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Proc Natl Acad Sci U S A. 2017 Apr 11;114(15):E3081-E3090. doi: 10.1073/pnas.1700766114. Epub 2017 Mar 27.

Spemann organizer transcriptome induction by early beta-catenin, Wnt, Nodal, and Siamois signals in Xenopus laevis.

Author information

1
Howard Hughes Medical Institute, University of California, Los Angeles, CA 90095-1662.
2
Department of Biological Chemistry, University of California, Los Angeles, CA 90095-1662.
3
Department of Medicine, University of California, Los Angeles, CA 90095-1662.
4
Department of Microbiology, University of California, Los Angeles, CA 90095-1662.
5
Department of Human Genetics, University of California, Los Angeles, CA 90095-1662.
6
Howard Hughes Medical Institute, University of California, Los Angeles, CA 90095-1662; ederobertis@mednet.ucla.edu.

Abstract

The earliest event in Xenopus development is the dorsal accumulation of nuclear β-catenin under the influence of cytoplasmic determinants displaced by fertilization. In this study, a genome-wide approach was used to examine transcription of the 43,673 genes annotated in the Xenopus laevis genome under a variety of conditions that inhibit or promote formation of the Spemann organizer signaling center. Loss of function of β-catenin with antisense morpholinos reproducibly reduced the expression of 247 mRNAs at gastrula stage. Interestingly, only 123 β-catenin targets were enriched on the dorsal side and defined an early dorsal β-catenin gene signature. These genes included several previously unrecognized Spemann organizer components. Surprisingly, only 3 of these 123 genes overlapped with the late Wnt signature recently defined by two other groups using inhibition by Dkk1 mRNA or Wnt8 morpholinos, which indicates that the effects of β-catenin/Wnt signaling in early development are exquisitely regulated by stage-dependent mechanisms. We analyzed transcriptome responses to a number of treatments in a total of 46 RNA-seq libraries. These treatments included, in addition to β-catenin depletion, regenerating dorsal and ventral half-embryos, lithium chloride treatment, and the overexpression of Wnt8, Siamois, and Cerberus mRNAs. Only some of the early dorsal β-catenin signature genes were activated at blastula whereas others required the induction of endomesoderm, as indicated by their inhibition by Cerberus overexpression. These comprehensive data provide a rich resource for analyzing how the dorsal and ventral regions of the embryo communicate with each other in a self-organizing vertebrate model embryo.

KEYWORDS:

Cerberus; Spemann organizer; Wnt signaling; embryonic induction; embryonic patterning

PMID:
28348214
PMCID:
PMC5393196
DOI:
10.1073/pnas.1700766114
[Indexed for MEDLINE]
Free PMC Article

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