Morphogenetic mechanisms regulating directed cell migration required to form the vertebrate posterior body

项目总结 许多脊椎动物的胚胎体是由最近发现的神经中胚层前体细胞形成的 种群位于早期胚胎的最后端，在一个被称为祖细胞带(PZ)的区域。 PZ逐渐释放分布在躯体(主要是肌肉)和神经中的中胚层细胞 形成脊髓的细胞，直到胚胎的完整前后轴被建立。 而控制神经中胚层细胞分化的机制越来越多。 了解这些细胞如何调控上皮向间充质转化(EMT)的完成 从PZ到体内的定向迁移在很大程度上仍然是一个谜，但这个过程对于 胚胎正确地形成其前后轴。 基于我们对斑马鱼突变体的分析，该突变体可以特异性地干扰中胚层细胞从 PZ，我们已经确定了一组独特的PZ表达的祖细胞骨架调节基因(PCRGs)， 我们认为必须下调细胞才能完成EMT并从PZ迁移到 分裂前中胚层(PSM)。使用我们最近开发的一种新的外植体试验，可以在体内成像 在目标1中，我们将确定如何使用PCRGs来调节 使用功能得失研究相结合的方法将细胞定向移动到PSM，以及 研究PCRG如何控制RHO活动。 在目标2中，我们将确定后部HOX基因是如何通过未知的机制控制 细胞从PZ到胚胎体内的有序移动，特别是通过使用 我们的新型外植体系统用于检测HOX表达的细胞定向迁移和突起活性 细胞。我们将测试HOX基因维持PCRGs表达的假设，从而 调节细胞进入PSM的时间。 总的来说，这些研究将检验这样一个前提，即细胞从PZ到PSM的迁移是 受PCRGs和后HOX基因共同作用的调控 新分化的中胚层细胞向前迁移，从而使脊椎动物胚胎 身体以惊人的保真度形成。因为很容易制造转基因株系，在时间上允许 PCRGs和Hox基因以及CRISPR突变株的控制表达，结合OUR 用于高分辨率成像的创新外植体系统，斑马鱼是了解 控制脊椎动物身体早期形成的机制。

PROJECT SUMMARY Much of the vertebrate embryonic body forms from a recently discovered neuromesodermal progenitor cell population located at the most posterior end of the early embryo, in a region called the Progenitor Zone (PZ). The PZ gradually releases mesodermal cells that populate the somites (primarily muscle) as well as the neural cells that form the spinal cord, until the complete anterior-posterior axis of the embryo has been established. While the mechanisms controlling the differentiation of the neuromesodermal cells are increasingly understood, how these cells regulate the completion of the epithelial to mesenchymal transition (EMT) and directional migration from the PZ into the body largely remains a mystery, yet this process is essential for the embryo to form its anterior-posterior axis correctly. Based on our analysis of a zebrafish mutant that specifically disrupts the migration of mesodermal cells from the PZ, we have identified a unique set of PZ-expressed Progenitor Cytoskeletal Regulatory Genes (PCRGs) that we propose must be down-regulated for cells to complete the EMT and migrate from the PZ into the presomitic mesoderm (PSM). Using a novel explant assay we recently developed that allows in vivo imaging of the migrating cells at very high resolution, in Aim 1 we will determine how the PCRGs are used to regulate the directional movement of cells into the PSM using a combination of gain and loss of function studies, as well as examining how the PCRGs control Rho activity. In Aim 2 we will determine how the posterior hox genes, which through unknown mechanisms control the orderly movement of cells from the PZ into the embryonic body, specifically regulate cell movements using our novel explant system to examine directional cell migration and protrusive activity of the hox-expressing cells. We will test the hypothesis that the hox genes act to sustain the expression of the PCRGs, and thereby regulate the timing of cell entry into the PSM. Collectively, these studies will examine the premise that the migration of cells from the PZ into the PSM is regulated by the action of the PCRGs and posterior hox genes, which acting together control the orderly anteriorward migration of newly differentiating mesodermal cells, thus allowing the vertebrate embryonic body to form with remarkable fidelity. With the ease of making transgenic lines that allow temporally controlled expression of the PCRGs and hox genes as well as CRISPR mutant lines, combined with our innovative explant system for high resolution imaging, zebrafish is an excellent system for understanding the mechanisms that control the early formation of the vertebrate body.