Abstract 14781: Computational Prediction of Protein Subdomain Stability as a Novel Approach to Cardiac Myosin Binding ProteinC Variant Adjudication and Clinical Risk Stratification in Hypertrophic Cardiomyopathy

Abstract

Introduction: Patients with HCM and a pathogenic sarcomere variant have a higher risk of adverse clinical outcomes compared to those without a sarcomere gene variant. Pathogenic truncating variants in MYBPC3 (encoding cardiac myosin binding protein C, MYBP-C) cause loss-of-function and are the most common genetic cause of HCM. However, a substantial number of patients carry missense variants in MYBPC3 that cannot be clearly classified as either pathogenic or benign. Interpretation of these variants of uncertain significance (VUS) remain a significant challenge. Hypothesis: We hypothesize that a structural-based algorithm, STRUM, which estimates the effect of missense variants on subdomain protein folding, will enable clinical risk stratification of patients with HCM and a MYBPC3 VUS. Methods and Results: Among the 7,963 patients in the multi-center Sarcomeric Human Cardiomyopathy Registry (SHaRe), 19 unique missense pathogenic variants and 120 missense VUSs in MYBPC3 were identified. Within SHaRe and GnomAD, 110 benign missense variants (allele frequency > 4e-05) were identified. Following structural modeling of each MyBP-C domain, variants were predicted to cause subdomain misfolding if ΔΔG < = -1.2 kcal/mol (STRUM+). 93% of benign variants were predicted to be STRUM (-). Time-event analysis for an overall composite clinical endpoint [defined as the first occurrence of ventricular arrhythmia, heart failure, all-cause mortality, atrial fibrillation (AF), or stroke] demonstrated that patients carrying a STRUM+ MYBPC3 VUS exhibited a higher rate of adverse events compared to those with a STRUM- VUS (Hazard Ratio=2.29, P=0.0282). Of the 120 missense VUSs, 34 (28%) were STRUM+. In silico saturation mutagenesis of MYBPC3 identified 4,943/23,427 (21%) missense variants predicted to cause subdomain misfolding. Conclusions: STRUM is capable of clinically risk stratifying HCM patients with a MYBPC3 VUSs . These findings support the routine use of STRUM in variant interpretation algorithms and clinical decision making.