EXPRESSION OF THE CHICKEN CYSTEINE-RICH FIBROBLAST GROWTH-FACTOR RECEPTOR (CFR) DURING EMBRYOGENESIS AND RETINA DEVELOPMENT

The expression of the chicken cysteine-rich fibroblast growth factor r eceptor (CFR) during organogenesis and specifically during retina form ation was studied by Northern blotting and a sensitive in situ hybridi zation, At days 2 and 4 of embryonic development (E2 and E4), CFR mRNA was present in a wide variety of developing organs; it was abundantly expressed in nervous structures, particularly in the retina, The leve ls of CFR transcripts were high during the proliferation and the subse quent differentiation phases of retinal neurogenesis, reached a maximu m around E11 during the onset of the major period of retinal cell deat h, and then declined progressively, CFR mRNA was not detected at late stages when the final arrangement of retinal cell layers has been esta blished. In prolonged primary cell cultures of chicken embryo retina, CFR expression showed a similar down-regulation to that seen with incr easing age in vivo, It was up-regulated either directly or indirectly by its ligands, The CFR expression pattern in the developing retina wa s complementary to that of two other fibroblast growth factor (FGF) re ceptors, namely FGF-R1 and FGF-R2, In regard to a progressive increase in the expression of their ligands during retinal development, we sug gest that CFR may have a role distinct from that of the tyrosine kinas e FGF receptors during retinogenesis, Finally, the comparison of CFR e xpression with those of the other high affinity receptors indicates a regulation of the FGF function at the receptor level during neural ret ina development. (C) 1996 Wiley-Liss, Inc.