Transgenic Xenopus embryos reveal that anterior neural development requires continued suppression of BMP signaling after gastrulation.
In vertebrates, BMP signaling before gastrulation suppresses neural development. Later in development, BMP signaling specifies a dorsal and ventral fate in the forebrain and dorsal fate in the spinal cord. It is therefore possible that a change in the competence of the ectoderm to respond to BMP signaling occurs at some point in development. We report that exposure of the anterior neural plate to BMP4 before gastrulation causes suppression of all neural markers tested. To determine the effects of BMP4 after gastrulation, we misexpressed BMP4 using a Pax-6 promoter fragment in transgenic frog embryos and implanted beads soaked in BMP4 in the anterior neural plate. Suppression of most anterior neural markers was observed. We conclude that most neural genes continue to require suppression of BMP signaling into the neurula stages. Additionally, we report that BMP4 and BMP7 are abundantly expressed in the prechordal mesoderm of the neurula stage embryo. This poses the paradox of how the expression of most neural genes is maintained if they can be inhibited by BMP signaling. We show that at least one gene in the anterior neural plate suppresses the response of the ectoderm to BMP signaling. We propose that the suppressive effect of BMP signaling on the expression of neural genes coupled with localized suppressors of BMP signaling result in the fine-tuning of gene expression in the anterior neural plate.
Hartley
K O
KO
Department of Zoology, Wellcome/CRC Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, United Kingdom.
Hardcastle
Z
Z
Friday
R V
RV
Amaya
E
E
Papalopulu
N
N
D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D055415:Bone Morphogenetic Protein 4; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004475:Ectoderm / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000502:physiology*; D005136:Eye Proteins; D005775:Gastrula / Q000502:physiology*; D049452:Green Fluorescent Proteins; D018398:Homeodomain Proteins / Q000235:genetics; D017403:In Situ Hybridization; D008164:Luminescent Proteins / Q000378:metabolism; D008648:Mesoderm / Q000378:metabolism; D008969:Molecular Sequence Data; D009432:Neural Crest; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta; D019076:Transgenes; D014981:Xenopus; D029867:Xenopus Proteins
D055415:Bone Morphogenetic Protein 4; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D005136:Eye Proteins; C117087:FOXG1 protein, Xenopus; D018398:Homeodomain Proteins; D008164:Luminescent Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus; C525822:bmp7.1 protein, Xenopus; D049452:Green Fluorescent Proteins; D012313:RNA; D004247:DNA