Investigating proteostasis in facioscapulohumeral muscular dystrophy

摘要 面肩肱骨肌营养不良症(FSHD)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。先前的研究表明，转录去激活 D4Z4区表观遗传改变导致双同源盒蛋白4(DUX4)的抑制 FSHD。表观遗传变化是由D4Z4序列从11-150个重复序列收缩引起的 在大约95%的患者中，未受影响的个体的单位减少到1-10个重复单位(FSHD1)，或者 D4Z4区的表观遗传调控因子(FSHD2)。DUX4的表达导致下游 分子和细胞变化，这有助于疾病的进展。以前的研究报告 然而，FSHD的蛋白质降解过程中存在缺陷，哪些蛋白质受到影响，以及 蛋白质合成是否受到影响尚不清楚。为了研究蛋白质丰度的动态变化 受影响的肌肉细胞，研究小组使用液相色谱进行了初步研究- 串联质谱学与代谢标记相结合。这项研究确定了不同的蛋白质 来自受FSHD影响的个体的成肌细胞与其未受影响的兄弟姐妹之间的图谱。我们 假设DUX4的表达是蛋白质稳态失调的原因，这是 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的FSHD成肌细胞的蛋白质合成和降解 在减少DUX4治疗后。在目标2中，我们将使用异种移植小鼠来验证体外研究结果。 模特。这个项目将发现被降解过程和合成过程错误调节的蛋白质。 FSHD的过程，这可能为治疗开发打开新的机会。调查结果将 还提供了对疾病机制的新见解，并评估了减少DUX4的疗效 使用针对DUX4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.