Chromatin Remodeling Mechanism of Gene Transcription in Memory

摘要 现在很清楚，表观遗传机制控制海马CA 1区的基因转录， 在年轻和成熟的成年期，正确的记忆形成所必需的。例如，我们发现， 表观遗传机制被认为在发育后是静态的，在成年期的有丝分裂后神经元中仍然活跃 对环境的体验非常敏感。组蛋白赖氨酸甲基化（HKM） 机制已被确定为一个重要的转录机制，在CA 1区subserving的过程， 联想记忆形成令人惊讶的是，人们对环境的影响，如衰老和 压力经历会导致记忆力随着年龄的增长而下降。我们的长期目标是识别HKM修改 由应力诱导以随着老化影响记忆形成。这对长期的... 持久的表观遗传效应，这在认知神经表观遗传学领域很少观察到。为了这笔补助金 根据该提案，我们将重点关注组蛋白赖氨酸甲基转移酶，G9 a介导组蛋白H3-赖氨酸9 二甲基化（H3 K9 me 2）标记CA 1区神经元。考虑到这一点，我们的初步结果表明， 严重的应激增加了年轻成年大鼠CA 1区G9 a-H3 K9 me 2的活性， 衰老此外，H3 K9 me 2高甲基化与年轻人和老年人的记忆力下降密切相关。 老年人。初步结果还表明，抑制海马体中的G9 a活性可以逆转应激- 导致记忆力受损基于这些初步结果，我们计划严格调查 应激后操纵CA 1中G9 a-H3 K9 me 2活性的影响，并确定对年龄相关的 记忆衰退为进一步阐明G9 a-H3 K9 me 2介导的应激相关基因的作用机制， 转录，我们将使用最先进的方法，如siRNA和CRISPR-dCas 9-VP 64技术， 在我们的动物模型系统中直接靶向G9 a。我们的中心假设是：1）压力异常增加G9 a- H3 K9 me 2介导的年轻成年大鼠海马基因沉默与正常大鼠相似 2）应激介导的G9 a-H3 K9 me 2高甲基化将与衰老受损相关，但与衰老无关。 未受损的动物，和3）在年轻成年人中经历的应激导致对H3 K9 me 2的潜在影响 随着年龄的增长，高甲基化可以通过G9 a抑制来克服。我们的具体目标如下：具体 目的1：应激通过增加大鼠海马G9 a-H3 K9 me 2活性干扰记忆形成。 具体目标2：应激对老年人海马中的G9 a-H3 K9 me 2有不同的影响， 具体目标3：应激经历增加G9 a-H3 K9 me 2 年轻人海马体的活动导致记忆力随着年龄的增长而下降。总的来说，这项提案 将确定长期持久的表观遗传机制参与压力相关的记忆力下降与年龄。此外，委员会认为， 我们希望增加我们对大脑衰老时压力对记忆力下降的影响的理解。

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.