rs397516946 — DSP DSP Q1810X

Desmoplakin Q1810X — A Dominant Truncation That Silently Remodels the Heart

The heart beats roughly 100,000 times per day. Each contraction generates forces that would tear ordinary tissue apart — forces absorbed by desmosomes¹¹ desmosomes
Disc-shaped protein complexes that mechanically interlock adjacent cardiac muscle cells, distributing tensile stress across the entire wall rather than concentrating it at any one point at the boundaries between cardiac muscle cells. Desmoplakin (DSP) is the largest and most abundant desmosomal protein, acting as the molecular anchor that links the desmosome's core to the intermediate filament cytoskeleton inside each cell. Without that anchor, desmosomes weaken, cardiac cells detach and die, and the dead tissue is replaced by fat and fibrous scar — tissue that conducts electricity erratically and can trigger fatal arrhythmias.

The rs397516946 variant introduces a premature stop codon²² premature stop codon
A single nucleotide change (c.5428C>T) that converts a glutamine codon (CAG) to a stop codon (TAG), halting translation at position 1,810 of the 2,872-amino-acid protein at position 1,810 in the DSP protein. This erases the entire carboxy-terminal tail domain — 1,062 amino acids that normally anchor the desmosome to the desmin intermediate filament network. The truncated protein is produced (nonsense-mediated decay is not expected at last-exon variants), but it cannot perform its anchoring function. A single copy is sufficient to cause disease: this is an autosomal dominant³³ autosomal dominant
One pathogenic allele on either chromosome is enough; each child of a carrier has a 50% chance of inheriting the variant condition.

The Mechanism

When one copy of DSP produces a tail-truncated protein, the desmosomal anchor at the cytoplasmic face of the junction is compromised. Over cycles of contraction and relaxation, junctions with weakened anchors accumulate micro-damage. Cardiomyocytes at these junctions die through apoptosis and are replaced by fibro-fatty tissue — the histological hallmark of arrhythmogenic cardiomyopathy. The fibrotic replacement creates slow-conduction corridors that sustain re-entrant ventricular arrhythmias⁴⁴ re-entrant ventricular arrhythmias
Electrical circuits that spin endlessly through scarred tissue, potentially accelerating to ventricular fibrillation and sudden cardiac death.

Unlike variants in PKP2 (the other common ARVC gene), DSP mutations preferentially affect the left ventricle. The fibro-fatty replacement is concentrated in the left ventricular sub-epicardium⁵⁵ fibro-fatty replacement is concentrated in the left ventricular sub-epicardium
Outer layer of the left ventricular wall, visible as late gadolinium enhancement on cardiac MRI even before systolic dysfunction develops. The disease also has an inflammatory phase — episodic myocardial injury episodes resembling acute myocarditis occur in approximately 15% of DSP carriers and mark a substantially higher subsequent arrhythmia and heart failure risk.

The Evidence

The most comprehensive characterization came from a multicenter study of 107 DSP and 81 PKP2 patients⁶⁶ multicenter study of 107 DSP and 81 PKP2 patients
Smith ED et al., Circulation 2020 that established DSP cardiomyopathy as a distinct clinical entity. Left ventricular predominance was found in 55% of DSP patients versus 0% of PKP2 patients. Late gadolinium enhancement (LGE) on cardiac MRI was present in 40% of DSP patients with MRI available, and critically, 35% of those with LGE had preserved systolic function at the time — meaning fibrosis precedes the ejection fraction decline that clinicians traditionally monitor. LVEF below 55% predicted severe ventricular arrhythmias with sensitivity of 85%.

The largest outcomes study to date enrolled 800 DSP variant carriers across 26 institutions in 9 countries⁷⁷ 800 DSP variant carriers across 26 institutions in 9 countries
Gasperetti A et al., European Heart Journal 2025. Over a median 3.7 years, 17.4% of carriers experienced sustained ventricular arrhythmias — an annual rate of 3.9%. Female sex, prior non-sustained ventricular tachycardia (NSVT), prior sustained ventricular arrhythmia, and LVEF ≤50% were all independent arrhythmia risk predictors on multivariable analysis. Myocardial injury episodes carried a 2.4-fold increased subsequent arrhythmia risk and 5-fold increased heart failure risk.

A dedicated arrhythmic follow-up study of 252 DSP patients⁸⁸ 252 DSP patients
Gasperetti A et al., JACC Advances 2024 found that 37.3% experienced ventricular arrhythmias over a median 44.5 months. The conventional ARVC risk calculator performed very poorly in this population (c-statistic 0.558 for LV-predominant disease), confirming that DSP cardiomyopathy requires gene-specific risk stratification tools rather than standard ARVC algorithms.

Practical Actions

Carriers of rs397516946 or any pathogenic DSP truncation should be evaluated by a specialist in inherited cardiac conditions (genetic cardiologist or electrophysiologist). The diagnostic workup centers on cardiac MRI with late gadolinium enhancement, which can detect the sub-epicardial fibrosis that precedes and predicts arrhythmia — traditional echocardiography misses this pattern in early disease. Annual cardiac MRI and 24-hour Holter monitoring are the standard surveillance intervals for carriers with normal baseline studies; symptomatic or high-risk carriers require more frequent assessment.

Physical activity carries a specific risk in desmosomal cardiomyopathy: intense aerobic exercise accelerates fibro-fatty remodeling and has been associated with more rapid disease progression and higher arrhythmia rates in carriers. Competitive and vigorous recreational sports should be restricted pending specialist evaluation of each carrier's individual risk profile and current disease extent.

ICD implantation is the primary means of preventing sudden cardiac death once significant arrhythmia risk is established — prior NSVT, extensive LGE, LVEF ≤50%, and prior myocardial injury episodes are the key risk indicators guiding device therapy decisions.

Interactions

DSP interacts genetically and functionally with other desmosomal proteins encoded by PKP2 (plakophilin-2, rs397516943-family), DSG2 (desmoglein-2), DSC2 (desmocollin-2), and JUP (junction plakoglobin). Compound heterozygosity — inheriting pathogenic variants in two desmosomal genes simultaneously — is associated with more severe and earlier-onset disease than single-gene pathogenic variants. The ClinGen gene curation⁹⁹ ClinGen gene curation
James CA et al., Circulation: Genomic and Precision Medicine 2021 identified DSP as one of 8 genes with definitive evidence for ARVC causation.

Environmental modifiers also interact with DSP status: intense endurance exercise is an established disease-accelerating factor in desmosomal cardiomyopathy carriers, and acute myocarditis-like inflammatory episodes can trigger rapid phenotypic conversion in previously unaffected carriers.