Abstract
Variable transcription of the cardiac sodium channel gene is a candidate mechanism determining arrhythmia susceptibility. We have previously cloned and characterized the core promoter and flanking region of SCN5A, encoding the cardiac sodium channel. Loss-of-function mutations in this gene have been reported in ∼20% of patients with Brugada syndrome, an inherited cardiac electrical disorder associated with a high incidence of life-threatening arrhythmias. In this study, we identified DNA variants in the proximal 2.8 kb promoter region of SCN5A and determined their frequency in 1121 subjects. This population consisted of 88 Brugada syndrome patients with no SCN5A coding region mutation, and 1033 anonymized subjects from various ethnicities. Variant promoter activity was assayed in CHO cells and neonatal cardiomyocytes by transient transfection of promoter–reporter constructs. Single-nucleotide polymorphisms (SNPs) were identified at ∼1/200 base pairs which are: 11 in the 5′-flanking region, 1 in exon 1, and 5 in intron 1. In addition, a haplotype consisting of two SNPs in complete linkage disequilibrium was identified. Minor allele frequencies were >5% in at least one ethnic panel at 5/19 polymorphic sites. In vitro functional analysis in cardiomyocytes identified four variants with significantly (P<0.05) reduced reporter activity (up to 63% reduction). The largest changes were seen with c.−225−1790 G>A, which reduced reporter activity by 62.8% in CHO cells and 55% in cardiomyocytes. From these results, we can conclude that the SCN5A core promoter includes multiple DNA polymorphisms with altered in vitro activity, further supporting the concept of interindividual variability in transcription of this cardiac ion channel gene.
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Acknowledgements
This work was supported by NIH Grants HL46681 and HL65962, Netherlands Heart Foundation Grants 2003B195 (CRB) and 2003T302 (AAMW), the Interuniversity Cardiology Institute of the Netherlands (project 27, AAMW), and BMBF Grants 01GI0204, 01GS0499 (SK, AP). Dr Roden is the William Stokes Professor of Experimental Therapeutics. Dr Bezzina is an Established Investigator of the Netherlands Heart Foundation (Grant 2005/T024).
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Yang, P., Koopmann, T., Pfeufer, A. et al. Polymorphisms in the cardiac sodium channel promoter displaying variant in vitro expression activity. Eur J Hum Genet 16, 350–357 (2008). https://doi.org/10.1038/sj.ejhg.5201952
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DOI: https://doi.org/10.1038/sj.ejhg.5201952
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