Fig 1: Generating iPS-derived atrial cardiomyocytes. (a) Cardiomyocyte differentiation protocol outline, (b) immunofluorescent images of cardiomyocytes stained for ventricular- and atrial-specific isoforms of myosin light chain, PAL—standard protocol, PAL + RA—atrial protocol, (c) characterization of cardiomyocyte populations based on fluorescent images analysis (cardiomyocytes positive for TnT, atrial—Mlc2a+/Mlc2v-) and qPCR, (d) characteristic path-clamp traces of atrial-like (MDP < -60 mV, APA > 100 mV, dV/dt max >5 V/s, APD90 < 300 ms, APD90/APD50 > 1.2), ventricular-like (MDP < -60 mV, APA > 100 mV, dV/dt max >5 V/s, APD90 > 400 ms, APD90/APD50 < 1.2), and nodal-like (MDP > -50 mV, APA < 100 mV, dV/dt max <5 V/s) cardiomyocytes, (e) characterization of cardiomyocyte populations based on patch-clamp data, and (f) electrophysiological parameters of iPSC-derived cardiomyocytes measured by patch-clamp. *p < 0.05. APD, action potential duration; MDP, minimal diastolic potential.