#genetics #arrhythmogenic-cardiomyopathy #ARVC #desmosome

PKP2 (Plakophilin-2)

Details

PKP2 encodes plakophilin-2, an armadillo protein and critical component of the cardiac desmosome at the intercalated disc. It is the most commonly mutated gene in hereditary ARVC, found in the majority of familial cases. PKP2 loss disrupts not only desmosomal integrity but also gap junction organization and sodium channel function — explaining the combined mechanical and electrical dysfunction in ARVC.

Key Facts

Variant type: Truncating variants predominate (signal-to-background odds ratio NT 1.3, EF 0.23; 10:1 case-over-population ratio). Large deletions/duplications account for 1–2% of cases and can be missed by Sanger sequencing. (sources/acm-hrs-2019)
Desmosomal role: PKP2 mediates attachment of intermediate filaments (desmin) to desmosomes via interaction with junction plakoglobin (JUP) and desmoplakin (DSP) at their N-terminal domains. Required for organization of intercalated disc structure and desmosomal function. (sources/acm-hrs-2019)
Ion channel interaction: PKP2 co-precipitates with Nav1.5; PKP2 knockdown reduces sodium current amplitude and kinetics. PKP2 variants are associated with a sodium channelopathy phenotype. Decreased Nav1.5 protein has been detected in the majority of human ARVC heart samples. (sources/acm-hrs-2019)
Gap junction remodeling: PKP2 knockdown decreases Cx43 (connexin-43) at the ID → reduced conduction velocity → increased re-entry arrhythmias. (sources/acm-hrs-2019)
Exercise-penetrance relationship: PKP2 variant carrier data form the strongest evidence base for exercise-induced ARVC; endurance athletes with PKP2 variants develop ARVC earlier and with higher burden of RV/LV dysfunction than non-athletic carriers. (sources/acm-hrs-2019)
Age-related penetrance: Disease expression between 20–50 years (40%); rare before age 14. Among PKP2 families, ~⅓ of relatives fulfill ARVC Task Force Criteria, ~⅓ have borderline disease, ~⅓ are unaffected. (sources/acm-hrs-2019)
Gene therapy: AAV9-PKP2 delivery prevents and reverses ARVC phenotype in knock-in mouse models; three clinical-stage candidates (LX2020, RP-A601, TN-401) in early-phase trials. (sources/gene-therapy-arrhythmia-2025)
Muller 2025 — Genotype-specific management review: PKP2 accounts for up to two-thirds of ARVC cases; loss-of-function/haploinsufficiency mechanism with no evidence that specific variants differ in severity. 2010 TFC validated mostly in PKP2 patients. ARVC risk calculator (2019) performs adequately in PKP2-ARVC. Male sex and exercise are penetrance risk factors. Electrical abnormalities (ECG/Holter) precede structural abnormalities (echo/CMR). (sources/ACM-Genotype-Mx-JCE-2024, rating: high)
Flecainide in PKP2-ARVC: In a PKP2 cardiac conditional knockout mouse model (PKP2cKO), adrenergic stimulation triggered excess SR Ca²⁺ release through RyR2 channels promoting arrhythmias; flecainide (RyR2 + Na⁺ channel blocker) eliminated VA occurrence. Suggests gene-specific antiarrhythmic efficacy. RCT in PKP2-ARVC patients pending (NCT03685149). (sources/ACM-Genotype-Mx-JCE-2024)
AAV-PKP2 gene therapy — three Phase I/II programs: (1) AAVrh74-PKP2 (Rocket RP-A601) — 100% survival >5 months in PKP2cKO mice, arrested LV/RV progression, effective after disease onset; (2) AAV9-PKP2 (LEXEO LX2020) — confirmed survival and function in PKP2cKO; (3) AAV9-PKP2 (Tenaya TN-401) — reduced pathology in human splice-site mutation model. Effective dose estimated at high 10^13 to low 10^14 vg/kg — at the threshold of immunogenic risk. MyoAAV4A variant may enable lower doses. Local delivery (antegrade intracoronary, retrograde coronary vein) being explored. (sources/ACM-Genotype-Mx-JCE-2024)
Exercise risk in PKP2: Exercise is the most established modifiable risk factor for PKP2-ARVC penetrance and VA — the strongest evidence base among all ACM genes. (sources/ACM-Genotype-Mx-JCE-2024)
PKP2 P/LP variants in AF <40 without overt ARVC/structural disease: In a prospective cohort of 122 patients with AF before age 40 specifically excluding structural heart disease (normal LVEF, no cardiomyopathy, normal CMR in 49%), 2 of 8 P/LP variant carriers had PKP2 variants. These patients did not meet criteria for SHD at inclusion. This is notable because PKP2 is classically associated with RV-predominant ARVC; its detection in structurally normal young AF patients suggests AF may be the initial clinical manifestation of a PKP2 cardiomyopathy genotype before overt ARVC develops. Careful longitudinal follow-up is warranted. (sources/eoaf-riskfactor-ehj-2026, rating: medium)
UK Biobank population-level AF association (n = 403,990): PKP2 pLOF variants were significantly associated with AF at exome-wide significance: OR 2.12 (95% CI 1.60–2.82; P = 2.21 × 10⁻⁷), replicated in an external cohort of >160,000 individuals. This provides the first population-scale confirmation that PKP2 pLOF — not merely missense variants in a GWAS locus — confers substantial AF risk. Prior GWAS had identified a common variant signal near the PKP2 locus; this study demonstrates that rare loss-of-function in the gene itself independently increases AF risk. PKP2 protein was confirmed to be predominantly expressed in cardiomyocytes. (sources/Biobank-AF-JAMA-2024, rating: high)
CJC 2024 Case 1 — Large PKP2 deletion presenting as isolated AF with sibling SCD: A 26-year-old man with persistent AF and normal biventricular function was found to carry a large PKP2 deletion spanning exons 4–14 on genetic testing. His younger brother had died during sleep at age 20 (autopsy attributed to myocarditis — a recognised inflammatory phase of ARVC). The same deletion was confirmed in the deceased brother retrospectively. Cascade screening identified the deletion in the mother and another brother — all 3 living carriers are now being monitored for ARVC. This case illustrates three key points: (1) large PKP2 deletions are missed by standard Sanger sequencing — NGS or MLPA required; (2) ARVC can present as isolated AF with normal ventricular function before structural disease emerges; (3) apparent "myocarditis" SCD in a young individual should prompt genetic evaluation in surviving relatives. (sources/genetic-af-cjc-2024, rating: high)

