title: Head induction in the chick by primitive endoderm of mammalian, but not avian origin.
abstract: Different types of endoderm, including primitive, definitive and mesendoderm, play a role in the induction and patterning of the vertebrate head. We have studied the formation of the anterior neural plate in chick embryos using the homeobox gene GANF as a marker. GANF is first expressed after mesendoderm ingression from Hensen's node. We found that, after transplantation, neither the avian hypoblast nor the anterior definitive endoderm is capable of GANF induction, whereas the mesendoderm (young head process, prechordal plate) exhibits a strong inductive potential. GANF induction cannot be separated from the formation of a proper neural plate, which requires an intact lower layer and the presence of the prechordal mesendoderm. It is inhibited by BMP4 and promoted by the presence of the BMP antagonist Noggin. In order to investigate the inductive potential of the mammalian visceral endoderm, we used rabbit embryos which, in contrast to mouse embryos, allow the morphological recognition of the prospective anterior pole in the living, pre-primitive-streak embryo. The anterior visceral endoderm from such rabbit embryos induced neuralization and independent, ectopic GANF expression domains in the area pellucida or the area opaca of chick hosts. Thus, the signals for head induction reside in the anterior visceral endoderm of mammals whereas, in birds and amphibia, they reside in the prechordal mesendoderm, indicating a heterochronic shift of the head inductive capacity during the evolution of mammalia.
authors.affiliation: Max-Planck-Institut für biophysikalische Chemie, Abteilung Molekulare Zellbiologie, Am Fassberg, D-37077 Göttingen, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Knoetgen
authors.forename: C
authors.initials: C
authors.lastname: Viebahn
authors.forename: M
authors.initials: M
authors.lastname: Kessel
mesh_terms: D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002352:Carrier Proteins; D002642:Chick Embryo; D004268:DNA-Binding Proteins / Q000235:genetics; D047108:Embryonic Development; D005314:Embryonic and Fetal Development; D004707:Endoderm / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D005801:Genes, Homeobox / Q000235:genetics*; D006257:Head / Q000196:embryology* / Q000254:growth & development; D006609:High Mobility Group Proteins / Q000235:genetics; D018398:Homeodomain Proteins; D017403:In Situ Hybridization; D008322:Mammals; D009419:Nerve Tissue Proteins / Q000235:genetics; D051857:Otx Transcription Factors; D011506:Proteins / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D055748:SOXB1 Transcription Factors; D016378:Tissue Transplantation; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors; D000099176:Noggin Protein
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D051857:Otx Transcription Factors; D011506:Proteins; D012333:RNA, Messenger; D055748:SOXB1 Transcription Factors; D015534:Trans-Activators; D014157:Transcription Factors; D000099176:Noggin Protein; C525810:Bmp4 protein, mouse; C527786:Sox3 protein, mouse