ERG甲基化作为无创产前诊断唐氏综合征标记的可行性研究

Feasibility study of Hypermethylated ERG as a marker of noninvasive prenatal diagnosis of Down's syndrome

目的探讨ERG基因是否可以作为孕早期血浆中检测胎儿DNA的通用标志物。方法随机选择早期妊娠孕妇70例,并以经体检确定为未孕健康妇女70例、分娩过21-三体胎儿的妇女11例和顺产后3 d妇女20例作为对照组。利用甲基化敏感限制性内切酶HpaⅡ、MspⅠ酶切后进行常规PCR的方法,检测血细胞、绒毛和血浆DNA目的基因ERG21-128序列的甲基化模式,并对妊娠组和对照组样本进行统计学分析。结果位于21号染色体上的ERG基因21-128序列在70例孕8、9、10周孕妇绒毛组织中甲基化而在母体血细胞中未甲基化,绒毛甲基化检出率为100%;在血浆中游离胎儿DNA ERG基因21-128序列的甲基化检出率为77.1%,敏感度为77.1%。其中8、9、10周甲基化差异无统计学意义(P>0.05)。在70例未孕健康妇女、11例生产过21三体胎儿的健康妇女和20例产后3 d妇女的对照组的血浆中ERG 21-128序列均未甲基化。结论在母体和胎儿DNA中,ERG基因21-128区的甲基化有显著性差异,实验方法也比较简单,提示了ERG是无创性产前诊断DS的一个潜在标记物。

Objective To investigate ERG as a universal fetal DNA marker in early pregnancy for noninvasive prenatal diagnosis of Down＇s syndrome（DS）.Methods Maternal blood samples and chorionic villus were obtained from 70 pregnant women during the first trimester（8-10 weeks,n=9） as study group and 70 nonpregnant women,11 women who had once production of DS fetus and 20 women after 72 hours postpartum as control group.Genomic DNA was extracted from peripheral blood leukocytes,chorionic villus and plasma,then ERG methylation was analyzed using methylation-sensitive restriction enzyme and conventional PCR.Results ERG 21-128 sequence was hypomethylation in digested peripheral blood leukocytes genomic DNA while was hypermethylation in chorionic villus genomic DNA in 70 pregnant women.Hypermethylated fetal ERG was detected in all chorionic villus samples（the detected rate was 100%） while was detected only in 54 of 70 cases in plasma DNA（the sensitivity was 77.1%）.The rate of methylation had no significant difference in 8,9,10 pregnant weeks.ERG 21-128 sequence was hypomethylation in digested DNA from the control group.Conclusion Hypermethylated ERG is a universal marker for fetal DNA and is easily detect in maternal plasma thus can be a marker of noninvasive prenatal diagnosis of DS.