Motility and Guidance Signals Control Migration of Muscle Precursors

贾里德·塔尔博特项目总结： 细胞迁移对于形成有图案的肌肉系统是至关重要的，但只有少数几个线索 激活细胞的运动性是已知的，目前还不清楚肌肉祖细胞是如何决定 朝着一个目的地而不是另一个目的地前进。在这里，我们将研究激活的线索 利用斑马鱼进行肌肉前体细胞运动(Aim 1)和引导迁移细胞(Aim 2) 胚胎作为一个模型系统。在脊椎动物胚胎中，肌肉前体细胞的迁移始于 上皮向间充质转化(EMT)；然后细胞被积极地从体节引导出来 以间充质细胞流的形式迁移到体内的新位置。在哺乳动物胚胎中， 这些细胞流起源于几个轴向水平，在许多水平上产生超过100块肌肉 身体部位。在斑马鱼胚胎中，同源迁移更简单，只产生了4个 肌肉：四肢肌肉、足底颈部肌肉和胸肌。与其他人配对 斑马鱼的优势，这种简单性使斑马鱼胚胎成为一个很好的模型系统 了解肌肉前体细胞的迁移。我们已经开发出转基因和变种 使我们能够研究斑马鱼胚胎中肌肉前体迁移的线条。使用这些 工具，我们最近证明了转录因子SIX1和SIX4(统称为 SIX1/4)是斑马鱼肌肉前体迁移所必需的。在SIX1/4突变体中，肌肉 前体细胞不能进行EMT，也不能激活迁移促进基因MET，这是 编码一种转移诱导受体蛋白。尽管SIX1/4突变体完全缺乏 前体迁移，这一过程只在斑马鱼MET突变体中延迟，表明 SIX1/4针对的是刺激运动的额外基因。在目标1A中，我们将使用不偏不倚的 化学筛选以确定刺激肌肉前体运动和 指导。在目标1B中，我们调查了这一筛选已经提出的一条影响 此迁移过程中的EMT。在目标2中，我们将研究趋化因子信号如何影响这一点 迁移。肌肉前体被认为被趋化因子(CXCL12)信号所吸引， 它由受体CXCR4接收，并被清除受体Ackr3拮抗；我们 认为这两种受体的相互作用使肌肉前体具有方向性 迁移。趋化因子信号将使用遗传突变体和化学调节剂来改变。 在转基因胚胎中，将使用3D细胞跟踪来分析细胞运动。把这些放在一起 实验将为肌肉前体细胞的启动和引导提供洞察力， 在其他依赖迁移的过程中的潜在应用，如肌肉再生和 转移。

Jared Talbot Project summary: Cell migrations are vital to generating a patterned musculature, but only a few of the cues that activate the cell’s motility are known and it remains unclear how muscle progenitors decide to move towards one destination versus another. Here, we will investigate the cues that activate muscle precursor cell motility (Aim 1) and guide the migrating cells (Aim 2) using zebrafish embryos as a model system. In vertebrate embryos, muscle precursor cell migration begins with an epithelial-to-mesenchymal transition (EMT); the cells are then actively guided from somites to new locations in the body, migrating as mesenchymal cell-streams. In mammalian embryos, these cell streams originate from several axial levels to generate over 100 muscles in many body regions. In zebrafish embryos, the homologous migrations are simpler, producing only four muscles: the two limb muscles, the sole neck muscle, and the chest muscle. Paired with other zebrafish strengths, this simplicity makes the zebrafish embryo an excellent model system for understanding muscle precursor cell migrations. We have developed transgenic and mutant lines that enable us to investigate muscle precursor migration in zebrafish embryos. Using these tools, we recently demonstrated that the transcription factors six1 and six4 (collectively termed “six1/4”) are essential for muscle precursor migration in zebrafish. In six1/4 mutants, the muscle precursors fail to undergo EMT and fail to activate the migration-promoting gene met, which encodes a metastasis-inducing receptor protein. Although the six1/4 mutants completely lack precursor migration, this process is only delayed in zebrafish met mutants, suggesting that six1/4 targets additional genes that stimulate motility. In Aim 1A, we will use an unbiased chemical screen to identify new molecules that stimulate muscle precursor motility and guidance. In Aim 1B, we investigate one pathway already suggested by this screen to influence EMT during this migration. In Aim 2, we will investigate how chemokine signals influence this migration. Muscle precursors are thought to be attracted by chemokine (Cxcl12) signaling, which is received by the receptor Cxcr4 and antagonized by the scavenging receptor Ackr3; we propose that the interplay of these two receptors imparts directionality to muscle precursor migration. Chemokine signaling will be altered using genetic mutants and chemical modulators. Cell movement will be analyzed using 3D cell tracking in transgenic embryos. Together these experiments will provide insights into the initiation and guidance of muscle precursor cells, with potential application in other migration-dependent processes like muscle regeneration and metastasis.