Genetic modifiers of Chrna5 deletion in mice: role in nicotine behaviors modulated by the medial habenula-IPN pathway

项目摘要/摘要 每10名试图戒烟的人中，只有不到1人能坚持戒烟1年。这个糟糕的离职率是 部分原因是目前用于帮助戒烟的药物仅适中 充其量也就是有效。因此，非常需要开发对吸烟更有效的新药 停止。这个项目的目标是使用一种新的遗传策略来识别新的生物靶点 新型戒烟药物的潜在开发。遗传策略的基础是识别 在编码CHRNA5的基因中存在零突变的小鼠中，改变尼古丁反应的修饰基因 烟碱受体α5亚单位。实际上，修饰基因是对生理和/或 分子过程对感兴趣的行为很重要，但通常在 在他们修饰的基因中没有扰动。因为CHRNA5的变异改变了尼古丁的风险 对人类的依赖和对啮齿动物的研究清楚地表明，CHRNA5对许多尼古丁- 相关行为，我们认为识别修改CHRNA5缺失对尼古丁影响的基因 行为将发现与尼古丁依赖相关的新基因，可能成为新的研究目标 戒烟药物疗法。重要的是，我们计划筛选修饰符的行为不是 仅依赖于CHRNA5，但也依赖于内侧缰核-IPN通路，这是一种神经通路 这被认为在尼古丁依赖中起着关键作用。确定基因修饰物的效果 针对CHRNA5缺失对尼古丁行为的影响，我们提出了3个目标。在特定目标1中，我们将培育CHRNA5空 对每个B6-Chra/J染色体替代菌株(CS)进行突变，并鉴定 CHRNA5缺失对三种尼古丁行为、口服尼古丁摄入量、 尼古丁戒断的躯体迹象，以及尼古丁条件性位置偏爱。对于具体目标2，我们将 使用连续的同源基因株精细定位那些含有修饰基因的染色体。通常为3 从一个css菌株开始的同源菌株的世代提供了与 任何高分辨率的测绘种群。最后，在特定的目标3中，我们将使用rna-seq来识别基因。 其表达被已识别的修饰基因改变。重要的是，我们将使用最先进的基因 策略将允许我们检查神经细胞群体中高度相关的基因表达 行为：脚间核表达CHRNA5的细胞。通过将这一目标的结果与 通过目标1和目标2确定的修饰基因座，我们希望缩小潜在候选修饰基因的列表 并确定特定受修饰基因影响的途径。简而言之，我们相信这一战略将 导致确定以前未知的基因和/或遗传途径，这些基因和/或遗传途径有助于 对尼古丁的反应很重要的生理和/或分子过程。这些基因和/或途径 可作为开发新的药物疗法以帮助戒烟的新靶点。

PROJECT SUMMARY/ABSTRACT Less than 1 in 10 individuals who attempt to quit smoking remain abstinent for 1 year. This poor quit rate is driven, in part, by the fact that currently available drugs used to aid in smoking cessation are only moderately effective, at best. Thus, there is a great need to develop novel drugs that are more effective for smoking cessation. It is the goal of this project to use a novel genetic strategy to identify new biological targets for the potential development of novel smoking cessation drugs. The genetic strategy is based upon identifying modifier genes that alter nicotine responses in mice that have a null mutation in Chrna5, the gene that codes for the nicotinic receptor α5 subunit. In effect, modifier genes are genes that contribute to physiological and/or molecular processes that are important for the behavior of interest but that generally go undetected in the absence of a perturbation in the gene that they modify. Because variants in Chrna5 alter risk for nicotine dependence in humans and studies in rodents clearly demonstrate that Chrna5 is critical for many nicotine- related behaviors, we believe that identifying genes that modify the effect of Chrna5 deletion on nicotine behaviors will uncover new genes relevant to nicotine dependence that may serve as novel targets for novel smoking cessation pharmacotherapies. Importantly, the behaviors that we plan to screen for modifiers are not only dependent upon Chrna5, but also dependent uponthe medial habenula-IPN pathway, a neural pathway that is thought to play a critical role in nicotine dependence. To identify genetic modifiers of the effect of Chrna5 deletion on nicotine behaviors, we propose 3 aims. In specific aim 1, we will breed the Chrna5 null mutation onto each of the B6-ChrA/J chromosome substitution strains (CSS) and identify chromosomes that harbor modifier genes for the effect of Chrna5 deletion on three nicotine behaviors, oral nicotine intake, somatic signs of nicotine withdrawal, and nicotine conditioned place preference. For specific aim 2, we will fine map those chromosomes that harbor modifier genes using sequential congenic strains. Typically, 3 generations of congenic strains starting from a CSS strain provides mapping resolution equivalent to that of any high resolution mapping population. Finally, in specific aim 3, we will use RNA-seq to identify genes whose expression is altered by the identified modifier genes. Importantly, we will use a state of the art genetic strategy that will allow us to examine gene expression in a neural cell population that is highly relevant to the behaviors: Chrna5 expressing cells of the interpeduncular nucleus. By combining the results of this aim with modifier loci identified through aims 1 and 2, we expect to narrow the list of potential candidate modifier genes and identify pathways specifically impacted by the modifier genes. In short, we believe that this strategy will lead to the identification of previously unknown genes and/or genetic pathways that contribute to the physiological and/or molecular processes important for the response to nicotine. These genes and/or pathways may serve as novel targets for the development of new pharmacotherapies to aid in smoking cessation.