Bromodomain inhibitors regulate the C9ORF72 locus in ALS.
Bromodomain inhibitors regulate the C9ORF72 locus in ALS.
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DOI：
10.1016/j.expneurol.2015.06.017
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发表时间：
2015-09
影响因子：
5.3
通讯作者：
Wahlestedt C
中科院分区：
文献类型：
--
作者：
Zeier Z;Esanov R;Belle KC;Volmar CH;Johnstone AL;Halley P;DeRosa BA;Khoury N;van Blitterswijk M;Rademakers R;Albert J;Brothers SP;Wuu J;Dykxhoorn DM;Benatar M;Wahlestedt C
位于C9ORF72基因内的六核苷酸重复扩增代表了肌萎缩侧索硬化症（ALS）的最常见已知原因，并将该疾病置于不断增长的重复扩增疾病家族中。RNA焦点，重复相关的翻译产物，和螯合的RNA结合蛋白的存在表明，有毒的RNA获得功能的病理学，而C9ORF72单倍不足可能是一个额外的病理因素。治疗扩增疾病的一种可行的治疗策略是使用表观遗传修饰蛋白的小分子抑制剂来重新激活扩增的遗传基因座。事实上，先前的研究已经通过增加药物诱导的扩增的（和异常异染色质化的）FMR 1、FXN和C9ORF72基因在相应患者细胞中的表达来证明这一原理。虽然表观遗传修饰蛋白越来越多地被认为是药物靶点，但在扩张性疾病的背景下，很少有筛选策略来解决这种药物发现途径。在这里，我们利用半高通量基因表达为基础的筛选，以确定siRNA和小分子抑制剂的表观遗传修饰蛋白，调节C9ORF72 RNA在患者成纤维细胞，淋巴细胞和重编程运动神经元。我们发现，几种布罗莫结构域小分子抑制剂增加C9ORF72 mRNA和前mRNA的表达，而不影响扩增的C9ORF72等位基因的抑制性表观遗传特征。这些数据表明，布罗莫结构域抑制增加了未扩增的C9ORF72等位基因的表达，因此可以补偿单倍不足，而不增加有毒RNA和蛋白质产物的产生，从而赋予治疗价值。
A hexanucleotide repeat expansion residing within the C9ORF72 gene represents the most common known cause of amyotrophic lateral sclerosis (ALS) and places the disease among a growing family of repeat expansion disorders. The presence of RNA foci, repeat-associated translation products, and sequestration of RNA binding proteins suggests that toxic RNA gain-of-function contributes to pathology while C9ORF72 haploinsufficiency may be an additional pathological factor. One viable therapeutic strategy for treating expansion diseases is the use of small molecule inhibitors of epigenetic modifier proteins to reactivate expanded genetic loci. Indeed, previous studies have established proof of this principle by increasing the drug-induced expression of expanded (and abnormally heterochromatinized) FMR1, FXN and C9ORF72 genes in respective patient cells. While epigenetic modifier proteins are increasingly recognized as druggable targets, there have been few screening strategies to address this avenue of drug discovery in the context of expansion diseases. Here we utilize a semi-high-throughput gene expression based screen to identify siRNAs and small molecule inhibitors of epigenetic modifier proteins that regulate C9ORF72 RNA in patient fibroblasts, lymphocytes and reprogrammed motor neurons. We found that several bromodomain small molecule inhibitors increase the expression of C9ORF72 mRNA and pre-mRNA without affecting repressive epigenetic signatures of expanded C9ORF72 alleles. These data suggest that bromodomain inhibition increases the expression of unexpanded C9ORF72 alleles and may therefore compensate for haploinsufficiency without increasing the production of toxic RNA and protein products, thereby conferring therapeutic value.