Fig. 5

A Schematic representation of Ca²⁺ transient parameters showing Ca²⁺ transient upstroke time, Ca²⁺ transient recovery time, Ca²⁺ transient amplitude, and diastolic Ca²⁺ levels. B Representative image of an isolated ventricular cardiomyocyte and a Ca²⁺ trace from adult ventricular cardiomyocyte of wild type and plna R14del mutants. Intracellular Ca²⁺ parameters were measured in adult ventricular cardiomyocytes of wild type (WT) and plna R14del, including C diastolic Ca²⁺ levels (mean ± SEM, *p = 0.05, WT n = 4, plna R14del n = 5), D systolic Ca²⁺ levels, E Calcium transient duration at 20%, 50, and 80% (mean ± SEM, CaD20: p = 0.026 and CaD50: p = 0.005, WT n = 4, plna R14del n = 5), and F Tau of Ca²⁺ decay (mean ± SEM, *p = 0.041, WT n = 4, plna R14del n = 5). All measurements were performed in three experimental replicates. G DNA construct and sensor dynamics of GCaMP6f (left panel). GCaMP6f was placed under the control of the myl7 promoter to restrict its expression to the heart. The Gal4FF-UAS system amplifies its expression. GCaMP6f consists of a circularly permutated enhanced green fluorescence protein (cpEGFP) fused to calmodulin (CaM) and the M13 peptide. When intracellular calcium (Ca²⁺) rises, CaM binds to M13, causing increased brightness of cpEGFP. Using a high-speed epifluorescence microscope, movies of 3 dpf non-contracting GCaMP6f embryonic hearts were recorded. Several intracellular Ca²⁺ parameters were measured, including H Frequency of Ca²⁺ transients, I Ca²⁺ transient recovery time, J normalized Ca²⁺ transient amplitude (mean ± SEM, *p = 0.0129, WT n = 10, plna R14del n = 12), K normalized diastolic Ca²⁺ levels, and L Tau of Ca²⁺ decay in wild-type (WT) and plna R14del embryonic zebrafish (mean ± SEM, *p = 0.0498, WT n = 10, plna R14del n = 12). All measurements were performed in three experimental replicates. Wild type is highlighted in black and plna R14del in red. Statistical test: unpaired Student’s t-test. nM nanomolar, ms milliseconds, CaM calmodulin, UAS upstream activation sequence, Ca²⁺ calcium. Source data are provided as a Source Data file.