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Fig. 6. Fgf8a induces NC at the anterior neural fold indirectly. (A) The anterior neural plate (blue) is devoid of NC tissue (orange) as a result of the activity of a Wnt inhibitor, Dkk1 (Carmona-Fontaine et al., 2007). Snail2 expression is shown in a control embryo at stage 15. (B) β-catenin misexpression (200 pg) can overcome this inhibition to induce NC markers (Snail2) at the anterior neural fold (arrows). (C) Fgf8a (5 pg) misexpression can also induce NC markers (Snail2 and Sox8) at the anterior neural fold (arrows), an activity that is mediated by upregulation of Wnt8 in this region of the embryo (arrows). (D) Normal pattern of expression of Wnt8 in a control embryo at the same stage. In all panels the embryos are viewed from the dorsal side, anterior to the top. |
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Fig. 2. Fgf8a and Wnt8 differ in their ability to restore NC progenitors in Wnt8- and Fgf8a-deficient embryos. (A) Fgf8a mRNA injection fails to rescue Snail2 and Sox8 expression at the neural plate border of embryos injected with Wnt8MO (25ng) or β-CatMO (25 ng). A single injection of Fgf8a mRNA (2.5 pg) expands Snail2 and Sox8 expression domains. (B) Conversely, Wnt8 (100 pg) or β-catenin (200 pg) plasmid DNA injection restores Snail2 and Sox8 expression in embryos injected with Fgf8aMO (50 ng). Injection of Wnt8 or β-catenin in sibling embryos expanded Snail2 and Sox8 expression domains. In all panels, embryos are viewed from the dorsal side with anterior to the top. The injected side is to the right. |