Fig. 3
Induction of HCN4-overexpressing human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). A Transmission electron microscopy (TEM) at high magnification showed aligned Z-bands (black arrowheads) and mitochondria (white arrowheads) in HCN4-overexpressing iPSC-CMs. B HCN4 (magenta) and cardiac troponin T (cTnT, green) expression in iPSC-CMs on differentiation day 30. Scale bar is 100 µm. C EGFP expression in HCN4-overexpressing iPSC-CMs on differentiation day 103. Scale bar is 200 µm. D Representative If currents in HCN4-overexpressing (upper) or non- overexpressing (bottom) iPSC-CMs. E If − V relationship curves in HCN4-overexpressing (red line, n = 6) or non-overexpressing (green line, n = 4) iPSC-CMs (The data are shown as means ± standard deviation. *P < 0.05, **P < 0.01)