Mechanisms Underlying Muscle Development in Drosophila

描述（由申请人提供）：肌腱交界处（MTJ）是从肌细胞内部，穿过其膜，并传递到细胞外基质（ECM）的力的主要部位。在健康肌肉组织中，MTJ提供对肌肉收缩过程中产生的机械应力的抵抗力，现在已知MTJ稳定性的任何降低都会导致多种生物的肌肉脱离。最重要的是，正是这种分离表型是人类一系列先天性进行性肌病的典型特征。虽然关于MTJ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都是保守的，但对遗传易感生物黑腹果蝇的研究已被证明有助于揭示MTJ组装、功能和肌肉发育所必需的许多蛋白质。因此，本应用程序的总体目标是使用蝇模型来更好地了解MTJ的形成以及MTJ稳定性缺陷如何导致肌病的发生和进展。进化上保守的Elmo-Myoblast city （Mbc）复合物在果蝇肌肉发育过程中激活小GTPase 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成分-包括启动和调节Elmo- Mbc活性的信号-仍然难以捉摸。这一建议扩展了初步数据，这些数据表明：(1)Elmo也是苍蝇正常的肌肉肌腱附着所必需的，(2)存在两种新的Elmo结合蛋白，这两种蛋白都是果蝇肌肉肌腱附着所必需的

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.