Chromatin Remodeling Mechanism of Gene Transcription in Memory

摘要 现在已经很清楚，表观遗传机制控制着海马区CA1区的基因转录，这些基因是 在年轻和成熟的成年期形成适当的记忆所必需的。例如，我们发现， 表观遗传机制在发育后被认为是静止的，在成年后有丝分裂后神经元中仍然活跃 并且对环境体验非常敏感。具体来说，组蛋白赖氨酸甲基化(HKM) 机制已被确定为一个关键的转录机制在CA1区辅助的过程 联想记忆的形成。令人惊讶的是，人们对环境的影响知之甚少，比如衰老和 压力经历会导致记忆力随着年龄的增长而下降。我们的长期目标是确定HKM的修改 由压力引起的影响随着年龄增长而形成的记忆。这对长久以来- 持久的表观遗传效应，这在认知神经表观遗传学领域是很少观察到的。为了这笔赠款 建议，我们将重点介绍介导组蛋白H3-赖氨酸9的组蛋白赖氨酸甲基转移酶G9a。 CA1区神经元的二甲基化(H3K9me2)标记。考虑到这一点，我们的初步结果表明 严重应激增加幼年大鼠CA1区G9a-H3K9me2活性 衰老。此外，H3K9me2超甲基化与年轻人和 年迈的成年人。初步结果还表明，抑制海马区G9a活性可逆转应激-- 诱导性记忆障碍。基于这些初步结果，我们计划严格调查 应激后操纵CA1区G9a-H3K9me2活性的影响及对年龄的影响 记忆力衰退。进一步深入了解G9a-H3K9me2介导的应激相关基因 转录，我们将使用最先进的方法，如siRNA和CRISPR-dCas9-VP64技术来 在我们的动物模型系统中直接靶向G9a。我们的中心假设是1)压力异常增加G9a- H3K9me2介导的幼年大鼠海马基因沉默与正常大鼠相似 老年成人，2)应激介导的G9a-H3K9me2甲基化将与老年受损而不是老年相关- 未受损的动物，以及3)年轻人经历的应激导致对H3K9me2的潜在影响 随着年龄的增长，高甲基化可以通过抑制G9a来克服。我们的具体目标如下：具体 目的1：应激通过增加大鼠海马区G9a-H3K9me2活性干扰记忆形成 特定目标2：应激对老年人海马区G9a-H3K9me2的不同影响 受损动物与老年未受损动物；和特定目标3：应激经历增加G9a-H3K9me2 年轻人海马体中的活动会导致记忆力随着年龄的增长而下降。总的来说，这项提案 将确定与压力相关的记忆随年龄下降有关的长期表观遗传机制。此外， 我们希望加深对压力对大脑老化时记忆力衰退的影响的理解。

Abstract It is now clear that epigenetic mechanisms control gene transcription in area CA1 of the hippocampus that are necessary for proper memory formation in young and mature adulthood. For example, we have discovered that epigenetic mechanisms thought to be static after development, remain active in postmitotic neurons in adulthood and very much responsive to environmental experiences. Specifically, histone lysine methylation (HKM) mechanisms have been identified as a crucial transcriptional mechanism in area CA1 subserving the process of associative memory formation. Surprisingly little is known about how environmental influences like aging and stress experiences contribute to memory decline with age. Our long-term goal is to identify HKM modifications induced by stress to impact memory formation with aging. This has tremendous implications with regard to long- lasting epigenetic effects, which is rarely observed in the field of cognitive neuroepigenetics. For this grant proposal, we will focus on the histone lysine methyltransferase, G9a that mediates histone H3-lysine 9 dimethylation (H3K9me2) marks in area CA1 neurons. With this in mind, our preliminary results demonstrate that severe stress increased G9a-H3K9me2 activity in area CA1 of young adult rats that was sustained with aging. Furthermore, H3K9me2 hypermethylation strongly correlated with memory decline in young adults and in aged adults. Preliminary results also demonstrate that inhibiting G9a activity in the hippocampus reverses stress- induced memory impairments. Based on these preliminary results, we plan to rigorously investigate the beneficial effects of manipulating G9a-H3K9me2 activity in CA1 following stress and determine effects on age-related memory decline. To gain further mechanistic insight into stress-related G9a-H3K9me2 mediated gene transcription, we will use state-of-the-art approaches such as siRNA and CRISPR-dCas9-VP64 technology to directly target G9a in our animal model system. Our central hypotheses are 1) stress abnormally increases G9a- H3K9me2- mediated silencing of hippocampal genes in young adult rats similar to what is observed in normal aging adults, 2) stress-mediated G9a-H3K9me2 hypermethylation will correlate with aged-impaired but not aged- unimpaired animals, and 3) stress experienced in young adults results in latent effects on H3K9me2 hypermethylation with aging that can be overcome by G9a inhibition. Our Specific Aims are as follows: Specific Aim 1: Stress interferes with memory formation by increasing G9a-H3K9me2 activity in the hippocampus of young adults; Specific Aim 2: Stress has differing effects on G9a-H3K9me2 in the hippocampus of aged- impaired versus aged-unimpaired animals; and Specific Aim 3: Stress experience increases G9a-H3K9me2 activity in the hippocampus of young adults contributing to memory decline with age. Collectively, this proposal will identify long-lasting epigenetic mechanisms involved in stress-related memory decline with age. Moreover, we hope to add to our understanding of stress-induced effects on memory decline as the brain ages.