Regulation of muscle fiber type and resistance to muscular dystrophy

描述(申请人提供)：某些肌营养不良症优先影响一种特定的骨骼肌纤维类型，无论是快抽动还是慢抽搐。特别是，在人类和小鼠Duchenne肌营养不良症(DMD)模型中，快肌纤维比慢纤维更容易受到损伤。在小鼠模型中，许多遗传和表观遗传因素可以改善DMD的影响，可能是通过促进缓慢的肌肉表型。然而，从这些研究中尚不清楚纤维类型的同一性是否确实是赋予肌营养不良的易感性或抵抗力所必需的。这个项目的最终目标是操纵骨骼肌纤维类型作为肌肉营养不良的治疗方法。该建议的目的是系统地测试纤维类型认同的遗传和表观遗传调节因子是否可以调节肌营养不良症的表型，并识别调节纤维类型分化的新的表观遗传分子。这一提议将直接检验一个基本假设：促进肌肉分化缓慢的因素将改善DMD的效果。最近的研究，包括我们实验室的工作，已经确定了调节纤维类型特性的关键遗传和表观遗传机制。这些研究现在创造了一个机会，可以直接测试纤维类型调制是否是治疗肌营养不良症的可行方法，并确定将为斑马鱼乃至最终哺乳动物的治疗研究提供基础的候选分子。这项提案将利用斑马鱼模型来解决两个具体目标。目的1将通过确定调节纤维类型分化的因素是增强还是抑制斑马鱼DMD表型，直接测试肌肉纤维类型是否赋予肌肉营养不良的易感性或抵抗力。我们将通过操纵纤维类型的调节器来启动我们的方法，这些纤维类型的调节器在缺乏营养不良蛋白的斑马鱼胚胎的早期发育中发挥作用。目的2利用共表达快肌和慢肌荧光报告基因的活体转基因斑马鱼筛选表观遗传化学文库，以确定调控肌肉纤维类型的新表观遗传因子。还将对表观遗传化学物质进行筛选，以确定其增强或抑制斑马鱼DMD表型的能力。因此，该项目将确定肌肉纤维类型身份的遗传和表观遗传调节因素，这些特征赋予肌肉营养不良的易感性或抵抗力。这些预期结果意义重大，因为这项提案确定的遗传和表观遗传调节因子极有可能为治疗研究提供新的靶点。表观化学筛查最近在其他发育和疾病过程中的成功突显了这种筛查将为骨骼肌分化和肌营养不良领域提供的特殊机会和创新。

DESCRIPTION (provided by applicant): Certain muscular dystrophies preferentially affect a specific skeletal muscle fiber type, either fast or slow twitch. In particular, fast muscle fibers re more susceptible to damage than slow fibers in human and mouse models of Duchenne Muscular Dystrophy (DMD). In the mouse model, many genetic and epigenetic factors can ameliorate the effects of DMD, possibly by promoting a slow muscle phenotype. However, it is not clear from these studies whether fiber type identity is indeed essential for conferring susceptibility or resistance to muscular dystrophy. This project is aimed at an ultimate goal of manipulating skeletal muscle fiber type as a treatment for muscular dystrophy. The objectives of this proposal are to systematically test whether genetic and epigenetic regulators of fiber-type identity can modulate the muscular dystrophy phenotype and to identify new epigenetic molecules that regulate fiber-type differentiation. This proposal will directly test a fundamental hypothesis: that factors that promote slow muscle differentiation will ameliorate the effects of DMD. Recent studies, including work from our lab, have identified critical genetic and epigenetic mechanisms that regulate fiber-type identity. These studies now create an opportunity to directly test whether fiber-type modulation is a viable therapeutic approach for muscular dystrophies and to identify candidate molecules that will provide the basis for therapeutic studies in zebrafish and, ultimately, in mammals. This proposal will take advantage of zebrafish models to address two Specific Aims. Aim 1 will directly test whether muscle fiber type confers susceptibility or resistance to muscular dystrophy by determining whether factors that regulate fiber-type differentiation enhance or suppress the zebrafish dmd phenotype. We will initiate our approach by manipulating fiber-type regulators that function early in development in zebrafish embryos lacking Dystrophin. Aim 2 will identify new epigenetic factors that regulate muscle fiber type by screening an epigenetic chemical library using live trans- genic zebrafish that co-express fluorescent reporters for fast and slow muscle. The epigenetic chemicals will also be screened for their abilities to enhance or suppress the zebrafish dmd phenotype. This project will thus identify genetic and epigenetic regulators of muscle fiber-type identities that confer susceptibility or resistance to muscular dystrophy. These expected outcomes are significant because the genetic and epigenetic regulators identified by this proposal are highly likely to provide new targets for therapeutic studies. The recent success of epigenetic chemical screening in other developmental and disease processes highlights the exceptional opportunity and innovation such screening will provide for the skeletal muscle differentiation and muscular dystrophy fields.