Dong Ling Liu, MD,PhD(*); Ming Yan MD,PhD; Wuxiang Liao, PhD and Yean Leng Lim, MD,PhD. Cardiac Research Laboratory, National Heart Centre, Outram Road, Singapore and Department of Obstetrics and Gynaecology, National University of Singapore, Kent Ridge, Singapore.
PURPOSE: Long QT (LQT) syndrome is a cardiac disorder that causes sudden death from ventricular tachyarrhythmias. Four LQT genes have been identified: KVLQT1 (LQT1, a cardiac potassium channel subunit gene), HERG (LQT2, a cardiac potassium channel gene), SCN5A (LQT3, a cardiac sodium channel gene) and Mink (LQT5, a cardiac potassium channel subunit gene). The aim of this study is to identify whether there are the mutations of KVLQT1 and SCN5A in a long-QT syndrome family in Singapore.
METHODS: We investigated the mutations of KVLQT1 and SCN5A genes by using polymerase chain reaction (PCR), restriction endonuclease analysis and gene sequencing in a LQT syndrome family in Singapore. Approval to use the blood samples was given by ethics Committee of Singapore General Hospital. The blood samples were obtained from a LQT syndrome family involved in 11 cases who three of them are LQT patients. 8 health people are as a control group. Genomic DNA was isolated from peripheral blood leukocytes. Oligonucleotide primer pairs were used to amplify to KVLQT1 pre-S6 and the SCN5A-coding region (exons 23 and 28) respectively. The restriction endonucleases (Hha I, Sty I and HgaI) and gene sequencing have been used to define KVLQT1 and SCN5A mutations respectively.
RESULTS: The results showed that the 195bp PCR products were cleaved into 129bp and 66bp fragments by using Hha I restriction endonuclease and the mutation point of A212E of KVLQT1 was not detected in the family. This was confirmed by gene sequencing. The mutation points at T1620M of the exons 28 and the codon 1397 of exon 23 of SCN5A were not found by using HagI and StyI restriction endonuclease and gene sequencing in the LQT syndrome family.
CONCLUSION: The mutation points of A212E of KVLQT1, T1620M of exons 28 and the codon 1397 of exon 23 of SCN5A were not detected in a LQT family of Singapore.
CLINICAL IMPLICATIONS: The molecular genetic testing may provide a diagnosis of or indication of risk for patients and relatives.
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