Effect of cMyBP-C ablation on Ca ²⁺ handling in hiPSC-ECT. (A and B) Absolute (A) and normalized (B) averaged Ca²⁺ transient (Ca²⁺TR) traces in day 40–54 cMyBP-C^+/+ (broken traces), cMyBP-C^+/− (grey traces), and cMyBP-C^−/− (black traces) hiPSC-ECTs loaded with Fura2-AM. (C) Normalized average traces focusing on the time from Ca²⁺ peak to 50% Ca²⁺-transient decay (Ca²⁺DT₅₀). (D–G) Box and whisker plots of cytoplasmic Ca²⁺-transient amplitude as estimated by the ∆F₃₄₀/F₃₈₀ ratio (Ca²⁺TR; D); time to Ca²⁺-transient peak (Ca²⁺T₁₀₀; E); time from Ca²⁺-transient peak to 50% decay (Ca²⁺DT₅₀; F) and time from 50 to 75% Ca²⁺-transient decay (Ca²⁺DT_50-75; G) in hiPSC-ECT. All experiments were performed at 37°C with pacing at 1.5 Hz. n ≥ 11 biological replicates; *P < 0.05; **P < 0.01; ***P < 0.001 as calculated by one-way ANOVA with Tukey’s multiple comparisons test; see Table S7 for specific P values.