Heart Rhythm
Volume 9, Issue 5 , Pages 760-769, May 2012

A novel rare variant in SCN1Bb linked to Brugada syndrome and SIDS by combined modulation of Nav1.5 and Kv4.3 channel currents

  • Dan Hu, MD, PhD

      Affiliations

    • Masonic Medical Research Laboratory, Utica, New York
    • ,
  • Hector Barajas-Martínez, PhD

      Affiliations

    • Masonic Medical Research Laboratory, Utica, New York
    • ,
  • Argelia Medeiros-Domingo, MD, PhD

      Affiliations

    • Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
    • ,
  • Lia Crotti, MD, PhD

      Affiliations

    • Department of Lung, Blood and Heart, Section of Cardiology, University of Pavia, Pavia, Italy
    • Institute of Human Genetics, Helmholtz Zentrum Muenchen, Neuherberg, Germany
    • Department of Cardiology, IRCCS Policlinico S. Matteo, Pavia, Italy
    • ,
  • Christian Veltmann, MD

      Affiliations

    • University Medical Centre Mannheim, Mannheim, Germany
    • ,
  • Rainer Schimpf, MD

      Affiliations

    • University Medical Centre Mannheim, Mannheim, Germany
    • ,
  • Janire Urrutia, PhD

      Affiliations

    • Department of Physiology, Universidad del País Vasco, Leioa, Spain
    • ,
  • Aintzane Alday, PhD

      Affiliations

    • Department of Physiology, Universidad del País Vasco, Leioa, Spain
    • ,
  • Oscar Casis, MD, PhD

      Affiliations

    • Department of Physiology, Universidad del País Vasco, Leioa, Spain
    • ,
  • Ryan Pfeiffer, BS

      Affiliations

    • Masonic Medical Research Laboratory, Utica, New York
    • ,
  • Elena Burashnikov, BS

      Affiliations

    • Masonic Medical Research Laboratory, Utica, New York
    • ,
  • Gabriel Caceres, BS

      Affiliations

    • Masonic Medical Research Laboratory, Utica, New York
    • ,
  • David J. Tester, BS

      Affiliations

    • Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
    • ,
  • Christian Wolpert, MD

      Affiliations

    • Department of Medicine-Cardiology, Klinikum Ludwigsburg, Ludwigsburg, Germany
    • ,
  • Martin Borggrefe, MD

      Affiliations

    • University Medical Centre Mannheim, Mannheim, Germany
    • ,
  • Peter Schwartz, MD

      Affiliations

    • Department of Lung, Blood and Heart, Section of Cardiology, University of Pavia, Pavia, Italy
    • Department of Cardiology, IRCCS Policlinico S. Matteo, Pavia, Italy
    • Laboratory of Cardiovascular Genetics, IRCCS Istituto Auxologico Italiano, Milan, Italy
    • Department of Medicine, Cardiovascular Genetics Laboratory, Hatter Institute for Cardiovascular Research, University of Cape Town, South Africa
    • Department of Medicine, University of Stellenbosch, Stellenbosh, South Africa
    • Chair of Sudden Death, Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
    • ,
  • Michael J. Ackerman, MD, PhD

      Affiliations

    • Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota
    • ,
  • Charles Antzelevitch, PhD, FAHA, FACC, FHRS

      Affiliations

    • Masonic Medical Research Laboratory, Utica, New York
    • Corresponding Author InformationAddress for reprint requests and correspondence: Dr Charles Antzelevitch, PhD, FAHA, FACC, FHRS, Masonic Medical Research Laboratory, 2150 Bleecker St, Utica, NY 13501

published online 08 December 2011.

Background

Cardiac sodium channel β-subunit mutations have been associated with several inherited cardiac arrhythmia syndromes.

Objective

To identify and characterize variations in SCN1Bb associated with Brugada syndrome (BrS) and sudden infant death syndrome (SIDS).

Methods

All known exons and intron borders of the BrS-susceptibility genes were amplified and sequenced in both directions. Wild type (WT) and mutant genes were expressed in TSA201 cells and studied using co-immunoprecipitation and whole-cell patch-clamp techniques.

Results

Patient 1 was a 44-year-old man with an ajmaline-induced type 1 ST-segment elevation in V1 and V2 supporting the diagnosis of BrS. Patient 2 was a 62-year-old woman displaying a coved-type BrS electrocardiogram who developed cardiac arrest during fever. Patient 3 was a 4-month-old female SIDS case. A R214Q variant was detected in exon 3A of SCN1Bb (Nav1B) in all three probands, but not in any other gene previously associated with BrS or SIDS. R214Q was identified in 4 of 807 ethnically-matched healthy controls (0.50%). Co-expression of SCN5A/WT + SCN1Bb/R214Q resulted in peak sodium channel current (INa) 56.5% smaller compared to SCN5A/WT + SCN1Bb/WT (n = 11–12, P<0.05). Co-expression of KCND3/WT + SCN1Bb/R214Q induced a Kv4.3 current (transient outward potassium current, Ito) 70.6% greater compared with KCND3/WT + SCN1Bb/WT (n = 10–11, P<0.01). Co-immunoprecipitation indicated structural association between Navβ1B and Nav1.5 and Kv4.3.

Conclusion

Our results suggest that R214Q variation in SCN1Bb is a functional polymorphism that may serve as a modifier of the substrate responsible for BrS or SIDS phenotypes via a combined loss of function of sodium channel current and gain of function of transient outward potassium current.

Keywords:  Brugada syndrome , Sudden infant death syndrome , Arrhythmias , SCN1Bb , Sodium , Potassium

Abbreviations:  AP, action potential, AV, atrioventricular, BrS, Brugada syndrome, ECG, electrocardiogram, INa, sodium channel current, Ito, transient outward potassium current, SCD, sudden cardiac death, SIDS, sudden infant death syndrome, WT, wild type

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 Dr Antzelevitch was supported by a grant from the National, Heart, Lung, and Blood Institute (grant number HL47678), grants from NYSTEM, and the Masons of New York State and Florida. Dr Ackerman was supported by the Mayo Clinic Windland Smith Rice Comprehensive Sudden Cardiac Death Program and the National Institutes of Health (grant number HD42569). Dr Casis was supported by a grant from MICINN (grant number SAF2010-16120/).

 The first four authors contributed equally.

 Dr Ackerman is a consultant for Transgenomic and its FAMILION genetic test for cardiac ion channel abnormalities. In addition, “cardiac channel gene screen” and “know-how relating to long QT genetic testing” license agreements, resulting in consideration and royalty payments, were established between Genaissance Pharmaceuticals (then PGxHealth and now Transgenomic, Omaha, Neb) and Mayo Medical Ventures (now Mayo Clinic Health Solutions, Rochester, Minn) in 2004. However, Transgenomic did not provide financial support for this study. The other authors have no financial or other considerations to disclose.

PII: S1547-5271(11)01461-5

doi:10.1016/j.hrthm.2011.12.006

Heart Rhythm
Volume 9, Issue 5 , Pages 760-769, May 2012

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