Contents lists available at ScienceDirect Gene journal homepage: www.elsevier.com/locate/gene Research paper Compound heterozygous KCNQ1 mutations (A300T/P535T) in a child with sudden unexplained death: Insights into possible molecular mechanisms based on protein modeling Erika Antúnez-Argüelles a , Arturo Rojo-Domínguez b , Ana Leticia Arregui-Mena b , Leonor Jacobo-Albavera a , Manlio Fabio Márquez c , Pedro Iturralde-Torres c , María Teresa Villarreal-Molina a,⁎ a Laboratorio de Genómica de Enfermedades Cardiovasculares, Instituto Nacional de Medicina Genómica, Mexico b Departamento de Ciencias Naturales, Universidad Autónoma Metropolitana Unidad Cuajimalpa, Mexico c Departamento de Electrofisiología, Instituto Nacional de Cardiología “Ignacio Chávez”, Mexico ARTICLE INFO Keywords: Molecular autopsy Recessive Romano Ward syndrome KCNQ1 Protein modeling ABSTRACT Sudden death in a child is a devastating event with important medical implications for surviving relatives. Because it may be the first manifestation of unknown inherited cardiac disease, molecular autopsy can be helpful to determine the cause of death and identify at risk family members. The aim of the study was to perform a molecular autopsy in a seven year-old girl with sudden unexplained death, to find evidence supporting the possible pathogenicity of mutations identified in inherited cardiac disease genes, and to clinically and genetically assess first-degree relatives. DNA from the index case was extracted from umbilical cord cells stored at birth, and DNA of first-degree relatives from blood samples. Targeted sequencing was performed using a Haloplex design including 81 cardiogenes. Possible functional consequences of the mutations were analyzed using protein modeling and structural mobility analyses. The child was compound heterozygous for KCNQ1 variants p.Ala300Thr and p.Pro535Thr. Ala300Thr is known to cause long QT syndrome in the homozygous state, while Pro535Thr is novel and of unknown clinical significance. The father and sibling were Ala300Thr heterozygous, and had normal QTc intervals at rest and during exercise. The asymptomatic mother was heterozygous for Pro535Thr, and showed borderline QTc at rest, but prolonged QTc during exercise. Protein modeling predicted that Ala300Thr alters the mobility profile of the Kv7.1 tetramer and Thr535 disrupts a calmodulin-binding site, probably causing co-assembly or trafficking defects of the mutant monomer. Altogether, the evidence strongly suggests that this child was affected with a recessive form of Romano Ward syndrome. 1. Introduction Sudden cardiac death (SCD) is a major cause of premature death in young adults and children (Michaud et al., 2009). If death remains unexplained after a thorough medical and legal investigation including autopsy, histopathology and toxicology, it is referred to as sudden un- explained death (SUD) (Christiansen et al., 2016). Post-mortem genetic testing, also known as molecular autopsy, has revealed that a sub- stantial number of these deaths are the result of inherited cardiac dis- ease, including arrhythmic channelopathies such as congenital long QT syndrome (LQTS) (Michaud et al., 2009; Steinberg et al., 2016). Thus, comprehensive or targeted genetic testing should be considered to es- tablish probable cause of death and to facilitate the identification of potentially at-risk relatives. A molecular autopsy in unexplained death is of uttermost im- portance for surviving relatives, particularly because surrogate genetic testing can lead to serious mistakes (Ackerman, 2016). Diagnostic yield of inherited cardiomyopathies or channelopathies varies widely, and a negative test does not exclude inherited cardiac disease (Tester & Ackerman, 2005; Tester & Ackerman, 2012; Hoffman, 2013; http://dx.doi.org/10.1016/j.gene.2017.06.011 Received 6 April 2017; Received in revised form 18 May 2017; Accepted 5 June 2017 ⁎ Corresponding author at: Instituto Nacional de Medicina Genómica, Periférico Sur 4809 Colonia Arenal Tepepan, CP14610, Delegación Tlalpan Mexico City, Mexico. E-mail address: mvillareal@inmegen.gob.mx (M.T. Villarreal-Molina). Abbreviations: aa, amino acid; BWA, Burrows-Wheeler aligner; CaM, calmodulin; CPR, cardiopulmonary resuscitation; DNA, deoxyribonucleic acid; ECG, electrocardiogram; GOF, gain of function; KCNE1, potassium voltage-gated channel subfamily E member 1; Kv7.1, voltage-gated potassium channel 7.1; Kv2.1, voltage-gated potassium channel 2.1; LQTS, long QT syndrome; minK, minimal potassium channel subunit; MOE, molecular operating environment; ms, milliseconds; NGS, next generation sequencing; QTc, corrected QT interval; RMSD, root mean square distance; SCD, sudden cardiac death; SUD, sudden unexplained death; TM, transmembrane; VUS, variant of unknown clinical significance; PDB, Protein Data Bank; VSD, voltage sensor domain; WT, wildtype Gene 627 (2017) 40–48 0378-1119/ © 2017 Elsevier B.V. All rights reserved. MARK