Xenbase Image ID: 24386

Fig. 9. Expression of various Wnts and Wnt antagonists establishes a Wnt activity gradient in the gastrulating Xenopus embryo. (A) Expression of Xanf1, Xwnt8 (a) in whole-mount and Xwnt3A (b) in sagittal section at late gastrula stage by in situ hybridization. Black arrowheads, dorsal blastopore lip; red arrowheads, leading edge. Note expression of Xwnt8 in proximity to presumptive posterior neuroectoderm (compare with fate map in Fig. 8A). Xwnt3A is expressed in chordamesoderm and in a ring surrounding the blastopore (not visible). (B) Expression domains in the late Xenopus gastrula of Wnts (a) and Wnt antagonists (b). Only ectodermal expressions are shown in a. The circumblastoporal expression of Xwnt3A is not depicted for simplicity. Note expression of Wnt antagonists in the anterior of the gastrulating embryo. (C) Simplified model for AP patterning of neuroectoderm by a Wnt activity gradient in Xenopus. Wnts (red) and Wnt antagonists (green) are expressed in the mesendoderm (ME, ochre) underlying the neuroectoderm (NE, blue). The expression of Wnts and Wnt antagonist in the neuroectoderm is not shown for simplicity (see B). Their combined activities result in the formation of a Wnt signalling gradient (dark orange) that patterns the AP neuraxis. The AP axis is indicated (A→P). Formation of the posterior nervous system also requires other factors (FGFs, RA) which are not shown here. (D) The AP and DV axes in the gastrulating Xenopus embryo are patterned by gradients of Wnts and BMPs, respectively (a). The Drosophila wing imaginal disc is patterned by gradients of Wingless (Wg) and Decapentaplegic (Dpp), which are secreted along the DV and AP compartment boundaries, respectively (b). Image published in: Kiecker C and Niehrs C (2001) Copyright © 2001. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. Gene Synonyms Species Stage(s) Tissue hesx1 anf2, hesx1-a, hesx1-b, rpx, Xanf, Xanf-1, XANF-2, Xanf1, Xanf2 Xenopus Throughout unspecified stage   wnt8a wnt-8, wnt8, Xwnt-8, Xwnt8 Xenopus Throughout NF stage 10 endomesoderm wnt3a wnt-3a, Xwnt-3a, xwnt3a Xenopus Throughout NF stage 12 axial mesoderm Image source: Published Larger Image Printer Friendly View

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