RNAi-Based Therapy of ALS

RNA干扰（RNAi）是一种广泛存在的基因沉默现象，由双链RNA转化为小干扰RNA（siRNA）引起。虽然siRNA沉默其靶基因表达的详细机制尚不清楚，但已经充分确定siRNA与RNA诱导的沉默复合物（RiSe）结合形成RNA-蛋白质复合物，该复合物可以识别和切割与siRNA序列互补的mRNA靶标。我们希望了解siRNA的化学修饰规则，以增强这些分子的稳定性和递送，从而在体内有效地沉默基因。基于RNAi的治疗的巨大潜在应用之一是在携带一个野生型和一个突变基因拷贝的人中控制由显性功能突变引起的疾病状态。这些疾病的一些最著名的例子是神经退行性疾病，包括亨廷顿氏病、肌萎缩侧索硬化症（ALS）的子集、阿尔茨海默氏病和帕金森氏病。虽然描述突变蛋白如何引起细胞变性的确切功能途径尚不完全清楚，但已知细胞毒性的起源是这些神经退行性疾病中的突变蛋白。我们推断RNAi可以用于降低突变蛋白浓度，从而减缓或阻断神经退行性疾病的进展。RNAi在减缓ALS进展中的有效性已经使用转基因递送的RNAi在体内证明。然而，转基因递送在临床应用中存在问题。在这个提案中，我们专注于开发siRNA作为小分子药物。我们建议开发和测试化学修饰的，稳定的，细胞可渗透的和沉默的siRNA在ALS动物模型表达突变铜，锌超氧化物歧化酶（SOD 1）的治疗。拟议研究的结果也将为开发其他神经退行性疾病的RNAi疗法提供重要的新视角。

RNA interference (RNAi) is a widespread gene-silencing phenomenon initiated by a double-stranded RNA that is converted into small interfering RNAs (siRNAs). Although the detailed mechanism whereby siRNA silences its target gene expression is not understood, it has been well established that siRNA associates with an RNAinduced silencing complex (RiSe) to form an RNA-protein complex that can recognize and cleave an mRNA target that complements the siRNA sequence. We would like to understand the rules for chemical modifications of siRNA to enhance the stability and delivery of these molecules for efficient gene silencing in vivo. One of the great potential applications of RNAi-based therapy is to control disease states caused by dominant, gain of function mutations in people bearing one wild-type and one mutant copy of the gene. Some of the best known examples of such diseases are neurodegenerative diseases including Huntingtqn's, a subset of amyotrophic lateral sclerosis (ALS), Alzheimer's and Parkinson's diseases. Although the exact functional pathways delineating how the mutant proteins cause cell degeneration are not entirely clear, the origin of the cellular toxicity is known to be the mutant proteins in these neurodegenerative diseases. We reason that RNAi could be employed to reduce the mutant protein concentrations and thereby slow or block the progression of neurodegenerative diseases. The effectiveness of RNAi in slowing down the ALS progression has been demonstrated in vivo using transgene delivered RNAi. However, the transgene-based delivery has problems in clinical application. In this proposal, we focus on developing siRNA as small molecule drugs. We propose to develop and test chemically modified, stabilized, cell-permeable and silencing competent siRNA in treatment of ALS animal models that express mutant Cu, Zn superoxide dismutase (SOD1). Findings of proposed research will also offer a new perspective important in developing RNAi-based therapies for other neurodegenerative diseases.