Molecular mechanism of FSHD pathology

描述（由申请人提供）：面肩肱型肌营养不良症（FSHD）是一种常染色体显性遗传性肌病，其特征为面部、肩部和上臂肌肉进行性减弱。FSHD不是由蛋白质编码基因突变引起的;相反，>98%病例中的遗传病变是染色体4 q35上非编码D4 Z4 DMA重复序列数量的收缩。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，定位于4 q35缺失附近的基因在FSHD影响的骨骼肌中错误表达。一个这样的基因是FRG 1（FSHD区域基因1），其是第一个被鉴定的定位于4 q35的转录基因，并且是介导FSHD病理的最佳总体候选基因。FRG 1基因与C.线虫对人类的作用，但对FRG 1蛋白（FRG 1 P）在任何系统中的功能仍然知之甚少。该建议直接解决了FRG 1 P的核功能和FRG 1 P表达水平在FSHD的新型脊椎动物模型中的误调节的影响。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，其外部发展和容易产生大量的转基因动物，是理想的可用模型系统中调查FRGIP的作用，FSHD发病机制。在目的1中，转基因FSHD样动物将在肌肉结构、物理特征和行为方面进一步表征FSHD型。目的2通过转基因青蛙改变FRG 1 P结构域在发育过程中的表达水平，直接研究FRG 1 P的功能，探讨FSHD病理的分子机制。与FRG 1 P相互作用的蛋白质和核酸将在Aim 3中鉴定。最终，FSHD研究的目标是找到治疗方法。FSHD中的表观遗传错误调节将非常难以解决。最好的治疗靶点是受影响的基因（FRG 1）或其下游靶点。目的1的扩展提出测试FSHD样青蛙通过减少或消除FRG 1过表达逆转或至少减轻FSHD表型的能力。这一系列实验的成功将表明FSHD治疗的小分子筛选的可行性。非洲爪蟾FSHD-蝌蚪外部发展，是透明的，使它们成为测试小分子疗法的理想选择，以找到FSHD的治愈方法。

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.