Investigating proteostasis in facioscapulohumeral muscular dystrophy

摘要 面肩肱型肌营养不良症是一种常染色体显性遗传性肌肉疾病 由复杂的遗传和表观遗传机制引起。以前的研究表明，转录去- 由于D4 Z4区域的表观遗传变化导致双同源框蛋白4（DUX 4）的抑制， FSHD。表观遗传变化是由D4 Z4阵列从11-150个重复的收缩引起的， 未受影响个体中的1-10个重复单位到大约95%患者中的1-10个重复单位（FSHD 1），或 D4 Z4区域的表观遗传调节因子（FSHD 2）。DUX 4的表达导致下游的 分子和细胞的变化，这有助于疾病的进展。先前的研究报告 FSHD中蛋白质降解过程的缺陷，但是哪些蛋白质受到影响， 蛋白质合成受到影响尚不清楚。为了研究蛋白质丰度的动态变化， 受影响的肌肉细胞，研究小组进行了初步研究，使用液相色谱- 串联质谱与代谢标记的组合。该研究确定了不同的蛋白质 受FSHD影响的个体和其未受影响的同胞的成肌细胞之间的谱。我们 假设DUX 4表达是蛋白质稳态紊乱的原因， 导致FSHD中观察到的下游分子和细胞缺陷。在拟议的研究中， 我们将首先研究永生化FSHD成肌细胞中的蛋白质合成和降解， 在DUX 4减少治疗之后。在目标2中，我们将使用异种移植小鼠验证体外研究结果 模型该项目将发现蛋白质，这些蛋白质被降解过程和合成过程错误调节。 FSHD中的过程，这可能为治疗开发开辟新的机会。其成果将 还提供了疾病机制的新见解，并评估DUX 4减少的功效。 使用靶向DUX 4的反义寡核苷酸治疗。

ABSTRACT Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant muscle disorder caused by complex genetic and epigenetic mechanisms. Previous studies showed that transcription de- repression of double homeobox protein 4 (DUX4) due to epigenetic changes in the D4Z4 region causes FSHD. The epigenetic changes are caused by either contraction of the D4Z4 array from 11-150 repeat units in unaffected individuals to 1-10 repeat units in roughly 95% of patients (FSHD1), or mutations in epigenetic regulators of the D4Z4 region (FSHD2). The expression of DUX4 leads to downstream molecular and cellular changes, which contribute to disease progression. Previous studies reported defects in protein degradation process in FSHD, however what proteins are affected and whether protein synthesis is affected is not clear. To study the dynamic changes in protein abundance in affected muscle cells, the research team conducted a preliminary study using liquid chromatography - tandem mass spectrometry in combination with metabolic labelling. The study identified distinct protein profiles between the myoblasts from individuals affected by FSHD and their unaffected siblings. We hypothesize that DUX4 expression is responsible for the disturbance of protein homeostasis, which contributes to the downstream molecular and cellular defects observed in FSHD. In the proposed study, we will first study the protein synthesis and degradation in immortalized FSHD myoblasts before and after a DUX4-reducing treatment. In aim 2, we will validate the in vitro findings using a xenograft mouse model. This project will discover proteins that are mis-regulated by degradative processes and synthetic processes in FSHD, which may open new opportunities for therapeutic development. The findings will also provide new insights of the disease mechanisms and evaluate the efficacy of a DUX4-reducing treatment using antisense oligonucleotides targeting the DUX4.