CNV-Seq联合核型分析在羊水穿刺胎儿染色体嵌合体诊断中的应用

目的 探讨低深度基因组拷贝数变异测序（CNV-Seq）联合染色体核型分析在胎儿嵌合体诊断中的应用。方法 选取2018年1月至2019年9月在中国科学技术大学附属第一医院妇产科产前诊断中心行常规产前诊断的孕妇为研究对象,B超引导下行羊膜腔穿刺术获取羊水标本3 320份,所有标本均同时进行染色体核型分析（双线独立操作）及CNV-Seq,将诊断为胎儿染色体嵌合体的病例纳入回顾性分析。结果 3 320例穿刺羊水标本中,共检测出胎儿染色体嵌合体19例（阳性检出率为0.57%）,其中,羊水核型检测出16例（阳性检出率为0.48%）,CNV-Seq检测出12例（阳性检出率为0.36%）。无创产前检查提示异常的标本检出嵌合体8例,超声、胎儿颈项透明层厚度提示异常的标本检出嵌合体5例,孕妇高龄检出嵌合体2例,唐氏筛查结果提示高风险孕妇检出嵌合体4例。在2种方法联合检出的19例嵌合体中,性染色体嵌合9例,常染色体嵌合10例。3例核型分析无明显异常嵌合的病例,CNV-Seq技术检测出嵌合,后经荧光原位杂交证实其为真性嵌合。结论 CNV-Seq联合染色体核型分析,可以弥补单一检测方法诊断羊水穿刺胎儿染色体嵌合体出现误诊的不足,有望为产前遗传咨询提供更加可靠的实验室诊断结果。

Application of CNV-Seq combined with karyotyping in amniocentesis for prenatal diagnosis of fetal chromosomal mosaicism

Objective To explore the application of low-depth copy number variation sequencing (CNV-Seq) combined with karyotyping in the diagnosis of fetal chromosomal mosaicism. Methods The pregnant women who underwent the routine prenatal diagnosis at the Prenatal Diagnostic Center, the First Affiliated Hospital of University of Science and Technology of China were selected as subjects, and 3320 amniotic fluid samples were obtained from ultrasound-guided amniocentesis. All the extracted samples from 3320 cases undergone amniocentesis were subjected to chromosomal karyotyping (two-line independent operation) and CNV-Seq detection, respectively. Then, the cases diagnosed as fetal mosaicism were collected for further retrospective analyses. Results Among the 3320 amniotic fluids samples, 19 mosaicism cases were detected (positive rate was 0.57%), of which 16 cases were detected by chromosomal karyotyping (positive rate was 0.48%), while 12 cases were detected by CNV-Seq (positive rate was 0.36%). Specifically, eight mosaicism cases were detected from pregnant women with abnormal non-invasive prenatal test (NIPT) results, five mosaicism cases were detected from pregnant women with abnormal ultrasound or nuchal translucency (NT) thickness, two mosaicism cases were detected from pregnant women with advanced age, four mosaicism cases were detected from pregnant women with high-risk Down''s syndrome screening. Among all the 19 mosaicism cases, nine were autosomal mosaicisms, while the other ten cases were sex chromosomal abnormalities. Notably, three cases without mosaicisms diagnosed by karyotyping, were detected as mosaicisms by CNV-Seq, which were further verified to be true mosaicisms by FISH analyses. Conclusion CNV-Seq technology combined with karyotyping could avoid the misdiagnosis of fetal chromosomal mosaicism with single technology, which may provide more convincing laboratory results for prenatal genetic counseling.