特异性5hmC丢失对阿尔茨海默病神经元退行性病变的影响及意义

项目名称： 特异性5hmC丢失对阿尔茨海默病神经元退行性病变的影响及意义

项目编号： No.81471313

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 医药、卫生

项目作者： 李家立

作者单位： 中国科学院昆明动物研究所

项目金额： 80万元

中文摘要： 5-羟甲基化胞嘧（5hmC）是一个新近发现的表观遗传标记，由于其在神经细胞内所呈现的高水平，提示它对神经元功能可能有重要作用。我们初步的研究结果证实在AD病人的大脑皮层及海马等区域的特定神经元5hmC含量发生明显地降低；同时，在AD 小鼠模型的大脑皮层及海马神经细胞也发现明显的选择性5hmC 减少。另外，我们也发现给予可溶性淀粉样蛋白小肽（Aβ）可直接诱导海马及皮层神经细胞发生显著的5hmC 降低。我们计划首先确认Aβ是否影响TETs 酶活性以及机制。另外，利用CRISPR/Cas9技术结合在体神经核团微量注射病毒靶基因或者通过离体特定脑片培养对TETs酶蛋白活性进行调控来观察5hmC 水平变化对AD神经退行性病变的影响。本课题的研究目的是确定特异性DNA 5-羟甲基胞嘧啶（5hmC）的变化在AD神经细胞退行性病变过程的作用及机制，为研发新的早期诊断及治疗手段提供一个全新理论与实验依据。

中文关键词： 神经退行性疾病；表观遗传学；DNA；甲基化；细胞周期再入；阿尔茨海默病

英文摘要： The aging of brain has been associated with abnormal alterations in multiple epigenetic systems including aberrant DNA methylation patterns. DNA 5-Hydroxymethylcytosin (5hmC), a new epigenetic hallmark which was discovered recently is becoming an interesting topic. The exact function of this base remains being poorly elucidated, but it is thought to involve gene expression or prompt active DNA demethylation. The levels of 5hmC in genomic DNA vary significantly depending on the cell type. The highest levels are found in neuronal cells of the central nervous system, implying its importance in gene regulation of central nervous system. While alterations of histone modification and DNA methylation have been well studied in Alzheimer's disease (AD), the extent of ten eleven Ten-eleven translocation enzymes TET-mediated conversion from DNA 5-methylcytosine (5mC) to 5hmC and their involvement in the pathology of the main neurodegenerative disorders is still mystery. The core hypothesis of this application is that loss of 5-hydroxymethylcytosine plays a critical and possibly vital supporting role in the death of neurons during late-onset Alzheimer's disease (AD). We present preliminary data showing that a significant loss of 5hmC was exclusively found in specific brain regions in postmortem samples from patients with confirmed diagnosis of Alzheimer's disease (AD) in comparison to age and sex matched healthy control subjects. These results indicate that the involvement of 5hmC in the pathology of neurodegenerative disorders and points out common and particular signatures that might aid in differential diagnosis as biomarkers or in the discovery of novel therapeutic targets. We will examine the level of 5mC and 5hmC as well as TET family proteins in human AD postmortem brain samples and assess whether loss of 5hmC is an hallmark related to classic neuropathological features found in AD. We will focus on exploring whether loss of 5hmC is a direct factor of neurodegeneration in human AD frontal and temporal cortex as well as hippocampus samples. We have developed preliminary data that demonstrate that a significant loss of 5hmC is selectively found in human AD as well as 3xTg AD mouse frontal cortex and hippocampus. We will quantify these findings by deep sequencing analyses of 5mC MeDIP and 5hmC hMeDIP in human patient samples. We will focus on the mechanism of loss of 5hmC in driving the selective degeneration of hippocampal and cortical neurons in AD by using 3xTg AD animal model. We have developed a new preliminary data that demonstrate that Tet-mediated the conversion from 5mC to 5hmC in primary neurons was downregulated by treatment of beta-amyloid (Aβ). We will examine whether the manipulation of TETs have directly effects on learning and memory loss in AD mouse modelby live mouse hippocampus lentiviral micro-injection as well as mouse hippocampal slice cultures with viral infection or CRISPR/Cas9 gene-editting.

英文关键词： neurodegeneration;epigenetics;DNA methylation;cell cycle reentry;Alzheimer's disease