Journal
MECHANISMS OF DEVELOPMENT
Volume 124, Issue 9-10, Pages 775-791Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.mod.2007.05.005
Keywords
beta-Catenin; Wnt8; vox; vent; Nodal signaling; FGF signaling; dorsoventral patterning; ichabod (ich)
Categories
Funding
- NICHD NIH HHS [R01-HD39272, R01 HD039272, R01 HD039272-05] Funding Source: Medline
- NINDS NIH HHS [R01 NS041398-04] Funding Source: Medline
- EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH &HUMAN DEVELOPMENT [R01HD039272] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE [R01NS041398] Funding Source: NIH RePORTER
Ask authors/readers for more resources
Using embryos transgenic for the TOP-GFP reporter, we show that the two zebrafish beta-catenins have different roles in the organizer and germ-ring regions of the embryo. beta-Catenin-activated transcription in the prospective organizer region specifically requires beta-catenin-2, whereas the ventrolateral domain of activated transcription is abolished only when both beta-catenins are inhibited. chordin expression during zebrafish gastrulation has been previously shown in both axial and paraxial domains, but is excluded from ventrolateral domains. We show that this gene is expressed in paraxial territories adjacent to the domain of ventrolateral beta-catenin-activated transcription, with only slight overlap, consistent with the now well-known inhibitory effects of Wnt8 on dorsal gene expression. Eliminating both Wnt8/beta-catenin signaling and organizer activity by inhibition of expression of the two beta-catenins results in massive ectopic circumferential expression of chordin and later, by formation of a distinctive embryonic phenotype ('ciuffo') that expresses trunk and anterior neural markers with correct relative anteroposterior patterning. We show that chordin expression is required for this neural gene expression. The Nodal gene squint has been shown to be necessary for optimal expression of chordin and is sufficient in some contexts for its expression. However, chordin is not normally expressed in the ventrolateral germ-ring despite robust expression of squint in this domain. We show the ectopic circumferential expression of chordin and other dorsal genes to be completely dependent on Nodal and FGF signaling, and to be independent of a functional organizer. We propose that whereas the axial domain of chordin expression is formed by cells that are derived from the organizer, the paraxial domain is the result of axial-derived anti-Wnt signals, which relieve the repression that otherwise is set by the Wnt8/beta-catenin/vox,vent pathway on latent germ-ring Nodal/FGF-activated expression. (C) 2007 Elsevier Ireland Ltd. All rights reserved.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available