先天性肾上腺皮质增生风险胎儿的CYP21基因分子产前诊断

Molecular Prenatal Diagnosis of a Fetus at the Risk of Congenital Adrenal Hyperplasia with Mutation of CYP21 Gene

目的报告1例先天性肾上腺皮质增生（CAH）CYP21基因缺陷风险胎儿的分子产前诊断。方法首先对携带者夫妇进行CYP21基因扩增和测序，确定这对夫妇均为CYP21基因缺陷的携带者。妻子孕29w时于B超的引导下抽取胎儿脐血，分离血浆进行17-羟孕酮的检测。从血细胞中提取DNA，用多态性住点D12S1701检测夫妇和胎儿DNA，以排除胎儿样本中无母体细胞污染，在此基础上，针对携带者突变位点对胎儿样本进行DNA扩增，PCR产物经正反方向测序分析。结果携带者夫妇均存在CYP21因子外显子4突变（g．1122T〉A，p．1172N）和外显子6的丛集突变（g．1503T〉A，g．1506T〉A，g．1512T〉A，p．1236N，p．V237E，p．M239K）。多态性位点检测排除胎儿样本中母体细胞污染，胎儿测序结果显示不带有与父母相同的突变。胎儿血浆17-羟孕酮结果正常。最后妻子足月分娩了一健康女婴。结论产前分子诊断对于CAH风险胎儿是非常重要的。用测序技术进行CYP21基因的分子产前诊断是可行的。

Objective Molecular prenatal diagnosis of a fetus at the risk of congenital adrenal hyperplasia（CAH） with mutation of CYP21 gene was reported. Methods Molecular diagnosis of CYP21 gene was performe by sequencing for the couple at first. After confirming the mutations of the couple, fetal genomie DNA was extracted from an umbilical blood sample obtained by puncturing at 29 weeks of gestation under guidance of ultrasound scan. Blood plasma was separated from the umbilical blood sample for analyzing the level of 17-hydroxyprogesterone （17-OHP）. Polymorphic analysis with locus D12S1701 was performed to exclude maternal contamination. PCR amplification of fetal DNA on exons 4 and 6 in CYP21 gene was carried out and their products were sequenced directly. Results The tandem mutations of exon 4 （g. 1122 T〉A,p. I172N） and exon 6 （g. 1503 T〉A,g. 1506 T〉A,g. 1512 T〉A,p. I236N,p. V237E,p. M239K） were detected on one allele from the couple, Maternal contamination was excluded by polymorphic analysis with locus D12S1701. The fetal results showed no mutation of exons 4 and 6 in CYP21 gene was found,identifying the fetus was carrying normal alleles without the same mutation as her parents. The fetal level of 17-OHP was normal,which was consistent with molecular result. Recently,a normal girl was born at 39 weeks of gestation, which confirmed that the technique was reliable for molecular prenatal diagnosis of CYP21 gene. Conclusion Molecular prenatal diagnosis is practical and for fetus at risk with CAH.