Cellular and Molecular Mechanisms of Myotube Pathfinding

项目摘要 先天性肌病(CM)是由早期发病定义的各种疾病的集合 低眼压。一些肌病可能会发展到极端的情况，患者会发展成 呼吸系统并发症，甚至需要辅助行动。相关基因的突变 在CMS患者中已发现肌动蛋白的动态变化，包括原肌球蛋白。我们发现 果蝇原肌球蛋白2(TM2)通过促进胚胎骨骼肌发育 成肌细胞融合、肌管延长和肌节组装。这些令人惊讶的结果表明 肌纤维发育缺陷与CMS相关的临床表型有关。 在我们对骨骼肌发育的理解中，仍然存在着关键的知识差距。在……里面 特别是，新生的肌管必须延长并附着到适当的肌腱细胞上，以形成 功能收缩单元。然而，引导肌管连接到肌肉的分子 地点在很大程度上仍不为人所知。此外，肌管反应的机制 趋化信号尚不清楚。我们使用了先进的基因筛查和尖端技术 转录图谱用于鉴定肌管导向分子和肌管细胞内效应分子 伸长率。我们的初步工作产生了独特的遗传工具和新颖的机械洞察力 这将使我们能够确定引导肌管的中央通路和机制的特征 伸长率。对这一应用的总体假设是丝状伪足是 肌管寻路，丝状径向行为由细胞内的外部寻路线索决定 蛋白激酶和肌动蛋白调节蛋白。本项目将实现以下目标：(1)明确 原肌球蛋白调节肌肉发生的细胞途径，(2)表征新的 肌管寻路的细胞内效应器，以及(3)表征趋化机制， 直接肌管寻路。这些研究将在一个新兴的领域取得实质性进展 肌肉生物学有可能发现导致肌肉疾病的新机制。

Project Summary Congenital myopathies (CM) are a heterogeneous collection of disorders defined by early onset hypotonia. Some myopathies can progress to extreme conditions in which patients develop respiratory complications and even require assistance for mobility. Mutations in genes associated with actin dynamics have been identified in patients with CMs, including Tropomyosins. We found that Drosophila Tropomyosin 2 (Tm2) directs embryonic skeletal muscle development by promoting myoblast fusion, myotube elongation, and sarcomere assembly. These surprising results argue that defects in myofiber development contribute to the clinical phenotypes associated with CMs. There remain critical knowledge gaps in our understanding of skeletal muscle development. In particular, nascent myotubes must elongate and attach to the appropriate tendon cells to form a functional contractile unit. However, the molecules that guide myotubes to their muscle attachment sites remain largely unknown. In addition, the mechanisms by which myotubes respond to chemotactic signals are unclear. We have used forward genetic screens and cutting edge transcriptional profiling to identify myotube guidance molecules and intracellular effectors of myotube elongation. Our preliminary work has generated unique genetic tools and novel mechanistic insights that will allow us to characterize the central pathways and mechanisms that direct myotube elongation. The overall hypothesis for this application is that filopodia are the key effectors of myotube pathfinding, and that filopodial behavior is dictated by external pathfinding cues, intracellular protein kinases, and actin regulatory proteins. This project will achieve the following aims: (1) define the cellular pathways by which Tropomyosin regulates myogenesis, (2) characterize novel intracellular effectors of myotube pathfinding, and (3) characterize chemotactic mechanisms that direct myotube pathfinding. These studies will make substantial inroads into an emerging area of muscle biology that has the potential to uncover novel mechanisms that contribute to muscle disease.