Protrusive behavior during collective cell migration

细胞迁移是形成发育中胚胎的基本过程之一。集体细胞迁移是 一种特殊的协调细胞迁移形式，其中细胞保持细胞与细胞的接触，群体极化， 和协调的行为。集体细胞迁移对发育过程中的许多过程都是必不可少的， 包括神经管关闭、血管分支和神经脊细胞迁移。因此，颠覆 在发育过程中这一过程的缺陷可能会导致严重的出生缺陷。也有越来越多的证据表明 上皮性肿瘤细胞在组织侵袭过程中以凝聚群的形式移动，这一过程被称为集体细胞 侵袭，这类似于胚胎发生期间的集体细胞迁移。因此，一个机械主义者 对集体细胞迁移的理解应该为组织形态发生提供重要的新见解 在胚胎发育和疾病中细胞的异常迁移。然而，分子机制是 对集体细胞迁移的调控仍然没有明确的定义。当细胞迁移时，它们必须将突起延伸到 与细胞外环境相互作用，感知趋化线索，并作为连接点和 信号中心来协调迁徙行为。对突出行为的调节已经被广泛地 在个体迁移的细胞中进行研究；然而，在整个集体中如何控制突出行为 还没有被很好地理解。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， 包括舒适的活体成像和先进的遗传方法。利用丝状菌的马赛克标记 肌动蛋白，我们发现在迁移的多个细胞中有丰富的刷状、基于肌动蛋白的突起。 集体行动。实时成像显示，这些以前未描述的结构是高度动态的、定向的 朝着移民的方向发展，并普遍存在于集体的领导部分。我们进一步展示了 这些突起是Arp2/3依赖的，是细胞集体迁移所必需的。我们之前已经 结果表明，在细胞集体迁移过程中，规范的Wnt信号是细胞运动所必需的。我们 还发现大量的Wnt靶基因是肌动蛋白动力学的已知调节基因；这些基因 在集体的不同区域表达，并且它们的表达模式在Wnt缺乏时被扰乱 条件。因此，我们假设在集体细胞迁移过程中的突出行为是由 调节肌动蛋白动态的Wnt靶基因的不同活性。为了检验这一假设，我们将1) 确定突起的类型和调节其活性的分子机制；2)确定突起的作用 主要的信号通路，包括Wnt和成纤维细胞生长因子，在调节这一行为；以及3)确定新的调节器 在集体细胞迁移过程中的突出行为。更好地理解集体细胞在 器官发育将有助于阐明这一过程是如何在各种发育障碍中被破坏的，因为 在癌症侵袭期间也是如此。

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.