摘要
目的探索将测序技术应用于缺失型脊髓性肌萎缩症(SMA)基因诊断的可行性。方法设计2对引物,PCR扩增SMA致病基因运动神经元生存基因(SMN1)与其同源基因SMN2之间5个不同碱基所在区域,第1对引物正向扩增SMN1内含子6至7间长度为501 bp片段,包含4个不同碱基位点g.31957、32006、32154及32269;第2对引物反向扩增SMN1外显子8区域,长度为189 bp,包含1个不同碱基位点g.32734。根据测序图谱区分SMA患者与携带者和(或)正常人。将此方法应用于7个临床疑似SMA家系的诊断,并与聚合酶链反应-限制性片段长度多态性分析(PCR-RFLP)法进行比较。结果 6例测序图谱显示SMN内含子6至外显子8之间5个SMN1和SMN2差异位点g.31957、32006、32154、32269及32734均只有SMN2特有碱基a、T、g、g和A,患儿父母(携带者)相同位点显示为a/g、T/C、g/a、g/a和A/G。说明患者缺失SMN1基因,缺失范围包括内含子6至外显子8;携带者则既有SMN1基因,又有SMN2基因,与患者能区分开。1例检测结果为a、T、g、g和A/G,说明其缺失范围不含外显子8。测序法与PCR-RFLP方法结果一致。结论测序技术在缺失型SMA患者的基因诊断上优于经典PCR-RFLP法,更方便快捷,结果更明确,建议替代常用的PCR-RFLP法。
Objective To investigate the feasibility of DNA sequencing analysis in molecular diagnosis for spinal muscular atrophy （SMA）. Methods Two pairs of primers were utilized to amplify the region including 5 different bases in SMA-causative gene SMN1 and its homologue copy SMN2 by polymerase chain reaction （PCR）. The first primer amplified a fragment 501 bp long spanning from SMN intron 6 to intron 7 targeting four different bases （g.31957, 32006, 32154 and 32269）. The second primer reversely amplified a 189 bp long fragment within SMN exon 8 including one base-pair differ-ence （g.32734）. PCR procedure was followed by Sanger sequencing technique to identify the 5 different bases. SMA patients caused by SMN1 homozygous deletion were distinguished from carriers or normal controls by absence of SMN1 specific bas-es in sequence chromatograms. This assay was performed in 7 SMA suspected patients and their parents. The specimens were also detected by PCR- restriction fragment length polymorphism （RFLP） method. Results It was found that 6 of 7 SMA suspected patients showed only SMN2 specific bases at the 5 different base positions among the region from intron 6 to exon 8, which meant the patient displaying only SMN2-specific nucleotide a, T, g, g and A at g.31957, 32006, 32154, 32269 and 32734, while their parents （carriers） showed a/g, T/C, g/a, g/a and A/G at the same sites. SMN1 gene was deleted in the patient, and the deletion region was inferred from intron 6 to exon 8. Because carriers had both SMN1 and SMN2 genes, they can be discriminated from the SMN1 deleted patient. One of 7 patients yield an unique sequence chromatogram of a, T, g, g and A/G, indicating that exon 8 of SMN1 was not deleted in this patient. Conclusion DNA sequencing analysis is an alter-native simple method for detecting SMA caused by homozygous deletion of SMN1. We recommend to replace the widely used PCR-RFLP method with DNA sequencing assay.
出处
《天津医药》
CAS
北大核心
2014年第7期697-700,共4页
Tianjin Medical Journal
基金
天津市卫生局科技基金资助项目(2011KZ34)
关键词
脊髓性肌萎缩
儿童
序列分析
DNA
多态性
限制性片段长度
基因诊断
SMN基因
spinal muscular atrophies of childhood
sequence analysis, DNA
polymorphism, restriction fragmentlength
genetic testing
SMN gene
