DNA总体低甲基化、错配修复基因启动子甲基化异常与神经管畸形的相关性

目的：研究神经管畸形（NTDs）胚胎脑组织和皮肤组织DNA总体甲基化以及错配修复基因启动子区甲基化水平。方法：在山西省吕梁地区以医院为基础进行病例-对照研究。从县级医院及妇幼保健院收集经B超诊断为NTDs的胎儿标本，同时收集非病理性引产、无畸形和发育迟缓的胎儿作为正常对照组。运用甲基化定量试剂盒测定脑组织和皮肤组织的DNA总体甲基化水平，甲基化特异性多连接依赖性探针扩增试剂盒检测7个错配修复基因（MLH1，MSH2，MSH6，MSH3，MLH3，PMS2和MGMT）启动子区甲基化水平。结果:共有65例NTDs胚胎，48例对照胚胎进入研究。①NTDs组的脑组织DNA总体甲基化水平显著低于对照组（5.3% vs 6.5%，P<0.001），DNA总体低甲基化显著增加了NTDs发生风险（OR=4.98， 95%CI：1.42~17.53）。皮肤组织DNA总体甲基化水平在两组间差异无统计学意义(13.3% vs 13.1%,P>0.05)；②NTDs和对照组的MSH6启动子（MSH6-301:2.5% vs 3.7%，P<0.05）和PMS2启动子（PMS2-328：5.7% vs 6.7%；PMS2-142：2.0% vs 2.7%,P<0.05）的甲基化水平存在显著差异。结论：DNA总体低甲基化、错配修复基因启动子区的异常甲基化修饰与NTDs发生有关。

The association between global DNA hypomethylation,disturbed methylation pattern in promoter region of mismatched repair genes and neural tube defects

Objectives：To study whether the abnormal global DNA methylation levels or disturbed promoter methylation pattern of DNA mismatched repair genes increases the incidence of neural tube defects (NTDs). Methods：A hospital-based case-control study was conducted in the Lvliang area of Shanxi Province, China. NTD-affected cases and controls matched in maternal age and gestational age were recruited from county hospitals and maternal and child health hospitals. All subjects were diagnosed by B-mode ultrasound and confirmed by autopsy. The methylation Quantification Ultra Kits (Epigentek) were used to determine the global DNA methylation levels in brain and skin tissues. The Methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) kits were used to quantify the methylation levels of promoter regions of 7 DNA mismatched repair genes (MLH1，MSH2，MSH6，MSH3，MLH3，PMS2 and MGMT). Results:65 NTD-affected fetuses and 48 normal controls were collected. ① In brain tissue, global DNA methylation levels were significantly decreased in NTD compared with control group (5.3% vs 6.5%，P<0.001). DNA hypomethylation caused a significant 4.98-fold increased risk for NTDs (CI:1.42-17.53). No statistical difference was seen for skin tissue in two groups (13.3% vs 13.1%, P>0.05).② Compared with control group, NTDs group had significantly lower methylation levels in the promoter regions of MSH6（MSH6-301:2.5% vs 3.7%, P<0.05）and PMS2（PMS2-328:5.7% vs 6.7%; PMS2-142:2.0% vs 2.7%, P<0.05）. Conclusions:Global DNA hypomethylation in fetal brain tissue is associated with NTD-affected pregnancy. Disturbed methylation patterns in promoter regions of two mismatched repair genes, MSH6 and PMS2 are associated with NTD-affected pregnancy.