Role of Orphan Nuclear Receptor Nurr1 in Fear Conditioning

描述(由候选人提供)：焦虑症是美国最常见的精神疾病，影响1910万成年人(13.3%)。后天恐惧是许多焦虑症的根源，包括创伤后应激障碍(PTSD)，旨在识别与恐惧学习有关的新基因的研究可能会导致对这些障碍的更有效治疗。巴甫洛夫恐惧条件作用是恐惧学习的一种形式，它涉及杏仁核外侧核(LA)中关于条件刺激(CS)和非条件刺激(US)的感觉信息的整合，在那里，突触传递的变化被认为是通过类似LTP的过程编码记忆的关键方面。与已研究的大多数记忆形式一样，恐惧条件反射的长期记忆(LTM)的形成需要转录因子cAMP反应元件结合蛋白(CREB)，它诱导早期反应基因的表达，并间接诱导晚期反应基因，这些基因被认为对长期突触可塑性和记忆形成的功能和/或结构变化至关重要。尽管已经鉴定出许多CREB反应基因，但尚不清楚恐惧学习需要多少这些基因。此外，许多可能参与LTM形成的CREB反应基因本身就是转录因子，有无数尚未鉴定的下游基因可能是LTM形成所必需的。本研究的目的是确定CREB反应性孤儿核受体Nurr1(NR4A2，HZF-3，NOT，RNR1)在巴甫洛夫恐惧条件反射中的作用。我们的初步实验表明，Nurr1在恐惧学习后以一种联想的方式进行调节。在这个提议中，我们试图了解Nurr1是否对恐惧记忆的形成是必需的，以及识别这种CREB调节的转录因子的新的下游靶点，它可能有助于LA中恐惧记忆的形成。将讨论以下具体目标：目标1：巴甫洛夫恐惧条件反射是否需要Nurr1？为此，我们将通过用腺相关病毒向杏仁核神经元递送siRNA来下调Nurr1基因的表达，从而询问Nurr1是否在巴甫洛夫恐惧条件反射的记忆形成中是必需的。目的II：受巴甫洛夫恐惧条件作用调节的Nurr1的直接或间接下游靶点是什么？在这里，我们将对恐惧条件动物的杏仁核组织进行微阵列基因表达分析，而在恐惧条件动物的杏仁核组织中，Nurr1的表达因AAV-siRNA(Nurr1)的表达而被消融。这项提案中概述的研究将为确定CREB介导的LA基因表达的新靶点以及研究它们在恐惧记忆形成中的作用奠定基础。

DESCRIPTION (provided by candidate): Anxiety disorders are the most common mental illness in the U.S., affecting 19.1 million (13.3%) of the adult population. Acquired fears are at the root of many anxiety disorders, including post-traumatic stress disorder (PTSD), and studies aimed at identifying novel genes involved in fear learning may lead to more effective treatments for these disorders. Pavlovian fear conditioning is a form of fear learning that involves integration of sensory information about the conditioned stimulus (CS) and unconditioned stimulus (US) in the lateral nucleus of the amygdala (LA), where alterations in synaptic transmission via an LTP-like process are thought to encode key aspects of the memory. Like most forms of memory that have been studied, long-term memory (LTM) formation of fear conditioning is known to require the transcription factor cAMP- response-element binding protein (CREB), which induces the expression of early response genes and indirectly induces late response genes that are thought to be critical for the functional and/or structural changes underling long-term synaptic plasticity and memory formation. Although many CREB responsive genes have been identified, it remains unclear how many of these genes are required for fear learning. In addition many CREB responsive genes likely to be involved in LTM formation are themselves transcription factors with countless yet unidentified downstream genes likely necessary for LTM formation. The goal of this proposal is to determine the role of the CREB responsive orphan nuclear receptor Nurr1 (NR4A2, HZF- 3, NOT, RNR1) in Pavlovian fear conditioning. Our preliminary experiments indicate that Nurr1 is regulated in an associative manner following fear learning. In this proposal, we seek to understand whether Nurr1 is obligatory for fear memory formation as well as to identify novel downstream targets of this CREB-regulated transcription factor that may contribute to formation of fear memories in the LA. The following Specific Aims will be addressed: Aim I: Is Nurr1 required for Pavlovian fear conditioning? In this aim, we will ask whether Nurr1 is required for memory formation of Pavlovian fear conditioning by knocking down Nurr1 gene expression using siRNA delivered to amygdala neurons using adeno-associated virus. Aim II: What are the direct or indirect downstream targets of Nurr1 regulated by Pavlovian fear conditioning? Here, we will perform microarray gene expression analysis on amygdala tissue from fear conditioned animals versus amygdala tissue from fear conditioned animals where Nurr1 expression has been ablated due to AAV- siRNA (Nurr1) expression. The studies outlined in this proposal will lay the groundwork for identifying novel targets of CREB-mediated gene expression in the LA and for examining their role in fear memory formation.