RESUMEN

Rare genetic diseases are typically studied in referral populations, resulting in underdiagnosis and biased assessment of penetrance and phenotype. To address this, we develop a generalizable method of genotype inference based on distant relatedness and deploy this to identify undiagnosed Type 5 Long QT Syndrome (LQT5) rare variant carriers in a non-referral population. We identify 9 LQT5 families referred to a single specialty clinic, each carrying p.Asp76Asn, the most common LQT5 variant. We uncover recent common ancestry and a single shared haplotype among probands. Application to a non-referral population of 69,819 BioVU biobank subjects identifies 22 additional subjects sharing this haplotype, which we confirm to carry p.Asp76Asn. Referral and non-referral carriers have prolonged QT interval corrected for heart rate (QTc) compared to controls, and, among carriers, the QTc polygenic score is independently associated with QTc prolongation. Thus, our innovative analysis of shared chromosomal segments identifies undiagnosed cases of genetic disease and refines the understanding of LQT5 penetrance and phenotype.

Asunto(s)

Bancos de Muestras Biológicas , Haplotipos , Síndrome de QT Prolongado , Humanos , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/diagnóstico , Femenino , Masculino , Adulto , Penetrancia , Persona de Mediana Edad , Fenotipo , Linaje , Predisposición Genética a la Enfermedad , Genotipo , Electrocardiografía

Asunto(s)

Electrocardiografía , Discapacidad Intelectual , Síndrome de QT Prolongado , Mutación , Acetiltransferasa A N-Terminal , Acetiltransferasa E N-Terminal , Humanos , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/diagnóstico , Discapacidad Intelectual/genética , Niño , Acetiltransferasa E N-Terminal/genética , Acetiltransferasa A N-Terminal/genética , Masculino , Propranolol/uso terapéutico , Exones , Heterocigoto , Femenino

Asunto(s)

Trastorno Autístico , Modelos Animales de Enfermedad , Síndrome de QT Prolongado , Sindactilia , Animales , Humanos , Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatología , Trastorno Autístico/genética , Trastorno Autístico/fisiopatología , Discapacidades del Desarrollo/genética , Técnicas de Sustitución del Gen , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/fisiopatología , Síndrome de QT Prolongado/diagnóstico , Porcinos , Sindactilia/genética

RESUMEN

BACKGROUND: The KCNQ1+KCNE1 (IKs) potassium channel plays a crucial role in cardiac adaptation to stress, in which ß-adrenergic stimulation phosphorylates the IKs channel through the cyclic adenosine monophosphate (cAMP)/PKA (protein kinase A) pathway. Phosphorylation increases the channel current and accelerates repolarization to adapt to an increased heart rate. Variants in KCNQ1 can cause long-QT syndrome type 1 (LQT1), and those with defective cAMP effects predispose patients to the highest risk of cardiac arrest and sudden death. However, the molecular connection between IKs channel phosphorylation and channel function, as well as why high-risk LQT1 mutations lose cAMP sensitivity, remain unclear. METHODS: Regular patch clamp and voltage clamp fluorometry techniques were utilized to record pore opening and voltage sensor movement of wild-type and mutant KCNQ1/IKs channels. The clinical phenotypic penetrance of each LQT1 mutation was analyzed as a metric for assessing their clinical risk. The patient-specific-induced pluripotent stem-cell model was used to test mechanistic findings in physiological conditions. RESULTS: By systematically elucidating mechanisms of a series of LQT1 variants that lack cAMP sensitivity, we identified molecular determinants of IKs channel regulation by phosphorylation. These key residues are distributed across the N-terminus of KCNQ1 extending to the central pore region of IKs. We refer to this pattern as the IKs channel PKA phosphorylation axis. Next, by examining LQT1 variants from clinical databases containing 10 579 LQT1 carriers, we found that the distribution of the most high-penetrance LQT1 variants extends across the IKs channel PKA phosphorylation axis, demonstrating its clinical relevance. Furthermore, we found that a small molecule, ML277, which binds at the center of the phosphorylation axis, rescues the defective cAMP effects of multiple high-risk LQT1 variants. This finding was then tested in high-risk patient-specific induced pluripotent stem cell-derived cardiomyocytes, where ML277 remarkably alleviates the beating abnormalities. CONCLUSIONS: Our findings not only elucidate the molecular mechanism of PKA-dependent IKs channel phosphorylation but also provide an effective antiarrhythmic strategy for patients with high-risk LQT1 variants.

