6616例脊髓性肌萎缩症携带者筛查及高风险胎儿产前诊断分析

Screening of 6616 Carriers of Spinal Muscular Atrophy and Analysis of Prenatal Genetic Diagnosis in High-Risk Fetus

目的:探讨脊髓性肌萎缩症(SMA)携带者筛查及产前诊断分析的临床价值。方法:应用多重PCR联合变性高效液相色谱法(PCR-DHPLC)技术和Sanger测序法对6616例孕妇(早孕产检孕妇6609例和具有SMA阳性家族史孕妇7例)进行SMN1、SMN2基因筛查与诊断,并对高风险胎儿进行产前基因分析。结果:①在6609例早孕产检孕妇中发现123例孕妇(检出率1.86%)可能是SMA的携带者,其中由于SMN1缺失形成的携带者84例(1.27%),SMN1转换成SMN2基因形成的携带者35例(0.53%),SMA携带者为SMN1∶SMN2=1∶0的样本4例(0.06%)。另外,丈夫同为SMA携带者21例(SMN1缺失形成的携带者14例,SMN1转换成SMN2基因形成的携带者7例)。②7例SMA阳性家族史孕妇中发现:2例先证者明确为SMN1基因exon7纯合缺失;4例先证者通过父母基因型推测可能为SMN1基因exon7纯合缺失;另1例SMA先证者通过PCR-DHPLC技术检测出SMN1基因exon7拷贝数为1,同时通过Sanger测序法发现该SMA先证者样本在SMN1基因上也存在c.570 G>A(p.Trp190*)杂合突变,为复合杂合突变。③对28例高风险胎儿进行产前基因诊断分析,其中SMN1基因型异常胎儿6例,胎儿可能为SAM携带者13例,胎儿基因型正常者9例。SMN1基因型异常胎儿6例均引产,16例出生后随访生长发育未见异常,4例继续妊娠,2例失访。结论:PCR-DHPLC技术可以对大部分人群和SMA患者进行筛查与诊断,且能对SMN1和SMN2拷贝数进行鉴定,少数复合杂合突变病例需要结合Sanger测序方法。对高风险家系孕妇行介入性产前基因诊断,对于优生优育、有效预防SMA胎儿的出生具有重要的临床意义。

Objective:To investigate the clinical value of SMN1 gene carrier screening for spinal muscular atrophy(SMA)and prenatal genetic diagnosis.Methods:Multiplex PCR combined with denaturing high performance liquid chromatography(PCR-DHPLC)and Sanger sequencing methods were performed on 6616 pregnant women,among them 6609 pregnant women were in the first trimester,7 pregnant women with SMA positive family history.Screening and diagnosis of SMN1 and SMN2 gene were performed in all of these pregnant women and prenatal genetic analysis was performed on high-risk fetuses.Results:①Among the 6609 pregnant women in the first trimester,123 pregnant women were SMA carriers,with a detection rate of 1.86%.There were 84 cases(1.27%)of carriers formed by SMN1 deletion.SMN1 was converted into carriers of SMN2 gene formation in 35 cases(0.53%)and 4 cases(0.06%)of SMA carriers were SMN1∶SMN2=1∶0.In addition,there was 21 cases with the husband carriers of SMA(14 carriers with SMN1 deletion,7 carriers with SMN1 converted to SMN2 gene formation).②Of the 7 cases with SMA positive family history,2 probands were identified as homozygous deletion of SMN1 gene exon7.4 probands were speculated to be homozygous deletion of exon7 gene of SMN1 through parental genotype.Another SMA proband detected by the exon7 copy number of SMN1 gene as 1 by PCR-DHPLC,and the SMA proband also had the c.570 G>A(p.Trp190*)heterozygous mutation on SMN1 gene,which was a complex heterozygous mutation by Sanger sequencing.③Analysis of prenatal genetic diagnosis was conducted on 28 high-risk fetuses.Among them,6 fetuses with abnormal SMN1 genotype,13 fetuses may be SAM carriers,and 9 fetuses with normal genotype.6 fetuses with abnormal SMN1 genotype were induced to abortion,16 fetuses were followed up with no abnormal growth and development after birth,4 fetuses were with continued pregnancy,and 2 fetuses were lost to follow-up.Conclusions:PCR-DHPLC technology can screen and diagnose most of the population and SMA patients,and can identify the copy number of SMN1 and SMN2.A few complex heterozygous mutations cases need to be diagnosed combined with Sanger sequencing.Interventional prenatal gene diagnosis for high-risk pregnant women is with great clinical significance for eugenics and effective prevention of SMA fetus.