MicroRNAs in Synaptic Plasticity and Cognitive Function

说明书(申请人提供)：microRNAs(MiRNAs)包括一大类小的(22nT)非编码RNA，它们参与翻译抑制靶mRNAs，在其3‘非翻译区具有不完全互补的序列。MiRNA依赖过程中的干扰被认为与精神障碍的病因有关，但miRNAs在哺乳动物大脑的突触和认知功能中的作用尚不清楚。这一应用的广泛、长期的目标是了解miRNAs在认知和行为基础的神经过程中的作用，特别是对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时间突触可塑性和记忆中的关键作用。我们的发现表明，通过Mark和mTOR通路对局部蛋白质合成的普遍上调对于突触连接和相关认知过程的持续修改是必要的。虽然这些结果表明了一般翻译机制的重要性，但对突触激活的翻译反应可能受到由顺式作用元件(如miRNA靶序列)介导的mRNA特异性机制的调节。因此，我们建议检验这一假设，即miRNAs在出生后大脑的神经元基因表达、突触可塑性和认知调控中发挥重要作用。更具体地说，我们假设依赖于miRNA的翻译控制选择性地调节依赖蛋白质合成的突触可塑性和记忆的巩固。为了解决这些问题，我们正在使用一种条件遗传学方法来灭活迪格尔，并取消出生后前脑神经元中miRNA的表达。对条件消融miRNA表达引起的表型的多学科分析将使我们能够评估miRNAs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miRNAs在以下方面的作用：(1)初级海马神经元中神经元活动依赖的翻译控制；(2)与出生后脑中突触修饰有关的特定蛋白质的时空表达模式；(3)蛋白质合成依赖和独立的海马区突触可塑性阶段；以及(4)与精神障碍相关的行为，特别是蛋白质合成依赖和杏仁核依赖的记忆阶段。这些研究的完成将对miRNAs在脑功能中的作用以及改变的miRNA依赖过程在精神障碍的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.