Deciphering mechanisms of myoblast fusion

 说明(申请人提供)：成肌细胞融合是骨骼肌在发育和再生过程中正常形成的基本过程。尽管成肌细胞融合对于肌肉的形成很重要，但支配这一过程的机制还没有完全被了解。阐明融合机制是了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一步。我们最近发现了一种肌肉特异性蛋白，名为myomaker，定位于成肌细胞的质膜。成肌细胞在发育和再生过程中的基因缺失会导致成肌细胞融合不能，从而导致骨骼肌形成的严重障碍。此外，在正常情况下不表达该蛋白的细胞中，肌瘤分子的表达导致了它们与肌肉细胞的融合。虽然肌瘤分子是成肌细胞融合的中心成分，但调控其活性和肌瘤分子的生化功能的调控机制仍不清楚。我们已经确定了对其功能至关重要的myomaker区域，以及与myomaker相互作用潜在地调节其活动的蛋白质。在他的项目中，我们将：1)了解肌瘤分子在融合过程中的功能；2)确定肌瘤分子活性的效应因子；3)评估异源融合和肌源性重编程的最佳细胞类型。我们将使用体内遗传功能丧失和功能获得的方法来研究肌瘤分子在融合过程中的作用。在我们的基于肌瘤分子的异源融合系统中，提出了广泛的分子方法来确定支配肌瘤分子作用的机制。肌瘤分子推动异种细胞与肌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病变肌肉的融合和随后的重新编程。这些目标的成功完成将通过揭示肌瘤分子如何被调控来诱导膜合并，从而深入了解成肌细胞融合的机制。最后，这些研究将对以肌细胞为基础的拯救遗传性肌肉疾病的策略具有重要意义。

 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.