ClinGen Gene-Disease Validity — PKP2

ARVC / ACM (Definitive): PKP2 has definitive gene-disease validity for arrhythmogenic cardiomyopathy — the strongest evidence classification. PKP2 is the most common genetic cause of ARVC, accounting for up to two-thirds of familial cases. (sources/clingen-summary-2026-05-09, rating: high)
DCM (Disputing, 05/30/2025): ClinGen classification for PKP2 in dilated cardiomyopathy is "Disputing" — the evidence claiming PKP2 variants cause DCM without an ARVC phenotype is insufficient or contradicted. Variants in PKP2 found in DCM patients should be interpreted with caution; the underlying diagnosis may be ARVC presenting with predominant LV dysfunction (arrhythmogenic DCM) rather than true PKP2-DCM. (sources/clingen-summary-2026-05-09, rating: high; ClinGen classification date: 05/30/2025)
Brugada Syndrome (Disputing, 11/21/2017): ClinGen classifies PKP2 as Disputing for Brugada syndrome. Published reports linking PKP2 to BrS are not supported by sufficient rigorous evidence; PKP2 variants causing a sodium channelopathy phenotype via Nav1.5 interaction does not equate to BrS causality at a population genetic level. (sources/clingen-summary-2026-05-09, rating: high; ClinGen classification date: 11/21/2017)
CPVT (Disputing, 01/20/2021): ClinGen classifies PKP2 as Disputing for CPVT. Published reports of PKP2 variants in CPVT patients are insufficient to establish causality; clinicians should be cautious before attributing a CPVT phenotype to PKP2 without ruling out RYR2, CASQ2, TECRL, or TRDN. (sources/clingen-summary-2026-05-09, rating: high; ClinGen classification date: 01/20/2021)

Contradictions / Open Questions

Nav1.5 reduction — PKP2-specific vs. universal desmosomal finding: PKP2 knockdown reduces sodium current amplitude via co-precipitation with Nav1.5. However, the degree to which other desmosomal gene variants (DSP, DSG2, DSC2) share the same sodium channelopathy phenotype is less well-characterized. Extrapolating the PKP2-Nav1.5 interaction to all desmosomal ACM variants is not supported by equivalent evidence and may over-attribute electrophysiological findings to a "final common pathway" shared across all ACM genes. (sources/acm-hrs-2019)
Exercise restriction extrapolated from PKP2 data to all ARVC variants: The strongest evidence for exercise-induced ARVC penetrance is from PKP2 carriers (endurance athletes with PKP2 variants develop disease earlier and with higher burden). Exercise restriction recommendations are formally extended to all ACM gene carriers, but the evidence base for non-desmosomal variants (FLNC, PLN, LMNA) is substantially weaker. The Class I exercise restriction guidance in ARVC is largely supported by PKP2 data. (sources/acm-hrs-2019)
ClinGen disputes PKP2 in DCM, BrS, and CPVT (2026): Despite PKP2's mechanistic interactions with Nav1.5 (potential BrS connection) and SR calcium release unit (potential CPVT connection), ClinGen does not validate these gene-disease associations. The DCM disputing classification (05/30/2025) is particularly important — PKP2 variants in DCM patients may represent ARVC with LV-dominant phenotype (arrhythmogenic DCM), not true PKP2-DCM. Clinicians receiving a "PKP2 pathogenic" report on a DCM panel should consider referring for ARVC evaluation (CMR with tissue characterisation, RV assessment, exercise testing). (sources/clingen-summary-2026-05-09, rating: high)
Large deletions/duplications in PKP2 missed by Sanger — clinical testing gap: Large deletions/duplications account for 1–2% of PKP2 pathogenic variants and cannot be detected by standard Sanger sequencing. In the current era of next-generation sequencing (NGS) gene panels, most clinical laboratories detect copy number variants — but older test results or restricted panels may have missed these variants. Patients with a clinically confident ARVC diagnosis and a Sanger-negative result should be considered for NGS panel re-testing. (sources/acm-hrs-2019)

Connections

Related to sources/genetic-af-cjc-2024
Related to concepts/Desmosome
Related to entities/ARVC
Related to concepts/Final-Common-Pathway
Related to entities/SCN5A
Related to concepts/Exercise-Restriction-in-ARVC
Related to concepts/Cascade-Family-Screening
Related to concepts/Early-Onset-Atrial-Fibrillation
Related to entities/Atrial-Fibrillation
Related to sources/Biobank-AF-JAMA-2024
Related to sources/ACM-Genotype-Mx-JCE-2024
Related to concepts/ClinGen-Gene-Disease-Validity
Related to sources/clingen-summary-2026-05-09