Molecular Mechanisms of Neuronal-dependent Muscle Plasticity

描述（由申请人提供）：目前，由于退行性疾病、遗传条件、衰老或创伤导致的骨骼肌损伤或衰竭的修复面临两个挑战：1)推进我们对成熟肌肉细胞表型如何维持的理解，以及2)识别和修改与肌肉特性变化相关的神经依赖过程。应对这些挑战将对开发针对肌肉功能受损患者的治疗方法具有重要意义。电鱼胸骨巨鱼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。在大鼠中，一些骨骼肌纤维完全分化，只经过融合和随后的形态学和生化特性的极端改变，转化为非收缩的电细胞，称为电细胞。成熟的电细胞通过继续表达一些（但不是全部）肌肉特异性蛋白来保留部分肌肉表型。电细胞中选择性肌肉基因表达的抑制依赖于连续的高频电激活模式。此外，在神经活动模式改变后，电细胞的肌肉表型缺陷是可逆的。初步数据加强了我们的目标，以确定参与介导活动依赖性重构的骨骼肌程序的分子过程。具体来说，我们将验证骨骼肌中肌肉基因的神经活动依赖性调节的转录机制在大鼠的电细胞中不同的假设。本提案的具体目的是：1)确定骨骼肌和电细胞中的转录谱；2)表征钙调神经磷酸酶/NFAT信号通路在介导电细胞中肌肉程序的神经依赖性调节中的作用；3)鉴定肌肉细胞与电细胞中肌源性转录因子调控的基因。为了确保研究的顺利完成，我们已经利用一系列分子和细胞工具建立了大鲵体内实验的适应性，并组建了一个具有强大导师支持和互补神经肌肉生物学技能和知识的研究团队。这项研究有望增强我们对神经输入控制肌源性基因表达和维持肌肉表型的过程的理解-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. PUBLIC HEALTH RELEVANCE: The significance of optimal skeletal muscle performance for the health of living organisms is profound, and failure of muscle tissue function that results from nerve and muscle degenerative diseases, trauma, genetic conditions, and aging is among the most universal problems of modern medicine. This proposal uses an innovative model system to explore the effects of nerve-induced electrical activity on muscle cell plasticity: a vertebrate fish wherein specific features of the skeletal muscle program can be suppressed by changes in neural input and lead to the transformation of muscle into non-contractile cells. This research is expected to enhance our understanding of the cellular and molecular processes that regulate the maintenance and plasticity of muscle properties - an understanding of muscle function with critical implications to therapeutic approaches for human muscle diseases.