FSHD as a Disorder of Impaired RNA Biogenesis

描述(由申请人提供)： 面肩臂肌营养不良症(FSHD)的临床特征是面部、肩部和上臂肌肉的进行性无力，是由4Q染色体端粒下的D4Z4大卫星重复序列收缩引起的。在美国，15.000人患有这种疾病，但没有治疗方法。FSHD的致病机制在很大程度上尚不清楚，但人们普遍认为D4Z4的收缩会引起一系列表观遗传事件，导致一个或多个疾病基因的转录失控。 FSHD的候选基因之一是FRG1。它被认为是FSHD的一个很好的候选基因，因为它的定位接近D4Z4，它的高度保守性，以及因为FRG1在小鼠肌肉中的特异性过表达导致肌肉营养不良。来自我们和其他实验室的观察一直表明FRG1在RNA生物发生中发挥作用，但其确切功能尚不清楚。 由于FRG1在有丝分裂活跃的细胞中高表达，FRG1在FSHD患者的原代成肌细胞培养中上调，高水平的FRG1导致人工核仁聚集，并且FSHD尚无可靠的细胞模型，我们的目标是研究FRG1-TAP过表达的条件永生细胞系，类似于在FSHD成肌细胞中观察到的情况。我们建议在蛋白质和RNA水平上，在增殖和分化过程中，询问这些细胞模型FRG1核糖核蛋白(RNP)复合体的确切组成。我们还建议通过定量(mRNA水平)和定性(外显子使用)转录组分析来研究FSHD样过表达FRG1在增殖和分化过程中的直接影响。 我们希望这项研究能够提供有关FRG1 RNP复合体在肌源性、增殖和分化过程中的详细信息，并提供关于FRG1微妙过度表达的即时影响的信息。这些知识对于更好地理解FSHD的致病机制是必不可少的。此外，从长远来看，我们预计具有明确定义的FSHD疾病参数的统一的肌源性细胞模型将对药物干预研究具有重要意义。

DESCRIPTION (provided by applicant): Facioscapulohumeral muscular dystrophy (FSHD) is clinically characterized by progressive weakness of the facial, shoulder and upper arm muscles and is caused by contraction of the D4Z4 macrosatellite repeat in the subtelomere of chromosome 4q. In the US 15.000 people suffer from this disease for which there is no therapy. The pathogenic mechanism underlying FSHD is largely unknown but it is generally accepted that D4Z4 contraction causes a cascade of epigenetic events leading to transcriptional deregulation of one or more disease genes. One of the candidate genes for FSHD is FRG1. It is considered a good candidate for FSHD because of its localization close to D4Z4, its high conservation, and because muscle-specific overexpression of FRG1 in mice causes muscular dystrophy. Observations from our and other laboratories consistently suggest a role for FRG1 in RNA biogenesis, but its exact function is unknown. As FRG1 expression levels are high in mitotic active cells, FRG1 is upregulated in primary myoblast cultures of FSHD patients, high levels of FRG1 causes artificial nucleolar aggregates, and there is no faithful cell model for FSHD, we aim to study conditionally immortal myogenic cell lines with physiological relevant levels of FRG1-TAP overexpression, similar to what is observed in FSHD myoblasts. We propose to interrogate these cell models for the exact composition of the FRG1 ribonucleoprotein (RNP) complex at the protein and RNA level, during proliferation and in differentiation. We also propose to study the immediate effects of FSHD-like overexpression of FRG1 by quantitative (mRNA levels) and qualitative (exon use) transcriptome analysis, during proliferation and differentiation. We expect this study to yield detailed information about the FRG1 RNP complex in a myogenic context, during proliferation and differentiation and to yield information on the immediate effects of subtle FRG1 overexpression. This knowledge will be essential to better understand the pathogenic mechanism underlying FSHD. Moreover, on the long term, we expect that uniform myogenic cell models with well-defined disease parameters for FSHD will be of importance for pharmaceutical intervention studies.