Epigenetic Gene Regulation in Morphin Addiction

描述（由申请人提供）：吗啡是一种常用的阿片类镇痛药，是一种高度成瘾的药物。在大脑中，吗啡作用于g蛋白偶联的阿片受体，触发信号转导事件，导致基因表达的长期变化。阿片依赖涉及神经元可塑性和调节情绪、疼痛、奖励和享乐稳态的内源性阿片系统的变化。吗啡在基因表达上留下不可磨灭印记的分子机制尚不清楚。组蛋白修饰和DNA甲基化介导的染色质重塑过程（也称为表观遗传机制）可以以活性依赖性和潜在的长期方式改变基因转录的音调。我们还发现，癫痫发作可诱导脑源性神经营养因子（BDNF）和内源性阿片前体促黑素皮质素（POMC）的表观遗传基因调控发生变化。先前显示的基因，包括BDNF和POMC，在长期暴露于吗啡后受到不同的调节，已经在它们的启动子处确定了表观遗传基因调节的特征。然而，活性依赖性吗啡诱导的表观遗传调控变化从未被研究过。随着对表观遗传基因调控可塑性的新认识，我们希望重新审视吗啡诱导的基因表达变化，并询问药物成瘾诱导的表观遗传变化在什么水平上发生。提出两个目标：目标1。利用定量RT-PCR和原位杂交技术，定量和进一步表征吗啡成瘾小鼠对慢性吗啡反应的基因表达变化；和Aim 2。利用染色质免疫沉淀和亚硫酸盐转换和测序分析表观遗传标记的变化，包括DNA甲基化、组蛋白乙酰化和甲基化，以及调节DNA甲基化和吗啡敏感基因启动子内组蛋白修饰的机制的关联。我们的研究将奠定基础，并开始揭示吗啡暴露可以改变基因调节的新机制。更好地了解与药物成瘾有关的表观遗传变化的分子性质，将有助于开发治疗这种终身疾病的新疗法。

DESCRIPTION (provided by applicant): Morphine, a commonly used opioid analgesic, is a highly addictive drug. In the brain, morphine acts on G-protein coupled opioid receptors, triggering signal transduction events that lead to long-term changes in gene expression. Opioid dependence involves changes in neuronal plasticity and in the endogenous opioid system which regulates mood, pain, reward, and hedonic homeostasis. The molecular mechanisms through which morphine imprints its indelible signature on gene expression are unknown. Histone modification- and DNA methylation-mediated chromatin remodeling processes (also called epigenetic mechanisms) can modify the tone of gene transcription in an activity-dependent and potentially long-term manner. We have also discovered that seizures induce changes in the epigenetic gene regulation of brain-derived neurotrophic factor (BDNF) and proopiomelanocortin (POMC), an endogenous opioid precursor. Genes previously shown to be differentially regulated following chronic exposure to morphine, including BDNF and POMC, already have identified features of epigenetic gene regulation at their promoters. However, activity-dependent morphine-induced changes in their epigenetic regulation have never been investigated. With new insight into the plasticity of epigenetic gene regulation, we look to reexamine morphine-induced changes in gene expression and ask at what level drug addiction-induced epigenetic changes take place. Two aims are proposed: Aim 1. To quantify and further characterize gene expression changes in response to chronic morphine, using quantitative RT-PCR and in situ hybridization of morphine-addicted mice; and Aim 2. To analyze changes in epigenetic marks including DNA methylation, histone acetylation and methylation as well as the association of the machinery that regulate DNA methylation and histone modifications within the promoters of morphine-sensitive genes, using chromatin immunoprecipitation and bisulfite conversion and sequencing. Our study will lay the groundwork and begin to reveal new mechanisms by which morphine exposure can alter gene regulation. A better understanding of the molecular nature of the epigenetic changes involved in drug addiction will facilitate the development of new therapies for treating this lifelong disease.