染色体微阵列分析在核型正常的颈项透明层增厚胎儿中的应用

摘要

目的 应用染色体微阵列分析技术(chromosomal microarray analysis,CMA)在全基因组水平分析颈项透明层(nuchal translucency,NT)增厚胎儿的遗传学病因.方法 选取78位孕妇早孕期(11+0～13+6孕周)NT厚度≥3.0mm且标准G显带染色体核型分析正常的胎儿样本,首先提取基因组DNA,严格按照美国Affymetrix CytoScanTM HD芯片的标准操作流程进行CMA检测,并应用CHAS软件和相关生物信息学数据库对结果进行分析.CMA检测所得拷贝数变异(copy number variations,CNVs)结果进一步行实时荧光定量PCR验证.结果 CMA在6例胎儿中检出致病性CNVs(7.69％),所检出致病性CNVs片段大小范围为0.41～15.87Mb,其中包含3种已知的微缺失/微重复综合征,分别为:Wolf-Hirschhom综合征、22q11微缺失综合征和ATR-16综合征.中孕期超声结构异常胎儿病例组和无结构异常胎儿病例组致病性CNVs的检出率分别为18.18％(2/11)和5.97％(4/67)(P=0.198,Fisher's检验);致病性CNVs胎儿病例组与非致病性CNVs胎儿病例组NT值的平均数分别是4.48mm和4.22 mm (P=0.735,Mann-Whitney检验).结论 在NT增厚胎儿中,染色体微阵列分析能检测传统核型分析无法识别的染色体微缺失/微重复,对临床产前诊断及遗传咨询具有重要价值,可将疾病诊断率额外提高7.69％.%Objective To explore the genetic etiology for fetuses with increased nuchal translucency (NT) but a normal karyotype at whole genome level by chromosome microarray analysis (CMA).Methods Seventy-eight fetuses with increased NT(≥ 3.0 mm) but a normal karyotype were collected between 11+0 and 13+6 gestational weeks.Genomic DNA was extracted,and microarray testing was performed using Affymetrix CytoScanTM HD arrays.The data was analyzed by CHAS software.All detected copy number variations (CNVs) were confirmed with real-time quantitative polymerase chain reaction.Results The CMA assay has detected pathogenic CNVs in 6 fetuses (7.69％),which have ranged from 0.41 Mb to 15.87 Mb.Well-known microdeletion or microduplication syndromes including Wolf-Hirschhorn syndrome,22q11 microdeletion syndrome and ATR-16 syndrome were identified in three cases.The detection rates in fetuses with or without structural abnormalities were 18.18％ and 5.97％,respectively (P=0.198 with Fisher's Exact Test).The average NT in fetuses with pathogenic CNVs and non-pathogenic CNVs has measured 4.48 mm and 4.22 mm (P=0.735 by Mann-Whitney Test).Conclusion For fetuses with increased NT,CMA can identify chromosomal microdeletion/microduplication unrecognizable by conventional karyotyping analysis.It may therefore play an important role in prenatal diagnosis and genetic counseling by improving the diagnostic rate.