Asunto(s)

Proteínas Quinasas Dependientes de AMP Cíclico , Células Madre Pluripotentes Inducidas , Canal de Potasio KCNQ1 , Humanos , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Fosforilación , Canal de Potasio KCNQ1/genética , Canal de Potasio KCNQ1/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Síndrome de Romano-Ward/genética , Síndrome de Romano-Ward/metabolismo , AMP Cíclico/metabolismo , Miocitos Cardíacos/metabolismo , Mutación , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/metabolismo , Células HEK293 , Canales de Potasio con Entrada de Voltaje

RESUMEN

KCNQ1, also known as Kv7.1, is a voltage gated potassium channel that associates with the KCNE protein family. Mutations in this protein has been found to cause a variety of diseases including Long QT syndrome, a type of cardiac arrhythmia where the QT interval observed on an electrocardiogram is longer than normal. This condition is often aggravated during strenuous exercise and can cause fainting spells or sudden death. KCNE1 is an ancillary protein that interacts with KCNQ1 in the membrane at varying molar ratios. This interaction allows for the flow of potassium ions to be modulated to facilitate repolarization of the heart. The interaction between these two proteins has been studied previously with cysteine crosslinking and electrophysiology. In this study, electron paramagnetic resonance (EPR) spectroscopy line shape analysis in tandem with site directed spin labeling (SDSL) was used to observe changes in side chain dynamics as KCNE1 interacts with KCNQ1. KCNE1 was labeled at different sites that were found to interact with KCNQ1 based on previous literature, along with sites outside of that range as a control. Once labeled KCNE1 was incorporated into vesicles, KCNQ1 (helices S1-S6) was titrated into the vesicles. The line shape differences observed upon addition of KCNQ1 are indicative of an interaction between the two proteins. This method provides a first look at the interactions between KCNE1 and KCNQ1 from a dynamics perspective using the full transmembrane portion of KCNQ1.

Asunto(s)

Canal de Potasio KCNQ1 , Canales de Potasio con Entrada de Voltaje , Canales de Potasio con Entrada de Voltaje/metabolismo , Canales de Potasio con Entrada de Voltaje/genética , Canales de Potasio con Entrada de Voltaje/química , Canal de Potasio KCNQ1/metabolismo , Canal de Potasio KCNQ1/genética , Canal de Potasio KCNQ1/química , Espectroscopía de Resonancia por Spin del Electrón/métodos , Unión Proteica , Humanos , Animales , Síndrome de QT Prolongado/metabolismo , Síndrome de QT Prolongado/genética

RESUMEN

The human ether-a-go-go-related gene (hERG) encodes the Kv11.1 (or hERG) channel that conducts the rapidly activating delayed rectifier potassium current (IKr). Naturally occurring mutations in hERG impair the channel function and cause long QT syndrome type 2. Many missense hERG mutations lead to a lack of channel expression on the cell surface, representing a major mechanism for the loss-of-function of mutant channels. While it is generally thought that a trafficking defect underlies the lack of channel expression on the cell surface, in the present study, we demonstrate that the trafficking defective mutant hERG G601S can reach the plasma membrane but is unstable and quickly degrades, which is akin to WT hERG channels under low K+ conditions. We previously showed that serine (S) residue at 624 in the innermost position of the selectivity filter of hERG is involved in hERG membrane stability such that substitution of serine 624 with threonine (S624T) enhances hERG stability and renders hERG insensitive to low K+ culture. Here, we report that the intragenic addition of S624T substitution to trafficking defective hERG mutants G601S, N470D, and P596R led to a complete rescue of the function of these otherwise loss-of-function mutant channels to a level similar to the WT channel, representing the most effective rescue means for the function of mutant hERG channels. These findings not only provide novel insights into hERG mutation-mediated channel dysfunction but also point to the critical role of S624 in hERG stability on the plasma membrane.

