Huntington's Disease Antisense Transcript

描述(申请人提供)：亨廷顿病(HD)是一种致命的神经退行性疾病，在美国约有30,000人受到影响，由位于染色体4p的基因Huntingtin中CAG重复序列(编码多谷氨酰胺)的扩大引起。虽然大量证据支持多谷氨酰胺毒性在亨廷顿病(HD)发病机制中的重要作用，但HD发病机制的完整解释仍然难以捉摸。最近的证据表明，基因的反义转录存在于整个基因组中。特别是在一些重复扩张性疾病，包括脆性X、强直性肌营养不良1型、脊髓小脑性共济失调8型和亨廷顿病样2等疾病的基因座上发现了可能在疾病发病机制中起作用的反义转录子。我们的初步数据表明：1)存在一个横跨HD基因座CAG/CTG重复区域的反义转录物(称为Huntingtin反义，简称HTTAS)，并在多个脑区表达；2)hTAS启动子活性与CAG/CTG重复序列长度成反比，3)hTAS在HD脑中的表达水平低于对照组，4)hTAS的外源过表达降低了亨廷顿蛋白(HTT)的水平，而hTAS的敲除则增加了hTT的水平。我们还开发了一系列模拟HD轨迹的结构，证明了HTTAS对HTT的重复长度相关的影响。基于这一初始数据，我们假设HTTAS以重复长度依赖的方式影响HTT的表达，从而影响HD的发病机制。我们将在目标1中通过在人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的活性，并确定HTTAS1在正常和HD脑中的表达模式来验证这一假说。在目标2中，我们将使用细胞模型来确定HTTAS对顺式和反式以及在正常和扩展重复序列设置中HTT表达的影响。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来竞争该项目的长期资金。最终，了解HTT和HTTAS之间的关系将为HD的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：反义转录本似乎在许多疾病中调节突变转录本，包括几种重复扩张性疾病。我们建议检验这一假设，即HD基因上的反义转录本调控亨廷顿蛋白。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.