Expression of FGF receptor gene in rat development.

We examined the expression of FGF-receptor (FGF-R) mRNA during rat development with in situ hybridization histochemistry. Embryonic tissues (E9, E12, E14, E17) and postnatal neural tissues (P1, P7, P14, adult) were examined. We detected significant levels of FGF-R mRNA in various tissues at different developmental stages. As postulated by previous studies using other methods, FGF-R gene expression was observed primarily in mesoderm- and neuroectoderm-derived tissues. In the nervous system, the pattern of gene expression was developmentally regulated; in embryos, FGF-R mRNA was mainly detected in the ependymal layer of the central nervous system (CNS). Postnatally, FGF-R transcripts were observed in specific neuronal populations, such as hippocampal neurons. FGF-R mRNA was also found in sensory systems such as trigeminal and dorsal root ganglia in late stage embryos; however, FGF-R mRNA decreased in the postnatal period. FGF-R mRNA expression was modulated in the developing retina: FGF-R messages were observed in the pigment epithelium and neuroblast layer at embryonic stages; in the postnatal period, they were found in the ganglion cell and inner granular layer. In non-neuronal embryonic tissues, a wide variety of organs expressed FGF-R message. Particularly, the prevertebral column, bone, kidney and skin showed high levels of expression. These observations reinforce the idea that FGF exerts effects on the development of various tissues.