title: Differential temporal control of Foxa.a and Zic-r.b specifies brain versus notochord fate in the ascidian embryo.
abstract: In embryos of an invertebrate chordate, Ciona intestinalis, two transcription factors, Foxa.a and Zic-r.b, are required for specification of the brain and the notochord, which are derived from distinct cell lineages. In the brain lineage, Foxa.a and Zic-r.b are expressed with no temporal overlap. In the notochord lineage, Foxa.a and Zic-r.b are expressed simultaneously. In the present study, we found that the temporally non-overlapping expression of Foxa.a and Zic-r.b in the brain lineage was regulated by three repressors: Prdm1-r.a (formerly called BZ1), Prdm1-r.b (BZ2) and Hes.a. In morphant embryos of these three repressor genes, Foxa.a expression was not terminated at the normal time, and Zic-r.b was precociously expressed. Consequently, Foxa.a and Zic-r.b were expressed simultaneously, which led to ectopic activation of Brachyury and its downstream pathways for notochord differentiation. Thus, temporal controls by transcriptional repressors are essential for specification of the two distinct fates of brain and notochord by Foxa.a and Zic-r.b Such a mechanism might enable the repeated use of a limited repertoire of transcription factors in developmental gene regulatory networks.
authors.affiliation: Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan i.tatsuro@ascidian.zool.kyoto-u.ac.jp.
authors.forename: Tatsuro
authors.identifier: 0000-0002-8503-8096
authors.initials: T
authors.lastname: Ikeda
authors.affiliation: Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
authors.forename: Yutaka
authors.identifier: 0000-0001-5193-0708
authors.initials: Y
authors.lastname: Satou
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics; D001921:Brain / Q000196:embryology* / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D002938:Ciona intestinalis / Q000196:embryology* / Q000235:genetics*; D004625:Embryo, Nonmammalian; D051858:Forkhead Transcription Factors / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D009672:Notochord / Q000196:embryology* / Q000378:metabolism; D014561:Urochordata / Q000196:embryology / Q000235:genetics
chemical_list: D051858:Forkhead Transcription Factors; D018398:Homeodomain Proteins
keywords: Ciona intestinalis; Temporal regulation; Transcriptional repressor