Asunto(s)

Membrana Celular , Canal de Potasio ERG1 , Síndrome de QT Prolongado , Humanos , Síndrome de QT Prolongado/metabolismo , Síndrome de QT Prolongado/genética , Membrana Celular/metabolismo , Canal de Potasio ERG1/metabolismo , Canal de Potasio ERG1/genética , Células HEK293 , Mutación Missense , Estabilidad Proteica , Canales de Potasio Éter-A-Go-Go/metabolismo , Canales de Potasio Éter-A-Go-Go/genética , Transporte de Proteínas , Sustitución de Aminoácidos , Animales

RESUMEN

BACKGROUND: CaM (calmodulin)-mediated long-QT syndrome is a genetic arrhythmia disorder (calmodulinopathies) characterized by a high prevalence of life-threatening ventricular arrhythmias occurring early in life. Three distinct genes (CALM1, CALM2, and CALM3) encode for the identical CaM protein. Conventional pharmacotherapies fail to adequately protect against potentially lethal cardiac events in patients with calmodulinopathy. METHODS: Five custom-designed CALM1-, CALM2-, and CALM3-targeting short hairpin RNAs (shRNAs) were tested for knockdown (KD) efficiency using TSA201 cells and reverse transcription-quantitative polymerase chain reaction. A dual-component suppression and replacement (SupRep) CALM gene therapy (CALM-SupRep) was created by cloning into a single construct CALM1-, CALM2-, and CALM3-specific shRNAs that produce KD (suppression) of each respective gene and a shRNA-immune CALM1 cDNA (replacement). CALM1-F142L, CALM2-D130G, and CALM3-D130G induced pluripotent stem cell-derived CMs were generated from patients with CaM-mediated long-QT syndrome. A voltage-sensing dye was used to measure action potential duration at 90% repolarization (APD90). RESULTS: Following shRNA KD efficiency testing, a candidate shRNA was identified for CALM1 (86% KD), CALM2 (71% KD), and CALM3 (94% KD). The APD90 was significantly prolonged in CALM2-D130G (647±9 ms) compared with CALM2-WT (359±12 ms; P<0.0001). Transfection with CALM-SupRep shortened the average APD90 of CALM2-D130G to 457±19 ms (66% attenuation; P<0.0001). Additionally, transfection with CALM-SupRep shortened the APD90 of CALM1-F142L (665±9 to 410±15 ms; P<0.0001) and CALM3-D130G (978±81 to 446±6 ms; P<0.001). CONCLUSIONS: We provide the first proof-of-principle suppression-replacement gene therapy for CaM-mediated long-QT syndrome. The CALM-SupRep gene therapy shortened the pathologically prolonged APD90 in CALM1-, CALM2-, and CALM3-variant CaM-mediated long-QT syndrome induced pluripotent stem cell-derived CM lines. The single CALM-SupRep construct may be able to treat all calmodulinopathies, regardless of which of the 3 CaM-encoding genes are affected.

Asunto(s)

Calmodulina , Terapia Genética , Síndrome de QT Prolongado , Humanos , Calmodulina/genética , Calmodulina/metabolismo , Terapia Genética/métodos , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/terapia , Síndrome de QT Prolongado/fisiopatología , Síndrome de QT Prolongado/metabolismo , Síndrome de QT Prolongado/diagnóstico , Miocitos Cardíacos/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Potenciales de Acción , Predisposición Genética a la Enfermedad , Mutación , Interferencia de ARN , Frecuencia Cardíaca/genética

Asunto(s)

Genotipo , Síndrome de QT Prolongado , Fenotipo , Humanos , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/diagnóstico , Síndrome de QT Prolongado/patología , Femenino , Masculino , Mutación

RESUMEN

Timothy syndrome, an extremely rare disease, is closely associated with a mutation in CACNA1C gene, which encodes the cardiac L-type voltage-gated calcium channel (Cav1.2). In this study, we generated a human induced pluripotent stem cell (iPSC) line from a Timothy syndrome infant carrying heterozygous CACNA1C mutation (transcript variant NM_000719.7c.1216G>A: p.G406R). The generated iPSC line showed typical stem cell morphology, positively expressed pluripotency and proliferation markers, normal karyotype, and trilineage differentiation potential. Therefore, this patient-specific iPSC can be of great significance in investigating the mechanisms underlying Timothy syndrome, and hence establishing effective intervention strategies.

