Knockdown of gata4 can rescue partially the mga morphant heart tube phenotype. A-C: Shown are representative embryos that are wildtype (A), injected with only the mga-specific MO1 (B), or injected first with MO1 and subsequently with the gata4 morpholino (C). The ratios shown represent the number of embryos with an apparently normal (non-edemic) phenotype in a representative experiment (which was reproduced several times). Note that the cardiac edema present in 100% of the single morphants (B) is rescued in a significant percentage (35%) of the co-injected embryos. The brain defect is also largely rescued, although in contrast, the regression in the yolk stalk extension persists. D-L: Similar experiments were carried out and imaged using embryos derived from cmlc2:gfp transgenic fish. In these experiments, initial heart looping was rescued in double-knockdown embryos compared to the mga morphants as shown in F (51/128, 40%) or I (32/77, 42%) at 3 dpf. J-L: Although it is not normal, a similar rescue (35/105, 33%) of heart looping was scored at 5 dpf. All views are lateral, dorsal to the top, and anterior to the right except for G-I, which are ventral, anterior to the right. HT, heart; YSE, yolk stalk extension.
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