Human genetic polymorphism impact in a mouse model

描述（由申请人提供）： CEBRA的这一应用解决了一个高风险、高影响的问题：人类遗传变异能否通过转基因小鼠模型来建模？这是一个迫切需要研究的问题，因为研究表明，小的遗传变异，如单核苷酸多态性（SNP），是药物成瘾脆弱性和其他行为变化的主要遗传因素。然而，需要一种方法来解决遗传变异和表型变化之间的因果关系。CEBRA的这一应用解决了这一问题，使用转基因小鼠模型复制人类遗传多态性，允许对所产生的表型差异进行严格测试，以评估遗传变化的影响。重点是高度相关的，有据可查的人类遗传变异-人类μ阿片受体基因中的功能性SNP。μ阿片受体是内源性阿片系统的关键组成部分，介导阿片类药物（包括吗啡和海洛因）的生理效应。我们和其他人已经确定的A118 G SNP是常见的，导致单个氨基酸变化，并且似乎通过增加细胞中β-内啡肽敏感性和受体表达水平来改变受体功能。最近的人类研究表明，这种遗传变异可能在体内具有重要的功能：它与人类功能研究中HPA轴的改变有关，并被认为是成瘾的重要因素。因此，A118 G SNP是一种理想的遗传多态性，可以测试人类遗传变异的小鼠模型的可行性，从而确定遗传变化与随后的行为和体内生理功能改变之间的因果关系。这是我们CEBRA提案的目标。 目标1。人类μ阿片受体基因多态性小鼠模型的建立。我们将在小鼠中模拟人类A118 G多态性。基于同源重组的基因靶向方法将用于将人类多态性变异“敲入”小鼠中的μ阿片受体基因，从而创建这种常见人类遗传变异的小鼠模型。 目标二。描述μ阿片受体多态性在体内的影响。我们将对目标1中生成的小鼠模型进行表征，以了解体内遗传多态性的影响。我们将研究多态性对受体表达和配体敏感性的影响。我们还将探索对阿片类药物调节行为的任何潜在影响。由于高风险、高影响的性质，我们选择在CEBRA资助机制下申请。药物滥用研究领域需要知道人类遗传脆弱性因素是否可以在转基因小鼠中建模和研究。我们建议的研究结果将作为药物滥用研究人员未来战略考虑的指导性范例。

DESCRIPTION (provided by applicant): This CEBRA application addresses a high-risk, high-impact question: Can human genetic variations be modeled by transgenic mouse models? This is a question in urgent need of examination, because studies have shown that small genetic variations, such as single nucleotide polymorphism (SNP), are the primary genetic factors for drug addiction vulnerability and other behavioral changes. However, there needs to be an approach to address causal relationship between genetic variations and phenotypic changes. This CEBRA application addresses this question, using genetically modified mouse models to reproduce human genetic polymorphisms, allowing rigorous testing for resulting phenotypic differences to assess the impact of genetic changes. The focus is on a highly relevant, well-documented human genetic variation - a functional SNP in the human mu opioid receptor gene. The mu opioid receptor is a key component of the endogenous opioid system, mediating the physiological effects of opioid drugs including morphine and heroin. The A118G SNP that we and others have identified is common, leads to a single amino acid change, and appears to alter receptor function by increasing beta-endorphin sensitivity and receptor expression level in cells. Recent human studies suggest that this genetic variant may be of functional importance in vivo: it is associated with alterations of the HPA-axis in functional studies in humans, and is implicated as an important contributor to addictions. Thus, the A118G SNP is an ideal genetic polymorphism to test the feasibility of mouse modeling for human genetic variations - so as to determine the causal relationship between a genetic change and subsequent functional alterations in behavior and in vivo physiology. This is the goal of our CEBRA proposal. Aim 1. Generating a mouse model for the human genetic polymorphism in the mu opioid receptor. We will model the human A118G polymorphism in the mouse. The homologous recombination-based gene targeting approach will be used to "knock-in" the human polymorphic variations into the mu opioid receptor gene in mouse, thus creating a mouse model of this common human genetic variation. Aim 2. Characterize impact of the mu opioid receptor polymorphism in vivo. We will characterize the mouse model generated in Aim 1 for impact of genetic polymorphism in vivo. We will examine the effects of the polymorphism on receptor expression and ligand sensitivity. We will also explore any potential impact on opioid-regulated behaviors. Because of the high-risk high-impact nature, we choose to apply under the CEBRA funding mechanism. The field of drug abuse research needs to know whether human genetic vulnerability factors can be modeled and studied in transgenic mice. The outcome from our proposed studies will serve as a guiding example for future strategic considerations by drug abuse researchers.