Mechanisms of dorsal-ventral patterning in noggin-induced neural tissue.
We have investigated mechanisms of dorsal-ventral patterning of neural tissue, using Xenopus ectoderm neuralized by noggin protein. This tissue appears to be patterned dorsoventrally; cp1-1, a gene expressed in the dorsal brain, and etr-1, a gene largely excluded from the dorsal brain, are expressed in separate territories in noggin-treated explants (Knecht, A. K., Good, P. J., Dawid, I. B. and Harland, R. M. (1995) Development 121, 1927-1936). Here we show further evidence that this pattern represents a partial dorsal-ventral organization. Additionally, we test two mechanisms that could account for this pattern: a dose-dependent response to a gradient of noggin protein within the explant, and regulative cell-cell interactions. We show that noggin exhibits concentration-dependent effects, inducing cp1-1 at low doses but repressing it at high doses. Since noggin acts by antagonizing Bone Morphogenetic Protein (BMP) signaling, this result suggests that BMPs also may act in a dose-dependent manner in vivo. However, in the absence of a noggin gradient, regulative cell-cell interactions can also pattern the tissue. Such regulation is facilitated by increased motility of noggin-treated cells. Finally, the response of cells to both of these patterning mechanisms is ultimately controlled by a third process, the changing competence of the responding tissue.
Knecht
A K
AK
Department of Molecular and Cell Biology, University of California at Berkeley, 94720-3204, USA.
Harland
R M
RM
D000818:Animals; D019521:Body Patterning; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics; D002465:Cell Movement; D004305:Dose-Response Relationship, Drug; D004475:Ectoderm / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000502:physiology; D004627:Embryonic Induction; D005775:Gastrula; D018507:Gene Expression Regulation, Developmental; D054834:Lipocalins; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011506:Proteins / Q000494:pharmacology / Q000502:physiology*; D015854:Up-Regulation; D014981:Xenopus / Q000196:embryology*; D029867:Xenopus Proteins; D000099176:Noggin Protein
D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D054834:Lipocalins; D011506:Proteins; D029867:Xenopus Proteins; D000099176:Noggin Protein; C105000:PTGDS protein, Xenopus; C525812:bmp4 protein, Xenopus