Morphological phenotypes and survival of zebrafish larvae. (A) Examples of 7 dpf WT and popdc1^S191F (S191F) larvae with normal morphology (no phenotype) or a moderate morphological phenotype, involving spinal (Sp) curvature and/or pericardial (Pc) effusion. (B) Survival of WT (n = 2005 larvae, N = 22 clutches), popdc1^S191F (n = 2469, N = 20), and popdc1^KO (KO; n = 1740, N = 19) larvae over the first 7 dpf. (C) Incidence of larvae with normal morphology or a moderate or severe morphological phenotype (spinal curvature, pericardial effusion, or both) in surviving larvae (WT = 1774 survivors; popdc1^S191F = 1670; popdc1^KO = 879) at 7 dpf.

Imaging setup. Schematics of the (A) in vivo larval and (B) ex vivo adult heart imaging setups, along with images of hearts from 7 dpf and adult WT zebrafish and representative fluorescent V_m and Ca²⁺ signals recorded from the atrium and ventricle.

Effects of popdc1 dysfunction on HR and AVN function in larval zebrafish. HR (left) and AV delay (right) in WT (n = 130, N = 6), popdc1^S191F (S191F), and popdc1^KO (KO) zebrafish larvae with no morphological phenotype (n = 137 and n = 143, N = 6) or a moderate phenotype (n = 69 and n = 57, N = 6). Groups were compared by the non-parametric Kruskal–Wallis test, with Dunn’s corrected post hoc tests for multiple comparisons. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.

Effects of popdc1 dysfunction on V_m dynamics in larval zebrafish. Atrial (left column) and ventricular (right column) AP upstroke speed (upper row) and APD₈₀ (lower row) in WT (n = 69, N = 4), popdc1^S191F (S191F), and popdc1^KO (KO) zebrafish larvae with no morphological phenotype (n = 69 and n = 59, N = 4) or a moderate phenotype (n = 50 and n = 50, N = 5). Groups were compared by the non-parametric Kruskal–Wallis test, with Dunn’s corrected post hoc tests for multiple comparisons. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.

Effects of popdc1 dysfunction on Ca²⁺ dynamics in larval zebrafish. Atrial (left column) and ventricular (right column) CaT upstroke speed (upper row) and CaTD₈₀ (lower row) in WT (n = 130, N = 6), popdc1^S191F (S191F), and popdc1^KO (KO) zebrafish larvae with no morphological phenotype (n = 137 and n = 143, N = 6) or a moderate phenotype (n = 67 and n = 57, N = 5). Groups were compared by the non-parametric Kruskal–Wallis test, with Dunn’s corrected post hoc tests for multiple comparisons. * p < 0.05, ** p < 0.01, **** p < 0.0001.

Effects of ISO on HR and AVN function in larval zebrafish. HR (left) and AV delay (right) in WT (n = 96, N = 5), popdc1^S191F (S191F; n = 53, N = 5), and popdc1^KO (KO; n = 95, N = 5) zebrafish larvae with a moderate morphological phenotype. Groups were compared by the non-parametric Kruskal–Wallis test, with Dunn’s corrected post hoc tests for multiple comparisons (** p < 0.01, **** p < 0.0001), and to values pre-ISO (from Figure 3) using unpaired two-tailed Student’s t-tests (^#p < 0.05, ^##p < 0.01, ^###p < 0.001, ^####p < 0.0001).

Effects of ISO on V_m and Ca²⁺ dynamics in larval zebrafish. (A) AP upstroke speed (upper row) and APD₈₀ (lower row) and (B) CaT upstroke speed (upper row) and CaTD₈₀ (lower row) in WT (n = 58 and n = 54, N = 5), popdc1^S191F (S191F; n = 47 and n = 56, N = 5), and popdc1^KO (KO; n = 55 and n = 54, N = 5) from the atrium (left column) and ventricle (right column) of zebrafish larvae with a moderate morphological phenotype. Groups were compared by the non-parametric Kruskal–Wallis test, with Dunn’s corrected post hoc tests for multiple comparisons (* p < 0.05, ** p < 0.01, **** p < 0.0001), and to values pre-ISO (from Figure 4 and Figure 5) using unpaired two-tailed Student’s t-tests (^#p < 0.05, ^###p < 0.001, ^####p < 0.0001).

Effects of ISO on AVN function in adult isolated zebrafish hearts. Incidence of 2:1 AV block in ex vivo hearts isolated from WT (n = 18) and popdc1^S191F (S191F; n = 18) adult zebrafish (left) and changes in AV delay during ISO exposure (right). Groups were compared by paired and unpaired two-tailed Student’s t-tests (** p < 0.01, **** p < 0.0001).

Effects of ISO on V_m and Ca²⁺ dynamics in adult isolated zebrafish hearts. (A) AP upstroke speed (upper row) and APD₈₀ (lower row) and (B) CaT upstroke speed (upper row) and CaTD₈₀ (lower row) in ex vivo hearts isolated from WT (n = 9) and popdc1^S191F (S191F; n = 9) adult zebrafish before (Pre) and during ISO exposure from the atrium (left column) and ventricle (right column). Groups were compared by paired and unpaired two-tailed Student’s t-tests (* p < 0.05, ** p < 0.01, *** p < 0.001).