Huntington's Disease Antisense Transcript

描述（由申请人提供）：亨廷顿氏病（HD）是一种致命的神经退行性疾病，影响美国约30，000人，由位于染色体4 p上的亨廷顿基因中的CAG重复序列（编码多聚谷氨酰胺）扩展引起。虽然大量证据支持多聚谷氨酰胺毒性在亨廷顿病（HD）发病机制中的主要作用，但HD发病机制的完整解释仍然难以捉摸。最近的证据表明，转录反义基因存在于整个基因组。特别是，在疾病发病机制中具有潜在作用的反义转录物已经在许多重复扩增疾病的基因座处被检测到，包括脆性X、强直性肌营养不良1型、脊髓小脑共济失调8型和亨廷顿病样2型。我们的初步数据表明：1）在HD基因座的CAG/CTG重复区，（称为亨廷顿蛋白反义，缩写为HTTAS）存在于多个脑区域中并在多个脑区域中表达; 2）HTTAS启动子活性与CAG/CTG重复序列的长度成反比，3）与对照脑相比，HD脑中HTTAS降低，和4）HTTAS的外源性过表达降低亨廷顿蛋白（HTT）水平，而HTTAS的敲低增加HTT水平。我们还开发了一系列构建HD基因座的模型，这表明HTTAS对HTT的重复长度依赖性影响。基于这些初步数据，我们假设HTTAS以重复长度依赖性方式影响HTT表达，从而影响HD发病机制。我们将在目标1中通过在人类和小鼠基因组中定位完整的HTTAS基因，确认启动子的重复长度依赖性活性，并确定HTTAS 1在正常和HD脑中的表达模式来验证这一假设。在目标2中，我们将使用细胞模型来确定HTTAS对HTT顺式和反式表达以及正常和扩增重复序列设置的影响。这些实验将使我们能够确定HTTAS的存在和功能，并为我们提供足够的初步数据，以争取该项目的长期资金。最终，了解HTT和HTTAS之间的关系将为HD发病机制提供新的见解，并可能导致新的治疗策略的发展。 公共卫生相关性：反义转录物似乎在许多疾病中调节突变转录物，包括几种重复扩增疾病。我们建议测试的假设，在HD基因座的反义转录调节亨廷顿蛋白。如果得到证实，反义调控将为理解HD的发病机制提供新的途径，并为开发HD的治疗药物提供新的途径。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a fatal neurodegenerative disorder, affecting about 30,000 people in the United State, and caused by an expansion of a CAG repeat (encoding polyglutamine) in the gene huntingtin located on chromosome 4p. While ample evidence supports a major role for polyglutamine toxicity in the pathogenesis of Huntington's disease (HD), the complete explanation for HD pathogenesis remains elusive. Recent evidence suggests that transcripts antisense to genes are present throughout the genome. In particular, antisense transcripts with potential roles in disease pathogenesis have been detected at the locus of a number of repeat expansion diseases, including fragile X, myotonic dystrophy type 1, spinocerebellar ataxia type 8, and Huntington's disease-like 2. Our preliminary data indicates that 1) an antisense transcript spanning the CAG/CTG repeat region at the HD locus (termed huntingtin antisense, abbreviated HTTAS) exists and is expressed in multiple brain regions; 2) HTTAS promoter activity is inversely proportional to the length of the CAG/CTG repeat, 3) HTTAS is decreased in HD brain compared to control brain, and 4) exogenous overexpression of HTTAS decreases huntingtin (HTT) levels, while knockdown of HTTAS increases HTT levels. We have also developed a series of constructs modeling the HD locus, which demonstrates the repeat-length dependent influence of HTTAS on HTT. Based on this initial data, we hypothesize that HTTAS influences HTT expression in a repeat length-dependent manner, with consequent impact on HD pathogenesis. We will test this hypothesis in Aim 1 by mapping the complete HTTAS gene in the human and mouse genome, confirming the repeat-length dependent actiivty of the promoter, and determining the pattern of HTTAS1 expression in normal and HD brain. In Aim 2, we will use cell models to determine the effect of HTTAS on HTT expression both in cis and in trans, and in the setting of normal and expanded repeats. These experiments will enable us to establish the existence and function of HTTAS, and provide us with sufficient preliminary data to compete for long term funding for this project. Ultimately, understanding the relationship between HTT and HTTAS will provide new insights into the mechanism of HD pathogenesis and may lead to the development of novel therapeutic strategies. PUBLIC HEALTH RELEVANCE: Antisense transcripts appear to regulate mutant transcripts in a number of diseases, including several repeat expansion diseases. We propose to test the hypothesis that an antisense transcript at the HD locus regulates huntingtin. If confirmed, antisense regulation would provide a new approach to understanding the pathogenesis of HD, and new approaches for developing therapeutic agents for HD.