Molecular Mechanisms of Neuronal-dependent Muscle Plasticity

描述(申请人提供)：由于退行性疾病、遗传条件、衰老或创伤造成的骨骼肌损伤或衰竭的修复中目前面临的两个挑战是：1)促进我们对成熟肌肉细胞表型如何保持的理解，以及2)识别和修改与肌肉特性变化相关的神经依赖过程。应对这些挑战将对针对肌肉功能受损患者的治疗方法的开发具有关键影响。电鱼Sternopygus macrurus是一个强大的脊椎动物模型系统，可以帮助阐明影响肌肉程序不同特征的细胞和分子机制。在斑马鱼中，一些骨骼肌纤维完全分化，只是经过融合和随后对其形态和生化特性的极端修改，转化为非收缩的产生电的细胞，称为电细胞。成熟的细胞通过继续表达一些但不是全部肌肉特异性蛋白来保持部分肌肉表型。在电细胞中，选择性肌肉基因表达的抑制依赖于一种连续的、高频的电激活模式。此外，随着神经活动模式的改变，细胞中这种肌肉表型的缺陷是可逆的。初步数据加强了我们的目标，即确定参与调节骨骼肌程序活动依赖的重塑的分子过程。具体地说，我们将测试这一假设，即介导骨骼肌中肌肉基因的神经活性依赖调控的转录机制在大沙门氏菌的电细胞中不同。这一建议的具体目的是：1)确定骨骼肌和电子细胞中的转录谱；2)鉴定钙调神经磷酸酶/NFAT信号通路在介导细胞中肌肉程序的神经依赖性调节中的作用；3)识别肌肉细胞和电子细胞中由生肌转录因子调控的基因。为了确保所提出的研究的成功完成，我们利用一系列分子和细胞工具确定了斑点金鱼对活体实验的适应性，并组建了一支拥有强大导师支持和互补的神经肌肉生物学技能和知识的研究团队。这项研究有望加强我们对神经输入控制肌源性基因表达和肌肉表型维持的过程的理解-对肌肉功能的理解对人类肌肉疾病的治疗方法具有重要意义。

DESCRIPTION (provided by applicant): Two current challenges in the repair of skeletal muscle injury or failure due to degenerative disease, genetic conditions, aging, or trauma are: 1) advancing our understanding of how the mature muscle cell phenotype is maintained, and 2) identification and modification of nerve-dependent processes that are coupled to changes in muscle properties. Meeting these challenges will have critical implications for development of therapies directed toward patients with impaired muscle function. The electric fish Sternopygus macrurus is a powerful vertebrate model system that can help elucidate cellular and molecular mechanisms that affect different features of the muscle program. In S. macrurus, some skeletal muscle fibers fully differentiate only to undergo fusion and subsequent extreme modifications in their morphological and biochemical properties to convert into non-contractile electrogenic cells called electrocytes. Mature electrocytes retain a partial muscle phenotype by continuing to express some, but not all muscle-specific proteins. The suppression of select muscle gene expression in electrocytes is dependent on a continuous, high frequency electrical activation pattern. Further, this deficient muscle phenotype in electrocytes is reversible upon changes in nerve activity patterns. Preliminary data intensified our goal to identify the molecular processes involved in mediating the activity-dependent remodeling of the skeletal muscle program. Specifically, we will test the hypothesis that the transcriptional mechanisms that mediate neural activity-dependent regulation of muscle genes in skeletal muscle differ in electrocytes of S. macrurus. The specific aims of this proposal are: 1) to determine the transcript profiles in skeletal muscle and electrocytes; 2) to characterize the role of the calcineurin/NFAT signaling pathway in mediating the neural-dependent regulation of the muscle program in electrocytes, and 3) to identify the genes regulated by myogenic transcription factors in muscle cells versus electrocytes. To ensure the successful completion of the studies proposed, we have established the amenability of S. macrurus to in vivo experimentation using a collection of molecular and cellular tools, and assembled a research team with strong mentorship support and complementary skills and knowledge in neuromuscular biology. This research is expected to enhance our understanding of the processes by which neural input controls myogenic gene expression and maintenance of the muscle phenotype - an understanding of muscle function with critical implications to therapeutic approaches for human muscle diseases.