Localization patterns of fibroblast growth factor 1 and its receptors FGFR1 and FGFR2 in postnatal mouse retina

Abstract

Fibroblast growth factors (FGFs) exert basic functions both during embryonic development and in the adult. In mammalian retinas, expression of FGFs and their receptors has been reported, however information on the organization of the FGF system is still incomplete. Here, we report detailed double label immunohistochemical investigations of the localization patterns of FGF1 and of its receptors FGFR1 and FGFR2 in adult and in early postnatal mouse retinas. In adult retinas, FGF1 is localized to ganglion cells, horizontal cells and photoreceptor inner and outer segments. FGFR1 is in ganglion cells and in Müller cells, while FGFR2 is primarily localized to ganglion cells and to the nuclei of Müller cells, in addition to glycine containing amacrine cells. During postnatal development, the patterns of FGF1, FGFR1 or FGFR2 immunostainings are similar to those in the adult, but transient FGF1 expressing cells are detected in the proximal inl before eye opening. These patterns are consistent with an important involvement of FGF1, FGFR1 and FGFR2 in ganglion cell maturation (during development) and survival (in the adult). In addition, FGF1 may affect amacrine cell development, while Müller cells appear to receive important regulation from both FGFR1 and FGFR2 throughout postnatal life. Finally, in immature retinas, large numbers of amacrine cells, including calbindin and glycine containing amacrine cells, display both FGF1 and FGFR2 immunoreactivities in their nuclei, suggesting an action of FGF1 on FGFR2 receptors during a restricted period of postnatal development for the maturation of these amacrine cells.