title: Autonomy of ascidian fork head/HNF-3 gene expression.
abstract: We have characterized the expression pattern of a class I fork head/HNF-3 gene (HrHNF3-1) of the ascidian Halocynthia roretzi. Zygotic HrHNF3-1 expression was detectable as early as the 16-cell stage, and the transcript was evident in blastomeres of the endoderm, notochord and mesenchyme lineages of the early embryos. After the late gastrula stage, HrHNF3-1 was also expressed in the presumptive spinal cord cells and some brain cells. The spinal cord of the ascidian tadpole consists of four layers of cells; the dorsal layer, two lateral layers and the ventral layer, the latter of which simply lies on the notochord. Cross-sections of in situ hybridized specimens showed that HrHNF3-1 was expressed in cells of the ventral layer, reminiscent of the floor plate of vertebrate embryos. In addition, we found autonomy in the initiation of early HrHNF3-1 expression, because the gene was expressed in blastomeres continuously dissociated from the first cleavage until the 16-cell stage.
authors.affiliation: Department of Zoology, Graduate School of Science, Kyoto University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Shimauchi
authors.forename: H
authors.initials: H
authors.lastname: Yasuo
authors.forename: N
authors.initials: N
authors.lastname: Satoh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001757:Blastomeres / Q000502:physiology; D015152:Blotting, Northern; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics; D004625:Embryo, Nonmammalian; D004707:Endoderm / Q000502:physiology; D051858:Forkhead Transcription Factors; D018507:Gene Expression Regulation, Developmental; D051542:Hepatocyte Nuclear Factor 3-beta; D008648:Mesoderm / Q000502:physiology; D008969:Molecular Sequence Data; D009672:Notochord / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013116:Spinal Cord / Q000196:embryology; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D014561:Urochordata / Q000196:embryology* / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; C477894:FOXI1 protein, human; C106349:FOXJ1 protein, human; D051858:Forkhead Transcription Factors; D009687:Nuclear Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051542:Hepatocyte Nuclear Factor 3-beta