title: Notch activates sonic hedgehog and both are involved in the specification of dorsal midline cell-fates in Xenopus.
abstract: We analysed the role of Notch signalling during the specification of the dorsal midline in Xenopus embryos. By activating or blocking the pathway we found that Notch expands the floor plate domain of sonic hedgehog and pintallavis and represses the notochordal markers chordin and brachyury, with a concomitant reduction of the notochord size. We propose that within a population of the early organiser with equivalent potential to develop either as notochord or floor plate, Notch activation favours floor plate development at the expense of the notochord, preferentially before mid gastrula. We present evidence that sonic hedgehog down-regulates chordin, suggesting that secreted Sonic hedgehog may be involved or reinforcing the cell-fate switch executed by Notch. We also show that Notch signalling requires Presenilin to modulate this switch.
authors.affiliation: Laboratorio de Embriología Molecular, Instituto de Biología Celular y Neurociencias, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, 3 degrees piso (1121), Buenos Aires, Argentina.
authors.forename: Silvia L
authors.initials: SL
authors.lastname: López
authors.forename: Alejandra R
authors.initials: AR
authors.lastname: Paganelli
authors.forename: María V Rosato
authors.initials: MV
authors.lastname: Siri
authors.forename: Oscar H
authors.initials: OH
authors.lastname: Ocaña
authors.forename: Paula G
authors.initials: PG
authors.lastname: Franco
authors.forename: Andrés E
authors.initials: AE
authors.lastname: Carrasco
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology* / Q000502:physiology*; D004627:Embryonic Induction / Q000502:physiology*; D005326:Fetal Proteins; D051858:Forkhead Transcription Factors; D018507:Gene Expression Regulation, Developmental; D006023:Glycoproteins; D053823:Hedgehog Proteins; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008648:Mesoderm / Q000502:physiology; D009024:Morphogenesis / Q000502:physiology; D009672:Notochord / Q000033:anatomy & histology / Q000502:physiology; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D051880:Receptors, Notch; D015398:Signal Transduction / Q000502:physiology; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000502:physiology*; D000098908:Brachyury Protein
chemical_list: D005326:Fetal Proteins; D051858:Forkhead Transcription Factors; D006023:Glycoproteins; D053823:Hedgehog Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D016376:Oligonucleotides, Antisense; D011506:Proteins; D051880:Receptors, Notch; D020825:T-Box Domain Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D029867:Xenopus Proteins; D000098908:Brachyury Protein; C000598904:FoxA4 protein, Xenopus; C054234:chordin