Regulation of Ci-tropomyosin-like, a Brachyury target gene in the ascidian, Ciona intestinalis

Anna Di Gregorio, Michael Levine

Research output: Contribution to journalArticle

Abstract

Brachyury is a sequence-specific transcriptional activator that is essential for notochord differentiation in a variety of chordates. In vertebrates, Brachyury is expressed throughout the presumptive mesoderm, but becomes restricted to the notochord at later stages of development. In ascidians, such as Ciona intestinalis, Brachyury is expressed exclusively in the notochord and does not exhibit an early pan-mesodermal pattern. Subtractive hybridization screens were recently used to identify potential Ciona Brachyury (Ci-Bra) target genes. Of the genes that were identified in this screen, one corresponds to a new member of the tropomyosin superfamily, Ciona tropomyosin (Ci-trop). Here we show that Ci-trop is specifically expressed in the developing notochord beginning at gastrulation, and expression persists in the notochord during tailbud and tadpole stages. A 3 kb region of the Ci-trop 5'-flanking sequence was characterized via electroporation of lacZ fusion genes into fertilized Ciona eggs. A minimal, 114 bp enhancer was identified that is sufficient to direct the expression of a heterologous promoter in the notochord. DNA binding assays indicate that this enhancer contains two sets of low-affinity Brachyury half-sites, which are bound in vitro by a GST/Ci-Bra fusion protein. Deletion of the distal sites inactivates the notochord-specific staining pattern mediated by an otherwise normal Ci-trop/lacZ transgene. These results suggest that Ci-trop is a direct target gene of Ci-Bra and that Brachyury plays an immediate role in the cellular morphogenesis of the notochord.

Original languageEnglish (US)
Pages (from-to)5599-5609
Number of pages11
JournalDevelopment
Volume126
Issue number24
StatePublished - Dec 1999

Fingerprint

Ciona intestinalis
Notochord
Urochordata
Tropomyosin
Genes
Chordata
Gastrulation
Lac Operon
Electroporation
Brachyury protein
Zygote
5' Flanking Region
Mesoderm
Transgenes
Morphogenesis
Larva
Vertebrates
Staining and Labeling

Keywords

  • Ascidian
  • Biachyury
  • Ciona intestinalis
  • Notochord
  • Tropomyosin

ASJC Scopus subject areas

  • Anatomy
  • Cell Biology

Cite this

Regulation of Ci-tropomyosin-like, a Brachyury target gene in the ascidian, Ciona intestinalis. / Di Gregorio, Anna; Levine, Michael.

In: Development, Vol. 126, No. 24, 12.1999, p. 5599-5609.

Research output: Contribution to journalArticle

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