Asunto(s)

Trastorno Autístico , Canales de Calcio Tipo L , Heterocigoto , Células Madre Pluripotentes Inducidas , Síndrome de QT Prolongado , Sindactilia , Humanos , Canales de Calcio Tipo L/genética , Canales de Calcio Tipo L/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Sindactilia/genética , Sindactilia/patología , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/patología , Síndrome de QT Prolongado/metabolismo , Trastorno Autístico/genética , Trastorno Autístico/patología , Mutación , Línea Celular , Diferenciación Celular , Lactante

RESUMEN

The KCNQ1 gene encodes a voltage-gated potassium channel required for cardiac action potentials. Mutations in this gene have been associated with hereditary long QT syndrome 1, Jervell and Lange-Nielsen syndromes, and familial atrial fibrillation. The NM_000218.3(KCNQ1): c.604 + 2T > C mutation has been categorized as the causative variant leading to LQT1. In this study, we generated a KCNQ1 (c.644 + 2T > C) mutation human embryonic stem cell line WAe009-A-1L based on CRISPR base editing system. WAe009-A-1L cell has the potential to differentiate cardiomyocytes and would be used as an in vitro disease model for mechanism exploration and drug screening.

Asunto(s)

Edición Génica , Células Madre Embrionarias Humanas , Canal de Potasio KCNQ1 , Mutación , Humanos , Células Madre Embrionarias Humanas/metabolismo , Células Madre Embrionarias Humanas/citología , Edición Génica/métodos , Canal de Potasio KCNQ1/genética , Canal de Potasio KCNQ1/metabolismo , Línea Celular , Sistemas CRISPR-Cas , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/metabolismo , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/citología , Diferenciación Celular , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas/genética

RESUMEN

Long QT Syndrome type 8 (LQT8) is a cardiac arrhythmic disorder associated with Timothy Syndrome, stemming from mutations in the CACNA1C gene, particularly the G406R mutation. While prior studies hint at CACNA1C mutations' role in ventricular arrhythmia genesis, the mechanisms, especially in G406R presence, are not fully understood. This computational study explores how the G406R mutation, causing increased transmural dispersion of repolarization, induces and sustains reentrant ventricular arrhythmias. Using three-dimensional numerical simulations on an idealized left-ventricular model, integrating the Bidomain equations with the ten Tusscher-Panfilov ionic model, we observe that G406R mutation with 11% and 50% heterozygosis significantly increases transmural dispersion of repolarization. During S1-S4 stimulation protocols, these gradients facilitate conduction blocks, triggering reentrant ventricular tachycardia. Sustained reentry pathways occur only with G406R mutation at 50% heterozygosis, while neglecting transmural heterogeneities of action potential duration prevents stable reentry, regardless of G406R mutation presence.

Asunto(s)

Potenciales de Acción , Canales de Calcio Tipo L , Simulación por Computador , Síndrome de QT Prolongado , Sindactilia , Humanos , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/fisiopatología , Canales de Calcio Tipo L/genética , Sindactilia/genética , Sindactilia/fisiopatología , Mutación , Trastorno Autístico/genética , Trastorno Autístico/fisiopatología , Ventrículos Cardíacos/fisiopatología , Modelos Cardiovasculares , Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatología , Taquicardia Ventricular/genética , Taquicardia Ventricular/fisiopatología

