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Repression of organizer genes in dorsal and ventral Xenopus cells mediated by maternal XTcf3

Douglas W Houston1, Matt Kofron, Ernesto Resnik

  • 1Division of Developmental Biology, Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA.

Development (Cambridge, England)
|August 7, 2002
PubMed

Insights

XTcf3 acts as a repressor in Xenopus development, preventing dorsal gene expression. Its depletion alone doesn't restore dorsal gene activation, highlighting the necessity of the activator VegT for proper axis specification.

Area of Science:

  • Developmental Biology
  • Molecular Biology
  • Genetics

Background:

  • The dorsal axis in early Xenopus embryos is established via Wnt signaling, involving beta-catenin and the transcription factor XTcf3.
  • The precise function of XTcf3 in this process remains unclear, with prior studies suggesting dual roles as an activator and repressor.

Purpose of the Study:

  • To elucidate the role of XTcf3 in dorsal axis specification during Xenopus embryogenesis.
  • To determine if XTcf3 acts as an activator or repressor of dorsal gene expression.

Main Methods:

  • Maternal XTcf3 mRNA was depleted in Xenopus oocytes using antisense deoxyoligonucleotides.
  • Depleted oocytes were fertilized, and developmental effects on morphogenesis and marker gene expression were analyzed.
  • Further experiments involved co-depletion of XTcf3 and the transcription factor VegT.

Main Results:

  • Depletion of XTcf3 primarily revealed its function as an inhibitor, preventing dorsal gene expression in both dorsal and ventral cells.
  • Relief from XTcf3-mediated repression alone was insufficient for dorsal gene activation.
  • Embryos lacking both XTcf3 and VegT failed to activate normally repressed dorsal genes.

Conclusions:

  • XTcf3 functions mainly as a repressor, inhibiting dorsal gene expression ventrally.
  • Dorsal gene expression requires the transcriptional activator VegT.
  • XTcf3 is essential for preventing inappropriate dorsal gene expression on the ventral side of the embryo.

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