Xenbase Image ID: 175615

Figure 3. Hox genes, morphogens and boundaries between axial domains. (a) The neck‐thorax boundary and Hoxc6 expression. Chick has a long neck (light blue) and short thorax (mid blue; 14 and 7 somites, respectively). Mouse has a short neck (light blue) and long thorax (mid blue; 7 and 14 somites, respectively). In each case, the Hoxc6 anterior expression boundary (C6, marked in red) is at the neck/thorax boundary. Other vertebrates with different axial formulae (goose, Xenopus, zebrafish) show the same relationship. Hoxc6 seems to be a special gene (Burke, Nelson, Bruce, Morgan, & Tabin, 1995). (b) Ectopic expression of the Wnt inhibitor Dickkopf (Dkk‐1) in the presence of the anti‐BMP dorsaliser, noggin, causes Xenopus embryos to develop head structures only (eye red arrowed); the anterior head‐posterior head boundary is blocked (Glinka et al., 1998). (c) Ectopic expression of Hoxa10 in the mouse. Right: Normal mouse skeleton showing thoracic ribs (marked by red arrows). Left: Hoxa10 GOF skeleton, showing no ribs. The whole thorax has become abdominal (lumbar vertebrae; thorax‐abdomen boundary deleted; Carapuço, Nóvoa, Bobola, & Mallo, 2005). (d) Normal and Gdx8−/− mice. The normal mouse (left) has a tail (red arrow). The Gdx−/− mouse essentially does not. The abdomen‐tail boundary is blocked (Jurberg, Aires, Varela‐Lasheras, Novoa, & Mallo, 2013). Image published in: Durston AJ (2019) © 2019 The Author. This image is reproduced with permission of the journal 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

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