scholarly journals Identification of Loss-of-function RyR2 Mutations Associated with Idiopathic Ventricular Fibrillation and Sudden Death

2021 ◽  
Author(s):  
Xiaowei Zhong ◽  
Wenting Guo ◽  
Jinhong Wei ◽  
Yijun Tang ◽  
Yingjie Liu ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Sudden Death ◽  
Negative Impact ◽  
Deficiency Syndrome ◽  
Dominant Negative ◽  
Exercise Stress ◽  
Hek293 Cells ◽  
Polymorphic Ventricular Tachycardia ◽  
Loss Of Function ◽  
Idiopathic Ventricular Fibrillation

Mutations in cardiac ryanodine receptor (RyR2) are linked to catecholaminergic polymorphic ventricular tachycardia (CPVT). Most CPVT RyR2 mutations characterized are gain-of-function (GOF), indicating enhanced RyR2 function as a major cause of CPVT. Loss-of-function (LOF) RyR2 mutations have also been identified and are linked to a distinct entity of cardiac arrhythmia termed RyR2 Ca2+ release deficiency syndrome (CRDS). Exercise stress testing (EST) is routinely used to diagnose CPVT, but it is ineffective for CRDS. There is currently no effective diagnostic tool for CRDS in humans. An alternative strategy to assess the risk for CRDS is to directly determine the functional impact of the associated RyR2 mutations. To this end, we have functionally screened 18 RyR2 mutations that are associated with idiopathic ventricular fibrillation (IVF) or sudden death. We found two additional RyR2 LOF mutations E4146K and G4935R. The E4146K mutation markedly suppressed caffeine activation of RyR2 and abolished store overload induced Ca2+ release in HEK293 cells. E4146K also severely reduced cytosolic Ca2+ activation and abolished luminal Ca2+ activation of single RyR2 channels. The G4935R mutation completely abolished caffeine activation of and [3H]ryanodine binding to RyR2. Co-expression studies showed that the G4935R mutation exerted dominant negative impact on the RyR2 wildtype channel. Interestingly, the RyR2-G4935R mutant carrier had a negative EST, and the E4146K carrier had a family history of sudden death during sleep, which are different from phenotypes of typical CPVT. Thus, our data further support the link between RyR2 LOF and a new entity of cardiac arrhythmias distinct from CPVT.

scholarly journals Novel RyR2 Mutation (G3118R) Is Associated With Autosomal Recessive Ventricular Fibrillation and Sudden Death: Clinical, Functional, and Computational Analysis

2021 ◽  
Author(s):  
Ayelet Shauer ◽  
Oded Shor ◽  
Jinhong Wei ◽  
Yair Elitzur ◽  
Nataly Kucherenko ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Sudden Death ◽  
Normal Mode Analysis ◽  
Dose Effect ◽  
Hek293 Cells ◽  
Polymorphic Ventricular Tachycardia ◽  
Mode Analysis ◽  
Dependent Manner ◽  
Hek 293 ◽  
Physiological Tests

Background The cardiac ryanodine receptor type 2 (RyR2) is a large homotetramer, located in the sarcoplasmic reticulum (SR), which releases Ca 2+ from the SR during systole. The molecular mechanism underlying Ca 2+ sensing and gating of the RyR2 channel in health and disease is only partially elucidated. Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT1) is the most prevalent syndrome caused by RyR2 mutations. Methods and Results This study involves investigation of a family with 4 cases of ventricular fibrillation and sudden death and physiological tests in HEK 293 cells and normal mode analysis (NMA) computation. We found 4 clinically affected members who were homozygous for a novel RyR2 mutation, G3118R, whereas their heterozygous relatives are asymptomatic. G3118R is located in the periphery of the protein, far from the mutation hotspot regions. HEK293 cells harboring G3118R mutation inhibited Ca 2+ release in response to increasing doses of caffeine, but decreased the termination threshold for store‐overload‐induced Ca 2+ release, thus increasing the fractional Ca 2+ release in response to increasing extracellular Ca 2+ . NMA showed that G3118 affects RyR2 tetramer in a dose‐dependent manner, whereas in the model of homozygous mutant RyR2, the highest entropic values are assigned to the pore and the central regions of the protein. Conclusions RyR2 G3118R is related to ventricular fibrillation and sudden death in recessive mode of inheritance and has an effect of gain of function on the protein. Despite a peripheral location, it has an allosteric effect on the stability of central and pore regions in a dose‐effect manner.

scholarly journals Cardiac ryanodine receptor calcium release deficiency syndrome

