Exploring the role of GADD45A in Alzheimer's disease

项目摘要 阿尔茨海默病（AD）是一种严重的痴呆症，影响超过500万美国人，使其成为世界上最严重的痴呆症之一。 最常见的神经退行性疾病AD患者表现出严重的渐进性记忆 目前的药物干预无法预防的损失，并且发展的风险增加 共病神经系统疾病，如癫痫。缺乏有效的治疗和重症监护 晚期AD患者所需的药物治疗也给家庭和美国人带来了巨大的经济负担。 医疗保健系统：估计每年约2000亿美元。最近的研究表明， 表观遗传修饰和AD。一种特别相关的表观遗传修饰是5-羟甲基胞嘧啶 （5 hmC），其在神经元中高度富集并且在神经发育期间动态调节。改变 在AD患者的大脑和小鼠AD模型中观察到了5 hmC，这提高了 DNA 5 hmC异常可能参与AD的发病。GADD 45 A介导5 hmC的建立 在细胞中，并且还具有RNA结合活性。有趣的是，Gadd 45 a-/-敲除小鼠表现出降低的 海马长时程增强（LTP）和受损的长期记忆和逆转学习，而 野生型小鼠锥体兴奋性神经元中Gadd 45 a的过表达增强LTP和记忆 合并。此外，我们的初步数据和公开的RNA-seq数据集表明，GADD 45 A 在从AD患者分离的神经元中下调。Gadd 45 a表达和5 hmC水平也降低 在AD的几种小鼠模型中（包括本提案中使用的3xTG AD模型）。基于这些 通过观察，我们推测GADD 45 A在神经元功能和认知中起重要作用 通过对5 hmC水平的表观遗传调节和随后对基因表达的调节， 神经元我们将在目标1中通过比较Gadd 45 a-/-之间的5 hmC水平和分布来检验这一假设。 无效突变体和WT同窝仔。我们还将对这些小鼠进行RNA-seq和ATAC-seq， 将观察到的5 hmC变化与基因表达和染色质可及性的特异性改变联系起来。给定 Gadd 45 a的过表达增强了LTP和记忆巩固，我们推测， GADD 45 A的上调将治疗AD。因此，在目标2中，我们将研究 在AD的3xTG小鼠模型中Gadd 45 a的过表达可以改善突触活性的缺陷，改善突触活性的降低， 学习和记忆，并减少自发性癫痫样放电。选择这些表型 因为它们代表了AD的重要病理特征，并且由于认知功能， AD脑的衰退被认为是由神经元过度兴奋性加速的。

PROJECT SUMMARY Alzheimer’s disease (AD) is a severe form of dementia that affects over 5 million Americans, making it one of the most common neurodegenerative disorders. Patients with AD exhibit a severe form of progressive memory loss that cannot be prevented with current pharmacological interventions, and are at increased risk of developing comorbid neurological disorders such as epilepsy. The lack of efficacious treatments and the intensive care required for late-stage AD patients also places a significant economic burden on families and the American healthcare system: an estimated ~$200 billion annually. Recent studies have demonstrated a link between epigenetic modifications and AD. One epigenetic modification of particular relevance is 5-hydroxymethylcytosine (5hmC) which is highly enriched in neurons and is dynamically regulated during neurodevelopment. Alterations in 5hmC have been observed in the brains of patients with AD and in mouse AD models, raising the possibility that aberrant DNA 5hmC might contribute to AD pathogenesis. GADD45A mediates the establishment of 5hmC in cells and also possesses RNA binding activity. Interestingly, Gadd45a-/- null mice exhibit decreased hippocampal long-term potentiation (LTP) and impaired long-term memory and reversal learning, whereas overexpression of Gadd45a in pyramidal excitatory neurons of wild-type mice enhances LTP and memory consolidation. In addition, our preliminary data and publicly available RNA-seq data sets indicate that GADD45A is downregulated in neurons isolated from AD patients. Gadd45a expression and 5hmC levels are also reduced in several mouse models of AD (including the 3xTG AD model to be used in this proposal). Based on these observations, we hypothesize that GADD45A plays an important role in neuronal function and cognition through epigenetic regulation of 5hmC levels and subsequent modulation of gene expression in neurons. We will test this hypothesis in Aim 1 by comparing 5hmC levels and distribution between Gadd45a-/- null mutants and WT littermates. We will also perform RNA-seq and ATAC-seq on these mice to functionally relate observed changes in 5hmC with specific alterations in gene expression and chromatin accessibility. Given that overexpression of Gadd45a enhances LTP and memory consolidation, we hypothesize that upregulation of GADD45A will be therapeutic in AD. Therefore, in Aim 2, we will examine whether overexpression of Gadd45a in the 3xTG mouse model of AD can ameliorate deficits in synaptic activity, improve learning and memory, and reduce spontaneous epileptiform discharges. These phenotypes were selected because they represent important pathological features of AD and are mechanistically related since cognitive decline in the AD brain is believed to be accelerated by neuronal hyperexcitability.