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Heart Rhythm. 2014 Jun;11(6):1015-1023. doi: 10.1016/j.hrthm.2014.02.021. Epub 2014 Feb 25.

A truncating SCN5A mutation combined with genetic variability causes sick sinus syndrome and early atrial fibrillation.

Author information

1
INSERM, UMR_S1166, Paris, France.
2
Sorbonne Universités, UPMC Univ Paris 06, UMR_S1166, Institute of Cardiometabolism and Nutrition (ICAN), Paris, France.
3
Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, OH, USA.
4
AP-HP, Hôpital Pitié-Salpêtrière, Département de Cardiologie, Paris, France.
5
AP-HP, Hôpital Bichat, Département de Cardiologie, Centre de Référence des Maladies Cardiaques Héréditaires, Paris, France.
#
Contributed equally

Abstract

BACKGROUND:

Mutations in the SCN5A gene, encoding the α subunit of the cardiac Na(+) channel, Nav1.5, can result in several life-threatening arrhythmias.

OBJECTIVE:

To characterize a distal truncating SCN5A mutation, R1860Gfs*12, identified in a family with different phenotypes including sick sinus syndrome, atrial fibrillation (AF), atrial flutter, and atrioventricular block.

METHODS:

Patch-clamp and biochemical analyses were performed in human embryonic kidney 293 cells transfected with wild-type (WT) and/or mutant channels.

RESULTS:

The mutant channel expressed alone caused a 70% reduction in inward sodium current (INa) density compared to WT currents, which was consistent with its partial proteasomal degradation. It also led to a negative shift of steady-state inactivation and to a persistent current. When mimicking the heterozygous state of the patients by coexpressing WT and R1860Gfs*12 channels, the biophysical properties of INa were still altered and the mutant channel α subunits still interacted with the WT channels. Since the proband developed paroxysmal AF at a young age, we screened 17 polymorphisms associated with AF risk in this family and showed that the proband carries at-risk polymorphisms upstream of PITX2, a gene widely associated with AF development. In addition, when mimicking the difference in resting membrane potentials between cardiac atria and ventricles in human embryonic kidney 293 cells or when using computer model simulations, R1860Gfs*12 induced a more drastic decrease in INa at the atrial potential.

CONCLUSION:

We have identified a distal truncated SCN5A mutant associated with gain- and loss-of-function effects, leading to sick sinus syndrome and atrial arrhythmias. A constitutively higher susceptibility to arrhythmias of atrial tissues and genetic variability could explain the complex phenotype observed in this family.

KEYWORDS:

Arrhythmia; Atrial fibrillation; Na(v)1.5; PITX2; Polymorphism; SCN5A; SNP; Sodium

PMID:
24582607
PMCID:
PMC4056672
DOI:
10.1016/j.hrthm.2014.02.021
[Indexed for MEDLINE]
Free PMC Article

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