iPSC and EHT methods. (A) Three human iPSC lines were used in the study: the HCM patient with the heterozygous c.574G>A (p.E192K) in TPM1 and two WT controls (WT1 and WT2) without any known mutations in sarcomeric genes showing homozygous WT alleles. All iPSC lines showed a normal karyotype. (B) WT2 and HCM iPSC lines were originally derived for this work and were tested for markers of pluripotency and differentiation into three lineages. Scale bars, 100 μm. (C) EHTs were created from decellularized porcine myocardium seeded with iPSC-CMs. Isometric mechanics, calcium transients, and length–force relationships were measured in EHTs.