2021 ◽  
Vol 13 (579) ◽  
pp. eaba7287
Author(s):  
Bo Sun ◽  
Jinjing Yao ◽  
Mingke Ni ◽  
Jinhong Wei ◽  
Xiaowei Zhong ◽  
...  
Keyword(s):  
Ryanodine Receptor ◽  
Ventricular Arrhythmias ◽  
Calcium Release ◽  
Deficiency Syndrome ◽  
Exercise Stress ◽  
Polymorphic Ventricular Tachycardia ◽  
Loss Of Function ◽  
Electrophysiological Studies ◽  
Genetic Evaluations ◽  
Cardiac Ryanodine Receptor

Cardiac ryanodine receptor (RyR2) gain-of-function mutations cause catecholaminergic polymorphic ventricular tachycardia, a condition characterized by prominent ventricular ectopy in response to catecholamine stress, which can be reproduced on exercise stress testing (EST). However, reports of sudden cardiac death (SCD) have emerged in EST-negative individuals who have loss-of-function (LOF) RyR2 mutations. The clinical relevance of RyR2 LOF mutations including their pathogenic mechanism, diagnosis, and treatment are all unknowns. Here, we performed clinical and genetic evaluations of individuals who suffered from SCD and harbored an LOF RyR2 mutation. We carried out electrophysiological studies using a programed electrical stimulation protocol consisting of a long-burst, long-pause, and short-coupled (LBLPS) ventricular extra-stimulus. Linkage analysis of RyR2 LOF mutations in six families revealed a combined logarithm of the odds ratio for linkage score of 11.479 for a condition associated with SCD with negative EST. A RyR2 LOF mouse model exhibited no catecholamine-provoked ventricular arrhythmias as in humans but did have substantial cardiac electrophysiological remodeling and an increased propensity for early afterdepolarizations. The LBLPS pacing protocol reliably induced ventricular arrhythmias in mice and humans having RyR2 LOF mutations, whose phenotype is otherwise concealed before SCD. Furthermore, treatment with quinidine and flecainide abolished LBLPS-induced ventricular arrhythmias in model mice. Thus, RyR2 LOF mutations underlie a previously unknown disease entity characterized by SCD with normal EST that we have termed RyR2 Ca2+ release deficiency syndrome (CRDS). Our study provides insights into the mechanism of CRDS, reports a specific CRDS diagnostic test, and identifies potentially efficacious anti-CRDS therapies.

scholarly journals Human RyR2 (Ryanodine Receptor 2) Loss-of-Function Mutations

2021 ◽  
Vol 14 (9) ◽  
Author(s):  
Yanhui Li ◽  
Jinhong Wei ◽  
Wenting Guo ◽  
Bo Sun ◽  
John Paul Estillore ◽  
...  
Keyword(s):  
Ventricular Tachycardia ◽  
Sudden Cardiac Death ◽  
Cardiac Death ◽  
Stress Testing ◽  
Functional Characterization ◽  
Catecholaminergic Polymorphic Ventricular Tachycardia ◽  
Exercise Stress ◽  
Polymorphic Ventricular Tachycardia ◽  
Loss Of Function

Background: The overall objective of the present study is to extend our understanding of the clinical phenotype and underlying mechanism of a newly discovered cardiac arrhythmia syndrome through a multicenter study. Gain-of-function mutations in the cardiac Ca 2+ release channel (RyR2 [ryanodine receptor 2]) cause catecholaminergic polymorphic ventricular tachycardia, whereas loss-of-function RyR2 mutations are linked to a new cardiac arrhythmia disorder termed Ca 2+ -release deficiency syndrome (CRDS). Catecholaminergic polymorphic ventricular tachycardia is an inherited arrhythmia disorder characterized by stress-induced bidirectional and polymorphic ventricular tachyarrhythmias and is routinely diagnosed by using exercise stress testing. Conversely, RyR2-CRDS is characterized by ventricular arrhythmias and sudden cardiac death but a negative exercise stress testing for catecholaminergic polymorphic ventricular tachycardia. There are currently no clinical diagnostic tests for CRDS and affected patients may manifest with sudden cardiac death as their first symptom. In the absence of effective clinical diagnostic tools, in vitro functional characterization of associated RyR2 mutations provides an alternative means to identify potential cases of CRDS. Methods: We searched for patients presenting with phenotypes compatible with CRDS that have RyR2 mutations and performed in vitro functional characterization. Results: We found that 3 novel (G570D, R4147K, and A4203V) and 2 previously reported (M4109R and A4204V) RyR2 mutations associated with CRDS phenotypes markedly reduced caffeine-induced Ca 2+ release and store overload-induced Ca 2+ release. We also characterized 2 additional loss-of-function RyR2 mutations previously reported (Q3925E and L4769S) that are located in the central and channel pore-forming domains critical for Ca 2+ activation and channel gating. Q3925E was identified through postmortem genetic testing in an individual who died suddenly, while L4769S is a variant of uncertain significance reported in ClinVar, suggesting that RyR2 CRDS may be under detected. Conclusions: These findings provide further support for the existence of an emerging RyR2 loss-of-function associated arrhythmia syndrome (CRDS) and shed new insights into the disease mechanism.

