ltbp1, ltbp3 DKO larvae develop ventricular dilation with molecular features of a stress response. (A,B) Confocal images of hearts in 5 dpf control (CTRL; A) and ltbp1−/−; ltbp3−/− (B) larvae immunostained for striated muscle (MF20, red). Ventricular size was measured by quantifying the area within the perimeter of the chamber (areas encircled by dashed lines). (C) Dot plot showing the ventricular areas of 5 dpf CTRL (n=22) and ltbp1−/−; ltbp3−/− (n=21) larvae. (D,E) Confocal images of hearts in 5 dpf CTRL (D) and ltbp1−/−; ltbp3−/− (E) larvae carrying the cmlc2:nucGFP transgene and immunostained for GFP. (F) Dot plot showing the number of ventricular cardiomyocytes in 5 dpf CTRL (n=7) and ltbp1−/−; ltbp3−/− (n=7) larvae. (G-H′) Single optical sections of hearts in 5 dpf CTRL (G,G′) and ltbp1−/−; ltbp3−/− (H,H′) larvae carrying the cmlc2:nucGFP transgene and immunostained for GFP. The boxed regions in G and H are shown enlarged in G′ and H′, respectively. Arrowheads highlight trabeculae, observed in seven out of seven ventricles for both experimental groups. (I,J) Dot plots showing the relative expression levels of nppa (I) and nppb (J) in 5 dpf CTRL and ltbp1−/−; ltbp3−/− larvae measured by qPCR. n=4 biological replicates and n=3 technical replicates per biological replicate. (K,L) Brightfield images of 5 dpf CTRL (K) and ltbp1−/−; ltbp3−/− (L) larvae processed for whole-mount in situ hybridization to detect nppa transcripts. Arrows in K and L highlight nppa expression in the heart. Little to no variation was observed between animals within each group (n>10/group). For all dot plots, statistical significance was determined with an unpaired t-test. Error bars show one standard deviation. ****P<0.0001; ***P<0.001; **P<0.01; ns, not significant. Scale bars: 20 µm.
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