Structural and electrochemical coupling of paired myocytes. Representative images of pairs of mononucleated (DAPI, blue) mouse neonate myocytes or mES or miPS-CMs stained for actin (A), β-catenin (B), and connexin-43 (C). Bar, 10 µm. GFP-tagged (green) mES- or miPS-CMs were used for heterogeneous pairing. (D) Representative ratiometric Ca²⁺ transients across several contraction cycles for different µtissue types. (E) Normalized cross-correlation functions and cross-correlation coefficients for different µtissue types. (F) Diastolic Ca²⁺ levels for each cell within a cell pair. Results are presented as mean ± SEM (n = 8, 13, 9, 15, and 6 for neonate-neonate, mES-mES, mES-neonate, miPS-miPS, and miPS-neonate, respectively). *, P < 0.05, statistically significant difference with homogeneous neonate pair.