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目的:探讨多氯联苯(PCB118)慢性暴露对小鼠着床期子宫内膜特定基因启动子区甲基化水平及基因表达的影响。方法:将40只3周大CD-1小鼠随机分为4组:空白对照组,1μg/kg PCB118剂量组,10μg/kg PCB118剂量组,100μg/kg PCB118剂量组。各组灌胃1个月后,行促排卵合笼,于妊娠第4.5天断椎处死小鼠,留取子宫内膜组织。采用甲基化DNA免疫共沉淀-实时定量PCR(MeDIP-qPCR)检测特定基因启动子区甲基化水平;实时定量RT-PCR检测特定基因mRNA表达水平。结果:MeDIP-qPCR显示,相对于空白对照组,剂量组中PCDH17、ITGB8、FREM2及FGF4这4个基因启动子呈现高甲基化,与我们前期DNA甲基化芯片结果一致,有显著统计学差异(P<0.05)。Real-time PCR显示,PCDH17、ITGB8、FREM2及FGF4基因的mRNA水平在各剂量组均显著降低(P<0.05),与其启动子区DNA甲基化水平呈现负相关。结论:慢性PCB118暴露诱导着床期特定基因启动子区发生高甲基化,进而引起这些基因表达沉默,这可能是PCB118生殖毒性产生的分子机制之一。
Objective: To investigate the effects of chronic exposure to polychlorinated biphenyls (PCB118) on the methylation level and gene expression of specific gene promoter in mouse endometrium during implantation. Methods: 40 3-week-old CD-1 mice were randomly divided into 4 groups: blank control group, 1μg / kg PCB118 dose group, 10μg / kg PCB118 dose group and 100μg / kg PCB118 dose group. After one month of intragastric administration, the rats in each group were ovulated and ovulated, the mice were sacrificed on the 4.5th day of gestation, and the endometrium was collected. The methylation level of specific gene promoter region was detected by methylation-specific DNA co-precipitation-real-time quantitative PCR (MeDIP-qPCR). The mRNA expression of specific genes was detected by real-time quantitative RT-PCR. Results: MeDIP-qPCR display, with respect to the control group, dose group PCDH17, ITGB8, FREM2 and FGF4 four gene promoter exhibits high methylation, consistent with our previous DNA methylation microarray results, there is a statistically significant difference ( P <0.05). Real-time PCR showed that the mRNA levels of PCDH17, ITGB8, FREM2 and FGF4 were significantly decreased in all dose groups (P <0.05), and negatively correlated with the DNA methylation level in their promoter regions. CONCLUSION: Chronic PCB118 exposure induces hypermethylation at the promoter region of specific genes during implantation, leading to the silencing of these genes. This may be one of the molecular mechanisms of PCB118 reproductive toxicity.