Front Biosci (Landmark Ed). 2026 Feb 12;31(2):49097. doi: 10.31083/FBL49097.
ABSTRACT
BACKGROUND: Long-QT syndrome type 2 (LQTS2), which is associated with life-threatening cardiac arrhythmias, is caused by pathogenic heterozygous loss-of-function mutations in the KCNH2 gene. This gene encodes the pore-forming Kv11.1 α-subunit of the ion channel that carries the rapid delayed rectifier potassium current (IKr). Pathogenic loss-of-function mutations reduce the amplitude of IKr, thereby prolonging the action potential (AP) of ventricular cardiomyocytes, and in turn, the QT interval of the electrocardiogram (ECG). The aim of the present in silico study was to test the extent to which allele-specific suppression ('silencing') of the mutant KCNH2 allele can alleviate the effects of dominant-negative LQTS2 mutations.
METHODS: Two recent and comprehensive models of the electrical activity of a single human ventricular cardiomyocyte, i.e., the 'Bartolucci-Passini-Severi model as published in 2020' and the 'Tomek-Rodriguez model following the O'Hara-Rudy dynamic (ORd) model' (known as the BPS2020 and ToR-ORd models, respectively) were used to assess the effects of mild and severe LQTS2 mutations on the AP duration at 90% repolarization (APD90) and the APD90 restitution obtained with an S1-S2 pacing protocol.
RESULTS: For severe mutations, the mutation-induced prolongation of the APD90 at a stimulation rate of 1 Hz is reduced from 166% to 99% in the BPS2020 model and from 111% to 71% in the ToR-ORd model upon 70% suppression of the mutant allele. For mild mutations, this prolongation is reduced from 77% to 44% and from 57% to 34%, respectively. An even greater effect is observed when the mutant KCNH2 allele is inhibited by up to 90%, but the greater suppression is only marginal for mild mutations. The steepness of the mutant APD90 restitution curves is considerably reduced upon suppression, which may exert an anti-arrhythmic effect.
CONCLUSIONS: Silencing of the mutant allele can substantially, but only partially, counteract the effects of mild or severe LQTS2 mutations on IKr. Allele-specific inhibition of the mutant KCNH2 allele alone is not sufficient to fully treat the effects of LQTS2 mutations and should be accompanied by a replacement gene therapy, creating a suppression-and-replacement ("SupRep") gene therapy.
PMID:41761963 | DOI:10.31083/FBL49097