CACNA1B gain-of-function mutation drives familial atrioventricular nodal re-entrant tachycardia through sympathetic hyperactivity

Background Familial clustering of atrioventricular nodal re-entrant tachycardia (AVNRT) suggests a genetic basis, yet the underlying molecular etiology remains undefined. CACNA1B encodes the α1 subunit of the N-type calcium channel (Ca V 2.2), a key regulator of sympathetic neurotransmission. We identify CACNA1B as a novel causative gene for familial AVNRT and define its neurogenic mechanism of arrhythmogenesis. Methods Whole-exome sequencing of a four-generation pedigree with autosomal dominant AVNRT revealed a novel heterozygous missense variant, CACNA1B p.K567R. Functional effects were assessed in zebrafish and an orthologous Cacna1b p.K565R knock-in rat using ambulatory telemetry, programmed electrical stimulation, patch-clamp electrophysiology, ultrastructural analyses, and integrated multi-omics of superior cervical ganglion (SCG) and AV nodal tissues. Pharmacological interventions were conducted using the selective N-type calcium channel inhibitor, Ω -conotoxin GVIA, and the clinically approved L- and N-type calcium channel blocker, cilnidipine. Results The CACNA1B p.K567R variant co-segregated with AVNRT and induced an accelerated cardiac rhythm in the mutant overexpressed zebrafish. Patch-clamp analysis demonstrated a marked Ca V 2.2 gain-of-function (GoF) driven by increased surface channel density. Cacna1b p.565R knock-in rats exhibited chronic sympathetic overactivity with significantly perturbed heart rate variability (HRV), dual AV nodal pathways with atrial echo beats, and inducible AVNRT. Single-cell and multi-omics profiling in SCG revealed functional hyperactivation of the glutamatergic subpopulation and upregulation of presynaptic exocytotic components (SYT1/SNAP25), producing sustained sympathetic hyperexcitability. This neurogenic drive triggered metabolic reprogramming and oxidative stress in downstream AV nodal transitional cells, establishing an arrhythmogenic substrate for reentry. Treatment with ω-conotoxin GVIA and cilnidipine reversed the hyperadrenergic phenotype and normalized cardiac autonomic tone and heart rate. Conclusions CACNA1B is a novel disease gene of familial AVNRT. Ca V 2.2 GoF induces sympathetic hyperactivity and secondary AV nodal remodelling, establishing a neurogenic substrate for reentrant tachycardia, and N-type calcium channel blockade represents a promising precision therapeutic strategy for CACNA1B -mediated, autonomic-driven arrhythmias. What is known Familial clusters of AVNRT suggest genetic predisposition consistent with autosomal dominant inheritance but mechanisms unknown. Sympathetic tone is a critical modulator of AV nodal conduction and a primary determinant of AVNRT susceptibility. What new information does this article contribute? CACNA1B (p.K567R) gain of function variant overexpression in HEK293T cells and zebrafish embryos demonstrate heart rate and electrophysiological abnormalities implicates CACNA1B as a disease gene of familial AVNRT. A Cacna1b (p.K565R) orthologous rat model recaptures sympathetic hyperactivity, severe autonomic dysregulation and arrhythmia susceptibility. Ca V 2.2 hyperactivity drives chronic sympathetic overactivation through SYT1-SNAP25 and secondary AV nodal remodeling. Novelty and Significance This work reframes the pathogenesis of familial AVNRT by establishing CACNA1B gain of function as a primary neurogenic driver of disease. Rather than arising solely from an anatomic dual pathway circuit, AVNRT can originate from genetically driven sympathetic hyperexcitability that secondarily remodels the AV node. The discovery that Ca V 2.2 overactivity expands glutamatergic sympathetic neurons, enhances presynaptic exocytotic cargo, and chronically hyperactivates the AV node provides a mechanistic bridge between autonomic dysfunction and reentrant arrhythmia. Cilnidipine, a clinically available dual L-/N type calcium channel blocker, normalizes sympathetic overactivity. These findings portray CACNA1B as a potential target and position N type calcium channel inhibition as a mechanism based therapeutic strategy for familial or refractory AVNRT. The study broadens the conceptual framework of AVNRT, highlights the autonomic nervous system as a modifiable arrhythmogenic source, and provides a translatable treatment avenue for patients carrying CACNA1B variants.