Protrusive behavior during collective cell migration

细胞迁移是胚胎发育的基本过程之一。集体细胞迁移是 一种协调细胞迁移的特殊形式，其中细胞保持细胞-细胞接触，群体极化， 协调的行为。集体细胞迁移对于发育过程中的许多过程是必不可少的， 包括神经管闭合、血管分支和神经嵴细胞迁移。因此，中断 在发育过程中，这一过程可能导致严重的出生缺陷。还有越来越多的证据表明 上皮肿瘤细胞在组织侵入过程中作为一个有凝聚力的群体移动， 入侵，这类似于胚胎发生期间的集体细胞迁移。因此，一种机械的 对集体细胞迁移的理解将为组织形态发生提供重要的新见解 在胚胎发生和异常细胞迁移的疾病。然而，分子机制， 调节集体细胞迁移的机制仍不明确。当细胞迁移时，它们必须伸出突起， 与细胞外环境相互作用，感觉趋化性线索，并作为附着点， 协调迁徙行为的信号中心。对过度行为的监管已经被广泛地 研究了单个迁移的细胞;然而，迁移行为是如何在整个集体中控制的， 并没有得到很好的理解。为了解决这个问题，我们正在利用斑马鱼模型系统的独特优势， 包括方便实时成像和先进的遗传方法。使用镶嵌标记丝状 肌动蛋白，我们发现了丰富的刷状，肌动蛋白为基础的突起在多个细胞跨越迁移 集体对实时成像显示，这些以前未描述的结构是高度动态的， 朝着迁移的方向，并在集体的领导部分盛行。我们进一步表明 这些突起是Arp 2/3依赖性的，并且是集体细胞迁移所必需的。我们先前已经 表明典型的Wnt信号传导对于集体细胞迁移期间的细胞运动是必需的。我们 还发现大量Wnt靶基因是已知的肌动蛋白动力学调节因子;这些基因 在不同区域的集体和他们的表达模式是扰动下Wnt缺陷 条件因此，我们假设集体细胞迁移过程中的迁移行为是由以下因素协调的： 调节肌动蛋白动力学的Wnt靶基因的差异活性。为了验证这一假设，我们将1） 定义突起的类型和调节其活性的分子机制; 2）确定 调节这种行为的主要信号通路，包括Wnt和Fgf;和3）识别新的调节因子 细胞集体迁移时的迁移行为。更好地理解集体细胞迁移， 器官发育将有助于阐明这一过程如何在各种发育障碍中被破坏， 以及在癌症侵袭期间。

Cell migration is one of the fundamental processes shaping the developing embryo. Collective cell migration is a specialized form of coordinated cellular migration where cells maintain cell-cell contacts, group polarization, and coordinated behavior. Collective cell migration is essential for numerous processes during development, including neural tube closure, blood vessel branching, and neural crest cell migration. Consequently, disruption of this process during development can lead to severe birth defects. There is also a growing body of evidence that epithelial tumor cells move as cohesive groups during tissue invasion, in a process termed collective cell invasion, which is analogous to collective cell migration during embryogenesis. Thus, a mechanistic understanding of collective cell migration should provide important new insights into tissue morphogenesis during embryogenesis and abnormal cell migration in diseases. However, the molecular mechanisms that regulate collective cell migration remain poorly defined. As cells migrate, they must extend protrusions to interact with the extracellular environment, sense chemotactic cues, and act as points of attachments and signaling centers to coordinate the migratory behavior. The regulators of protrusive behavior have been widely studied in cells that migrate individually; however, how protrusive behavior is controlled throughout collectives is not well understood. To tackle this problem, we are using unique advantages of the zebrafish model system, including amenity to live imaging and advanced genetic approaches. Using mosaic labeling of filamentous actin, we discovered an abundance of brush-like, actin-based protrusions in multiple cells across the migrating collective. Live imaging revealed that these previously undescribed structures are highly dynamic, oriented towards the direction of migration, and prevalent in the leading part of the collective. We further demonstrated that these protrusions are Arp2/3 dependent and are required for collective cell migration. We have previously shown that the canonical Wnt signaling is necessary for cell movement during collective cell migration. We have also found that a high number of Wnt target genes are known regulators of actin dynamics; these genes are expressed in distinct regions of the collective and their expression pattern is perturbed under Wnt-deficient conditions. We therefore hypothesize that protrusive behavior during collective cell migration is coordinated by a differential activity of Wnt target genes that regulate actin dynamics. To test this hypothesis, we will 1) define the type of protrusions and molecular machinery that regulates their activity; 2) determine the role of major signaling pathways, including Wnt and Fgf, in regulating this behavior; and 3) identify novel regulators of protrusive behavior during collective cell migration. Better understanding of collective cell migration during organ development will help to elucidate how this process is disrupted in various developmental disorders as well as during cancer invasion.