孕妇血清中胎儿游离DNA产前筛查Down’s综合征初探

Detection of cell-free fetal DNA in maternal serum for a new prenatal screening marker of Down's syndrome

目的应用TaqMan探针实时定量聚合酶链反应（Real-time quantitative PCR）技术检测孕妇血清中胎儿游离DNA含量，探讨以其含量变化作为Down’s综合征产前筛查新指标的可行性。方法选择42例孕中期（16-19周）的妇女作为研究对象，其中7例为孕21三体男胎的妇女，18例为孕正常男胎的妇女，17例为孕正常女胎的妇女，提取其外周血血清中游离DNA，应用TaqMan探针实时定量聚合酶链反应技术检测Y染色体上的DYS14基因，以此确定母体血清中的胎儿游离DNA含量，并同时检测代表母体与胎儿总游离DNA的β-actin基因作为对照。结果孕21三体男胎组血清胎儿游离DNA含量明显高于孕正常男胎组，它们分别为94．5基因当量（genome equivalents，GE）／ml及42．8GE／ml（P〈0．01），孕21三体男胎组血清中的胎儿游离DNA含量为孕正常男胎组的2．2倍。孕正常女胎组血清中未检测到Y-染色体上的DYS14基因。结论胎儿游离DNA可能成为产前筛查Down’s综合征的候选指标。

Objective Detection of cell-free fetal DNA in maternal serum by TaqMan probe real-time quantitative polymerase chain reaction（real-time quantitative PCR） and on the basis of it＇s amount to discuss the feasibility as a new prenatal screening indicator of Down＇ s syndrome. Methods Cell-free fetal DNA in maternal serum was isolated from 42 samples in the midtrimester （ 16 - 19w） pregnancy. Samples consisted of 7 women carrying male trisomy 21 fetuses, 18 carrying euploid male fetuses,and 17 carrying female fetuses.TaqMan probe real-time quantitative PCR was used to detect both DYS14 gene on Y chromosome and β-actin gene of the mothers and the fetuses. Results Abnormal high concentrations of cell-free fetal DNA were found in a proportion of women carrying male trisomy 21 fetuses. Mean serum fetal DNA concentrations were 94.5 genomic equivalents （GE）/ml for Down＇ s syndrome cases and 42.8 GE/ml for the euploid controls （ P 〈 0.01 ）. Down＇s syndrome pregnancies exhibit 2.2-hold higher levels of maternal serum cell-free fetal DNA compared with matched controls, None of the samples from women carrying female fetuses had detectable Y-chromosomal signals. Conclusion Cell-free fetal DNA in matemal serum is a potential prenatal screening maker for trisomy 21.