MicroRNAs in Synaptic Plasticity and Cognitive Function

描述（由申请人提供）：微小RNA（miRNAs）包括一个大家族的小（22 nt）非编码RNA，其涉及在其3 '非翻译区中携带不完全互补序列的靶mRNA的翻译抑制。已经提出miRNA依赖性过程的干扰有助于精神障碍的病因学，但是miRNA在哺乳动物大脑中的突触和认知功能中的作用是完全未知的。本申请的广泛、长期目标是了解miRNAs在认知和行为基础的神经过程中的作用，特别是在出生后大脑中神经元基因表达和突触可塑性的调节。我们最近采用了多学科的方法来证明翻译控制在持久的突触可塑性和记忆中的关键作用。我们的研究结果表明，通过MARK和mTOR途径的局部蛋白质合成的普遍上调是突触连接和相关认知过程的持续修饰所必需的。虽然这些结果指出了一般翻译机制的重要性，但突触激活的翻译反应可能受到顺式作用元件（如miRNA靶序列）介导的mRNA特异性机制的调节。因此，我们建议测试的假设，即miRNAs在神经元基因表达的调控，突触可塑性和认知在出生后的大脑中发挥重要作用。更具体地说，我们假设，miRNA依赖的翻译控制选择性地调节蛋白质合成依赖的突触可塑性和记忆的巩固。为了解决这些问题，我们正在采用条件遗传方法来消除Dicer并消除出生后前脑神经元中的miRNA表达。对miRNA表达条件性消融引起的表型的多学科分析将使我们能够评估miRNA对出生后大脑神经过程的整体贡献。我们的具体目标集中于miRNA在以下方面的作用：（1）原代海马神经元中神经元活性依赖性翻译控制，（2）与出生后大脑中突触修饰有关的特定蛋白质表达的时空模式，（3）海马突触可塑性的蛋白质合成依赖性和非依赖性阶段，以及（4）与精神障碍相关的行为，特别是海马和杏仁核依赖性记忆的蛋白质合成依赖性和非依赖性阶段。完成拟议的研究应该产生重要的见解miRNAs在脑功能中的作用，以及改变的miRNAs依赖性过程在精神障碍的发病机制中的可能参与。

DESCRIPTION (provided by applicant): MicroRNAs (miRNAs) comprise a large family of small (22 nt) noncoding RNAs that have been implicated in translational repression of target mRNAs bearing imperfectly complementary sequences in their 3' untranslated regions. Disturbances in miRNA-dependent processes have been proposed to contribute to the etiology of mental disorders, but the role of miRNAs in synaptic and cognitive function in the mammalian brain is entirely unknown. The broad, long-term objective of this application is to understand the role of miRNAs in neural processes underlying cognition and behavior, particularly regulation of neuronal gene expression and synaptic plasticity in the postnatal brain. We recently employed a multidisciplinary approach to demonstrate a crucial role for translational control in long-lasting synaptic plasticity and memory. Our findings suggested that general upregulation of local protein synthesis through the MARK and mTOR pathways is necessary for persistent modifications of synaptic connectivity and associated cognitive processes. While these results point to the importance of general translational mechanisms, the translational response to synaptic activation is likely to be modulated by mRNA-specific mechanisms mediated by cis-acting elements, such as miRNA target sequences. Therefore, we propose to test the hypothesis that miRNAs play essential roles in the regulation of neuronal gene expression, synaptic plasticity and cognition in the postnatal brain. More specifically, we postulate that miRNA-dependent translational control selectively regulates the protein synthesis-dependent consolidation of synaptic plasticity and memory. To address these questions, we are employing a conditional genetic approach to inactivate Dicer and abolish miRNA expression in neurons of the postnatal forebrain. Multidisciplinary analysis of the phenotypes caused by conditional ablation of miRNA expression will allow us to evaluate the global contribution of miRNAs to neural processes in the postnatal brain. Our Specific Aims focus on the role of miRNAs in (1) neuronal activity-dependent translational control in primary hippocampal neurons, (2) spatiotemporal patterns of expression of specific proteins implicated in synaptic modifications in the postnatal brain, (3) protein synthesis-dependent and -independent phases of hippocampal synaptic plasticity, and (4) behaviors relevant to mental disorders, particularly protein synthesis-dependent and -independent phases of hippocampus- and amygdala-dependent memory. Accomplishment of the proposed studies should yield important insights into the role of miRNAs in brain function, and the possible involvement of altered miRNA-dependent processes in the pathogenesis of mental disorders.