Sequencing Technology in Molecular Diagnosis of Spinal Muscular Atrophy Caused by SMN1 Deletion
10.3969/j.issn.0253-9896.2014.07.021
- VernacularTitle:测序技术在缺失型脊髓性肌萎缩症基因诊断中的应用
- Author:
Yingtao MENG
;
Jianbo SHU
- Publication Type:Journal Article
- Keywords:
spinal muscular atrophies of childhood;
sequence analysis,DNA;
polymorphism,restriction fragment length;
genetic testing;
SMN gene
- From:
Tianjin Medical Journal
2014;(7):697-700
- CountryChina
- Language:Chinese
-
Abstract:
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.
