DNMT1的异常表达机制及其对帕金森病相关基因调控的研究

Parkinson’s disease (PD) is a neurodegenerative disorder invovling both genetic and environmental factors. It has been shown that DNA hypomethylation was associated with PD pathogenesis, and that DNA methyltransferase 1 (DNMT1) was down-regulated in the postmortem brain samples of sporadic PD cases. However, the mechanisms underlying the down-regulation of DNMT1 and its effect on PD-associated genes remain to be explored. We have previously shown that the protein expression of DNMT1 was decreased in multiple neurotoxin-induced PD cellular models and that the reduced DNMT1 level could promote the expression of SNCA. Meanwhile, we found that an array of miRNAs may be involved in the regulation of DNMT1 expression. We thus proposed a novel hypothesized pathway of “environmental factors-DNMT1-PD related genes (genetic factors)” in the PD pathogenesis . This study is to apply methods including biochemical and molecular biology techniques and is aimed to investigate the mechanisms underlying the dysregulation of DNMT1 and its impact in PD related gene in a series of PD cellular and animal models. We also aim to compare the levels of DNMT1, methylation and expression of PD-related genes in blood mononuclear cells between PD cases and controls. Our findings will have important implications on the understanding of PD pathogenesis, as well as the exploration of PD biomarkers.

帕金森病（PD）是由多种环境因素和遗传因素参与的神经退行性疾病，DNA甲基化调控异常被认为与PD发病相关,并且PD患者脑组织DNA甲基转移酶1（DNMT1）的表达水平下降，然而DNMT1异常表达的具体机制及其是否对PD相关基因存在表观调控尚待明确。课题组前期在多种PD细胞模型中发现DNMT1的表达减少，同时DNMT1的下降能够促进SNCA（α-synuclein）的表达，并初步发现了miRNAs介导的翻译调控可能参与对DNMT1水平的调控，进而提出了在PD发病过程中存在“环境因素-DNMT1-靶基因”调控通路的假说。本项目拟采用生物化学和分子生物学等方法，在多种PD细胞和动物模型中探讨DNMT1下降的机制并明确其对PD相关基因的影响；同时在PD患者和对照外周血中检测并比较DNMT1、靶基因的甲基化及表达水平等。研究成果将对加深认识PD复杂发病机制，寻找潜在的PD外周血指标有重要参考价值。

帕金森病（PD）是由多种环境因素和遗传因素参与的神经退行性疾病，DNA甲基化调控异常被认为与PD发病相关，并且PD患者脑组织DNA甲基转移酶1（DNMT1）的表达水平下降，然而DNMT1异常表达的具体机制及其是否对PD相关基因存在表观调控尚待明确。本项目通过采用生物化学和分子生物学等方法，在多种PD细胞和动物模型中探讨了DNMT1下降的机制并明确其对PD相关基因的影响。同时在PD患者和对照外周血中检测并比较相关miRNAs的表达，筛选可以诊断PD的潜在生物标志物。我们的研究发现：1）PD模型中DNMT1的表达下降，进而引起SNCA 1号内含子甲基化水平降低和表达升高；2）miR-17和miR-19a通过DNMT1参与调控SNCA 1号内含子甲基化和表达；3）PD细胞模型中，抑制miR-17的表达能够缓解DNMT1蛋白水平的下降、SNCA 1号内含子区CpG岛甲基化的下降和表达的上升；4）血浆中miR-17、miR-433和miR-133b表达水平在PD组和健康对照组之间有显著差异，其可能作为潜在的生物标志物用于PD的诊断；5）DNMT1基因的rs16999593与PD风险相关，在PD患者和对照组之间，四种tag-SNPs组成的单倍型分布存在显著差异。总之，我们的研究结果表明DNMT1与PD发病风险相关，miRNAs介导的DNMT1是PD中SNCA表达的表观遗传调控的基础。我们的结果为散发性PD的发病机制提供了连接环境因素和遗传变化的桥梁。本研究的成果对认识PD的发病机制以及寻找潜在的外周血生物学指标或者治疗靶点有着重要的意义。