Probing the Link between RNA Editing and Drug Addiction

描述(由申请人提供)：人类对药物成瘾的易感性存在广泛的个体差异。了解这些差异的基础，包括风险和保护因素，可能有助于理解药物滥用和依赖(SAD)的病因学。这项建议旨在研究5-羟色胺2C受体(5-HT2CR)基因编辑的个体差异，作为SAD的潜在易感因素。RNA编辑是一种转录后机制，可以改变一个或多个翻译密码子，从而从一个基因产生几个功能不同的蛋白质。5-HT2CR的信使核糖核酸编辑产生多种异构体，每种异构体都有其独特的信号特性，编辑程度越高的异构体功能越弱。我们最近发现，在自杀受害者的背外侧前额叶皮质(DLPFC)和有自我给药成瘾倾向的大鼠的内侧前额叶皮质(MPFC)，5-HT2CR编辑增加。此外，有几条证据表明上瘾行为、冲动和自杀之间存在关联。这种关联被认为源于共同的遗传或表观遗传因素，导致前额叶抑制性调节受损。因此，我们假设，通过编辑相关大脑回路来调节5-HT2CR功能可能会影响对成瘾和冲动行为的抑制控制。因此，这些回路中5-HT2CR编辑的个体差异可能会导致SAD的倾向。为了检验这一假设，我们将采用两种独立但相互关联的方法。首先，我们将使用来自三个相关大脑区域[DLPFC，眶前皮质和伏隔核(NAcc)]的死后标本，以确定滥用海洛因的人和没有滥用海洛因的人之间是否存在5-HT2CR RNA编辑的不同。此外，我们将研究海洛因摄入是否会导致5-HT2CR编辑的变化。这将包括处理海洛因对编辑的影响，如果存在的话，可能会因药物滥用的固有倾向而不同。为此，我们将使用动物模型来比较两种表型的大鼠，这两种表型代表了自我给药各种成瘾药物的极端倾向。这些结果还将为解释人类数据提供重要的见解，在这些数据中，吸毒者的先天差异和海洛因诱导的差异可能很难分离。在人类和大鼠的研究中，5-HT2CR编辑将使用下一代测序进行分析，与以前使用的方法相比，这种方法提供了显著提高的精确度和灵敏度。由于从未研究过RNA编辑与人类药物滥用脆弱性的关系，拟议中的研究构成了一项高风险但高回报的工作。如果我们的假设得到支持，这项研究有望为药物成瘾易感性的生物学基础提供重要的见解，并为开发SAD的治疗策略确定新的方法。 公共卫生相关性：人类和动物在对药物成瘾的易感性方面表现出广泛的个体差异。然而，成瘾的生物学基础仍然难以捉摸。这项建议旨在研究5-羟色胺2C受体的mRNA编辑(一种最近发现的表观遗传机制)，作为物质滥用和依赖的潜在易感因素。拟议的研究有可能为成瘾的病因提供重要的见解，并为开发更有效的治疗策略确定新的靶点(与RNA编辑过程有关)。

DESCRIPTION (provided by applicant): Humans show a wide range of individual differences in susceptibility to drug addiction. An understanding of the basis for these differences, which can include both risk and protective factors, may help to understand the etiology of substance abuse and dependence (SAD). This proposal aims to study individual differences in mRNA editing of the serotonin 2C receptor (5-HT2CR) as a potential vulnerability factor for SAD. RNA editing is a post-transcriptional mechanism that can alter one or more translational codons, thereby giving rise to several functionally distinct proteins from a single gene. mRNA editing of the 5-HT2CR produces numerous isoforms, each of which has its unique signaling properties, with more highly edited isoforms exhibiting decreased function. We recently found increased 5-HT2CR editing in the dorsolateral prefrontal cortex (DLPFC) of suicide victims and in the medial prefrontal cortex (mPFC) of rats with high propensity to self-administer addictive drugs. In addition, several lines of evidence indicate an association among addictive behaviors, impulsivity and suicide. This association has been hypothesized to stem from common genetic or epigenetic contributions that result in impaired prefrontal inhibitory modulation. Thus, we hypothesize that regulation of 5-HT2CR function via editing in the relevant brain circuits may influence inhibitory control over addictive and impulsive behaviors. Individual differences in 5-HT2CR editing in these circuits may, therefore, contribute to propensity toward SAD. To test this hypothesis, we will employ two independent, but interrelated, approaches. First, we will use postmortem specimens from three relevant brain regions [DLPFC, orbitofrontal cortex, and nucleus accumbens (NAcc)], to determine if 5-HT2CR RNA editing differs between humans who abused heroin and those who did not. In addition, we will examine whether or not heroin intake induces changes in 5-HT2CR editing. This will include addressing the possibility that the effect of heroin on editing, if it exists, may differ depending on inherent liability to drug abuse. To this end, we will employ an animal model to compare two phenotypes of rats that represent the extremes in the propensity to self-administer a variety of addictive drugs. The results will also provide important insights in interpreting the human data in which innate vs. heroin-induced differences in drug addicts may be difficult to dissociate. In both human and rat studies, 5-HT2CR editing will be analyzed using Next Generation Sequencing, which provides substantially increased precision and sensitivity compared to previously used methods. Since RNA editing has never been examined in relation to drug abuse vulnerability in humans, the proposed study constitutes a high-risk but high reward undertaking. If our hypothesis is supported, this research holds promise to provide important insights into the biological underpinnings of drug addiction vulnerability as well as to identify novel approaches for the development of treatment strategies for SAD. PUBLIC HEALTH RELEVANCE: Humans and animals show a wide range of individual differences in susceptibility to drug addiction. The biological underpinnings of addiction, however, remain elusive. This proposal aims to study mRNA editing (a recently discovered epigenetic mechanism) of the serotonin 2C receptor as a potential vulnerability factor for substance abuse and dependence. The proposed research has the potential to provide important insight into the etiology of addiction, as well as to identify novel targets (related to the RNA editing process) for the development of more effective treatment strategies.