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Figure 8
(A) ISH for myl7 at 50 hpf in wild type siblings, oug mutants and tbx5a;tbx2b double mutants. (B) Confocal maximum projections of 2dpf tg(nppa:mCitrine) hearts. In the tbx5a;tbx2b double mutants, atrial expression of nppa, which was lost in oug mutants, is re-instated. (C) Quantification and comparison of AV canal angles in wild-type siblings, tbx5a mutants and tbx5a;tbx2b double mutants. Quantification of AV canal angle is carried out as reported in Figure 5D. (D–D’’’) 48 hpf tg(myl7:Gal4FF; UAS:RFP; 0.2Intr1spaw-GFP) hearts. Wt (D) and tbx5-/- (D’) are shown for comparison. tbx2b-/- hearts (D’’) display robust dextral looping and left-originating cardiomyocytes (green) at the ventricle outer curvature, similar to wt (arrowheads in D; Figure 3B). In double homozygous mutants tbx5a-/-; tbx2b-/- (D’’’) rescue of cardiac looping is observed, accompanied by presence of left-originating cardiomyocytes at the ventricle OC (Compare with D, D’’). (C): Horizontal bars: mean value ± SEM. Legends: R: Right; L: Left; S: Superior side; I: Inferior side. Scale bars: 100 µm.
Defective cardiac looping in oug mutants is alleviated by simultaneous loss of tbx2b.