Fig. 1

Generation of JellyOp expressing mouse ESCs and light-induced cAMP production in cardiomyocytes. a Plasmid for expression of JellyOp in fusion with the 1D4 rhodopsin epitope and with an internal ribosome entry site (IRES) for co-expression of the green fluorescence protein (GFP) under control of the chicken β-actin promoter (CAG). b Immunostaining of a transgenic ESC colony expressing GFP (green) and JellyOp (red: 1D4 rhodopsin epitope staining) (nuclear staining in blue, bars: 10 μm; insert: 5 µm). c GFP positive (green) cardiomyocytes indicated by α-actinin (yellow) staining (nuclear staining in blue, bar: 20 µm). d cAMP levels in JellyOp and GFP EBs after illumination (2.9 mW mm⁻², 5 min, MDL: 100 µM MDL-12,330A) or isoprenaline (Iso, 1 µM, 5 min) application (n = 5–12, Welch ANOVA: p = 0.0014, Games–Howell post-test: *p < 0.05, **p < 0.01). e Relationship between cAMP levels and light intensity in lactate-purified (see Methods) cardiomyocytes fitted with Hill equation (n = 5–12). Error bars: S.E.M.