Mechanisms of Pathogenicity of Hypertrophic Cardiomyopathy-Associated Troponin T (TNNT2) Variant R278C+/- During Development

Abstract

Hypertrophic cardiomyopathy (HCM) is one of the most common heritable cardiovascular diseases and variants of TNNT2 (cardiac troponin T) are linked to increased risk of sudden cardiac arrest despite causing limited hypertrophy. In this study, a TNNT2 variant, R278C+/-, was generated in both human cardiac recombinant/reconstituted thin filaments (hcRTF) and human-induced pluripotent stem cells (hiPSCs) to investigate the mechanisms by which the R278C+/- variant affects cardiomyocytes at the proteomic and functional levels. The results of proteomics analysis showed a significant upregulation of markers of cardiac hypertrophy and remodeling in R278C+/- vs. the isogenic control. Functional measurements showed that R278C+/- variant enhances the myofilament sensitivity to Ca2+, increases the kinetics of contraction, and causes arrhythmia at frequencies >75 bpm. This study uniquely shows the profound impact of the TNNT2 R278C+/- variant on the cardiomyocyte proteomic profile, cardiac electrical and contractile function in the early stages of cardiac development. Translational PerspectiveHypertrophic cardiomyopathy (HCM) is the leading known cause of sudden cardiac arrest in the young. Thin-variant associated HCM variants make up to 15% of familial HCM yet their molecular mechanisms remain less clear relative to thick filament variants. Here, we employ computational modeling, human cardiac recombinant/reconstituted thin filaments (hcRTF), and hiPSC-CMs to study the thin filament TNNT2 R278C+/- variant, revealing its extensive pathogenicity and potential mechanisms by which it can lead to HCM and sudden death. Mavacamten, the recently FDA-approved treatment, was effective in alleviating contractile dysfunction in TNNT2 R278C+/- hiPSC-CMs, positing it as a potential therapy for thin filament HCM. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=117 HEIGHT=200 SRC="FIGDIR/small/542948v2_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@102a8b0org.highwire.dtl.DTLVardef@190e356org.highwire.dtl.DTLVardef@13d3f9aorg.highwire.dtl.DTLVardef@1a9c33_HPS_FORMAT_FIGEXP M_FIG C_FIG