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Science 335 (6068): 590-593

Copyright © 2012 by the American Association for the Advancement of Science

Sequential Signaling Crosstalk Regulates Endomesoderm Segregation in Sea Urchin Embryos

Aditya J. Sethi,1 Radhika M. Wikramanayake,2 Robert C. Angerer,1 Ryan C. Range,1 Lynne M. Angerer1,*

Abstract: The segregation of embryonic endomesoderm into separate endoderm and mesoderm fates is not well understood in deuterostomes. Using sea urchin embryos, we showed that Notch signaling initiates segregation of the endomesoderm precursor field by inhibiting expression of a key endoderm transcription factor in presumptive mesoderm. The regulatory circuit activated by this transcription factor subsequently maintains transcription of a canonical Wnt (cWnt) ligand only in endoderm precursors. This cWnt ligand reinforces the endoderm state, amplifying the distinction between emerging endoderm and mesoderm. Before gastrulation, Notch-dependent nuclear export of an essential β-catenin transcriptional coactivator from mesoderm renders it refractory to cWnt signals, insulating it against an endoderm fate. Thus, we report that endomesoderm segregation is a progressive process, requiring a succession of regulatory interactions between cWnt and Notch signaling.

1 National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
2 Department of Public Health, University of Oxford, Oxford, UK.

* To whom correspondence should be addressed. E-mail: langerer{at}mail.nih.gov


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Axial patterning interactions in the sea urchin embryo: suppression of nodal by Wnt1 signaling.
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