title: Spatial and temporal properties of ventral blood island induction in Xenopus laevis.
abstract: Questions of dorsoventral axis determination and patterning in Xenopus seek to uncover the mechanisms by which particular mesodermal fates, for example somite, are specified in the dorsal pole of the axis while other mesoderm fates, for example, ventral blood island (VBI), are specified at the ventral pole. We report here that the genes Xvent-1, Xvent-2, and Xwnt-8 do not appear to be in the pathway of VBI induction, contrary to previous reports. Results from the selective inhibition of bone morphogenetic protein (BMP) activity, a key regulator of VBI induction, by ectopic Noggin, Chordin, or dominant negative BMP ligands and receptors suggest an alternative route of VBI induction. Injection of noggin or chordin RNA into animal pole blastomeres effectively inhibited VBI development, while marginal zone injection had no effect. Cell autonomous inhibition of BMP activity in epidermis with dominant negative ligand dramatically reduced the amount of (&agr;)T3 globin expression. These results indicate that signaling activity from the Spemann Organizer alone may not be sufficient for dorsoventral patterning in the marginal zone and that an inductive interaction between presumptive VBIs and ectoderm late in gastrulation may be crucial. In agreement with these observations, other results show that in explanted blastula-stage marginal zones a distinct pattern develops with a restricted VBI-forming region at the vegetal pole that is independent of the patterning activity of the Spemann Organizer.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, and Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, USA.
authors.forename: G
authors.initials: G
authors.lastname: Kumano
authors.forename: L
authors.initials: L
authors.lastname: Belluzzi
authors.forename: W C
authors.initials: WC
authors.lastname: Smith
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001757:Blastomeres; D019521:Body Patterning / Q000235:genetics; D055415:Bone Morphogenetic Protein 4; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction / Q000235:genetics; D005260:Female; D005775:Gastrula; D018507:Gene Expression Regulation, Developmental; D005914:Globins / Q000235:genetics / Q000378:metabolism; D006023:Glycoproteins; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D008648:Mesoderm / Q000637:transplantation; D009024:Morphogenesis; D009154:Mutation; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D020897:Organizers, Embryonic / Q000502:physiology; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000097:blood* / Q000196:embryology*; D029961:Zebrafish Proteins; D000099176:Noggin Protein
chemical_list: D000199:Actins; D055415:Bone Morphogenetic Protein 4; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D005914:Globins; D006023:Glycoproteins; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D017570:MyoD Protein; D011506:Proteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D000099176:Noggin Protein; C525812:bmp4 protein, Xenopus; C525813:bmp4 protein, zebrafish; C525822:bmp7.1 protein, Xenopus; C525826:bmp7a protein, zebrafish; C112507:ventx1.2 protein, Xenopus; C099992:ventx2.1 protein, Xenopus; C495248:wnt8a protein, Xenopus; C054234:chordin