RESUMEN

Objective: To explore the genetic background and clinical features of patients with long QT syndrome type 3 (LQT3). Methods: This retrospective cohort included patients diagnosed with LQT3 at the Department of Cardiology, Renmin Hospital of Wuhan University from January 1998 to December 2022. Patients were categorized into compound type group and single type group based on the presence of a single SCN5A mutation. The two groups were followed up and the differences in baseline characteristics, electrocardiograms, and clinical events between the two groups and probands were compared. Kaplan-Meier curves were used for survival analysis, and the log-rank test was employed to compare the event-free survival rates of first cardiac events between the groups and probands. Results: A total of 97 LQT3 patients were enrolled, including 59 probands. The age at diagnosis was (23.45±19.86) years, with 46 patients (47.4%) being male. Among them, 89 patients were classified as single type group, while 8 patients were classified as compound type group. Genetic testing identified 49 SCN5A mutations, with missense mutations being the majority (91.8%), primarily located in transmembrane regions (40.8%, n=20), interdomain linker regions (28.6%, n=14), and C-terminus (22.4%, n=11). The first cardiac event occurred in 44 patients (45.4%), with an onset age of (13.82±12.50) years. The main trigger was identified as rest or sleep (54.5%, n=24). Compared with patients in single type group, patients in compound type group were younger at diagnosis ((10.35±10.28) years vs. (24.63±20.13) years, P=0.040), had a significantly higher proportion of syncope (87.5% (7/8) vs. 33.7% (30/89), P=0.009), aborted cardiac arrest (62.5% (5/8) vs. 11.2% (10/89), P=0.001), and a lower incidence of event-free survival rates of first cardiac events (12.5% (1/8) vs.58.4% (52/89), log-rank P=0.001). The probands in compound type group had a significantly higher proportion of aborted cardiac arrest comparing to probands in single type group (62.5% (5/8) vs. 17.6% (9/51), P=0.020), while the difference in the incidence rate of event-free survival rates of first cardiac events between the probands in two groups was not statistically significant (12.5% (1/8) vs. 39.2% (20/51), log-rank P=0.08). Conclusion: Compound type LQT3 patients are not uncommon. Such patients are diagnosed at a younger age and exhibit more severe phenotypes, requiring close follow-up and proactive intervention strategies.

Asunto(s)

Síndrome de QT Prolongado , Mutación , Canal de Sodio Activado por Voltaje NAV1.5 , Humanos , Masculino , Femenino , Síndrome de QT Prolongado/genética , Estudios Retrospectivos , Adulto , Adulto Joven , Adolescente , Niño , Canal de Sodio Activado por Voltaje NAV1.5/genética , Persona de Mediana Edad , Preescolar , Electrocardiografía , Trastorno del Sistema de Conducción Cardíaco

RESUMEN

Genetic arrhythmia disorders are rare diseases; however, they are a common cause of sudden cardiac death in children, adolescents, and young adults. In principle, a distinction can be made between channelopathies and cardiomyopathies in the context of genetic diseases. This paper focuses on the channelopathies long and short QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT). Early diagnosis of these diseases is essential, as drug therapy, behavioral measures, and if necessary, implantation of a cardioverter defibrillator can significantly improve the prognosis and quality of life of patients. This paper highlights the pathophysiological and genetic basis of these channelopathies, describes their clinical manifestations, and comments on the principles of diagnosis, risk stratification and therapy.

Asunto(s)

Arritmias Cardíacas , Síndrome de Brugada , Canalopatías , Humanos , Arritmias Cardíacas/genética , Arritmias Cardíacas/diagnóstico , Arritmias Cardíacas/terapia , Arritmias Cardíacas/fisiopatología , Canalopatías/genética , Canalopatías/diagnóstico , Canalopatías/terapia , Síndrome de Brugada/genética , Síndrome de Brugada/diagnóstico , Síndrome de Brugada/fisiopatología , Síndrome de Brugada/terapia , Taquicardia Ventricular/genética , Taquicardia Ventricular/terapia , Taquicardia Ventricular/diagnóstico , Taquicardia Ventricular/fisiopatología , Adolescente , Niño , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/diagnóstico , Síndrome de QT Prolongado/terapia , Síndrome de QT Prolongado/fisiopatología , Muerte Súbita Cardíaca/prevención & control , Muerte Súbita Cardíaca/etiología , Adulto , Desfibriladores Implantables , Electrocardiografía

Asunto(s)

Síndrome de QT Prolongado , Humanos , Síndrome de QT Prolongado/congénito , Síndrome de QT Prolongado/diagnóstico , Síndrome de QT Prolongado/genética , Medición de Riesgo , Muerte Súbita Cardíaca/prevención & control , Muerte Súbita Cardíaca/etiología , Factores de Riesgo

Asunto(s)

Síndrome de QT Prolongado , Humanos , Síndrome de QT Prolongado/fisiopatología , Síndrome de QT Prolongado/diagnóstico , Síndrome de QT Prolongado/genética

