Deciphering mechanisms of myoblast fusion

 描述（由申请人提供）：成肌细胞融合是发育和再生过程中适当骨骼肌形成的基本过程。尽管成肌细胞融合对肌肉形成的重要性，但管理这一过程的机制尚未完全了解。阐明融合机制是理解肌肉发育和开发新的治疗策略以增强骨骼肌疾病的关键步骤。我们最近发现了一种肌肉特异性蛋白，命名为myomaker，定位于成肌细胞的质膜。在发育和成体再生过程中，成肌因子的基因缺失使成肌细胞不能融合，从而导致显著不能形成骨骼肌。此外，在通常不表达这种蛋白质的细胞中表达肌母细胞因子导致它们与肌肉细胞融合。虽然myomaker是成肌细胞融合的核心成分，但其活性和生化功能的调控机制仍不清楚。我们已经确定了对肌源性因子功能至关重要的肌源性因子区域，以及与肌源性因子相互作用以潜在地调节其活性的蛋白质。在他的项目中，我们将：1）了解肌母细胞因子在融合过程中的功能2）鉴定肌母细胞因子活性的效应物3）评估用于异源融合和肌源性重编程的最佳细胞类型。我们将在体内使用基因功能丧失和获得的方法来研究肌母细胞因子在融合过程中的作用。广泛的分子方法在我们的myomaker为基础的异源融合系统，提出了确定的机制，管理myomaker行动。myomaker驱动异源细胞与肌肉细胞融合的能力将成为修复病变骨骼肌的基础。我们将使用细胞移植实验来评估非肌肉细胞与正常和患病肌肉的融合和随后的重编程。这些目标的成功完成将提供深入了解成肌细胞融合的机制，揭示如何myomaker的调节，以诱导膜合并。最后，这些研究将对基于肌瘤标记物介导的细胞的策略来拯救遗传性肌肉疾病具有重要意义。

 DESCRIPTION (provided by applicant): Myoblast fusion is a fundamental process for proper skeletal muscle formation during development and regeneration. Despite the importance of myoblast fusion for muscle formation, the mechanisms that govern this process are not fully understood. Elucidation of fusion mechanisms is a critical step for understanding muscle development and to develop new therapeutic strategies to augment skeletal muscle disease. We recently discovered a muscle-specific protein, named myomaker, that localizes to the plasma membrane of myoblasts. Genetic deletion of myomaker during development and adult regeneration renders myoblasts fusion incompetent, which results in a dramatic inability to form skeletal muscle. Moreover, expression of myomaker in cells that normally do not express this protein causes their fusion with muscle cells. While myomaker is a central component for myoblast fusion, the regulatory mechanisms that govern its activity and the biochemical function of myomaker remain unknown. We have identified the regions of myomaker that are critical for its function and the proteins that interact with myomaker to potentially regulate its activity. In his project we will: 1) understand the function of myomaker within the fusion process 2) identify effectors of myomaker activity 3) evaluate the optimal cell type for heterologous fusion and myogenic reprogramming. We will use genetic loss-of- and gain-of-function approaches in vivo to investigate the role of myomaker during fusion. Extensive molecular approaches within our myomaker-based heterologous fusion system are proposed to identify the mechanisms that govern myomaker action. The ability of myomaker to drive fusion of heterologous cells with muscle cells will serve as the foundation to repair diseased skeletal muscle. We will use cell transplantation experiments to assess fusion and subsequent reprogramming of non-muscle cells with normal and diseased muscle. Successful completion of these aims will provide insight into the mechanisms of myoblast fusion by revealing how myomaker is regulated to induce membrane merger. Finally, these studies will have significant implications for a myomaker-mediated cell based strategy to rescue genetic muscle diseases.