FSHD as a Disorder of Impaired RNA Biogenesis

描述（由申请人提供）： 面肩肱型肌营养不良症（FSHD）的临床特征是面部、肩部和上臂肌肉的进行性无力，并且是由染色体4 q的亚端粒中的D4 Z4大卫星重复的收缩引起的。在美国，有15000人患有这种疾病，没有治疗方法。FSHD的致病机制在很大程度上是未知的，但普遍认为D4 Z4收缩引起级联的表观遗传事件，导致一个或多个疾病基因的转录失调。 FSHD的候选基因之一是FRG 1。它被认为是FSHD的一个很好的候选者，因为它的定位接近D4 Z4，它的高度保守性，并且因为FRG 1在小鼠中的肌肉特异性过表达会导致肌营养不良。我们和其他实验室的观察一致表明FRG 1在RNA生物合成中的作用，但其确切功能尚不清楚。 由于FRG 1在有丝分裂活性细胞中表达水平高，FRG 1在FSHD患者的原代成肌细胞培养物中上调，高水平的FRG 1引起人工核仁聚集，并且FSHD没有忠实的细胞模型，我们的目的是研究具有生理相关水平的FRG 1-TAP过表达的条件永生肌细胞系，类似于在FSHD成肌细胞中观察到的。我们建议询问这些细胞模型的确切组成的FRG 1核糖核蛋白（RNP）复合物在蛋白质和RNA水平，在增殖和分化。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，在增殖和分化过程中，研究FRG 1的FSHD样过表达的直接影响。 我们希望这项研究能够产生有关FRG 1 RNP复合物在肌源性背景下，在增殖和分化过程中的详细信息，并产生有关微妙的FRG 1过表达的直接影响的信息。这些知识对于更好地理解FSHD的致病机制至关重要。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.