Costamere Defects in Muscular Dystrophies

描述（由申请人提供）：肌膜是横纹肌细胞中肌膜下的蛋白质集合，它将产生力的肌节与肌膜物理地结合在一起。由于一些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，因此Costameres对正常肌肉功能显然是重要的。我们之前已经证明，沿海细胞骨架富含非肌肉“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型的进行性肌病。这次更新的主要目的是阐明细胞和细胞的重要但鲜为人知的功能。骨骼肌中细胞肌动蛋白同种异构体。我们将利用我课题组在原项目期间产生的新型条件动物模型和异构体特异性试剂来解决正常骨骼肌功能和人类骨骼肌组织疾病中细胞质肌动素的几个基本问题。在目标1中，我们将调查？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和肌营养不良肌的收缩性损伤机制。在目标2中，细胞和细胞的不同和重叠的作用。细胞-肌动蛋白在发育和成年骨骼肌，特别是在costameres，将通过表征小鼠系的细胞-肌动蛋白，或细胞-和？细胞肌动蛋白在骨骼肌中被敲除。在目标3中，我们将在体内和体外测试异常细胞-肌动蛋白定位在脊髓性肌萎缩发病机制中的假设作用。提出的研究结果将最明确地解决细胞质肌动蛋白异构体对正常和患病骨骼肌功能的独特和重要贡献。

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.