RESUMEN

BACKGROUND: Despite major advances in the clinical management of long QT syndrome, some patients are not fully protected by beta-blocker therapy. Mexiletine is a well-known sodium channel blocker, with proven efficacy in patients with sodium channel-mediated long QT syndrome type 3. Our aim was to evaluate the efficacy of mexiletine in long QT syndrome type 2 (LQT2) using cardiomyocytes derived from patient-specific human induced pluripotent stem cells, a transgenic LQT2 rabbit model, and patients with LQT2. METHODS: Heart rate-corrected field potential duration, a surrogate for QTc, was measured in human induced pluripotent stem cells from 2 patients with LQT2 (KCNH2-p.A561V, KCNH2-p.R366X) before and after mexiletine using a multiwell multi-electrode array system. Action potential duration at 90% repolarization (APD90) was evaluated in cardiomyocytes isolated from transgenic LQT2 rabbits (KCNH2-p.G628S) at baseline and after mexiletine application. Mexiletine was given to 96 patients with LQT2. Patients were defined as responders in the presence of a QTc shortening ≥40 ms. Antiarrhythmic efficacy of mexiletine was evaluated by a Poisson regression model. RESULTS: After acute treatment with mexiletine, human induced pluripotent stem cells from both patients with LQT2 showed a significant shortening of heart rate-corrected field potential duration compared with dimethyl sulfoxide control. In cardiomyocytes isolated from LQT2 rabbits, acute mexiletine significantly shortened APD90 by 113 ms, indicating a strong mexiletine-mediated shortening across different LQT2 model systems. Mexiletine was given to 96 patients with LQT2 either chronically (n=60) or after the acute oral drug test (n=36): 65% of the patients taking mexiletine only chronically and 75% of the patients who performed the acute oral test were responders. There was a significant correlation between basal QTc and ∆QTc during the test (r= -0.8; P<0.001). The oral drug test correctly predicted long-term effect in 93% of the patients. Mexiletine reduced the mean yearly event rate from 0.10 (95% CI, 0.07-0.14) to 0.04 (95% CI, 0.02-0.08), with an incidence rate ratio of 0.40 (95% CI, 0.16-0.84), reflecting a 60% reduction in the event rate (P=0.01). CONCLUSIONS: Mexiletine significantly shortens cardiac repolarization in LQT2 human induced pluripotent stem cells, in the LQT2 rabbit model, and in the majority of patients with LQT2. Furthermore, mexiletine showed antiarrhythmic efficacy. Mexiletine should therefore be considered a valid therapeutic option to be added to conventional therapies in higher-risk patients with LQT2.

Asunto(s)

Animales Modificados Genéticamente , Células Madre Pluripotentes Inducidas , Síndrome de QT Prolongado , Mexiletine , Miocitos Cardíacos , Mexiletine/farmacología , Mexiletine/uso terapéutico , Animales , Humanos , Conejos , Miocitos Cardíacos/efectos de los fármacos , Síndrome de QT Prolongado/tratamiento farmacológico , Síndrome de QT Prolongado/fisiopatología , Síndrome de QT Prolongado/genética , Células Madre Pluripotentes Inducidas/efectos de los fármacos , Masculino , Femenino , Adulto , Potenciales de Acción/efectos de los fármacos , Antiarrítmicos/farmacología , Antiarrítmicos/uso terapéutico , Adolescente , Persona de Mediana Edad , Adulto Joven , Canal de Potasio ERG1/genética , Canal de Potasio ERG1/antagonistas & inhibidores , Canal de Potasio ERG1/metabolismo , Frecuencia Cardíaca/efectos de los fármacos , Modelos Animales de Enfermedad , Niño , Resultado del Tratamiento

