Deciphering mechanisms of myoblast fusion

项目总结/摘要 尽管成肌细胞融合对正常肌肉发育和生理学的重要性， 在成肌细胞融合反应过程中直接作用于重塑细胞膜的分子。 阐明融合机制对于充分理解肌肉发育和鉴定新的 增加骨骼肌疾病的治疗策略。我们以前发现，myomaker（Mymk） 和Myomerger（Mymx）对于骨骼肌祖细胞的融合是必需的。此外，异位 这两种膜蛋白的表达诱导否则非融合细胞（成纤维细胞）的融合。为 这是第一次用成肌细胞融合原（无论有多少）建立了基于细胞的重建系统 关于这两种蛋白质如何诱导融合存在问题。我们最近发现，myomaker和 肌融合器通过一种独特的细胞机制，通过分裂它们独立的膜， 重塑活动明显影响融合过程。很明显细胞膜重塑 myomaker和myomerger的活性必须受到高度调节，否则它们可能有可能 危及细胞完整性事实上，我们的初步实验探索肌生成素的需求， 在营养不良性疾病进展过程中的融合意外地揭示了肌母细胞因子在营养不良性疾病中的表达， 肌纤维是有害的本课题的主要研究内容如下：1）测定肌源性蛋白激酶（myomaker）的膜重塑活性 控制脂质混合（半融合）2）识别和询问半融合所需的其他因素3） 阐明肌融合器弹性膜应力驱动融合孔形成的机制。 此外，我们将在慢性肌肉疾病（肌营养不良症）的背景下研究这些融合子。我们 将使用细胞生物学、生物化学和遗传小鼠模型来研究和确定肌生成因子的活性 和myomaker，从而阐明成肌细胞融合的机制。我们还将开发一个重组的 成肌细胞融合的蛋白脂质体系统。这些研究将提供独特的洞察机制， 哺乳动物成肌细胞融合总的来说，这项工作有望为细胞研究开辟一个新的领域。 肌肉的生物学和积极影响利用融合的可能性，以改善再生医学。

Project Summary/Abstract Despite the importance of myoblast fusion for normal muscle development and physiology, relatively little is known about the molecules that directly function to remodel membranes during the myoblast fusion reaction. Elucidation of fusion mechanisms is critical to fully understand muscle development and to identify novel therapeutic strategies to augment skeletal muscle disease. We previously discovered that myomaker (Mymk) and myomerger (Mymx) are essential for the fusion of skeletal muscle progenitors. Moreover, ectopic expression of these two membrane proteins induces fusion of otherwise non-fusogenic cells (fibroblasts). For the first time, this establishes a cell-based reconstitution system with myoblast fusogens, however many questions exist as to how these two proteins induce fusion. We have recently found that myomaker and myomerger drive fusion through a unique cellular mechanism, by dividing their independent membrane remodeling activities to distinctly impact the fusion process. It stands to reason that the membrane-remodeling activities of myomaker and myomerger must be highly regulated or they could have the potential to compromise cellular integrity. Indeed, our preliminary experiments probing the requirement of myomaker for fusion during dystrophic disease progression unexpectedly revealed that myomaker expression in dystrophic myofibers is deleterious. In this project we will: 1) determine the membrane-remodeling activities of myomaker that control lipid mixing (hemifusion) 2) identify and interrogate the additional factors required for hemifusion 3) elucidate the mechanisms by which myomerger elicits membrane stresses that drive fusion pore formation. Additionally, we will study these fusogens in the context of chronic muscle disease (muscular dystrophy). We will use cell biology, biochemistry, and genetic mouse models to study and define the activities of myomaker and myomaker, thereby elucidating the mechanisms of myoblast fusion. We will also develop a reconstituted proteoliposome system for myoblast fusion. These studies will provide unique insight into the mechanisms of mammalian myoblast fusion. Overall, this work promises to open up a new area of investigation into the cell biology of muscle and positively impact the possibility to harness fusion to improve regenerative medicine.