrane protrusions. PUBLIC HEALTH RELEVANCE: In animals, including humans, a variety of morphogenetic processes known as collective cell migrations are essential for physiological and pathological phenomena such as embryonic development, wound healing, de novo vessel formation and cancer metastasis. We propose to study the molecular and cellular mechanisms that control directed collective cell migration using the simplest possible model, which consists of two cells migrating as a polarized pair in embryos of the marine invertebrate, the tunicate Ciona intestinalis. Because of the evolutionary proximity with vertebrates, studies using this simple model will decipher the basic mechanisms driving collective cell migration with potential applications for regenerative medicine and the prevention of cancer metastasis.