TET3介导miR-124羟甲基化修饰在抑郁发生中的作用及机制研究

Currently, high expression of miR-124 is closely associated with the development of major depressive disorder (MDD). However, the regulatory mechanism of miR-124 in MDD is still unclear. A research suggests that up-regulated expression level of miR-124 is related to a low methylation status of the promoter region of miR-124 gene. The Ten-eleven translocation (TET) enzymes (TET1, TET2, and TET3) are implicated in DNA demethylation through hydroxymethylation modification. Our previous cell experiments suggested that there may be a positive regulatory relationship between TET3 and miR-124. Moreover, we found that mice exposed to chronic social defeat stress exhibited significant increase in hippocampal TET3 and miR-124 levels. Based on these results, we propose a research hypothesis that TET3 could upregulate miR-124 expression by DNA hydroxymethylation, which may contribute to MDD. To confirm this hypothesis, we intend to 1) determine the relationship between serum TET3 levels and MDD through clinical sample testing. 2) elucidate the role and molecular mechanism of TET3 in depression-like behavior induced by chronic social defeat stress in mice, by using a well-established mice model of depression, constructing adeno-associated virus vector, stereotaxic injection and molecular detection techniques, etc. This study aims to provide a new strategy to explore the pathogenesis of MDD.

目前miR-124的表达上调被认为与抑郁发生密切相关，但miR-124的上游调控机制仍不明确。有研究提示miR-124表达上调可能与编码基因启动子区低甲基化状态有关，而双加氧酶TET家族蛋白 (TET1、TET2及TET3)主要通过介导DNA羟甲基化修饰发挥去甲基化作用。我们前期在细胞实验中已发现TET3与miR-124可能存在正向调控关系，并在慢性社会挫败应激抑郁小鼠海马中发现TET3与miR-124水平显著升高。据此，我们提出假说：TET3可能通过羟甲基化作用上调miR-124表达来参与抑郁发生。为验证这一假说，我们拟1)通过临床样本检测，探究血清TET3水平与抑郁症的关系；2)应用动物模型、腺相关病毒载体构建、脑立体定位注射及分子学检测等技术揭示TET3在慢性社会挫败应激所致小鼠抑郁样行为中的作用及其分子机制。本研究旨在为探索抑郁症病因提供新的策略。

MiR-124上调被认为与抑郁症发生密切相关,但其调控机制仍不清楚。本课题项目开展了如下研究：1.验证miR-124在慢性不可预期轻度应激(CUMS)中的表达，并探索下游靶基因。结果显示，CUMS小鼠海马脑区存在miR-124显著上调，同时也引起一些自噬相关蛋白改变，而氟西汀能够逆转这种变化。2.探索抑郁症患者miR-124前体基因甲基化水平。结果表明抑郁症患者miR-124的三个前体基因均存在广泛低甲基化状态，提示甲基化与miR-124表达调控密切相关。3.探索羟甲基化调控机制是否与抑郁发生有关。我们前期细胞学数据提示去甲基化关键酶TET3参与miR-124调控。我们进一步研究发现TET3在抑郁症患者和CUMS应激易感小鼠海马脑区中均存在表达上调。另在19名抑郁症患者和17名健康对照中，通过整合羟甲基化及转录组测序揭示出羟甲基化修饰可能通过调控T细胞受体信号通路，Th1 and Th2细胞分化，Th17细胞分化等免疫炎症通路参与抑郁发生。本研究提出TET3及羟甲化修饰机制可能参与抑郁发生，并进一步支持miR-124参与抑郁症病理生理过程。