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β-Catenin-driven binary fate specification segregates germ layers in ascidian embryos
Clare Hudson1, Narudo Kawai, Takefumi Negishi
1Université Pierre et Marie Curie and Centre National de la Recherche Scientifique, Laboratoire de Biologie du Développement de Villefranche-sur-Mer, Observatoire Océanologique, 06234 Villefranche-sur-mer, France. hudson@obs-vlfr.fr
Current Biology : CB
|March 5, 2013
Summary
β-catenin signaling guides early embryonic development. In ascidians, sequential cell divisions and differential β-catenin activity precisely segregate ectoderm, mesendoderm, and endoderm fates, revealing an ancient developmental mechanism.
Area of Science:
- Developmental Biology
- Molecular Biology
- Evolutionary Biology
Background:
- β-catenin is a key transcriptional cofactor in the canonical Wnt signaling pathway.
- Nuclear β-catenin domains specify endoderm/mesendoderm in many metazoans, indicating an ancient role.
- Mechanisms for segregating mesoderm and endoderm from mesendoderm remain unclear.
Purpose of the Study:
- To investigate the role of β-catenin in segregating the three germ layers in ascidian embryos.
- To elucidate the interplay between cell division and β-catenin activity in fate determination.
Main Methods:
- Analysis of nuclear β-catenin activity during early ascidian embryonic cell divisions.
- Tracking cell fate following specific animal-vegetal oriented cell divisions.
Main Results:
- Ascidian germ layer subdivision relies on differential nuclear β-catenin activity and early animal-vegetal cell divisions.
- The first division separates ectoderm from mesendoderm.
- The second division distinguishes margin (notochord/neural) from endoderm based on β-catenin activation sequence (ON-to-ON for endoderm, OFF-to-OFF for ectoderm, ON-to-OFF for margin).
Conclusions:
- β-catenin-dependent cell divisions provide a binary fate choice mechanism during early embryogenesis.
- This process highlights an evolutionarily conserved mechanism for germ layer specification.
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