Figure 5

SERCA activity in STX12‐deficient cardiomyocytes and its role in calcium dynamics. a) Zebrafish RNAseq GO enrichment analysis revealed the association of STX12 with cardiac functions. b) Volcano plot of zebrafish RNAseq data. The genes that were significantly changed (p < 0.05) are marked with light red dots, while the rest were marked with gray dots. Stx12 and the ortholog of SERCA2 in zebrafish were marked with green and dark red dots, respectively. c) Western blot analysis of SERCA2 expression in control (Stx12^flox/flox) and Stx12‐cKO (Stx12^flox/flox with CTnT‐Cre) mice. d) Quantification of Western blot in (c). SERCA2 level was significantly decreased in Stx12‐cKO compared with control (Stx12‐flox) (Flox‐control, n = 4, cKO, n = 4, p = 0.0019). e) The normalized action potential curves of cardiomyocytes in vitro before and after adding thapsigargin (TG), with the arrow indicating the shift of the curve over time. f) The calcium dynamical curves with the arrow indicate the shift of the curve over time (0, 10, 20 min). g) The change in the decaying tau of Ca²⁺ in cardiomyocytes before and after adding TG (10 min). Tau was significantly increased after adding TG (control, n = 157 curves; TG, n = 72 curves, t‐test, p < 0.0001). h) The Ca²⁺ change curves under different SR Ca²⁺ pumps (SERCA) activities were obtained through model simulation. i) Curve of tau constants of Ca²⁺ during the decay phase of Ca²⁺ curves obtained through single exponential fitting under different SERCA Ca²⁺ pump activities. Statistical results: **p < 0.01, ****p < 0.0001; t‐test.