Expression patterns and ectopic expressions of fibroblast growth factor genes (Fgf4, Fgf8) during early chick eye development

We used whole-mount in situ hybridization to examine expression patterns of Fgf4 and Fgf8 genes during chick eye development, and found that Fgf8 is expressed in the inner and outer layers of the early optic cup, while Fgf4 transcripts were not detectable in the developing ocular tissues examined. Furthermore, to learn Fgf gene functions during chick eye development, the genes were ectopically expressed in the developing chick eye using a retrovirus. The outer layer of the optic cup overexpressing either Fgf gene became depigmented and thickened like a second neural retina. These results suggest that FGF 8 is an endogenous factor involved in neural retinal differentiation.