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，在美国影响约30,000人，由位于4p染色体上的亨廷顿基因CAG重复扩增（编码多谷氨酰胺）引起。虽然有充分的证据支持聚谷氨酰胺毒性在亨廷顿舞蹈病（HD）的发病机制中起主要作用，但对亨廷顿舞蹈病发病机制的完整解释仍然难以捉摸。最近的证据表明，基因的反义转录本存在于整个基因组中。特别是，在许多重复扩张疾病的位点上发现了在疾病发病机制中具有潜在作用的反义转录物，包括脆性X、1型肌强直性营养不良、8型脊髓小脑共济失调和亨廷顿病样2。我们的初步数据表明：1)在HD基因座的CAG/CTG重复区存在一个反义转录物（称为亨廷顿蛋白反义，简称HTTAS），并在多个脑区表达；2) HTTAS启动子活性与CAG/CTG重复序列的长度成反比；3)与对照组相比，HD脑中的HTTAS减少；4)外源过表达HTTAS降低huntingtin （HTT）水平，而敲低HTTAS则增加HTT水平。我们还开发了一系列构建HD基因座的模型，证明了HTTAS对HTT的重复长度依赖性影响。基于这些初始数据，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Aim 1中通过绘制人类和小鼠基因组中的完整HTTAS基因来验证这一假设，确认启动子的重复长度依赖活性，并确定HTTAS1在正常和HD大脑中的表达模式。在Aim 2中，我们将使用细胞模型来确定HTTAS对顺式和反式以及正常和扩展重复序列中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这个项目的长期资助。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。

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.