XB-IMG-24382
Xenbase Image ID: 24382
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Fig. 5. Wnt signalling is necessary and sufficient to pattern neuroectoderm in a long-range fashion. (A) Experimental design: pigmented 8-cell stage embryos (donors) were injected into the four animal blastomeres with mRNAs encoding Wnt pathway activators or Wnt antagonists. At late blastula stage, small groups of pigmented animal cap cells were grafted into the presumptive neural plate of early gastrula albino embryos (hosts). The hosts were cultured until neurula stages and analysed for marker gene expression by in situ hybridization. (B) Grafted donor caps were uninjected (a) or injected with 0.25 ng/blastomere Xwnt3A mRNA (b) and placed in the presumptive anterior host neural plate. Embryos were analysed at neural plate stage for expression of Krox20 (black) and En2 (red) and are shown in lateral view, dorsal side upwards. Grafts are indicated by asterisks. Note ectopic induction of En2 and Krox20 with reversed AP polarity by the Xwnt3A expressing graft (arrowheads in b). (C) Grafted donors were injected with 0.25 ng/blastomereXdkk1 mRNA and placed in the presumptive posterior (a) or anterior (b) host neural plate, respectively. Embryos were analysed at neural plate stage for expression of Bf1 (a) and Krox20 (b) and are shown in dorsofrontal view. Grafted tissue is outlined in red in panel a. Note posterior expansion of Bf1 expression in a and downregulation of Krox20 (arrowheads in b). (D) Grafted donors were uninjected (a,a′) or injected with 1.5 ng/blastomereXgsk3β mRNA (b,b′) and placed in the presumptive posterior host neural plate. Embryos were analysed at neural plate stage for expression of HoxD1 and are shown in dorsal view, anterior down. Grafted tissue is outlined in red in panels a,b. The same embryos as in panels a,b are shown following bleaching in panels a′,b′. Note holes in HoxD1 expression in panel b′ compared to continuous expression in panel a′. 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. Larger Image Printer Friendly View |