title: Dorsoventral patterning of the vertebrate neural tube is conserved in a protochordate.
abstract: The notochord and dorsal ectoderm induce dorsoventral compartmentalization of the vertebrate neural tube through the differential regulation of genes such as HNF-3beta, Pax3, Pax6 and snail. Here we analyze the expression of HNF-3beta and snail homologues in the ascidian, Ciona intestinalis, a member of the subphylum Urochordata, the earliest branch in the chordate phylum. A combination of in situ hybridization and promoter fusion analyses was used to demonstrate that the Ciona HNF-3beta homologue is expressed in the ventralmost ependymal cells of the neural tube, while the Ciona snail homologue is expressed at the junction between the invaginating neuroepithelium and dorsal ectoderm, similar to the patterns seen in vertebrates. These findings provide evidence that dorsoventral compartmentalization of the chordate neural tube is not an innovation of the vertebrates. We propose that precursors of the floor plate and neural crest were present in a common ancestor of both vertebrates and ascidians.
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Berkeley 94720, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Corbo
authors.forename: A
authors.initials: A
authors.lastname: Erives
authors.forename: A
authors.initials: A
authors.lastname: Di Gregorio
authors.forename: A
authors.initials: A
authors.lastname: Chang
authors.forename: M
authors.initials: M
authors.lastname: Levine
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D002490:Central Nervous System / Q000196:embryology* / Q000502:physiology; D002938:Ciona intestinalis / Q000196:embryology; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000502:physiology; D004627:Embryonic Induction / Q000235:genetics; D004805:Ependyma / Q000502:physiology; D051858:Forkhead Transcription Factors; D005775:Gastrula; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D009132:Muscles / Q000196:embryology / Q000502:physiology; D009672:Notochord / Q000196:embryology / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000235:genetics; D014561:Urochordata / Q000196:embryology*; D014714:Vertebrates / Q000196:embryology*
chemical_list: D004268:DNA-Binding Proteins; D051858:Forkhead Transcription Factors; D009687:Nuclear Proteins; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors