A Dynamic Spatio‐Temporal Expression Pattern of FGFR Isoforms During Scleral Ossicle Development

Abstract

Fibroblast growth factors (FGFs) are an important family of proteins that play several roles during early vertebrate development. The FGF ligands bind to their membrane bound receptors (FGFRs) and activate downstream signalling pathways. Although the role of FGFRs has been widely studied in the development of endochondral bones, little is known about their role in the development of neural crest derived intramembranous bones. Scleral ossicles are a ring of 13–15 neural crest derived intramembranous bones in the eye of the chicken (Gallus gallus) and have been identified as a model for intramembranous bone formation. These bones are induced by a corresponding ring of epithelial thickenings, the conjunctival papillae. Using whole mount in situ hybridization, the spatio‐temporal expression patterns of ‘b’ and ‘c’ isoforms of FGFRs1–3 were determined during the stages of conjunctival papillae (HH30–33) as well as scleral ossicle development (HH34–37). The expression of both ‘b’ and ‘c’ isoforms of FGFRs1–3 were observed during conjunctival papillae development and their downregulation was observed during the stages of scleral ossicle induction. ImageJ was further used to study changes in the intensity of expression and to give a more precise indication of the stages of downregulation for each gene. Additionally, although all FGFRs were expressed in the epithelium, only FGFRs 1c, 2c, 3b and 3c were observed in the mesenchyme. The dynamic spatio‐temporal expression pattern of the FGFR isoforms during conjunctival papillae development implicates several FGF ligands in conjunctival papillae induction. This research will further our understanding of the signalling pathways potentially involved in the scleral ossicle system. FGF signaling is likely to interact with the Bone Morphogenetic Protein and Hedgehog pathways, already identified to play a role in the scleral ossicle system.Support or Funding InformationThis research was funded by the Natural Sciences and Engineering Research Council of CanadaThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.