Molecular mechanism of FSHD pathology

描述（由申请人提供）：面肩肱肌营养不良症（FSHD）是一种常染色体显性肌病，其特征是面部、肩部和上臂肌肉的进行性减弱。FSHD不是由蛋白质编码基因突变引起的；相反，在bb0 98%的病例中，遗传病变是染色体4q35上非编码D4Z4 DMA重复序列数量的减少。这种基因组缺失如何导致病理尚不清楚，然而，强有力的证据表明，位于4q35缺失近端的基因在受FSHD影响的骨骼肌中错误表达。其中一个基因是FRG1 (FSHD区域基因1)，它是第一个定位于4q35的转录基因，也是介导FSHD病理的最佳候选基因。FRG1基因从秀丽隐杆线虫到人类都是保守的，但对于FRG1蛋白（FRG1P）在任何系统中的功能仍然知之甚少。这一提议直接解决了FRG1P的核功能和FRG1P表达水平失调对FSHD新脊椎动物模型的影响。这些研究的系统是脊椎动物发育模式生物非洲爪蟾（非洲爪蛙）。非洲爪蟾由于其外部发育和易于产生大量转基因动物，是研究FRGIP在FSHD发病机制中的作用的理想模型系统。在Aim 1中，转基因FSHD样动物将在肌肉结构、身体特征和行为方面进一步表征FSHD pehntype。目的2通过利用转基因青蛙改变发育过程中FRG1P结构域的表达水平，直接解决FRG1P的功能问题，确定FSHD病理的分子机制。与FRG1P相互作用的蛋白和核酸将在Aim3中被鉴定出来。最终，FSHD研究的目标是找到治疗方法。FSHD的表观遗传错误调控将极难解决。治疗的最佳可行靶点是受影响的基因（FRG1）或其下游靶点。Aim 1的扩展提议通过减少或消除FRG1过表达来测试FSHD样蛙逆转或减轻FSHD表型的能力。这一系列实验的成功将表明小分子筛选FSHD治疗的可行性。爪蟾FSHD蝌蚪在外部发育，并且是透明的，使它们成为测试小分子疗法以寻找FSHD治疗方法的理想选择。

DESCRIPTION (provided by applicant): Facioscapulohumeral Muscular Dystrophy (FSHD) is an autosomal dominant myopathy characterized by progressive weakening of the facial, shoulder, and upper arm muscles. FSHD is not caused by a mutation in a protein-encoding gene; instead the genetic lesion in >98% of cases is a contraction in the number of non-coding D4Z4 DMA repeats specifically on chromosome 4q35. How this genome deletion leads to pathology is not understood, however, strong evidence indicates that genes localized proximal to the 4q35 deletion are mis-expressed in FSHD affected skeletal muscles. One such gene is FRG1 (FSHD region gene 1) the first transcribed gene identified that localized to 4q35 and the best overall candidate for mediating the pathology of FSHD. The FRG1 gene is conserved from C. elegans to humans, but still very little is known about the function of the FRG1 protein (FRG1P) in any system. This proposal directly addresses the nuclear function of FRG1P and the effects of misregulation of FRG1P expression levels in a novel vertebrate model for FSHD. The system for these studies is the vertebrate developmental model organism, Xenopus laevis (African clawed frog). Xenopus, with its external development and the ease of generating large numbers of transgenic animals, is ideal among available model systems for investigating FRGIP's role in FSHD pathogenesis. In Aim 1 the transgenic FSHD-like animals will be further characterized for an FSHD pehntype in regards to muscle structure, physical characteristics, and behavior. Aim 2 directly address function of FRG1P by using transgenic frogs to alter the expression levels of FRG1P domains during development, identifying the molecular mechanism of FSHD pathology. Proteins and nucleic acids that interact with FRG1P will be identified in Aim3. Ultimately, the goal of FSHD research is to find treatments. The epigenetic mis-regulation in FSHD will be extremely difficult to adress. The best viable targets for therapy are the affected gene (FRG1) or its downstream targets. An extension of Aim 1 proposes to test the FSHD-like frogs for thier ability to have the FSHD phenotype reversed or at leased lessened by reducing or eliminating FRG1 over-expression. Success of this line of experiments will indicate the feasibility of a small molecule screen for FSHD treatments. Xenopus FSHD-tadpoles develop externally and are transparent rendering them ideal for testing small molecule therapeutics to find a cure for FSHD.