Expression patterns of two fibroblast growth factor receptor genes during early chick eye development.

The expression patterns of two distinct types of fibroblast growth factor receptor (FGFR) genes, FGFR1 and FGFR2, were compared during early chick eye development. In situ hybridization was performed with riboprobes synthesized from cDNA fragments of FGFRs cloned by the polymerase chain reaction method. FGFR1 was expressed in the prospective lens, neural retina, pigment epithelium and mandibular mesenchyme. In contrast, FGFR2 was expressed predominantly in the periocular mesenchyme of a 2.5 day-old embryo. In the 5.5-day-old embryo, transcripts of FGFR2 were detected in the prospective corneal epithelium. The results suggest that expression patterns of FGFR1 and FGFR2 are complementary and ligands of each FGFR might be involved differentially in early chick eye development. It is concluded that the action of FGFs on pigment epithelium and lens cells reported so far, probably occurs through FGFR1, and both types of FGFR are involved in head mesenchymal development.