Muscular Dystrophy Specialized Research Center: Project 1

项目1项目概要 我们研究的总体目标是阐明细胞和分子机制， 为了促进新的治疗策略和定量的合理设计， 用于评估靶标接合和治疗方法的有效性的测定。我们目前的研究 重点是肌营养不良症，一组先天性/肢带型肌营养不良症引起的 细胞外基质（ECM）受体α-肌营养不良蛋白聚糖（α-DG）翻译后加工缺陷。 含有层粘连蛋白-G-样（LG）结构域的ECM蛋白通过独特的杂多糖与α-DG结合 [-GlcA-β 1，3-Xyl-α 1，3-]n称为基质聚糖。遗传学研究表明，至少一种基因的突变 18个编码α-DG翻译后加工所需的酶的基因导致缺乏 或基质聚糖减少，从而损害α-DG受体功能。虽然取得了重大进展， 虽然在肌营养不良基因的鉴定和表征方面取得了进展，但我们仍然没有完全 了解基质聚糖的生物化学和生理功能，或者它的缺失或减少是如何在 长度导致肌肉萎缩症。本研究的总体目标是提供 深入了解基质聚糖在α-DG受体功能中的作用以及在 肌营养不良聚糖病我们研究的首要假设是，对（a） 在营养不良性聚糖病患者中缩短的基质聚糖结构和导致的α-DG受体功能障碍 和（B）肌营养不良聚糖病的病理生理学基础的机制，将导致更多的 可靠的诊断和新颖的治疗策略。具体目标1将建立以下关系 α-DG基质聚糖长度和α-DG基质聚糖上的层粘连蛋白结合特性 肌营养不良聚糖病患者成纤维细胞和肌肉活检。这些研究将揭示出 α-DG的翻译后加工，导致基质聚糖缩短，对层粘连蛋白的亲和力降低 导致肌肉萎缩具体目标2将定义基质聚糖合成的生化调节 及其在α-DG受体功能中的作用。这些研究将确定基质聚糖的要求 蛋白质的合成以及蛋白质-蛋白质和蛋白质-糖相互作用如何调节其合成。具体目标 3将定义肌营养不良聚糖病的病理生理学基础的新机制，并确定 改善肌肉功能所需的结构和层粘连蛋白结合特性。这些研究将使用 在LARGE基因治疗前后评估的具有已建立的营养不良肌肉病理学的myd小鼠 转移总的来说，这些目标将提供一个理解的病理机制， 肌营养不良聚糖病，这将需要开发一个合理的设计新的诊断和 治疗策略，以及监测治疗参与和疗效的方法。

Project 1 Project Summary The overall goal of our research is to elucidate the cellular and molecular mechanisms that underly muscular dystrophies in order to facilitate the rational design of novel therapeutic strategies and quantitative assays to assess target engagement and the effectiveness of therapeutic approaches. Our current research focuses on the dystroglycanopathies, a group of congenital/limb-girdle muscular dystrophies caused by defects in post-translational processing of the extracellular matrix (ECM) receptor α-dystroglycan (α-DG). ECM proteins that contain laminin-G-like (LG) domains bind to α-DG via a unique heteropolysaccharide [-GlcA-β1,3-Xyl-α1,3-]n called matriglycan. Genetic studies have shown that mutations in any one of at least eighteen genes encoding enzymes required for α-DG post-translational processing lead to the absence of or a reduction in matriglycan and thus impair α-DG receptor function. Although significant progress has been made in the identification and characterization of dystroglycanopathy genes, we still do not fully understand the biochemical and physiological function of matriglycan, or how its absence or reduction in length causes muscular dystrophy. The overall objective of the proposed research is to provide mechanistic insights into the role matriglycan plays in α-DG receptor function and in the pathophysiology of the dystroglycanopathies. The overarching hypothesis of our research is that a thorough understanding of (a) the shortened matriglycan structure and resulting α-DG receptor dysfunction in dystroglycanopathy patients and (b) the mechanisms underlying the pathophysiology of the dystroglycanopathies, will lead to more reliable diagnostics and novel therapeutic strategies. Specific Aim 1 will establish the relationship between α-DG matriglycan length and laminin-binding properties of matriglycan on α-DG in control and dystroglycanopathy patient fibroblasts and muscle biopsies. These studies will reveal abnormalities in the post-translational processing of α-DG that result in shorter matriglycan with reduced affinity for laminin leading to muscular dystrophy. Specific Aim 2 will define the biochemical regulation of matriglycan synthesis and its role in the receptor function of α-DG. These studies will define the requirements for matriglycan synthesis and how its synthesis is regulated by protein-protein and protein-sugar interactions. Specific Aim 3 will define novel mechanisms underlying the pathophysiology of the dystroglycanopathies and determine the structure and laminin binding properties required to improve muscle function. These studies will use myd mice with established dystrophic muscle pathology that are evaluated before and after LARGE gene transfer. Collectively, these aims will provide an understanding of the pathological mechanisms underlying dystroglycanopathies, which will be needed to develop a rationale for the design of novel diagnostic and therapeutic strategies, as well as approaches to monitoring therapeutic engagement and efficacy.