Identification of a novel exon3 deletion of RYR2 in a family with catecholaminergic polymorphic ventricular tachycardia

Abstract

Background RYR2, encoding cardiac ryanodine receptor, is the major responsible gene for catecholaminergic polymorphic ventricular tachycardia (CPVT). Meanwhile, KCNJ2, encoding inward‐rectifier potassium channel (IK1), can be the responsible gene for atypical CPVT. We recently encountered a family with CPVT and sought to identify a responsible gene variant.MethodsA targeted panel sequencing (TPS) was employed in the proband. Copy number variation (CNV) in RYR2 was identified by focusing on read numbers in the TPS and long‐range PCR. Cascade screening was conducted by a Sanger method and long‐range PCR. KCNJ2 wild‐type (WT) or an identified variant was expressed in COS‐1 cells, and whole‐cell currents (IK1) were recorded using patch‐clamp techniques.ResultsA 40‐year‐old female experienced cardiopulmonary arrest while cycling. Her ECG showed sinus bradycardia with prominent U‐waves (≥0.2 mV). She had left ventricular hypertrabeculation at apex. Exercise induced frequent polymorphic ventricular arrhythmias. Her sister died suddenly at age 35 while bouldering. Her father and paternal aunt, with prominent U‐waves, received permanent pacemaker due to sinus node dysfunction. The initial TPS and cascade screening identified a KCNJ2 E118D variant in all three symptomatic patients. However, after focusing on read numbers, we identified a novel exon3 deletion of RYR2 (RYR2‐exon3 deletion) in all of them. Functional analysis revealed that KCNJ2 E118D generated IK1 indistinguishable from KCNJ2 WT, even in the presence of catecholaminergic stimulation.ConclusionsFocusing on the read numbers in the TPS enabled us to identify a novel CNV, RYR2‐exon3 deletion, which was associated with phenotypic features of this family.

RyR2 disease mutations at the C-terminal domain intersubunit interface alter closed-state stability and channel activation

“…Interestingly, the NTD harbors a number of RyR2 mutations associated with cardiomyopathies. (16,21,(27)(28)(29)(30)(31)(32)(33). A common defect of NTD RyR2 mutations is a reduced threshold for Ca 2+ release termination and an increased amplitude of fractional Ca 2+ release (34).…”

“…The NTD (residues 1–642) comprises three subdomains: NTD-A, NTD-B, and NTD-C. We showed that NTD-A is important for Ca 2+ release termination, NTD-B is involved in channel suppression, and NTD-C is critical for channel activation and expression ( 26 ). Interestingly, the NTD harbors a number of RyR2 mutations associated with cardiomyopathies ( 16 , 21 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ). A common defect of NTD RyR2 mutations is a reduced threshold for Ca 2+ release termination and an increased amplitude of fractional Ca 2+ release ( 34 ).…”

Increased Ca 2+ Transient Underlies RyR2-Related Left Ventricular Noncompaction

“…Mutations in the RYR2 gene have been linked to cardiac arrhythmias (eg, CPVT and CRDS) [4][5][6][7][8]16 and cardiomyopathies such as left ventricular noncompaction (LVNC). 6,[17][18][19][20][21][22][23][24][25][26][27][28][29][30] The mechanisms underlying RyR2-associated cardiac arrhythmias have been extensively studied. 7,16 However, the underlying mechanism for RyR2-associated LVNC remains poorly understood.…”

“…6,7,[17][18][19][20][21][22][23] For instance, several unrelated families with an in-frame deletion of exon-3 in the RYR2 gene presented with an expanding spectrum of phenotypes, including left ventricular noncompaction cardiomyopathy (LVNC) as well as CPVT. 6,[24][25][26][27][28][29][30] In vitro functional characterization revealed that the exon-3 deletion reduced the threshold for store overload-induced spontaneous Ca 2+ release, 31 which may account for the increased propensity for stress-induced ventricular arrhythmias (VAs; ie, CPVT). Interestingly, the exon-3 deletion also markedly reduced the threshold at which spontaneous Ca 2+ release terminates.…”

Genetic Complexity of Sinoatrial Node Dysfunction

“…CPVT is also commonly induced by RYR2 variants and has been highly associated with bradycardia ( Miyata et al, 2018 ). An exon 3 deletion of RYR2 (c.169-353_273 + 657del) was found in a family with a history of SND and CPVT ( Dharmawan et al, 2019 ). Exon 3 deletions were identified in two additional families that showed symptoms of SND ( Bhuiyan et al, 2007 ).…”