Regulation of muscle fiber type and resistance to muscular dystrophy

描述（由申请人提供）：某些肌肉营养不良症优先影响特定的骨骼肌纤维类型，或快或慢抽搐。特别是，在杜氏肌营养不良（DMD）的人类和小鼠模型中，快肌纤维比慢肌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，可能是通过促进慢肌表型。然而，从这些研究中尚不清楚纤维类型是否确实是赋予肌营养不良易感性或抗性的必要条件。这个项目的最终目标是通过控制骨骼肌纤维类型来治疗肌肉萎缩症。本提案的目的是系统地测试纤维类型识别的遗传和表观遗传调节因子是否可以调节肌营养不良表型，并识别调节纤维类型分化的新表观遗传分子。这一提议将直接验证一个基本假设：促进肌肉缓慢分化的因素将改善DMD的影响。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识别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节是否是肌营养不良症的可行治疗方法，并确定候选分子，为斑马鱼和最终哺乳动物的治疗研究提供基础。本提案将利用斑马鱼模型来解决两个具体目标。Aim 1将通过确定调节纤维类型分化的因素是否增强或抑制斑马鱼dmd表型，直接测试肌纤维类型是否赋予肌肉营养不良的易感性或抗性。我们将通过操纵在缺乏肌营养不良蛋白的斑马鱼胚胎发育早期起作用的纤维型调节因子来启动我们的方法。目的2将通过筛选活转基因斑马鱼的表观遗传化学文库来确定调节肌肉纤维类型的新表观遗传因子，这些活转基因斑马鱼可共同表达快肌和慢肌的荧光报告基因。表观遗传化学物质也将筛选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特征的遗传和表观遗传调节因子，这些调节因子赋予肌肉萎缩症的易感性或抗性。这些预期的结果是重要的，因为该建议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。最近在其他发育和疾病过程中的表观遗传化学筛选的成功突出了这种筛选将为骨骼肌分化和肌肉萎缩症领域提供特殊的机会和创新。

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.