Isogenic Pairs of hiPSC-CMs with Hypertrophic Cardiomyopathy/LVNC-Associated ACTC1 E99K Mutation Unveil Differential Functional Deficits.

James G.W Smith,Jamie R Bhagwan,Elizabeth Scott,Roberto Barriales-Villa,Lorenzo Monserrat,Steve Marston,Diogo Mosqueira,Chris Denning,Thomas Owen,Sian E Harding,Ingra Mannhardt,Thomas Eschenhagen,Arne Hansen,Asha Patel

doi:10.1016/j.stemcr.2018.10.006

Abstract

SummaryHypertrophic cardiomyopathy (HCM) is a primary disorder of contractility in heart muscle. To gain mechanistic insight and guide pharmacological rescue, this study models HCM using isogenic pairs of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the E99K-ACTC1 cardiac actin mutation. In both 3D engineered heart tissues and 2D monolayers, arrhythmogenesis was evident in all E99K-ACTC1 hiPSC-CMs. Aberrant phenotypes were most common in hiPSC-CMs produced from the heterozygote father. Unexpectedly, pathological phenotypes were less evident in E99K-expressing hiPSC-CMs from the two sons. Mechanistic insight from Ca2+ handling expression studies prompted pharmacological rescue experiments, wherein dual dantroline/ranolazine treatment was most effective. Our data are consistent with E99K mutant protein being a central cause of HCM but the three-way interaction between the primary genetic lesion, background (epi)genetics, and donor patient age may influence the pathogenic phenotype. This illustrates the value of isogenic hiPSC-CMs in genotype-phenotype correlations.

Highlights

Cardiomyopathies are defined as primary disorders of contractility in heart muscle
Differentiation to high purity (>90% a-actinin+) cardiomyocytes (Figures 1C and 1D) allowed reactivity to an antibody specific to the mutant E99K peptide to be tested. This showed positive protein expression in $50% of the E99K1 and E99K2 human induced pluripotent stem cell (hiPSC)-CMs, suggesting that only one allele of the ACTC1 gene is active in any given cell
E99K peptide reactivity was not detected in non-carrier relative (NC) hiPSC-CMs (Figures 1C and 1D)

Summary

Introduction

Cardiomyopathies are defined as primary disorders of contractility in heart muscle. Most classifications of cardiomyopathy divide the disease into acquired and inherited disease due to a mutation and into hypocontractile phenotype with reduced ejection fraction or hypercontractile phenotype with preserved ejection fraction (Maron et al, 2006).

Results

Discussion

Conclusion