Hyperactivation of canonical TGFβ signaling in the distended OFTs of ltbp1, ltbp3 DKO larvae. (A,B,D,E) Confocal images of OFTs in 5 dpf (A,B) and 3 dpf (D,E) control (CTRL; A,D) and ltbp1−/−; ltbp3−/− (B,E) larvae double immunostained for striated muscle (MF20, red) and phosphorylated Smad3 (pSmad3; green). (C,F) Dot plots showing the relative mean pSmad3 fluorescence intensities in the OFTs of 5 dpf (C) or 3 dpf (F) CTRL (n=9 in C; n=6 in F) and ltbp1−/−; ltbp3−/− (n=9 in C; n=3 in F) larvae. For C and F, statistical significance was determined with an unpaired t-test. Error bars indicate one standard deviation. ***P<0.01; ns, not significant. Scale bars: 20 µm.