rs397516943 — DSP

Desmoplakin p.Arg160Ter — When the Cardiac Glue Breaks

Your heart muscle is held together by molecular anchors called desmosomes¹¹ desmosomes
protein complexes at the intercalated discs between cardiomyocytes — they transmit mechanical force and maintain cell-cell adhesion during every heartbeat. Desmoplakin (DSP) is the largest desmosomal protein and acts as the structural linchpin, connecting desmosomal cadherins at the cell surface to the intermediate filament cytoskeleton deep inside the cell. Without functional desmoplakin, cardiac cells cannot hold together under the mechanical stress of beating, leading to cell death, fibrofatty replacement of the myocardium, and the substrate for life-threatening arrhythmias.

The p.Arg160Ter mutation (c.478C>T, NM_004415.4) converts arginine at position 160 into a premature stop codon. The resulting truncated mRNA is targeted for nonsense-mediated decay²² nonsense-mediated decay
a cellular quality-control mechanism that degrades mRNA transcripts containing premature stop codons, preventing production of toxic truncated proteins — meaning the mutant allele produces essentially no functional desmoplakin protein. The result is haploinsufficiency: only one functional DSP allele remains to supply desmoplakin to every intercalated disc in every cardiomyocyte, leaving the heart structurally vulnerable.

This variant is classified Pathogenic/Likely pathogenic by 10 major genetic testing laboratories in ClinVar (VCV000044922), including GeneDx, Mayo Clinic Laboratories, Ambry Genetics, Labcorp Genetics, and the Stanford Center for Inherited Cardiovascular Disease — the highest possible evidence tier for rare disease variants.

The Mechanism

The p.Arg160Ter variant sits in the N-terminal head domain of DSP, upstream of the plakin domain and both spectrin repeat rod domains. A stop codon this early in the protein eliminates the entire functional architecture of desmoplakin. Recent experimental work³³ Recent experimental work
Smith et al., bioRxiv 2025 demonstrated that truncating DSP variants reduce DSP protein levels by 23–62% of normal in patient-derived cardiomyocytes. Under conditions of heightened contractile stress (simulated by endothelin-1 exposure), DSP-haploinsufficient cardiomyocytes showed 75% adhesion failure versus only 8% in controls. At baseline contractile load, adhesion was intact — explaining why carriers can appear clinically normal for decades before disease manifests during physiological or pathological stress (intense exercise, myocarditis, pregnancy).

The loss of desmosomal integrity triggers a cascade: cardiomyocytes detach and die, the immune system responds with inflammation, and myofibroblasts replace the lost muscle with fibrous and fatty tissue. This fibrofatty replacement creates late gadolinium enhancement⁴⁴ late gadolinium enhancement
a signal on cardiac MRI that indicates fibrous scar tissue, where gadolinium contrast agent persists because normal cardiomyocytes wash it out but scar tissue cannot visible on cardiac MRI and provides the electrical substrate for reentrant ventricular tachycardia and ventricular fibrillation.

The Evidence

DSP cardiomyopathy is now recognized as a distinct entity from classical arrhythmogenic right ventricular cardiomyopathy (ARVC). The landmark multicenter study by Smith et al., Circulation 2020⁵⁵ multicenter study by Smith et al., Circulation 2020
107 DSP and 81 PKP2 patients established that DSP mutations produce left-dominant disease in 55% of patients (versus 0% for PKP2), with LV late gadolinium enhancement in 40% and acute myocardial injury episodes — a myocarditis-like inflammatory flare — in 15%. Right ventricular cardiomyopathy was present in only 14% of DSP patients, meaning classical ARVC diagnostic criteria systematically miss DSP disease.

The largest outcomes study to date, Gasperetti et al., Eur Heart J 2025⁶⁶ Gasperetti et al., Eur Heart J 2025
800 patients with pathogenic DSP variants across 26 international institutions, found that 17.4% of DSP carriers experienced sustained ventricular arrhythmias (3.9%/year). Myocardial injury episodes — which 8.8% of carriers experienced — dramatically amplified subsequent risk: hazard ratio 2.394 for sustained VA and 5.064 for heart failure hospitalization.

For variants specifically triggering nonsense-mediated decay of both major DSP isoforms⁷⁷ nonsense-mediated decay of both major DSP isoforms
both DSP-I (ubiquitous isoform) and DSP-II (heart-enriched shorter isoform) are eliminated, maximizing the desmoplakin deficit in cardiac tissue — as p.Arg160Ter does — the Hoorntje et al., Circ Genom Precis Med 2023⁸⁸ Hoorntje et al., Circ Genom Precis Med 2023
170 DSP patients from an international cohort study found these individuals were dramatically overrepresented among clinically affected patients versus unaffected carriers (83.6% vs 16.4%, p<0.0001). Ventricular arrhythmia occurred in 33% of affected individuals in this cohort.

Genotype-phenotype analysis confirms that DSP non-missense variants (truncating, frameshift, splice site — all producing haploinsufficiency) carry substantially worse LV involvement than missense variants: LV dysfunction in 76.5% vs 10%⁹⁹ LV dysfunction in 76.5% vs 10% (p=0.001) and LV MRI involvement in 92% vs 22% (p=0.001).

Practical Actions

Carriers of pathogenic DSP variants require cardiomyopathy-specialist care, not routine cardiology follow-up. The standard ARVC Task Force Criteria are specifically less sensitive for DSP disease because they prioritize right ventricular findings — a cardiac MRI protocol looking for subepicardial LV late gadolinium enhancement is the key diagnostic test.

Risk stratification now has a validated clinical tool: the DSP risk score integrates female sex, NSVT history, PVC burden, LVEF, and RV function to stratify 5-year VA risk as low (<5%), intermediate (5–20%), or high (>20%). Patients in the high-risk category should be considered for ICD implantation regardless of whether they have had a documented arrhythmic event. Patients who experience a myocardial injury episode (acute troponin rise with myocarditis- like presentation) should be urgently re-evaluated, as this dramatically escalates risk.

First-degree family members (parents, siblings, children) each carry a 50% risk of inheriting this variant. Cascade genetic testing and cardiac imaging of all adult relatives is standard of care.

Interactions

The R160* variant eliminates both major DSP isoforms (DSP-I and DSP-II) through nonsense-mediated decay — this biallelic isoform impact distinguishes early-truncating variants from variants that spare the heart-enriched DSP-II isoform and may explain the particularly high clinical penetrance observed.

DSP haploinsufficiency can interact with physiological demands that stress desmosomal integrity: intense endurance or resistance exercise, viral myocarditis, and pregnancy have all been associated with acute myocardial injury episodes (inflammatory flares) in DSP cardiomyopathy carriers. These events — detectable by troponin elevation — independently predict subsequent arrhythmia and heart failure and should prompt immediate cardiac evaluation.

Among desmosomal gene variants, double-variant carriers (a pathogenic DSP variant plus a pathogenic variant in PKP2, DSG2, or DSC2) show substantially worse outcomes than single-variant carriers in the desmosomal cardiomyopathy cohort data. If additional desmosomal variants are identified on clinical genetic testing, this escalates management urgency.