Mechanisms Underlying Muscle Development in Drosophila

描述(申请人提供)：肌腱连接(MTJ)是肌细胞内部、跨其膜、向细胞外基质(ECM)传递力量的主要部位。在健康的肌肉组织中，MTJ可以抵抗肌肉收缩过程中产生的机械应力，现在已经知道，MTJ稳定性的任何下降都会导致不同生物的肌肉脱落。最重要的是，正是这种脱离表型代表了人类一系列先天性的进行性肌病。虽然许多关于MTJ的形成、结构和功能的特征在脊椎动物和无脊椎动物之间都是保守的，但对遗传易驯化的生物果蝇的研究已被证明有助于揭示MTJ的组装、功能和肌肉发育所必需的许多蛋白质。因此，该应用程序的总体目标是使用Fly模型来更好地了解MTJ的形成以及MTJ稳定性缺陷如何导致肌病的发生和发展。进化上保守的Elmo-Myoblast City(MBC)复合体在果蝇肌肉发育过程中激活了小GTP酶Rac。虽然Rac的主要作用在于调节肌动蛋白细胞骨架，但在Elmo介导的肌肉发生中起作用的其他信号成分--包括启动和调节Elmo-MBC活动的信号--仍然难以捉摸。这一建议对初步数据进行了扩展，这些数据表明：(I)ELMO也是苍蝇肌肉-肌腱连接所必需的，以及(Ii)存在两种新的Elmo结合蛋白，这两种蛋白都是 下颌关节的肌肉附着处。这些包含Elmo的复合体的作用(S)将用成熟的果蝇MTJ作为肌肉-肌腱信号和肌肉收缩产生的随后的力传递的模型来检验。为了检验我们的总体假设，即这些新的Elmo蛋白复合体在果蝇肌肉附着过程中介导细胞骨架的重新排列，我们将使用遗传学、生化和成像方法的强大组合来追求以下特定目标：(1)剖析Elmo在MTJ形成和/或Rac激活中的角色；(2)确定Elmo和相关蛋白质维持稳定MTJ的功能的机制；以及(3)了解Elmo复合体在肌肉附着过程中线粒体定位中的功能。

DESCRIPTION (provided by applicant): The myotendinous junction (MTJ) is the primary site for force transmission from the interior of the muscle cell, across its membrane, and to the extracellular matrix (ECM). In healthy muscle tissue, the MTJ provides resistance against the mechanical stress generated during muscle contraction, and it is now known that any decrease in MTJ stability leads to muscle detachment in diverse organisms. Most significantly, it is this detachment phenotype that typifies a series of congenital, progressive myopathies in humans. While many features concerning MTJ formation, structure, and function are conserved between both vertebrates and invertebrates, studies in the genetically tractable organism Drosophila melanogaster have proven instrumental in uncovering many proteins essential for MTJ assembly and function and muscle development as a whole. Therefore, the overall goal of this application is to use the fly model to better understand MTJ formation and how defects in MTJ stability may lead to the onset and progression of myopathies. The evolutionarily conserved Elmo-Myoblast city (Mbc) complex activates the small GTPase Rac during Drosophila muscle development. While the primary role of Rac lies in regulation of the actin cytoskeleton, other signaling components that function in Elmo-mediated myogensis - including the signals that initiate and regulate Elmo- Mbc activity - have remained elusive. This proposal expands upon preliminary data which show that (i) Elmo is also required for proper muscle-tendon attachment in the fly, and that (ii) there exist two new Elmo-binding proteins, both of which are required for muscle attachment at the MTJ. The role(s) of these Elmo-containing complexes will be examined using the mature Drosophila MTJ as a model for both muscle-tendon signaling and subsequent force transmission generated upon muscle contraction. To test our overall hypothesis that these new Elmo protein complexes function to mediate cytoskeletal rearrangement during Drosophila muscle attachment, we will use a powerful combination of genetic, biochemical, and imaging approaches to pursue the following specific aims: (1) dissect the role of Elmo in MTJ formation and/or Rac activation; (2) identify the mechanism by which Elmo and associated proteins function to maintain stable MTJs; and (3) understand the function of Elmo complexes in mitochondrial localization during muscle attachment.