Browsing by Author "Ezekian, Jordan E"
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Open Access ATP1A3-Encoded Sodium-Potassium ATPase Subunit Alpha 3 D801N Variant Is Associated With Shortened QT Interval and Predisposition to Ventricular Fibrillation Preceded by Bradycardia.(Journal of the American Heart Association, 2021-09) Moya-Mendez, Mary E; Ogbonna, Chiagoziem; Ezekian, Jordan E; Rosamilia, Michael B; Prange, Lyndsey; de la Uz, Caridad; Kim, Jeffrey J; Howard, Taylor; Garcia, John; Nussbaum, Robert; Truty, Rebecca; Callis, Thomas E; Funk, Emily; Heyes, Matthew; Dear, Guy de Lisle; Carboni, Michael P; Idriss, Salim F; Mikati, Mohamad A; Landstrom, Andrew PBackground Pathogenic variation in the ATP1A3-encoded sodium-potassium ATPase, ATP1A3, is responsible for alternating hemiplegia of childhood (AHC). Although these patients experience a high rate of sudden unexpected death in epilepsy, the pathophysiologic basis for this risk remains unknown. The objective was to determine the role of ATP1A3 genetic variants on cardiac outcomes as determined by QT and corrected QT (QTc) measurements. Methods and Results We analyzed 12-lead ECG recordings from 62 patients (male subjects=31, female subjects=31) referred for AHC evaluation. Patients were grouped according to AHC presentation (typical versus atypical), ATP1A3 variant status (positive versus negative), and ATP1A3 variant (D801N versus other variants). Manual remeasurements of QT intervals and QTc calculations were performed by 2 pediatric electrophysiologists. QTc measurements were significantly shorter in patients with positive ATP1A3 variant status (P<0.001) than in patients with genotype-negative status, and significantly shorter in patients with the ATP1A3-D801N variant than patients with other variants (P<0.001). The mean QTc for ATP1A3-D801N was 344.9 milliseconds, which varied little with age, and remained <370 milliseconds throughout adulthood. ATP1A3 genotype status was significantly associated with shortened QTc by multivariant regression analysis. Two patients with the ATP1A3-D801N variant experienced ventricular fibrillation, resulting in death in 1 patient. Rare variants in ATP1A3 were identified in a large cohort of genotype-negative patients referred for arrhythmia and sudden unexplained death. Conclusions Patients with AHC who carry the ATP1A3-D801N variant have significantly shorter QTc intervals and an increased likelihood of experiencing bradycardia associated with life-threatening arrhythmias. ATP1A3 variants may represent an independent cause of sudden unexplained death. Patients with AHC should be evaluated to identify risk of sudden death.Item Open Access TBX5-encoded T-box transcription factor 5 variant T223M is associated with long QT syndrome and pediatric sudden cardiac death.(American journal of medical genetics. Part A, 2021-03) Markunas, Alexandra M; Manivannan, Perathu KR; Ezekian, Jordan E; Agarwal, Agnim; Eisner, William; Alsina, Katherina; Allen, Hugh D; Wray, Gregory A; Kim, Jeffrey J; Wehrens, Xander HT; Landstrom, Andrew PLong QT syndrome (LQTS) is a genetic disease resulting in a prolonged QT interval on a resting electrocardiogram, predisposing affected individuals to polymorphic ventricular tachycardia and sudden death. Although a number of genes have been implicated in this disease, nearly one in four individuals exhibiting the LQTS phenotype are genotype-negative. Whole-exome sequencing identified a missense T223M variant in TBX5 that cosegregates with prolonged QT interval in a family with otherwise genotype-negative LQTS and sudden death. The TBX5-T223M variant was absent among large ostensibly healthy populations (gnomAD) and predicted to be pathogenic by in silico modeling based on Panther, PolyPhen-2, Provean, SIFT, SNAP2, and PredictSNP prediction tools. The variant was located in a highly conserved region of TBX5 predicted to be part of the DNA-binding interface. A luciferase assay identified a 57.5% reduction in the ability of TBX5-T223M to drive expression at the atrial natriuretic factor promotor compared to wildtype TBX5 in vitro. We conclude that the variant is pathogenic in this family, and we put TBX5 forward as a disease susceptibility allele for genotype-negative LQTS. The identification of this familial variant may serve as a basis for the identification of previously unknown mechanisms of LQTS with broader implications for cardiac electrophysiology.Item Open Access Variant R94C in TNNT2-Encoded Troponin T Predisposes to Pediatric Restrictive Cardiomyopathy and Sudden Death Through Impaired Thin Filament Relaxation Resulting in Myocardial Diastolic Dysfunction.(Journal of the American Heart Association, 2020-03) Ezekian, Jordan E; Clippinger, Sarah R; Garcia, Jaquelin M; Yang, Qixin; Denfield, Susan; Jeewa, Aamir; Dreyer, William J; Zou, Wenxin; Fan, Yuxin; Allen, Hugh D; Kim, Jeffrey J; Greenberg, Michael J; Landstrom, Andrew PBackground Pediatric-onset restrictive cardiomyopathy (RCM) is associated with high mortality, but underlying mechanisms of disease are under investigated. RCM-associated diastolic dysfunction secondary to variants in TNNT2-encoded cardiac troponin T (TNNT2) is poorly described. Methods and Results Genetic analysis of a proband and kindred with RCM identified TNNT2-R94C, which cosegregated in a family with 2 generations of RCM, ventricular arrhythmias, and sudden death. TNNT2-R94C was absent among large, population-based cohorts Genome Aggregation Database (gnomAD) and predicted to be pathologic by in silico modeling. Biophysical experiments using recombinant human TNNT2-R94C demonstrated impaired cardiac regulation at the molecular level attributed to reduced calcium-dependent blocking of myosin's interaction with the thin filament. Computational modeling predicted a shift in the force-calcium curve for the R94C mutant toward submaximal calcium activation compared within the wild type, suggesting low levels of muscle activation even at resting calcium concentrations and hypercontractility following activation by calcium. Conclusions The pathogenic TNNT2-R94C variant activates thin-filament-mediated sarcomeric contraction at submaximal calcium concentrations, likely resulting in increased muscle tension during diastole and hypercontractility during systole. This describes the proximal biophysical mechanism for development of RCM in this family.