Chicken Similar Expression to FGF Protein (SEF)
Identification and Characterization


Expression of chicken SEF under FGF4/8 treatment

Leibbrandt A, Werzowa J, Neubüser A

   Fibroblast growth factors, in particular FGF8, secreted by ectodermal cells critically influence mesenchymal cell proliferation and differentiation during development of the vertebrate face (Firnberg N, Neubuser A, 2001). To identify FGF-regulated genes, facial mesenchyme isolated from the nasal region of stage 18/19 chicken embryos (according to Hamburger and Hamilton, 1951) was cultured in vitro in the presence and absence of FGF4/8 and used for a microarray-based screen. A new transcript fragment was identified in that screen and its sequence was extended with RACE PCR (accession AJ508679). This novel cDNA encodes a 697 AA protein fragment highly similar to Danio rerio so-called SEF protein (AAL78817) and represents the likely SEF ortholog in chicken.

The SEF expression domains in chicken embryos are compliant with the expected expression pattern of a FGF8 inducible gene.
    In-situ hybridization using FGF8-soaked beads placed on facial mesenchyme explants and the use of a FGFR antagonist confirm FGF dependent SEF expression. Sef is induced around FGF8 soaked beads but not but can not be detected in explants cultured with PBS beads. Whole mount in situ hybridizations, as well as isolation and culture of explants were performed as described in Firnberg and Neubüser (2002).


   A, B Whole mount in situ hybridization of stage 19 chick embryos with Fgf8 (A) and Sef (B) probes. Fgf8 is expressed at the mid-hindbrain boundary (mh), in the tailbud (tb), the somites (s), the AER of the limbs (AER), and in the ectoderm covering the branchial arches (ba) and the nasal region. Sef expression can be detected in the same regions in slightly larger domains, as would expected for an FGF8 inducible gene.
   C, D Nasal explants consisting of ectoderm and mesenchyme isolated from stage 19 embryos cultured in the absence (C) or in the presence (D) of 60 mm of the FGFR antagonist SU5402 and hybridized to a Sef probe. Sef expression requires FGF signaling.
   E, F Nasal mesenchyme cultured without the ectoderm in the presence of heparin acrylic beads soaked in recombinant FGF8 protein (E) or beads soaked in PBS.