Identification of Large Gene Deletions and Duplications in KCNQ1 and KCNH2 in Patients With Long QT Syndrome

Heart Rhythm. 2008 Sep;5(9):1275-81. doi: 10.1016/j.hrthm.2008.05.033. Epub 2008 Jun 4.

Abstract

Background: Sequencing or denaturing high-performance liquid chromatography (dHPLC) analysis of the known genes associated with the long QT syndrome (LQTS) fails to identify mutations in approximately 25% of subjects with inherited LQTS. Large gene deletions and duplications can be missed with these methodologies.

Objective: The purpose of this study was to determine whether deletions and/or duplications of one or more exons of the main LQTS genes were present in an LQTS mutation-negative cohort.

Methods: Multiplex ligation-dependent probe amplification (MLPA), a quantitative fluorescent approach, was used to screen 26 mutation-negative probands with an unequivocal LQTS phenotype (Schwartz score >4). The appropriate MLPA kit contained probes for selected exons in LQTS genes KCNQ1, KCNH2, SCN5A, KCNE1, and KCNE2. Real-time polymerase chain reaction was used to validate the MLPA findings.

Results: Altered exon copy number was detected in 3 (11.5%) patients: (1) an ex13-14del of the KCNQ1 gene in an 11-year-old boy with exercise-induced collapse (QTc 580 ms); (2) an ex6-14del of the KCNH2 gene in a 22-year-old woman misdiagnosed with epilepsy since age 9 years (QTc 560 ms) and a sibling with sudden death at age 13 years; and (3) an ex9-14dup of the KCNH2 gene in a 12 year-old boy (QTc 550 ms) following sudden nocturnal death of his 32-year-old mother.

Conclusion: If replicated, this study demonstrates that more than 10% of patients with LQTS and a negative current generation genetic test have large gene deletions or duplications among the major known LQTS susceptibility genes. As such, these findings suggest that sequencing-based mutation detection strategies should be followed by deletion/duplication screening in all LQTS mutation-negative patients.

Publication types

  • Case Reports
  • Multicenter Study
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Adolescent
  • Adult
  • Child
  • ERG1 Potassium Channel
  • Ether-A-Go-Go Potassium Channels / genetics*
  • Female
  • Gene Deletion*
  • Genotype
  • Humans
  • KCNQ1 Potassium Channel / genetics*
  • Long QT Syndrome / genetics*
  • Male
  • Middle Aged
  • Mutation
  • Nucleic Acid Amplification Techniques
  • Pedigree
  • Pilot Projects
  • Risk Factors
  • Young Adult

Substances

  • ERG1 Potassium Channel
  • Ether-A-Go-Go Potassium Channels
  • KCNH2 protein, human
  • KCNQ1 Potassium Channel
  • KCNQ1 protein, human