Expression of chicken SEF under FGF4/8 treatment
Leibbrandt A, Werzowa J, Neubüser A
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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).
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 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.
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