[采用聚合酶链反应-短串联重复序列法进行唐氏综合征快速产前筛查的实用性]

Guan Lixue, Ren Cuiai, Li Haibo, Gao Li, Jia Nan, Guan Hui

Stem Cell Laboratory, Weifang People's Hospital, Weifang, Shandong 261041, P.R. China.

Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2013 Jun;30(3):277-82. doi: 10.3760/cma.j.issn.1003-9406.2013.03.006.

OBJECTIVE

To assess the practicality of rapid prenatal screening for Down syndrome (DS) by polymerase chain reaction-short tandem repeat (PCR-STR) method, and to determine the genotypes of 7 STR loci in ethnic Chinese Han from Weifang region.

METHODS

Seven STR markers (D21S11, D21S1411, D21S1412, D21S1413, D21S1414, D21S1432 and D21S2039) from chromosome 21q22.1-22.2 region were selected. Amniotic samples from 978 high-risk pregnancies and peripheral blood samples from 82 patients suspected with DS were tested with PCR-STR. And the results were verified with G-banding analysis.

RESULTS

(1) All of the 1060 samples were successfully tested by PCR-STR. For normal individuals, the patterns obtained by PCR-STR were two bands with 1:1 area ratio or a single band. For DS cases, by contrast, the patterns revealed either three bands with area ratio of 1:1:1 for two STR loci, or three bands with area ratio of 1:1:1 for one STR loci and two bands with 2:1 or 1:2 area ratio for two STR loci. Based on analysis of the 7 STR markers, 14 amniotic fluid samples and 26 peripheral blood samples were regarded as DS positive. (2) For the 978 amniotic fluid samples, cytogenetic analysis was successful in 961 (98.3%), among which 44 had an abnormal karyotype. These included 14 trisomy 21 (12 standard type, 1 mosaicism and 1 translocation). 17 cases which failed amniocytic culture were normal upon fetal blood karyotyping. (3) Cytogenetic analysis was successful in all of the 82 peripheral blood samples, and has identified 30 (36.6%) abnormal karyotypes, among which 26 were trisomy 21 (including 4 with translocation form). (4) For DS positive cases, STR 1-4 showed three bands with area ratio of 1:1:1, or there were 2-4 loci with two bands with an area ratio of 2:1 or 1:2. All of the DS cases detected by PCR-STR were confirmed by karyotyping. (5) All of the 7 selected loci were informative, with their degrees of heterozygosity ranging between 0.624 and 0.812. D21S2039 and D21S1412 had the highest heterozygosities (> 0.80), D21S1411 and D21S1432 had the lowest (< 0.70). D21S11 and D21S2039 showed the highest rate (≥ 40%) of three bands with area ratio 1:1:1. However, D21S1411, D21S1432 and D21S1413 markers had the highest rate of homozygosity (≥ 30%).

CONCLUSION

PCR-STR assay may provide an effective alternative for rapid prenatal DS screening. The 7 selected STR markers are highly informative. The result has featured good accuracy and reliability.

目的

评估聚合酶链反应-短串联重复序列（PCR-STR）法进行唐氏综合征（DS）快速产前筛查的实用性，并确定潍坊地区汉族人群7个STR位点的基因型。

方法

选择21号染色体q22.1-22.2区域的7个STR标记（D21S11、D21S1411、D21S1412、D21S1413、D21S1414、D21S1432和D21S2039）。采用PCR-STR技术检测978例高危妊娠的羊水样本和82例疑似DS患者的外周血样本，并通过G显带分析进行结果验证。

结果

（1）1060份样本均成功通过PCR-STR检测。正常个体的PCR-STR图谱为两条面积比为1:1的条带或一条单带。相比之下，DS病例的图谱显示，两个STR位点出现三条面积比为1:1:1的条带，或一个STR位点出现三条面积比为1:1:1的条带，另外两个STR位点出现两条面积比为2:1或1:2的条带。基于对7个STR标记的分析，14份羊水样本和26份外周血样本被判定为DS阳性。（2）978份羊水样本中，961份（98.3%）成功进行了细胞遗传学分析，其中44份核型异常。包括14例21三体（12例标准型、1例嵌合型和1例易位型）。17例羊水细胞培养失败的病例经胎儿血液核型分析为正常。（3）82份外周血样本均成功进行了细胞遗传学分析，共检出30例（36.6%）核型异常，其中26例为21三体（包括4例易位型）。（4）DS阳性病例中，STR 1-4显示三条面积比为1:1:1的条带，或有2-4个位点出现两条面积比为2:1或1:2的条带。所有经PCR-STR检测出的DS病例均经核型分析证实。（5）所选的7个位点均具有信息性，杂合度在0.624至0.812之间。D21S2039和D21S1412的杂合度最高（>0.80），D21S1411和D21S1432的杂合度最低（<0.70）。D21S11和D21S2039出现面积比为1:1:1的三条条带的比率最高（≥40%）。然而，D21S1411、D21S1432和D21S1413标记的纯合率最高（≥30%）。