MicroRNAs in Synaptic Plasticity and Cognitive Function

描述（由申请人提供）：MicroRNAs （miRNAs）包括一个大的小（22 nt）非编码rna家族，这些非编码rna与靶mrna的翻译抑制有关，靶mrna在其3'非翻译区具有不完全互补序列。mirna依赖过程的紊乱被认为是精神障碍的病因，但mirna在哺乳动物大脑突触和认知功能中的作用是完全未知的。该应用的广泛、长期目标是了解mirna在认知和行为背后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。我们最近采用了一种多学科的方法来证明翻译控制在长期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通路的局部蛋白合成的普遍上调对于突触连通性和相关认知过程的持续改变是必要的。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是由顺式作用元件（如miRNA靶序列）介导的mrna特异性机制调节的。因此，我们提出验证miRNAs在出生后大脑神经元基因表达、突触可塑性和认知调节中发挥重要作用的假设。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，我们正在采用一种条件遗传方法来灭活Dicer并消除出生后前脑神经元中的miRNA表达。对miRNA表达条件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在mirna在以下方面的作用：(1)海马初级神经元的神经元活动依赖的翻译控制，(2)与出生后大脑突触修饰相关的特定蛋白质的时空表达模式，(3)海马突触可塑性的蛋白质合成依赖和独立阶段，以及(4)与精神障碍相关的行为。特别是海马体和杏仁体依赖记忆的蛋白质合成依赖和独立阶段。这些研究的完成将对mirna在脑功能中的作用以及mirna依赖过程在精神障碍发病机制中的可能参与产生重要的见解。

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.