Idiopathic ventricular fibrillation: the ongoing quest for diagnostic refinement

EP Europace ◽  
2020 ◽  
Author(s):  
Giulio Conte ◽  
John R Giudicessi ◽  
Michael J Ackerman
Keyword(s):  
Ventricular Fibrillation ◽  
Heart Diseases ◽  
Sudden Cardiac Arrest ◽  
Polymorphic Ventricular Tachycardia ◽  
Molecular Evidence ◽  
Idiopathic Ventricular Fibrillation ◽  
Diagnostic Approaches ◽  
Exercise Induced ◽  
Definition Of ◽  
Electrocardiogram Ecg

Abstract Prior to the recognition of distinct clinical entities, such as Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and long QT syndrome, all sudden cardiac arrest (SCA) survivors with ventricular fibrillation (VF) and apparently structurally normal hearts were labelled as idiopathic ventricular fibrillation (IVF). Over the last three decades, the definition of IVF has changed substantially, mostly as result of the identification of the spectrum of SCA-predisposing genetic heart diseases (GHDs), and the molecular evidence, by post-mortem genetic analysis (aka, the molecular autopsy), of cardiac channelopathies as the pathogenic basis for up to 35% of unexplained cases of sudden cardiac death (SCD) in the young. The evolution of the definition of IVF over time has led to a progressively greater awareness of the need for an extensive diagnostic assessment in unexplained SCA survivors. Nevertheless, GHDs are still underdiagnosed among SCA survivors, due to the underuse of pharmacological challenges (i.e. sodium channel blocker test), misrecognition of electrocardiogram (ECG) abnormalities/patterns (i.e. early repolarization pattern or exercise-induced ventricular bigeminy) or errors in the measurement of ECG parameters (e.g. the heart-rate corrected QT interval). In this review, we discuss the epidemiology, diagnostic approaches, and the controversies related to role of the genetic background in unexplained SCA survivors with a default diagnosis of IVF.

scholarly journals Loss-of-function mutation of the SCN3B-encoded sodium channel  3 subunit associated with a case of idiopathic ventricular fibrillation

2009 ◽  
Vol 86 (3) ◽  
pp. 392-400 ◽  
Author(s):  
C. R. Valdivia ◽  
A. Medeiros-Domingo ◽  
B. Ye ◽  
W. K. Shen ◽  
T. J. Algiers ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Sodium Channel ◽  
Loss Of Function ◽  
Idiopathic Ventricular Fibrillation

scholarly journals Disease-Associated Human Telomerase RNA Variants Show Loss of Function for Telomere Synthesis without Dominant-Negative Interference

2008 ◽  
Vol 28 (20) ◽  
pp. 6510-6520 ◽  
Author(s):  
Timothy M. Errington ◽  
Dragony Fu ◽  
Judy M. Y. Wong ◽  
Kathleen Collins
Keyword(s):  
Negative Impact ◽  
Dominant Negative ◽  
Telomere Maintenance ◽  
General Mechanism ◽  
Genome Replication ◽  
Telomerase Rna ◽  
Loss Of Function ◽  
Wild Type ◽  
Human Telomerase

ABSTRACT Telomerase adds simple-sequence repeats to chromosome ends to offset the terminal sequence loss inherent in each cycle of genome replication. Inherited mutations in genes encoding subunits of the human telomerase holoenzyme give rise to disease phenotypes including hematopoietic failure and pulmonary fibrosis. Disease-associated variants of the human telomerase RNA are expressed in heterozygous combination with wild-type telomerase RNA. Here, we exploit a sensitized human primary cell assay system to investigate the biological function of disease-linked telomerase RNA variants and their impact on the function of coexpressed wild-type telomerase RNA. We find that telomerase RNA variants discovered in patients with dyskeratosis congenita or aplastic anemia show loss of function without any indication of dominant-negative impact on telomere maintenance by the coexpressed wild-type RNA. To reconcile this result with contradictory findings from reconstitution assays in vitro, we demonstrate that the lack of dominant-negative impact on telomere maintenance correlates with physiological assembly of active human telomerase holoenzyme ribonucleoproteins harboring monomers rather than higher-order multimers of telomerase RNA and telomerase reverse transcriptase. These findings support loss of function of telomerase RNA as a general mechanism of human disease.

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