XCubn and XFgf8 are together necessary for normal head formation in the frog embryo.
A–C′, representative whole-mount mRNA staining of tailbud stage frog embryos unilaterally injected with control (A–C) and MoCubn (A′–C′) morpholinos. A and A′, XFgf8 is expressed in the ANR (arrowhead) and the isthmus (arrow) of the MoCubn-treated embryos. B and B′, reduced XFoxg1 expression domain in the telencephalon (arrowhead) and eye (arrow) after MoCubn injection. C and C′, reduced expression domain of XOtx2 in the developing telencephalon (arrowhead), eye (arrow), and slightly in the midbrain of the MoCubn treated embryo. D, telencephalic and eye (arrowhead) hypoplasia and down-regulation of XFoxg1 mRNA staining in the injected part of the embryo (dotted line, inj). E, increased levels of cleaved caspase-3 in cephalic extracts of MoCubn-treated embryos. F, telencephalic hypoplasia and down-regulation of XFoxg1 in MoFgf8-injected embryos. G and H, low MoFgf8 (0.5 pmol) or MoCubn (0.25 pmol) concentrations do not affect telencephalic development and XFoxg1 expression. I, strong reduction of XFoxg1 in embryos co-injected with MoCubn and MoFgf8 at the same low concentrations. J, reduced or normal expression of XFoxg1 after co-injection of MoCubn and MoFgf8 at the concentrations indicated. The number of embryos analyzed is indicated. Scale bars, A–C, and F–I, 250 μm; D, 75 μm.