Morphological boundary forms by a novel inductive event mediated by Lunatic fringe and Notch during somitic segmentation.
Boundary formation plays a central role in differentiating the flanking regions that give rise to discrete tissues and organs during early development. We have studied mechanisms by which a morphological boundary and tissue separation are regulated by examining chicken somite segmentation as a model system. By transplanting a small group of cells taken from a presumptive border into a non-segmentation site, we have found a novel inductive event where posteriorly juxtaposed cells to the next-forming border instruct the anterior cells to become separated and epithelialized. We have further studied the molecular mechanisms underlying these interactions by focusing on Lunatic fringe, a modulator of Notch signaling, which is expressed in the region of the presumptive boundary. By combining DNA in ovo electroporation and embryonic transplantation techniques we have ectopically made a sharp boundary of Lunatic fringe activity in the unsegmented paraxial mesoderm and observed a fissure formed at the interface. In addition, a constitutive active form of Notch mimics this instructive phenomenon. These suggest that the boundary-forming signals emanating from the posterior border cells are mediated by Notch, the action of which is confined to the border region by Lunatic fringe within the area where mRNAs of Notch and its ligand are broadly expressed in the presomitic mesoderm.
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara, 630-0101, Japan.
Yuki
Y
Sato
Kunio
K
Yasuda
Yoshiko
Y
Takahashi
D000818:Animals; D030161:Avian Proteins; D019521:Body Patterning / Q000502:physiology*; D017690:Cell Transplantation; D002642:Chick Embryo; D003370:Coturnix / Q000196:embryology; D018274:Electroporation; D004627:Embryonic Induction / Q000502:physiology*; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008648:Mesoderm / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000378:metabolism; D051880:Receptors, Notch; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015534:Trans-Activators / Q000378:metabolism
D030161:Avian Proteins; D018398:Homeodomain Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D051880:Receptors, Notch; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; C064045:delta protein; D016695:Glycosyltransferases; C498394:LFNG protein, Gallus gallus