Nodal signals mediate interactions between the extra-embryonic and embryonic tissues in zebrafish

Article, Other literature type English OPEN
Fan, Xiang ; Hagos, Engda G. ; Xu, Bo ; Sias, Christina ; Kawakami, Koichi ; Burdine, Rebecca D. ; Dougan, Scott T. (2007)
  • Publisher: Elsevier BV
  • Journal: Developmental Biology, volume 310, issue 2, pages 363-378 (issn: 0012-1606)
  • Related identifiers: doi: 10.1016/j.ydbio.2007.08.008
  • Subject: Molecular Biology | Cell Biology | Developmental Biology | Article
    mesheuropmc: embryonic structures

In many vertebrates, extra-embryonic tissues are important signaling centers that induce and pattern the germ layers. In teleosts, the mechanism by which the extra-embryonic yolk syncytial layer (YSL) patterns the embryo is not understood. Although the Nodal-related protein Squint is expressed in the YSL, its role in this tissue is not known. We generated a series of stable transgenic lines with GFP under the control of squint genomic sequences. In all species, nodal-related genes induce their own expression through a positive feedback loop. We show that two tissue specific enhancers in the zebrafish squint gene mediate the response to Nodal signals. Expression in the blastomeres depends upon a conserved Nodal response element (NRE) in the squint first intron, while expression in the extra-embryonic enveloping layer (EVL) is mediated by an element upstream of the transcription start site. Targeted depletion experiments demonstrate that the zebrafish Nodal-related proteins Squint and Cyclops are required in the YSL for endoderm and head mesoderm formation. Thus, Nodal signals mediate interactions between embryonic and extra-embryonic tissues in zebrafish that maintain nodal-related gene expression in the margin. Our results demonstrate a high degree of functional conservation between the extra-embryonic tissues of mouse and zebrafish.
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