rs397516933 — DSP DSP Gln1277Ter

DSP Gln1277Ter — When the Cardiac Scaffolding Breaks

Heart muscle cells endure relentless mechanical force with every beat — roughly 100,000 contractions per day. Holding adjacent cells together at sites of peak stress are desmosomes¹¹ desmosomes
protein complexes that act as molecular rivets between cardiac muscle cells, and desmoplakin (DSP) is their central load-bearing component. The Gln1277Ter variant — a C-to-T change at genomic position chr6:7,580,019 — introduces a premature stop codon that truncates the DSP protein at amino acid 1277, eliminating the entire C-terminal domain responsible for anchoring intermediate filaments to the desmosomal plaque. Cells carrying this truncated protein cannot maintain adhesion under mechanical load.

The Mechanism

The c.3829C>T substitution converts codon 1277 from glutamine (CAA) to a stop codon (TAA), producing either a truncated 1276-amino-acid protein or triggering nonsense-mediated mRNA decay²² nonsense-mediated mRNA decay
a cellular quality-control process that degrades mRNAs with premature stop codons, often eliminating the protein entirely. Either outcome results in desmoplakin haploinsufficiency — roughly half the normal desmoplakin output from a single functional copy. Under the mechanical stress of cardiac contraction, DSP-haploinsufficient cardiomyocytes show a 75% adhesion failure rate versus 8% in controls (P<0.001)³³ DSP-haploinsufficient cardiomyocytes show a 75% adhesion failure rate versus 8% in controls (P<0.001), with individual cells detaching from their neighbors. The consequence is fibrosis — the heart patches torn adhesion junctions with scar tissue — and a pro-arrhythmic substrate of patchy LV fibrosis that can trigger dangerous ventricular rhythms even before systolic function deteriorates.

DSP-related arrhythmogenic cardiomyopathy (DSP-ACM) differs clinically from classical arrhythmogenic right ventricular cardiomyopathy (ARVC). In a landmark study of 107 DSP-mutation carriers, 55% showed exclusive left ventricular involvement compared with 0% of PKP2-mutation carriers⁴⁴ 55% showed exclusive left ventricular involvement compared with 0% of PKP2-mutation carriers — an almost diametrically opposite distribution. Episodes resembling acute myocarditis (chest pain, troponin rise, ST changes) occur in 15–39% of carriers, often as the first clinical presentation, and can recur. These episodes accelerate fibrosis and significantly raise subsequent arrhythmia and heart failure risk.

The Evidence

Three large recent studies have defined the clinical burden. Gasperetti et al. (European Heart Journal, 2025)⁵⁵ Gasperetti et al. (European Heart Journal, 2025) followed 800 DSP pathogenic variant carriers and documented sustained ventricular arrhythmia in 17.4% of the cohort (3.9% per year). A striking 32.5% of carriers did not meet established diagnostic criteria for any cardiomyopathy subtype, underscoring how easily DSP-ACM is missed by standard workups. Myocardial injury episodes — the myocarditis-like flares — were associated with a 2.4-fold increase in ventricular arrhythmia risk and a 5.1-fold increase in heart failure hospitalizations.

Hoorntje et al. (Circ Genomic Precis Med, 2023)⁶⁶ Hoorntje et al. (Circ Genomic Precis Med, 2023) studied 170 individuals with DSP truncating variants and found ventricular arrhythmia (sudden cardiac arrest, sustained VT, or appropriate ICD therapy) in 33%. Critically, they showed that variants in positions subject to nonsense-mediated decay — which the Gln1277Ter variant likely is, given its location in exon 23 of 24 — were significantly more arrhythmogenic than truncating variants that escape decay and produce a stable truncated protein. Variant location is now recognized as an independent risk stratification tool.

Lota et al. (Circulation, 2022)⁷⁷ Lota et al. (Circulation, 2022) found DSP truncating variants in 3.1% of acute myocarditis patients versus 0.4% of healthy controls (OR 8.2, P=0.001). Five-year all-cause mortality was 11.1% for genotype-positive myocarditis patients versus 3.3% for genotype-negative — nearly a 3.5-fold difference.

Practical Actions

Heterozygous carriers of this variant require cardiac surveillance even in the absence of symptoms. The standard approach includes baseline cardiac MRI with late gadolinium enhancement (the primary tool for detecting early fibrosis), Holter monitoring, and genetic cascade testing for first-degree relatives. Vigorous competitive athletics is generally discouraged pending formal cardiological assessment, as high mechanical cardiac stress may precipitate adhesion failure. Episodes of chest pain, palpitations, or unexplained troponin elevation in a carrier should be evaluated urgently as possible myocarditis-like events, not dismissed as common causes.

Interactions

DSP-ACM risk is modified by other desmosomal gene variants. Compound heterozygosity — carrying pathogenic variants in two different desmosomal genes (e.g. DSP + PKP2, DSP + DSG2, or DSP + JUP) — is associated with earlier onset and more severe disease in clinical series. Carriers of this DSP variant who also carry variants in PKP2 (rs111517471) or DSG2 (rs397516946) may warrant particularly aggressive surveillance protocols. These interactions should be assessed by a specialist in inherited cardiomyopathies. Physical activity level appears to act as an environmental modifier: endurance athletes with desmosomal variants develop cardiomyopathy at substantially higher rates than sedentary carriers.