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Rev Esp Cardiol (Engl Ed). 2018 Apr 21. pii: S1885-5857(18)30098-7. doi: 10.1016/j.rec.2018.03.012. [Epub ahead of print]

Digenic Heterozigosity in SCN5A and CACNA1C Explains the Variable Expressivity of the Long QT Phenotype in a Spanish Family.

[Article in English, Spanish]

Author information

1
Departamento de Farmacología, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, CIBERCV, Madrid, Spain.
2
Unidad de Arritmias, Hospital Universitario Virgen de las Nieves, Instituto de Investigación Biosanitaria de Granada, Granada, Spain.
3
Departamento de Cardiología Pediátrica, Hospital Universitario Virgen de las Nieves, Granada, Spain.
4
Departamento de Cardiología Pediátrica, Hospital San Joan de Déu, Hospitalet de Llobregat, Barcelona, Spain.
5
Departamento de Cardiología, Health in Code, A Coruña, Spain.
6
Departamento de Farmacología, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, CIBERCV, Madrid, Spain. Electronic address: edelpon@med.ucm.es.

Abstract

INTRODUCTION AND OBJECTIVES:

A known long QT syndrome-related mutation in Nav1.5 cardiac channels (p.R1644H) was found in 4 members of a Spanish family but only 1 of them showed prolongation of the QT interval. In the other 3 relatives, a novel missense mutation in Cav1.2 cardiac channels was found (p.S1961N). Here, we functionally analyzed p.S1961N Cav1.2 channels to elucidate whether this mutation regulates the expressivity of the long QT syndrome phenotype in this family.

METHODS:

L-type calcium current (ICaL) recordings were performed by using the whole-cell patch-clamp technique in Chinese hamster ovary cells transiently transfected with native and/or p.S1961N Cav1.2 channels.

RESULTS:

Expression of p.S1961N channels significantly decreased ICaL density. Using Ba as a charge carrier to suppress the Ca-dependent inactivation of Cav1.2 channels, we demonstrated that the mutation significantly accelerates the voltage-dependent inactivation of Cav1.2 channels decreasing the inactivation time constant. As a consequence, the total charge flowing through p.S1961N Cav1.2 channels significantly decreased. The effects of the p.S1961N Cav1.2 and p.R1644H Nav1.5 mutations alone or their combination on the action potential (AP) morphology were simulated using a validated model of the human ventricular AP. The p.S1961N Cav1.2 mutation shortens the AP duration and abrogates the prolongation induced by p.R1644H Nav1.5 channels.

CONCLUSIONS:

The p.S1961N mutation in Cav1.2 channels decreased the ICaL, an effect which might shorten ventricular AP. The presence of the loss-of-function Cav1.2 mutation could functionally compensate the prolonging effects produced by the Nav1.5 gain-of-function mutation.

KEYWORDS:

CACNA1C; Canalopatías; Cav1.2; Channelopathies; I(CaL); I(NaL); Long QT syndrome; Nav1.5; Patch-clamp; SCN5A; Síndrome de QT largo

PMID:
29691127
DOI:
10.1016/j.rec.2018.03.012

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