Costamere Defects in Muscular Dystrophies

描述（由申请人提供）：Costameres是横纹肌细胞中的肌膜下蛋白质组装体，其将产生力的肌节与肌膜物理偶联。Costameres对于正常的肌肉功能显然是重要的，因为几种组成蛋白是人类肌营养不良症和扩张型心肌病的主要缺陷部位。我们以前证明，costameric细胞骨架是丰富的非肌肉"细胞质"？细胞肌动蛋白和肌肉特异性消融？细胞肌动蛋白引起一种新形式的进行性肌病。这次更新的主要目标是阐明重要的，但知之甚少的功能，无论是细胞和？骨骼肌中的细胞肌动蛋白亚型。我们将利用新的条件性动物模型和异构体特异性试剂，由我的小组在原来的项目期间，以解决几个基本问题的细胞质肌动蛋白在正常的骨骼肌功能和人类疾病的骨骼肌组织。在目标1，我们将调查的具体贡献？细胞肌动蛋白对骨骼肌力学功能的影响，这也可能揭示正常肌肉和肌营养不良蛋白缺陷肌肉收缩诱导损伤的机制。在目标2，不同的和重叠的作用，细胞和？细胞肌动蛋白在发展和成人骨骼肌，特别是在costameres，将通过小鼠品系的特点，无论是细胞肌动蛋白，或细胞和？细胞肌动蛋白在骨骼肌中被特异性地敲除。在目标3中，我们将在体内和体外测试脊髓性肌萎缩症发病机制中异常细胞肌动蛋白定位的假设作用。拟议的研究结果将最明确地解决细胞质肌动蛋白亚型的功能正常和患病骨骼肌的独特和重要的贡献。 公共卫生相关性：众所周知，肌节肌动蛋白亚型在骨骼肌和心肌收缩中发挥重要作用。然而，非肌肉细胞质肌动蛋白亚型在特化肌肉结构的发育/维持中的作用及其对骨骼肌疾病的贡献也很重要，但仍知之甚少。通过对转基因小鼠骨骼肌的严格表征，其中一种或两种非肌肉细胞质肌动蛋白被选择性地消除，并结合对分离细胞和蛋白质的补充实验，拟议的研究将最明确地解决非肌肉细胞质肌动蛋白亚型对正常和患病骨骼肌功能的独特和重要贡献。特别是，本项目对了解杜氏肌营养不良症和脊髓性肌萎缩症的病理机制具有高度相关性。

DESCRIPTION (provided by applicant): Costameres are subsarcolemmal protein assemblies in striated muscle cells that physically couple force-generating sarcomeres with the sarcolemma. Costameres are clearly important for normal muscle function because several constituent proteins are the primary sites of defect in human muscular dystrophies and dilated cardiomyopathies. We previously demonstrated that the costameric cytoskeleton is enriched in non-muscle "cytoplasmic" ?cyto-actin and that muscle-specific ablation of ?cyto-actin causes a novel form of progressive myopathy. The major objective of this renewal is to elucidate the important, but poorly understood functions of both ¿cyto- and ?cyto-actin isoforms in skeletal muscle. We will make use of novel conditional animal models and isoform-specific reagents generated by my group during the original project period to address several fundamental questions about cytoplasmic actins in normal skeletal muscle function and in human diseases of skeletal muscle tissue. In aim 1, we will investigate the specific contribution of ?cyto-actin to the mechanical function of skeletal muscle, which may also shed light into the mechanism of contraction-induced injury of normal and dystrophin-deficient muscle. In aim 2, the distinct and overlapping roles of ¿cyto- and ?cyto- actins in developing and adult skeletal muscle, particularly in costameres, will be investigated through the characterization of mouse lines in which either ¿cyto-actin, or ¿cyto- and ?cyto-actins have been knocked out specifically in skeletal muscle. In aim 3, we will test the hypothesized role for aberrant ¿cyto-actin localization in the pathogenesis of spinal muscular atrophy both in vivo and in vitro. The results of the proposed studies will most definitively address the unique and important contributions of cytoplasmic actin isoforms to the function of normal and diseased skeletal muscle. PUBLIC HEALTH RELEVANCE: The sarcomeric actin isoforms are well known for their important role in contraction of skeletal and cardiac muscle. However, the roles of non-muscle cytoplasmic actin isoforms in the development/maintenance of specialized muscle structures and their contribution to diseases of skeletal muscle are also important, but remain poorly understood. Through rigorous characterization of skeletal muscle in genetically-modified lines of mice where one or both non-muscle cytoplasmic actins are selectively eliminated in combination with complementary experiments on isolated cells and proteins, the proposed studies will most definitively address the unique and important contributions of non-muscle cytoplasmic actin isoforms to the function of normal and diseased skeletal muscle. In particular, this project is highly relevant to understanding the pathological mechanism of Duchenne muscular dystrophy and spinal muscular atrophy.