RESUMEN

AIMS: Common genetic variations in the nitric oxide synthase-1 adaptor protein (NOS1AP) gene are associated with QT-interval prolongation. In a previous study, we observed an association between the rs10494366 variant of this gene and an increased QT-interval shortening in digoxin users. As QT-interval shortening is a risk factor for sudden cardiac death (SCD), in this study, we investigated whether the association between digoxin use and risk of SCD differs in participants with different NOS1AP rs10494366 genotypes. METHODS: We included 11 377 individuals from the prospective population-based cohort of the Rotterdam Study. We used Cox proportional hazard regression analysis with digoxin as time-dependent exposure to estimate the associations between current digoxin use and the risk of SCD among different rs10494366 genotype groups in the adjusted models. We also studied whether such an association was dose-dependent, comparing high dosage (≥ 0.250 mg), moderate dosage (0.125 mg ≤ dose< 0.250 mg) and low dosage (< 0.125 mg) digoxin users with non-users. RESULTS: The median baseline age of the total study population was 62 (interquartile range [IQR] 58-71) years. The cumulative incidence of SCD was 4.1% (469 cases), and among them, 74 (15.7%) individuals were current digoxin users at the time of death, during a median follow-up of 11.5 (IQR 6.5-17) years. Current digoxin users had an increased risk of SCD (multivariable adjusted model hazard ratio [HR]: 3.07; 95% confidence interval [CI]: 2.38-3.98), with no significant differences between the three genotype groups. The adjusted HRs were 4.03 [95% CI: 1.98-8.21] in the minor homozygous GG, 3.46 [95% CI: 2.37-5.04] in the heterozygous TG and 2.56 [95%CI: 1.70-3.86] in the homozygous TT genotype groups. Compared to low- and moderate-dose, high-dose digoxin users with GG genotype had the highest risk of SCD (HR: 5.61 [95% CI: 1.34-23.47]). CONCLUSIONS: Current use of digoxin is associated with a significantly increased risk of SCD. The NOS1AP gene rs10494366 variant did not modify the digoxin-associated risk of SCD in a population of European ancestry.

Asunto(s)

Proteínas Adaptadoras Transductoras de Señales , Muerte Súbita Cardíaca , Digoxina , Genotipo , Humanos , Digoxina/efectos adversos , Digoxina/administración & dosificación , Femenino , Masculino , Persona de Mediana Edad , Muerte Súbita Cardíaca/etiología , Muerte Súbita Cardíaca/epidemiología , Anciano , Estudios Prospectivos , Proteínas Adaptadoras Transductoras de Señales/genética , Factores de Riesgo , Relación Dosis-Respuesta a Droga , Polimorfismo de Nucleótido Simple , Países Bajos/epidemiología , Cardiotónicos/efectos adversos , Cardiotónicos/administración & dosificación , Cardiotónicos/uso terapéutico , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/inducido químicamente

RESUMEN

The voltage-gated potassium ion channel KV11.1 plays a critical role in cardiac repolarization. Genetic variants that render Kv11.1 dysfunctional cause long QT syndrome (LQTS), which is associated with fatal arrhythmias. Approximately 90% of LQTS-associated variants cause intracellular protein transport (trafficking) dysfunction, which pharmacological chaperones like E-4031 can rescue. Protein folding and trafficking decisions are regulated by chaperones, protein quality control factors, and trafficking machinery comprising the cellular proteostasis network. Here, we test whether trafficking dysfunction is associated with alterations in the proteostasis network of pathogenic Kv11.1 variants and whether pharmacological chaperones can normalize the proteostasis network of responsive variants. We used affinity-purification coupled with tandem mass tag-based quantitative mass spectrometry to assess protein interaction changes of WT KV11.1 or trafficking-deficient channel variants in the presence or absence of E-4031. We identified 572 core KV11.1 protein interactors. Trafficking-deficient variants KV11.1-G601S and KV11.1-G601S-G965∗ had significantly increased interactions with proteins responsible for folding, trafficking, and degradation compared to WT. We confirmed previous findings that the proteasome is critical for KV11.1 degradation. Our report provides the first comprehensive characterization of protein quality control mechanisms of KV11.1. We find extensive interactome remodeling associated with trafficking-deficient KV11.1 variants and with pharmacological chaperone rescue of KV11.1 cell surface expression. The identified protein interactions could be targeted therapeutically to improve KV11.1 trafficking and treat LQTS.

