PNAS：美国成功利用反义寡核苷酸ASOs阻止毒性RNA积累并选择性降

一项新研究成功使用反义寡核苷酸ASOs的遗传物质片段阻止毒性RNA的积累并选择性地降解毒性RNA。这项研究是由美国加州大学圣地亚哥分校医学院和路德维希研究所研究人员领导的研究小组完成的。相关文章发表于2013年10月29日的《PNAS》杂志上。

这是研究小组发现了一种新的方法来治疗ALS(ALS主要是由遗传原因引发的)，肌萎缩侧索硬化(Amyotrophic lateral sclerosis，ALS)是成人运动神经元病中最常见的形式。

研究人员使用称为反义寡核苷酸ASOs的遗传物质片段，成功阻止毒性RNA的积累并选择性地降解毒性RNA(毒性RNA是诱发ALS的最常见原因)，同时不影响相同基因生成正常的RNA。

新的方法也可能用于额颞叶变性或额颞叶痴呆(FTD)的治疗，额颞叶变性或额颞叶痴呆(FTD)是一种大脑功能紊乱疾病，特征是行为和性格、语言和运动技能发生变化。

在2011年，科学家发现，一个特定基因C9orf72是ALS最常见的遗传性原因。基因C9orf72突变是一个非常特异性的突变，C9orf72突变不涉及蛋白质水平的变化，而是涉及一组核苷酸(RNA的基本组成部分)序列的重复。一个正常的C9orf72基因包含少于30个核苷酸重复单元--GGGGCC，而突变C9orf72基因可能包含数百个重复单元，这些重复单元形成RNA聚集点。第一作者Clotilde Lagier-Tourenne医学博士说：值得注意的是，我们发现了两个不同的RNA聚集点，一个含有在有义方向转录的RNA，另一个含有反义rnas。

研究人员使用ASOs靶向有义链，减少了rna聚集点的积累，更重要的是，研究人员发现，使用ASOs靶向有义链可以去除毒性RNA，同时不影响编码C9orf72蛋白的正常RNA，这种选择性沉默毒性RNA基因是治疗肌萎缩侧索硬化的一重大进步。

原文摘要：

Targeted degradation of sense and antisense C9orf72 RNA foci as therapy for ALS and frontotemporal degeneration

C. Lagier-Tourenne, M. Baughn, F. Rigo, S. Sun, P. Liu, H.-R. Li, J. Jiang, A. T. Watt, S. Chun, M. Katz, J. Qiu, Y. Sun, S.-C. Ling, Q. Zhu, M. Polymenidou, K. Drenner, J. W. Artates, M. McAlonis-Downes, S. Markmiller, K. R. Hutt, D. P. Pizzo, J. Cady, M. B. Harms, R. H. Baloh, S. R. Vandenberg, G. W. Yeo, X.-D. Fu, C. F. Bennett, D. W. Cleveland, J. Ravits

Expanded hexanucleotide repeats in the chromosome 9 open reading frame 72 (C9orf72) gene are the most common genetic cause of ALS and frontotemporal degeneration (FTD). Here, we identify nuclear RNA foci containing the hexanucleotide expansion (GGGGCC) in patient cells, including white blood cells, fibroblasts, glia, and multiple neuronal cell types (spinal motor, cortical, hippocampal, and cerebellar neurons). RNA foci are not present in sporadic ALS, familial ALS/FTD caused by other mutations (SOD1, TDP-43, or tau), Parkinson disease, or nonneurological controls. Antisense oligonucleotides (ASOs) are identified that reduce GGGGCC-containing nuclear foci without altering overall C9orf72 RNA levels. By contrast, siRNAs fail to reduce nuclear RNA foci despite marked reduction in overall C9orf72 RNAs. Sustained ASO-mediated lowering of C9orf72 RNAs throughout the CNS of mice is demonstrated to be well tolerated, producing no behavioral or pathological features characteristic of ALS/FTD and only limited RNA expression alterations. Genome-wide RNA profiling identifies an RNA signature in fibroblasts from patients with C9orf72 expansion. ASOs targeting sense strand repeat-containing RNAs do not correct this signature, a failure that may be explained, at least in part, by discovery of abundant RNA foci with C9orf72 repeats transcribed in the antisense (GGCCCC) direction, which are not affected by sense strand-targeting ASOs. Taken together, these findings support a therapeutic approach by ASO administration to reduce hexanucleotide repeat-containing RNAs and raise the potential importance of targeting expanded RNAs transcribed in both directions.