Effect of cMyBP-C ablation on strain and Ca ²⁺ -handling properties in hiPSC-CM plated on micropatterns. (A–C) Images of cMyBP-C^+/+ (A), cMyBP-C^+/− (B), and cMyBP-C^−/− (C) hiPSC-ECT immune-stained for α-actinin (green fluorescence) and β-catenin (white fluorescence). (D–I) Box and whisker plots of maximum strain produced (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); cytoplasmic Ca²⁺-transient amplitude following caffeine administration as estimated by the ∆F₃₄₀/F₃₈₀ ratio (CaffTR; H); and fractional SR Ca²⁺ release as estimated by the Ca²⁺TR/CaffTR ratio (H). n ≥ 21 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 S4 for specific P values.