Cellular and Molecular Mechanisms of Myotube Guidance

项目总结 调节骨骼肌形态并使肌肉形态与 总体身体计划仍然知之甚少。在胚胎发育期间，肌肉前体被称为 肌管经历戏剧性的形态发生，其中肌管的前缘伸长，导航到 肌腱，然后选择预先确定的位置进行肌肉附着。肌管引导指的是 结合前沿导航和目标决策的细胞过程，将肌肉与 纠正肌腱。 我们利用果蝇胚胎中的肌肉发生作为切入点来鉴定细胞和分子 肌管引导的机制。使用正向遗传筛选和基于基因组学的反向遗传学，我们 确定了多个引导肌管前沿迁移的导航信号，并发现了转录 指导肌肉形态发生的因素。我们的活体成像方法显示肌管活跃 通过与肌腱细胞的一种假定的接触依赖机制选择正确的肌肉附着位置。 我们假设短程导航信号、形态发生基因调控的综合作用 网络，和接触依赖的细胞识别程序直接肌管指导，以确保肌肉 地形与人体平面图完美配合。 为了实现对肌管引导的全面理解，我们将研究 导航、细胞识别和基因调控模块。我们建议(1)研究多个 导航信号共同调节细胞骨架以引导肌管前沿迁移，(2)使用 功能基因组学，以了解形态发生基因调控网络如何调节对 导航信号和指导接触依赖的细胞识别，以及(3)发现异嗜性蛋白- 肌管和肌腱细胞之间建立肌腱密码的蛋白质相互作用。我们期待着 这项研究中提出的基础性工作将是理解如何导航、 细胞识别和基因调控模块合作，在更复杂的系统和 人类疾病。

PROJECT SUMMARY The mechanisms that regulate skeletal muscle topography and perfectly align muscle morphology with the overall body plan remain poorly understood. During embryonic development, muscle precursors known as myotubes undergo a dramatic morphogenesis in which the myotube leading edges elongate, navigate to tendons, and then choose pre-determined sites for muscle attachment. Myotube guidance refers to the combined cellular processes of leading edge navigation and targeting decisions that connect muscles with the correct tendons. We have used myogenesis in the Drosophila embryo as an entry point to identify the cellular and molecular mechanisms of myotube guidance. Using forward genetic screens and genomics-based reverse genetics, we identified multiple navigational signals that direct myotube leading edge migration, and uncovered transcription factors that direct muscle morphogenesis. Our live imaging approaches revealed that myotubes actively choose the correct muscle attachment site through a putative contact-dependent mechanism with tendon cells. We hypothesize that the integrated actions of short-range navigational signals, morphogenetic gene regulatory networks, and contact-dependent cell recognition programs direct myotube guidance to ensure muscle topography perfectly complements the body plan. To achieve a comprehensive understanding of myotube guidance, we will investigate the interplay between navigation, cell recognition, and gene regulatory modules. We propose (1) to investigate how multiple navigational signals co-regulate the cytoskeleton to direct myotube leading edge migration, (2) to use functional genomics to understand how a morphogenetic gene regulatory network modulates responses to navigational signals and directs contact-dependent cell recognition, and (3) to uncover the heterophilic protein- protein interactions between myotubes and tendon cells that establish a myotendinuos code. We expect the foundational work proposed in this study will be a necessary first step toward understanding how navigational, cell recognition, and gene regulatory modules cooperate to direct myogenesis in more complex systems and human disease.