Molecular mechanism of FSHD pathology

描述(申请人提供)：面肩肩周肌营养不良症(FSHD)是一种常染色体显性遗传性肌病，以面部、肩部和上臂肌肉进行性减弱为特征。FSHD不是由编码蛋白质的基因突变引起的；相反，98%的病例中的遗传损害是染色体4q35上特定的非编码D4Z4DMA重复数的收缩。这种基因组缺失是如何导致病理的还不清楚，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。其中一个这样的基因是FSHD区域基因1(FSHD Region Gene 1)，它是第一个被发现定位于4q35的转录基因，是介导FSHD病理的最佳候选基因。FRG1基因从线虫到人类都是保守的，但对FRG1蛋白(FRG1P)在任何系统中的功能仍知之甚少。这一建议直接解决了FRG1P的核功能以及FRG1P表达水平的错误调控对FSHD新的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蛙。非洲爪哇由于其外部发育和容易产生大量转基因动物，是研究FRGIP在FSHD发病机制中作用的理想模型系统。在目标1中，转基因类FSHD动物将在肌肉结构、身体特征和行为方面进一步表征FSHD基因类型。目的2利用转基因蛙直接定位FRG1P的功能，改变FRG1P结构域在发育过程中的表达水平，探讨FSHD发病的分子机制。与FRG1P相互作用的蛋白质和核酸将在Aim3中确定。最终，FSHD研究的目标是找到治疗方法。FSHD的表观遗传失调将极难纠正。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的一个扩展建议测试类似FSHD的青蛙通过减少或消除FRG1的过度表达来逆转或减少FSHD表型的能力。这一系列实验的成功将表明小分子筛查用于FSHD治疗的可行性。非洲爪哇FSHD-蝌蚪在外部发育，是透明的，使它们成为测试小分子疗法寻找FSHD治愈方法的理想选择。

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.