MicroRNAs in Synaptic Plasticity and Behaviors Relevant to Autism

描述（由申请人提供）：我研究的主要目标是促进我们对认知和认知障碍的分子和细胞机制的理解。突触蛋白合成的调控已成为突触可塑性和记忆巩固的关键控制点。最近的证据表明突触蛋白合成不适当或过度与认知障碍和自闭症的发病机制有关。例如，在结节性硬化症和脆性X综合征中失活的基因产物作为翻译抑制因子发挥作用。我们最近提出，突触蛋白合成正常约束的丧失可能会促进突触连接异常，损害神经网络调节认知的性能，并导致认知障碍和自闭症的发展。该应用的广泛、长期目标是了解microrna在突触可塑性、突触连通性和自闭症相关行为中的翻译抑制作用。MicroRNAs包括一个内源性20-23个核苷酸的非编码rna大家族，它们通过结合靶mrna中的互补序列来抑制蛋白质合成。microrna与大脑发育和神经元存活有关，但对其在突触过程或行为中的作用知之甚少。有趣的是，脆性X智力迟钝蛋白（FMRP）在物理和遗传上与介导microrna翻译抑制的分子机制相互作用。此外，microRNA表达的减少与人类自闭症障碍有关。基于这些观察结果，我们假设microrna调节蛋白质合成依赖的突触可塑性和记忆，microrna介导的翻译抑制的缺失可能导致突触蛋白合成过度，突触连通性改变和自闭症行为表型。我们最近产生了条件敲除小鼠，在这些小鼠中，出生后前脑中的microRNA表达部分或完全失活。这些缺乏microrna的小鼠在2-3个月大时看起来非常正常，没有神经退行性变的迹象。我们建议将这些microrna缺陷小鼠与fmrp缺陷小鼠一起分析与自闭症相关的行为缺陷（目的1）、蛋白质合成依赖性突触可塑性和记忆的损伤（目的2）以及突触连通性的异常（目的3）。在后一项研究中，我们提出了一种新的使用“Brainbow”小鼠的方法来观察microRNA或FMRP表达缺失对兴奋性突触连接的影响。这些目标的实现将为研究microRNA的功能和自闭症的发病机制提供新的见解。拟议的研究与我的nimh资助的R01是互补的，并紧密结合在一起。详细的职业发展计划包括关键合作和获得增强的多学科研究技能。K02奖提供的薪酬支持将有助于我专注于研究和职业发展活动，而不必承担过多的临床责任。

DESCRIPTION (provided by applicant): The primary goal of my research is to advance our understanding of the molecular and cellular mechanisms underlying cognition and cognitive disorders. Regulation of synaptic protein synthesis has emerged as a key control point in the consolidation of synaptic plasticity and memory. Recent evidence has implicated inappropriate or excessive synaptic protein synthesis in the pathogenesis of cognitive impairment and autism. For example, the gene products inactivated in tuberous sclerosis complex and fragile X syndrome function as translational repressors. We recently proposed that loss of the normal constraints on synaptic protein synthesis may promote abnormal synaptic connectivity, compromising the performance of neuronal networks mediating cognition, and leading to the development of cognitive impairment and autism. The broad, long-term goals of this application are to understand the role of translational repression by microRNAs in synaptic plasticity, synaptic connectivity and behaviors relevant to autism. MicroRNAs comprise a large family of endogenous 20-23 nucleotide noncoding RNAs that repress protein synthesis by binding to complementary sequences in target mRNAs. MicroRNAs have been implicated in brain development and neuronal survival, but little is known about their roles in synaptic processes or behavior. Intriguingly, the fragile X mental retardation protein (FMRP) interacts physically and genetically with the molecular machinery mediating translational repression by microRNAs. In addition, reduced microRNA expression has been associated with human autistic disorders. Based on these observations, we hypothesize that microRNAs regulate protein synthesis-dependent synaptic plasticity and memory, and that loss of microRNA-mediated translational repression may lead to excessive synaptic protein synthesis, altered synaptic connectivity and autistic behavioral phenotypes. We have recently generated conditional knockout mice in which microRNA expression is partially or completely inactivated in the postnatal forebrain. These microRNA-deficient mice appear grossly normal and display no evidence of neurodegeneration at 2-3 months of age. We propose to analyze these microRNA-deficient mice in parallel with FMRP-deficient mice for behavioral deficits relevant to autism (Aim 1), impairments in protein synthesis-dependent synaptic plasticity and memory (Aim 2), and abnormalities in synaptic connectivity (Aim 3). In the latter Aim, we propose a novel use of "Brainbow" mice to visualize the impact of loss of microRNA or FMRP expression on excitatory synaptic connections. Accomplishment of these Aims should offer new insights into microRNA function and autism pathogenesis. The proposed studies are complementary to and closely integrated with my NIMH-funded R01. The detailed career development plan includes key collaborations and acquisition of enhanced multidisciplinary research skills. The salary support provided by the K02 award will be instrumental in allowing me to focus on research and career development activities without excessive clinical responsibilities. PUBLIC HEALTH RELEVANCE: The proposed project has direct relevance to the brain mechanisms responsible for normal cognition and behavior as well as cognitive and behavioral disorders. The molecular pathways to be investigated have been implicated in the pathogenesis of autism and other mental disorders. Accomplishment of the proposed goals will increase our understanding of the molecular and synaptic defects responsible for these disorders, and possibly identify new therapeutic targets or strategies.