Fig. 4

JellyOp function in isolated mouse ventricular cardiomyocytes. a Overview of GFP fluorescence in an intact JellyOp mouse heart. b Section of the left ventricle with membrane-bound JellyOp-1D4 epitope signals (yellow) in GFP (green) positive cardiomyocytes (nuclear staining in blue, bar: 20 µm, insert: 5 µm). c Heart weight (HW) to femur length (FL) ratio in JellyOp (Jelly) and wild-type (WT) mice (>6 months of age, n = 5, two-sided unpaired Student's t-test: p = 0.8915). d, e Representative changes in peak L-type Ca²⁺ current (I_Ca,L) in a JellyOp ventricular cardiomyocyte upon illumination (d, blue bar, 100 µW mm⁻², 10 s) and original traces taken from time points indicated (e). f, g Statistical analysis of maximal I_Ca,L before (Contr., black) and after illumination (f, blue, 100 µW mm⁻², 10 s, n = 8, two-sided paired Student's t-test: p = 0.0035) or isoprenaline application (g, red, 1 µM, 75–100 s,  n = 13, two-sided paired Student's t-test: p = 0.00003). h Original trace (upper panel) of cell length measurement from an electrically stimulated isolated JellyOp ventricular cardiomyocyte upon illumination (blue bar, 100 µW mm⁻², 10 s) with corresponding fractional shortening (FS, middle panel) and relaxation constant τ_rel (lower panel). i, j Single traces of relative cell length in % of resting length (i) and normalized to maximal shortening (j) evoked by electrical stimulation (red line) before (1, black), 40 s (2, light blue) and 80 s (3, dark blue) after illumination (time points indicated in (h)). k, l Statistical analysis of maximal fractional shortening (k) and relaxation speed (τ_rel, l) before (black) and after (blue) illumination (100 µW mm⁻², 10 s, n = 10, two-sided paired Student's t-test, p = 0.0011 (k); Wilcoxon signed rank test, p = 0.004 (l)). m Delay from illumination onset to maximal effect on fractional cell shortening (FS, dark blue) and relaxation speed (τ_rel, light blue) (n = 8, Wilcoxon signed rank test, p = 0.04). Error bars: S.E.M.