The Role of DNA Demethylation by Gadd45b in Memory and Synaptic Plasticity

项目摘要 记忆障碍仍然是美国主要的医疗保健负担。随着人口老龄化， 与年龄相关的认知能力下降的流行率预计会增加。有效治疗记忆 缺乏疾病，需要新的药理学方法。尽管一个新兴的机构， 研究致力于研究记忆及其功能障碍的疾病状态，细节背后的分子 记忆的调节仍然难以捉摸。最近的研究指出了表观遗传机制在遗传学中的一种新功能。 记忆形成表观遗传学传统上被描述为一套可遗传的分子机制 稳定地影响基因表达;这些报告表明，大部分有丝分裂后的大脑已经吸收了这些 转录的动态和持续调节过程。对神经元活动的研究- DNA胞嘧啶碱基的依赖性甲基化和组蛋白、核心染色质的共价修饰 与DNA紧密并列的成分证实了这些机制在记忆形成中的功能作用。DNA 甲基转移酶催化活性DNA甲基化，但实际上没有一致的证据存在， 逆反应的分子调节剂。然而，最近的两项研究揭示了生长停滞的作用。 和DNA损伤诱导蛋白45（Gadd 45）家族在DNA去甲基化中的作用。值得注意的是， β亚型对海马体神经元去极化有反应，海马体是记忆的关键脑区 处理. Gadd 45 b作为DNA去甲基化介导因子和即刻早期基因的功能 这表明它可能会诱导记忆形成中的DNA去甲基化。本研究的目的 本研究的目的是研究Gadd 45 b在依赖于大脑皮层的记忆形成中的作用。遗传 将使用具有Gadd 45 b基因座的工程化缺失的小鼠的方法来解决这个问题。 为了研究Gadd 45 b在记忆形成中的功能，将在一个实验室中评估野生型和突变小鼠。 研究记忆和基线行为的行为测试。长期记忆巩固是 突触功效的持续变化，这种现象称为突触可塑性。研究 Gadd 45 b在海马长时程增强中的功能，来自两种基因型的海马记录将 被带走进一步的研究旨在研究Gadd 45 b介导的去甲基化的遗传靶点。 将在切片中进行DNA去甲基化的药理学诱导，以测定推定的靶点。最后， 将采取体内方法;动物将接受联想记忆任务的训练， 将研究海马中基因表达的调节。初步数据显示 Gadd 45 b在记忆巩固中的作用这表明DNA甲基化和去甲基化 相反的功能不仅在分子过程中，而且在行为中。拟议的研究旨在 研究DNA去甲基化在进一步研究中的行为学、生理学和分子作用的广度。 详细

Project Summary Disorders of memory remain a major health care burden in the United States. As the population ages, the prevalence of aging-associated cognitive decline is expected to grow. Effective treatment of memory disorders is lacking, and novel pharmacological approaches are necessary. Despite a burgeoning body of research dedicated to the study of memory and its dysfunction in disease states, details behind the molecular regulation of memory remains elusive. Recent studies point to a novel function of epigenetic mechanisms in memory formation. Epigenetics has traditionally been described as a set of heritable molecular mechanisms that stably influence gene expression; these reports indicate the largely postmitotic brain has co-opted these processes for both dynamic and persistent regulation of transcription. Investigations into neuronal activity- dependent methylation of DNA at cytosine bases and covalent modification of histones, core chromatin constituents closely apposed to DNA, confirm functional roles of these mechanisms in memory formation. DNA methyltransferases catalyze active DNA methylation, but virtually no consistent evidence existed for a molecular regulator of the reverse reaction. Two recent studies, however, uncover the role of the Growth arrest and DNA damage-inducible protein 45 (Gadd45) family in DNA demethylation. Notably, the expression of the beta isoform responds to neuronal depolarization in the hippocampus, a brain region critical to memory processing. The function of Gadd45b as a mediator of DNA demethylation and as an immediate early gene suggests that it potentially induces DNA demethylation in memory formation. The purpose of this research proposal is to study the contribution of Gadd45b in hippocampus-dependent memory formation. A genetic approach using mice with engineered deletion of the gadd45b locus will be employed to address this question. To study the function of Gadd45b in memory formation, wildtype and mutant mice will be assessed in a behavioral battery designed to study memory and baseline behavior. Long-term memory consolidation is subserved by lasting changes in synaptic efficacy, a phenomenon known as synaptic plasticity. To study the function of Gadd45b in hippocampal long-term potentiation, hippocampal recordings from both genotypes will be taken. Further studies are designed to study the genetic targets of Gadd45b-mediated demethylation. Pharmacological induction of DNA demethylation in slices will be performed to gauge putative targets. Finally, an in vivo approach will be taken; animals will be trained in an associative memory task, and epigenetic regulation of gene expression in the hippocampus will be studied. Preliminary data indicate a suppressive function of Gadd45b in memory consolidation. This suggests DNA methylation and demethylation perform opposing functions not only in molecular processes but also in behavior. The proposed study is designed to investigate the breadth of the ethological, physiological and molecular role of DNA demethylation in further detail.