Figure 3. Both inhibition of Notch signaling and inhibition of the H^+/K⁺-ATPase cause bilateral expression of nodal in the endomesoderm and randomize nodal expression in the ectoderm.

A, nodal expression in control embryos and in embryos treated with DAPT or omeprazole starting after fertilization or injected with a morpholino oligonucleotide against Delta. Black arrowheads show an ectopic expression of nodal on the left side. The percentages indicate the proportion of embryos showing the same sidedness of nodal expression as that showed in the panel. B, At pluteus stage, nodal and univin expression in DAPT-treated embryos or in Delta-morpholino injected embryos is randomized. C, The expression of pitx2, sox9 and foxF in the coelomic pouch precursors as well as the expression of tropomyosin in the muscle cell precursors is strongly reduced or absent in DAPT-treated embryos. D, Time course of DAPT treatments. Embryos were treated with DAPT starting at different stages and nodal expression was scored at pluteus stages. DAPT treatments perturb left-right asymmetry only when performed before hatching. VEB, very early blastula; EB, early blastula; SB, swimming blastula; MB, mesenchyme blastula. E, The window during which DAPT treatments interfere with left-right asymmetry coincides with the period during which non skeletogenic mesoderm precursors are induced by Delta/Notch signaling. AV, Animal views; DV, Dorsal views; L, Left; R, Right.