嵌合体形成及其对产前筛查及诊断结果的影响

The Formation of Chromosome Mosaicism and Its Influence for Prenatal Screening and Diagnosis

随着细胞分子生物学时代的来临,产前筛查和诊断方法也随之发生改变,更多的数据需要正确解读,这对产前诊断医生无疑是一项挑战。其中,染色体嵌合是影响产前筛查与诊断准确性的重要因素之一,受母亲、父亲以及胎盘等多种因素影响,人类普遍存在染色体嵌合,嵌合形成的主要原因是有丝分裂期染色体错误分离。受多种因素的影响,嵌合的临床表现对每个个体都具有唯一性。嵌合对产前筛查和诊断的影响主要为2个方面:(1)母血中胎儿游离细胞DNA(cell-free fetal DNA,cf DNA)筛查(无创产前筛查)。虽然大量文献报道无创产前筛查对于21,18,13三体有较高的检出率,但由于其检测的母血中cf DNA来源于胎盘,并非真正的胎儿自身DNA,因此当发生胎盘局限性嵌合时会严重影响无创产前筛查结果的准确性。(2)绒毛染色体核型分析提示存在嵌合时需要行羊膜腔穿刺进行验证。总之,正确认识染色体嵌合的起源、机制和临床结果,可以为病人提供更多有价值的遗传信息,是做好产前筛查与诊断工作并提供遗传咨询的重要前提。

With the advent of cell-molecular biology, prenatal screening and diagnostic methods have also changed, and more data need to be interpreted correctly,which is a challenge for prenatal diagnosis doctors. Among them, chromosome mosaicism is one of the most important factors that affect the accuracy of prenatal screening and diagnosis. Chromosome mosaicism is prevalence in human and affected by many factors, such as mother, father, placental and other factors. The main reason for the formation of mosaicism is chromosomal error separation in mitotic. The clinical manifestations of mosaicism are affected by a variety of factors, and their clinical outcomes are unique to each individual. The effect of mosaicism on prenatal screening and diagnosis are mainly in two aspects:(1)Screening of cell-free fetal DNA(cf DNA) in maternal blood. Although a large number of related literature reported its higher detection rate for 21,18,13 trisomy, while cf DNA from the placenta, and confined placental mosaicism is an important factor affecting the accuracy of the results.(2)If the chronic karatype is mosaicism,amniocentesis is required for futher confirmation. In conclusion, understanding the origin, mechanism and clinical outcome of chromosome mosaicism correctly, can provide patients with more valuable genetic information, and it ′s importance for providing genetic counseling in prenatal screening and diagnosis.