Comparison of contractile and Ca ²⁺ -handling characteristics in two independent cMyBP-C ^−/− hiPSC-ECT lines. (A–H) Box and whisker plots of maximum twitch force amplitude (TF; A); time to peak developed force (CT₁₀₀; B); time from peak to 50% twitch force decay (RT₅₀; C) and time from 50 to 90% twitch force decay (RT_50-90; D); cytoplasmic Ca²⁺-transient amplitude as estimated by the ∆F₃₄₀/F₃₈₀ ratio (Ca²⁺TR; E); time to Ca²⁺-transient peak (Ca²⁺T₁₀₀; F); time from Ca²⁺-transient peak to 50% decay (Ca²⁺DT₅₀; G) and time from 50 to 75% Ca²⁺-transient decay (Ca²⁺DT_50-75; H) in DF-CR8 12-1 (grey boxes; n ≥ 15 biological replicates) and DF-CR8-18 (hashed boxes; n ≥ 3 biological replicates) hiPSC-ECT carrying cMyBP-C compound heterozygous and homozygous frame-shift mutations. All experiments were performed at 37°C with pacing at 1.5 Hz. Absolute P values calculated by Student’s unpaired t test with Welch’s correction indicated in each panel.