Epithelium is required for maintaining FGFR-2 expression levels in facial mesenchyme of the developing chick embryo.
In the developing chick embryo, fibroblast growth factor-2 (FGFR-2) expression patterns correlate with outgrowth of facial prominences. Frontonasal mass prominences that form the pre-nasal cartilage and upper beak express high levels of FGFR-2 receptor, whereas maxillary prominences that form the flattened corners of the beak and palatal shelves express low FGFR-2 transcript levels. Facial epithelium is an abundant source of FGFs and is required to support outgrowth of mesenchymal tissue, including cartilage rod formation. Because FGFR-2 is highly expressed in regions of facial outgrowth and because epithelium is required for outgrowth of facial prominences, epithelium could be required to maintain FGFR-2 transcripts in facial mesenchyme. To test this hypothesis, we removed epithelium to inhibit outgrowth of regions of the embryonic face, grafted frontonasal mass and maxillary prominences into a host limb bud, and then examined changes in FGFR-2 expression using in situ hybridization. We also hybridized adjacent sections with collagen II probe to identify regions undergoing chondrogenesis. Our results indicate that removal of epithelium from frontonasal mass led to a decrease in FGFR-2 and collagen II expression 24 hr after grafting to host and that neither FGFR-2 nor collagen II expression increased to expected levels at 48 hr. These results suggest that there are signals in the epithelium required for increasing FGFR-2 and collagen II gene transcription, and the expression of these genes are linked to outgrowth of facial prominences.
Matovinovic
E
E
Department of Oral Health Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
Richman
J M
JM
D000818:Animals; D002642:Chick Embryo; D003094:Collagen / Q000378:metabolism; D004848:Epithelium / Q000196:embryology / Q000378:metabolism*; D005145:Face / Q000196:embryology; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis*; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000096:biosynthesis*; D015398:Signal Transduction
D017468:Receptors, Fibroblast Growth Factor; D003094:Collagen; D020794:Receptor Protein-Tyrosine Kinases; D051497:Receptor, Fibroblast Growth Factor, Type 2