Allelic dropout in long QT syndrome genetic testing: A possible mechanism underlying false-negative results

被引:36
作者
Tester, David J.
Cronk, Lisa B.
Carr, Janet L.
Schulz, Vincent
Salisbury, Benjamin A.
Judson, Richard S.
Ackerman, Michael J.
机构
[1] Mayo Clin & Mayo Fdn, Sudden Death Genom Lab, Dept Internal Med, Coll Med, Rochester, MN 55905 USA
[2] Mayo Clin & Mayo Fdn, Dept Pediat, Coll Med, Rochester, MN 55905 USA
[3] Mayo Clin & Mayo Fdn, Dept Mol Pharmacol & Expt Therapeut, Coll Med, Rochester, MN 55905 USA
[4] Mayo Clin & Mayo Fdn, Div Cardiovasc Dis & Pediat Cardiol, Coll Med, Rochester, MN 55905 USA
[5] Genaissance Pharmaceut, New Haven, CT USA
关键词
long QT syndrome; genetics; polymerase chain reaction;
D O I
10.1016/j.hrthm.2006.03.016
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
Background Genetic testing for congenital Long QT syndrome (LQTS) has been performed in research Laboratories for the past decade. Approximately 75% of patients with high clinical probability for LQTS have a mutation in one of five LQTS-causing cardiac channel genes. Possible explanations for the remaining genotypenegative cases include LQTS mimickers, novel LQTS-causing genes, unexplored regions of the known genes, and genetic testing detection failures. Objectives The purpose of this study was to explore the possibility of allelic dropout as a possible mechanism underlying false-negative test results. Methods The published primers currently used by many research laboratories to conduct a comprehensive analysis of the 60 translated exons in the KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6) genes were analyzed for the presence of common intronic single nucleotide polymorphisms (SNPs). Repeat mutational analysis, following primer/amplicon redesign using polymerase chain reaction, denaturing high-performance liquid chromatography, and DNA sequencing, was performed on a cohort of 541 consecutive, unrelated patients referred for LQTS genetic testing. Results Common (>1% minor allele frequency) intronic SNPs were discovered within the primer sequences of five of 60 translated exons. Following primer redesign to eliminate the possibility of allelic dropout, four previously genotype-negative index cases were found to possess LQTS-causing mutations: R591H-KCNQ1 and R594Q-KCNQ1 for exon 15 and E229X-KCNH2 in two unrelated cases. Repeat examination of these two amplicons in 400 reference alleles did not identify these or any additional amino acid variants. Conclusion Allelic dropout secondary to intronic SNP-primer mismatch prevented the discovery of LQTS-causing mutations in four cases. Considering that many LQTS genetic testing research laboratories have used these primers, patients who reportedly are genotype negative may benefit from re-examination of those regions susceptible to allelic dropout due to primer-disrupting SNPs, particularly exon 15 in KCNQ1 and exon 4 in KCNH2.
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页码:815 / 821
页数:7
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