Asunto(s)

Síndrome de QT Prolongado , Transporte de Proteínas , Proteostasis , Humanos , Síndrome de QT Prolongado/metabolismo , Síndrome de QT Prolongado/genética , Células HEK293 , Canales de Potasio Éter-A-Go-Go/metabolismo , Canales de Potasio Éter-A-Go-Go/genética , Canal de Potasio ERG1/metabolismo , Canal de Potasio ERG1/genética , Animales

RESUMEN

Cardiac channelopathies are a group of heritable disorders that affect the heart's electrical activity due to genetic variations present in genes coding for ion channels. With the advent of new sequencing technologies, molecular diagnosis of these disorders in patients has paved the way for early identification, therapeutic management and family screening. The objective of this retrospective study was to understand the efficacy of whole-genome sequencing in diagnosing patients with suspected cardiac channelopathies who were reported negative after whole exome sequencing and analysis. We employed a 3-tier analysis approach to identify nonsynonymous variations and loss-of-function variations missed by exome sequencing, and structural variations that are better resolved only by sequencing whole genomes. By performing whole genome sequencing and analyzing 25 exome-negative cardiac channelopathy patients, we identified 3 pathogenic variations. These include a heterozygous likely pathogenic nonsynonymous variation, CACNA1C:NM_000719:exon19:c.C2570G:p. P857R, which causes autosomal dominant long QT syndrome in the absence of Timothy syndrome, a heterozygous loss-of-function variation CASQ2:NM_001232.4:c.420+2T>C classified as pathogenic, and a 9.2 kb structural variation that spans exon 2 of the KCNQ1 gene, which is likely to cause Jervell-Lange-Nielssen syndrome. In addition, we also identified a loss-of-function variation and 16 structural variations of unknown significance (VUS). Further studies are required to elucidate the role of these identified VUS in gene regulation and decipher the underlying genetic and molecular mechanisms of these disorders. Our present study serves as a pilot for understanding the utility of WGS over clinical exomes in diagnosing cardiac channelopathy disorders.

Asunto(s)

Canalopatías , Secuenciación del Exoma , Linaje , Secuenciación Completa del Genoma , Humanos , Canalopatías/genética , Canalopatías/diagnóstico , Femenino , Masculino , Canal de Potasio KCNQ1/genética , Canales de Calcio Tipo L/genética , Adulto , Estudios Retrospectivos , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/diagnóstico , Niño , Mutación , Exoma/genética , Predisposición Genética a la Enfermedad

RESUMEN

Drug-induced QT prolongation (diLQTS), and subsequent risk of torsade de pointes, is a major concern with use of many medications, including for non-cardiac conditions. The possibility that genetic risk, in the form of polygenic risk scores (PGS), could be integrated into prediction of risk of diLQTS has great potential, although it is unknown how genetic risk is related to clinical risk factors as might be applied in clinical decision-making. In this study, we examined the PGS for QT interval in 2500 subjects exposed to a known QT-prolonging drug on prolongation of the QT interval over 500ms on subsequent ECG using electronic health record data. We found that the normalized QT PGS was higher in cases than controls (0.212±0.954 vs. -0.0270±1.003, P = 0.0002), with an unadjusted odds ratio of 1.34 (95%CI 1.17-1.53, P<0.001) for association with diLQTS. When included with age and clinical predictors of QT prolongation, we found that the PGS for QT interval provided independent risk prediction for diLQTS, in which the interaction for high-risk diagnosis or with certain high-risk medications (amiodarone, sotalol, and dofetilide) was not significant, indicating that genetic risk did not modify the effect of other risk factors on risk of diLQTS. We found that a high-risk cutoff (QT PGS ≥ 2 standard deviations above mean), but not a low-risk cutoff, was associated with risk of diLQTS after adjustment for clinical factors, and provided one method of integration based on the decision-tree framework. In conclusion, we found that PGS for QT interval is an independent predictor of diLQTS, but that in contrast to existing theories about repolarization reserve as a mechanism of increasing risk, the effect is independent of other clinical risk factors. More work is needed for external validation in clinical decision-making, as well as defining the mechanism through which genes that increase QT interval are associated with risk of diLQTS.

Asunto(s)

Electrocardiografía , Síndrome de QT Prolongado , Herencia Multifactorial , Humanos , Masculino , Femenino , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/inducido químicamente , Persona de Mediana Edad , Herencia Multifactorial/genética , Factores de Riesgo , Anciano , Adulto , Torsades de Pointes/inducido químicamente , Torsades de Pointes/genética , Estudios de Casos y Controles , Fenetilaminas/efectos adversos , Puntuación de Riesgo Genético , Sulfonamidas