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bioRxiv · 10.64898/2026.03.07.710328

Recessive POPDC1 Truncation Causes Lethal Short-QT Pattern Arrhythmogenic Cardiomyopathy with Multi-Ion Channel Remodeling and Ankyrin-G Scaffold Disruption

luo, R.·Zheng, C.·Lan, H.·He, Y.·Wang, Y.·Sheng, Q.·Li, S.·Deng, H.·Yao, L.·Li, Y.·Lim, W.-W.·Hua, W.·Wu, X.·Li, X.
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Abstract

AimsBiallelic variants in Popeye domain containing 1 (POPDC1) classically cause limb-girdle muscular dystrophy, but their impact on cardiac system remains unclear. We investigated the functional consequence of a POPDC1 frameshift variant (c.448delT), first identified in a consanguineous family with arrhythmogenic cardiomyopathy (ACM) and sudden death. Methods and resultsComprehensive clinical and genetic evaluation was followed by mechanistic studies in an orthologous Popdc1 knock-in rat model. Functional characterization included biotelemetry and programed electrical stimulation, optical mapping, patch clamp, intracellular Ca2+ imaging, proteomics, and oxidative stress assays. Homozygous mutants (Popdc1fs/fs) exhibited a shortened QTc interval and high incidence of ventricular tachycardia compared to wild-type (Popdc1+/+). Urethane anesthesia provoked second-degree AV block in all 10 Popdc1fs/fs rats but in only 1 of 9 Popdc1+/+ littermates. Optical mapping demonstrated abbreviated action potentials, slowed conduction velocity, and inducible polymorphic VT. Patch clamp confirmed accelerated repolarization, with upregulated transient outward potassium currents (Ito) and L-type calcium currents (ICa, L), but downregulated peak sodium currents (INa). Multi-omics and ultrastructural analyses revealed a post-translational collapse of intercalated disc: POPDC1 loss destabilized Ankyrin-G and its membrane-anchored cargo, Nav1.5, coinciding with enhanced Kv4.3 and Cav1.2 protein levels. These disruptions create a convergence of delayed conduction and shortened refractoriness, forming substrate for malignant re-entry. ConclusionWe defined a recessive short-QT ACM leading to potentially fatal arrhythmias caused by biallelic POPDC1 truncation driving Ankyrin-G disruption, manifesting as a triad: (1) bradycardia/AV block, (2) accelerated repolarization as short-QT pattern/diffuse T-wave flattening or inversion, and (3) progressive cardiomyopathy and sudden death. Whats new?O_LIWe define a novel diagnostic triad for recessive short-QT arrhythmogenic cardiomyopathy (rSQT-ACM) in a loss-of-function POPDC1 truncation: (1) early-onset bradyarrhythmia (sinus bradycardia or AV block); (2) a paradoxical short-QT interval with maladaptive rate response/diffuse T-wave flattening or inversion; and (3) progressive cardiomyopathy accompanied accompanied by with SCD. C_LIO_LIMechanistically, biallelic POPDC1 truncation induces collapse of the POPDC1-AnkG hub, which triggers a unique "opposing remodeling" phenotype (severe INa reduction coupled with paradoxical upregulation of Kv4.3-mediated Ito), and established a unified "slow-conduction, short-wavelength" substrate that underpins malignant re-entry. C_LIO_LIImplications for safety and device therapy: Nav1.5 deficiency indicates that sodium channel blockers may be contraindicated, and early ICD implantation may be preferable to bradycardia pacing. C_LIO_LIMechanism-directed treatments: POPDC1s recessive inheritance and small gene size make it a strong candidate for AAV-mediated gene supplementation aimed at restoring the intercalated disc architecture and ion-channel anchoring. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/710328v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@1012d79org.highwire.dtl.DTLVardef@5073dcorg.highwire.dtl.DTLVardef@1e69bc2org.highwire.dtl.DTLVardef@fc15ec_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

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luo, R., Zheng, C., Lan, H., He, Y., Wang, Y., Sheng, Q., Li, S., Deng, H., Yao, L., Li, Y., Lim, W.-W., Hua, W., Wu, X., Li, X.. 2026-03-10. Recessive POPDC1 Truncation Causes Lethal Short-QT Pattern Arrhythmogenic Cardiomyopathy with Multi-Ion Channel Remodeling and Ankyrin-G Scaffold Disruption. https://doi.org/10.64898/2026.03.07.710328

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