Three distinct lineages of mesenchymal cells in Ciona intestinalis embryos demonstrated by specific gene expression

Dev Biol. 2004 Oct 1;274(1):211-24. doi: 10.1016/j.ydbio.2004.07.007.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cell Lineage / genetics*
  • Cell Lineage / physiology
  • Ciona intestinalis / embryology*
  • DNA Primers
  • DNA, Complementary / genetics
  • Embryo, Nonmammalian / cytology
  • Embryo, Nonmammalian / embryology
  • Fibroblast Growth Factors / genetics
  • Fibroblast Growth Factors / metabolism
  • Gene Expression Profiling
  • Gene Expression Regulation, Developmental / physiology*
  • Helix-Loop-Helix Motifs / genetics
  • In Situ Hybridization
  • Mesoderm / physiology*
  • Molecular Sequence Data
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Analysis, DNA
  • Sequence Homology
  • Signal Transduction / genetics*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Twist-Related Protein 1


  • DNA Primers
  • DNA, Complementary
  • Nuclear Proteins
  • Transcription Factors
  • Twist-Related Protein 1
  • Fibroblast Growth Factors