title: Three distinct lineages of mesenchymal cells in Ciona intestinalis embryos demonstrated by specific gene expression.
abstract: The ascidian embryonic mesenchyme, comprising about 900 cells, forms mesodermal tissues or organs of the adult body after metamorphosis. The mesenchyme originates from the A7.6 [trunk lateral cells (TLCs)], B7.7, and B8.5 blastomeres of the 110-cell stage embryo. Previous studies showed that FGF9/16/20 is required for specification of the mesenchyme in Ciona embryos and that two different (A7.6 and B8.5/B7.7) but partially overlapping molecular mechanisms are associated with the expression of a basic helix-loop-helix (bHLH) transcription factor gene, Twist-like1, in the mesenchymal precursors, which triggers the differentiation process of mesenchyme cells. In the present study, we examined whether the three embryonic lineages express the same mesenchyme-specific structural genes under the control of a common mechanism or whether the three lineages are characterized by the expression of genes specific to each of the lineages. We characterized nine mesenchyme-specific genes in Ciona embryos and found that five were expressed in A7.6/B8.5/B7.7, two in B8.5/B7.7, and two in B7.7 only. FGF9/16/20 and Twist-like1 were required for the expression of all the mesenchyme-specific genes, except for three A7.6/B8.5/B7.7-specific genes in A7.6 progenitors. Overexpression of FGF9/16/20 or Twist-like1 upregulated the expression of A7.6/B8.5/B7.7- and B8.5/B7.7-specific genes, while it downregulated the expression of B7.7-specific genes. These results provide evidence that the differentiation of each of the three mesenchyme lineages of Ciona embryos is characterized by the expression of a specific set of genes, whose expression is controlled differentially.
authors.affiliation: Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan. miki@ascidian.zool.kyoto-u.ac.jp
authors.forename: Miki
authors.initials: M
authors.lastname: Tokuoka
authors.forename: Kaoru S
authors.initials: KS
authors.lastname: Imai
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Satou
authors.forename: Nori
authors.initials: N
authors.lastname: Satoh
mesh_terms: D000818:Animals; D001483:Base Sequence; D019070:Cell Lineage / Q000235:genetics* / Q000502:physiology; D002938:Ciona intestinalis / Q000196:embryology*; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D017403:In Situ Hybridization; D008648:Mesoderm / Q000502:physiology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D015398:Signal Transduction / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D051879:Twist-Related Protein 1
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D009687:Nuclear Proteins; D014157:Transcription Factors; D051879:Twist-Related Protein 1; D005346:Fibroblast Growth Factors