Figure 2

Increased Ca²⁺ levels, Ca²⁺ transient amplitude, and bradycardia in 3 dpf larvae injected with tnnt2a MO. (A) Ratiometric images of hearts in pseudocolor and their corresponding atrial (red) and ventricular (black) Ca²⁺ traces from representative 3 dpf Tg(myl7:Twitch-4) sibling and morphant larvae. Images from siblings and MO controls show the ventricular mechanical systole. The calibration square shows the distance in µm (horizontal length), whereas the hue codes for the emission ratio, and intensity codes for the fluorescence intensity. (B) Atrial and ventricular systolic Ca²⁺ (Twitch-4 emission ratio), diastolic Ca²⁺, and Ca²⁺ transient amplitude in sibling (n = 29), water-injected (n = 39), control morphant (n = 29), and tnnt2a morphant (n = 41) larvae. (C) Atrial CaT frequency (min⁻¹) in these larvae. (D) Time-averaged Ca²⁺ levels (L/L_max) measured by bioluminescence of 3 dpf Tg(myl7:GFP-aequorin) sibling (n = 6), control morphant (n = 6), and tnnt2a morphant (n = 8) larvae. Diacetyl h-coelenterazine was used as the aequorin substrate. Statistical analysis was performed using a one-way ANOVA test with Tukey’s multiple comparisons post-test or Kruskal–Wallis with Dunn’s multiple comparisons post-test, for parametric or non-parametric statistics, respectively. In (B,C), the mean of MO-tnnt2a morphants was compared with the mean of the other groups. Data are shown as the mean ± SD (* for p < 0.05 and **** p < 0.0001 for parametric statistics; ^xxxx for p < 0.0001 for non-parametric statistics).