Key result
Combined heterozygous RYR2-A1855D and SCN10A-Q1362H variants in proband-derived cardiomyocytes accentuated Ca2+ homeostasis disorders and action potential prolongation compared to single variants.
Why the study?
The study investigated cardiomyocyte phenotypes using induced pluripotent stem cells in a family pedigree with novel heterozygous RYR2-A1855D and SCN10A-Q1362H variants occurring alone and in combination.
iPSC models may dissect effects of compound RYR2/SCN10A variants; leaves open clinical translation pending validation.
We illustrate use of induced pluripotent stem cells (iPSCs) as platforms for investigating cardiomyocyte phenotypes in a human family pedigree exemplified by novel heterozygous RYR2-A1855D and SCN10A-Q1362H variants occurring alone and in combination. The proband, a four-month-old boy, presented with polymorphic ventricular tachycardia. Genetic tests revealed double novel heterozygous RYR2-A1855D and SCN10A-Q1362H variants inherited from his father (F) and mother (M), respectively. His father showed ventricular premature beats; his mother was asymptomatic. Molecular biological characterizations demonstrated greater TNNT2 messenger RNA (mRNA) expression in the iPSCs-induced cardiomyocytes (iPS-CMs) than in the iPSCs. Cardiac troponin Ts became progressively organized but cytoplasmic RYR2 and SCN10A aggregations occurred in the iPS-CMs. Proband-specific iPS-CMs showed decreased RYR2 and SCN10A mRNA expression. The RYR2-A1855D variant resulted in premature spontaneous sarcoplasmic reticular Ca 2+ transients, Ca 2+ oscillations and increased action potential durations. SCN10A-Q1362H did not confer any specific phenotype. However, the combined heterozygous RYR2-A1855D and SCN10A-Q1362H variants in the proband iPS-CMs resulted in accentuated Ca 2+ homeostasis disorders, action potential prolongation and susceptibility to early afterdepolarizations at high stimulus frequencies. These findings attribute the clinical phenotype in the proband to effects of the heterozygous RYR2 variant exacerbated by heterozygous SCN10A modification. This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
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Zhou et al. (2023) studied Polymorphic ventricular tachycardia (n=3). Combined heterozygous RYR2-A1855D and SCN10A-Q1362H variants vs. Single variants (RYR2-A1855D or SCN10A-Q1362H) was evaluated on Ca2+ homeostasis and action potential duration in iPSC-induced cardiomyocytes. Combined heterozygous RYR2-A1855D and SCN10A-Q1362H variants in proband-derived cardiomyocytes accentuated Ca2+ homeostasis disorders and action potential prolongation compared to single variants.
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