Role of FMRP in Cocaine-Dependent Behavioral Plasticity

FMRP 在可卡因依赖性行为可塑性中的作用

• 批准号: 8606280
• 负责人: Christopher W Cowan
• 金额: $ 19.75万
• 依托单位: MCLEAN HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-30 至 2013-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8606280
• 关键词: Role; FMRP; Cocaine; Dependent; Behavioral

DESCRIPTION (provided by applicant): Identifying key molecules that mediate brain reward plasticity remains an important goal of current drug abuse research. We recently identified a key role for the Fragile X Mental Retardation Protein (FMRP), a RNA binding protein involved in regulating protein synthesis in dendrites, as an essential downstream component of MEF2-dependent synapse elimination. Moreover, we observed significant deficits in cocaine-induced behavioral plasticity in FMRP-deficient mice. Taken together with the recently documented role for MEF2 in repeated cocaine-induced structural and functional plasticity, our findings in the Fmr1 KO mice suggest an important role for synapse elimination as a process that promotes long-lasting behavioral plasticity associated with chronic cocaine use. In this proposal, we will test the hypothesis that FMRP mediates an acute process of synapse elimination/remodeling in the NAc that is required for behavioral plasticity associated with repeated cocaine exposure. To this end, we propose the following: Specific Aim 1: Our preliminary findings indicate that Fmr1-/- mice have significantly reduced cocaine sensitization and place preference to cocaine. As these are developmental knockout mice, the precise populations of cells where FMRP exerts its function on cocaine-induced behaviors is not clear. To this end, we will take a two-pronged approach: 1) we will express WT FMRP in the nucleus accumbens (NAc) using viral- mediated gene delivery in the Fmr1 KO mice and test for functional rescue of cocaine behaviors, and 2) we will selectively knockout the Fmr1 gene in the NAc using viral-mediated gene delivery of Cre recombinase in adult conditional Fmr1 knockout mice and test the requirement for FMRP in the adult NAc during cocaine-induced behavioral plasticity. Specific Aim 2: Our recent findings revealed that FMRP is strictly required for MEF2-dependent regulation of synapse number in hippocampal pyramidal neurons, and NAc expression of active MEF2 enhances both sensitized locomotion and place preference to cocaine. Therefore, we will test the hypothesis that FMRP functions in the NAc to mediate MEF2-induced sensitized behavioral responses to cocaine. To this end, we will use established viral-mediated gene delivery to determine whether MEF2-modulated behavioral responses to cocaine require FMRP function in vivo using Fmr1-/- mice and established behavioral assays. Specific Aim 3: We previously demonstrated that inhibition of MEF2 activity is necessary and sufficient to regulate the chronic cocaine-induced increase in NAc MSN spine density. Since we found that FMRP is required for MEF2-regulated excitatory synapse density in hippocampal neurons, we will test the hypothesis that the cocaine-induced increase in NAc spine density requires FMRP in vivo. Using established spine imaging methods, we will assess the basal and chronic cocaine-regulated NAc spine density in Fmr1 KO mice.

描述（由申请人提供）：识别介导大脑奖励可塑性的关键分子仍然是当前药物滥用研究的重要目标。我们最近发现了脆性 X 智力迟钝蛋白 (FMRP) 的关键作用，FMRP 是一种参与调节树突蛋白质合成的 RNA 结合蛋白，是 MEF2 依赖性突触消除的重要下游成分。此外，我们观察到 FMRP 缺陷小鼠的可卡因诱导的行为可塑性存在显着缺陷。结合最近记录的 MEF2 在反复可卡因诱导的结构和功能可塑性中的作用，我们在 Fmr1 KO 小鼠中的发现表明，突触消除作为促进与长期可卡因使用相关的持久行为可塑性的过程具有重要作用。在本提案中，我们将测试以下假设：FMRP 介导 NAc 中突触消除/重塑的急性过程，这是与重复可卡因暴露相关的行为可塑性所必需的。为此，我们提出以下建议： 具体目标 1：我们的初步研究结果表明，Fmr1-/- 小鼠对可卡因的敏感性显着降低，并且对可卡因有偏爱。由于这些是发育敲除小鼠，FMRP 对可卡因诱导行为发挥作用的精确细胞群尚不清楚。为此，我们将采取双管齐下的方法：1）我们将在 Fmr1 KO 小鼠中使用病毒介导的基因递送在伏隔核（NAc）中表达 WT FMRP，并测试可卡因行为的功能性拯救；2）我们将在成人条件性 Fmr1 敲除中使用病毒介导的 Cre 重组酶基因递送选择性敲除 NAc 中的 Fmr1 基因 小鼠并测试可卡因诱导的行为可塑性期间成人 NAc 中对 FMRP 的需求。 具体目标 2：我们最近的研究结果表明，FMRP 是海马锥体神经元中 MEF2 依赖性突触数量调节所必需的，并且活性 MEF2 的 NAc 表达增强了对可卡因的敏化运动和位置偏好。因此，我们将测试以下假设：FMRP 在 NAc 中发挥作用，介导 MEF2 诱导的对可卡因的敏化行为反应。为此，我们将使用 Fmr1-/- 小鼠和已建立的行为测定，利用已建立的病毒介导的基因传递来确定 MEF2 调节的可卡因行为反应是否需要体内 FMRP 功能。 具体目标 3：我们之前证明，抑制 MEF2 活性对于调节可卡因慢性诱导的 NAc MSN 脊柱密度增加是必要且充分的。由于我们发现海马神经元中 MEF2 调节的兴奋性突触密度需要 FMRP，因此我们将测试可卡因诱导的 NAc 棘密度增加在体内需要 FMRP 的假设。使用已建立的脊柱成像方法，我们将评估 Fmr1 KO 小鼠的基础和慢性可卡因调节的 NAc 脊柱密度。