Neurotrophin-Induced Regulation of the microRNA Processing Factor Lin28a

描述（由申请人提供）：突触可塑性被认为是学习和记忆的细胞相关性，涉及对神经元活动做出反应时突触的选择性增强和减弱。基因表达与新蛋白合成的变化长期以来被认为是突触连接持续变化的必要条件。然而，令人惊讶的是，最近的研究表明，转录水平的调控并不一定与翻译水平的调控相关，因此细胞中mRNA的谱只与蛋白质组适度相关。脑源性神经营养因子（BDNF）是突触连通性长期变化的关键调节因子。它在巩固学习和记忆中起着重要作用，并在广泛的神经和认知障碍（包括情绪障碍、焦虑症、精神分裂症以及神经退行性疾病）中被错误调节。有趣的是，BDNF通过调节microRNA生物发生途径的组分来增强转录mrna的一个非常特定子集（约4%）的表达。这种调节的一个重要方面是诱导一种叫做Lin28a的蛋白质，这是一种多能因子，可以抑制特定microrna的生物发生，以前被认为在成熟细胞类型（如神经元）中不存在。本研究的第一个目标是了解BDNF增强Lin28a蛋白的分子机制和信号通路，从而调节基因表达。了解BDNF信号通路中涉及的这种机制有可能发现调节点，这可能是未来治疗的目标。本节的实验将需要分子、生化和遗传方法来分析培养小鼠海马神经元中的BDNF信号转导结果。此外，本研究的第二个目标是在体外和体内神经系统中增强和抑制Lin28a蛋白的活性。分析这些操作后的细胞形态和行为数据将直接表明bdnf介导的Lin28a蛋白诱导如何影响神经元结构和认知功能。这些实验有可能直接提出治疗认知和神经障碍的药物。本节的方法将包括免疫组织化学、固定细胞成像和分析，以及野生型和基因操纵小鼠海马学习任务的评估。总的来说，拟议的实验将增强我们目前对正常学习和记忆的分子机制的了解，这些机制可能在疾病和大脑紊乱中失调。

DESCRIPTION (provided by applicant): Synaptic plasticity, regarded as the cellular correlate of learning and memory, involves a selective strengthening and weakening of synapses in response to neuronal activity. Changes in gene expression combined with novel protein synthesis have long been recognized as necessary for lasting changes in synaptic connections. However, surprising recent studies have shown that regulation at the level of transcription is not necessarily correlated with regulation at the level of translation, and thus that the profile of mRNA in a cell is only moderately correlated with the proteome. Brain-derived neurotrophic factor (BDNF) is a crucial regulator of long-lasting changes in synaptic connectivity. It plays an important role in consolidation of learning and memory, and is misregulated in a wide range of neurologic and cognitive disorders including mood disorders, anxiety disorders, and Schizophrenia as well as neurodegenerative disease. Interestingly, BDNF enhances the expression of an extraordinarily specific subset (about 4%) of transcribed mRNAs by regulating components of the microRNA biogenesis pathway. One important aspect of this regulation is the induction of a protein called Lin28a, which is a pluripotency factor that inhibits biogenesis of specific microRNAs and was thought previously to be absent from mature cell types such as neurons. The first goal of the proposed research is to understand the molecular mechanisms and signaling pathways through which BDNF enhances Lin28a protein, thus regulating gene expression. Understanding such mechanisms involved in the BDNF signaling pathway has the potential to uncover regulatory points that could be the target of future therapeutics. Experiments in this section will require molecular, biochemical, and genetic approaches to analyze BDNF signaling outcomes in cultured mouse hippocampal neurons. Additionally, the second goal of the proposed research is to enhance and repress activity of Lin28a protein in in vitro and in vivo neuronal systems. Analysis of cell morphological and behavioral readouts following these manipulations will directly indicate how BDNF-mediated induction of Lin28a protein may impact neuronal structure as well as cognitive function. These experiments have the potential to directly suggest therapeutic agents for cognitive and neurologic disorders. Methods in this section will include immunohistochemistry, fixed cell imaging and analysis, and assessment of hippocampal-based learning tasks in wild type and genetically manipulated mice. Overall, the proposed experiments will enhance our current knowledge of the molecular mechanisms that underlie learning and memory normally and that may be dysregulated in diseases and disorders of the brain.