Deciphering mechanisms of myoblast fusion

项目摘要/摘要 尽管成肌细胞融合对正常肌肉发育和生理很重要，但相对较少。 已知在成肌细胞融合反应中直接起重塑细胞膜功能的分子。 阐明融合机制对于充分理解肌肉发育和识别新的 加强骨骼肌疾病的治疗策略。我们先前发现myomaker(Mymk) 和Mymerger(Mymx)是骨骼肌祖细胞融合所必需的。此外，异位 这两种膜蛋白的表达可以诱导非融合细胞(成纤维细胞)的融合。为 第一次，这建立了一个基于细胞的重建系统，无论成肌细胞融合原有多少 关于这两种蛋白质是如何诱导融合的问题还存在。我们最近发现，肌动蛋白和 肌聚体通过一种独特的细胞机制，通过分裂它们独立的膜来驱动融合 重塑活动明显影响融合过程。顺理成章的是膜重塑 肌构体和肌聚体的活动必须受到高度调控，否则它们可能会 损害细胞的完整性。事实上，我们的初步实验探索了肌肉机对 营养不良疾病进展过程中的融合意外显示在营养不良患者中肌瘤分子的表达 肌纤维是有害的。在本项目中，我们将：1)测定myomaker的膜重塑活性 控制脂肪混合(半输血)2)确定和询问半输血所需的其他因素3) 阐明肌聚体引起驱动融合孔形成的膜压力的机制。 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基因。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定义肌瘤分子的活动 和肌瘤分子，从而阐明成肌细胞融合的机制。我们还将开发一种重组的 用于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力，以了解 哺乳动物成肌细胞融合。总体而言，这项工作有望开辟细胞研究的新领域 这对利用融合来改善再生医学的可能性产生了积极的影响。

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.