Mechanisms Underlying Muscle Development in Drosophila

描述（由申请人提供）：肌腱连接（MTJ）是力从肌细胞内部穿过其膜传递到细胞外基质（ECM）的主要部位。在健康的肌肉组织中，MTJ提供抵抗肌肉收缩期间产生的机械应力的阻力，并且现在已知MTJ稳定性的任何降低都会导致不同生物体中的肌肉脱离。最重要的是，这种脱附表型是人类一系列先天性、进行性肌病的典型表现。虽然关于MTJ的形成，结构和功能的许多特征在脊椎动物和无脊椎动物之间是保守的，但在遗传上易处理的生物体黑腹果蝇中的研究已经证明有助于揭示许多对MTJ组装和功能以及肌肉发育至关重要的蛋白质。因此，本申请的总体目标是使用飞行模型来更好地理解MTJ形成以及MTJ稳定性的缺陷如何导致肌病的发作和进展。在果蝇肌肉发育过程中，进化上保守的Elmo-成肌细胞城（Mbc）复合体激活了小GT3-Rac。虽然Rac的主要作用在于调节肌动蛋白细胞骨架，但在Elmo介导的肌生成中起作用的其他信号传导组分-包括启动和调节埃尔莫- Mbc活性的信号-仍然难以捉摸。该建议扩展了初步数据，这些数据表明：（i）埃尔莫也是苍蝇中正确的肌肉-肌腱附着所需的，以及（ii）存在两种新的Elmo结合蛋白，这两种蛋白都是苍蝇中正确的肌肉-肌腱附着所需的。 MTJ处的肌肉附着。将使用成熟的果蝇MTJ作为肌肉-肌腱信号传导和肌肉收缩后产生的后续力传递的模型来检查这些含Elmo的复合物的作用。为了验证我们的总体假设，即这些新的埃尔莫蛋白复合物在果蝇肌肉附着过程中起介导细胞骨架重排的作用，我们将使用遗传学、生物化学和成像方法的强大组合来追求以下特定目标：（1）剖析埃尔莫在MTJ形成和/或Rac激活中的作用;（2）鉴定埃尔莫和相关蛋白发挥作用以维持稳定的MTJ的机制;（3）了解埃尔莫复合物在肌附着过程中线粒体定位中的作用。

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.