@article{85381,
  author = {Xiang Fan and Engda Hagos and Bo Xu and Christina Sias and Koichi Kawakami and Rebecca Burdine and Scott Dougan},
  title = {Nodal signals mediate interactions between the extra-embryonic and embryonic tissues in zebrafish.},
  abstract = {<p>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.</p>},
  year = {2007},
  journal = {Developmental biology},
  volume = {310},
  pages = {363-78},
  month = {10/2007},
  issn = {0012-1606},
  language = {eng},
}