Abstract
Abstract: :
Purpose: To investigate the presence and localization of FGF9 and its preferred the high affinity receptors FGFR2 and FGFR3 in developing and adult rat retina. Methods: Occurence of FGF9 and FGFR transcripts were studied by RT–PCR using total RNA from rat retina obtained by acid phenol–cloroform extraction. For the relative abundance of the FGF9 transcript in postnatal (PN0–PN30) and adult rat retina, ß–actin was used as an internal control. Amplifications were carried out in the exponential phase and the products were detected by Southern blotting using 32P–labelled nested oligonucleotide. FGF9 transcript sizes were revealed by northern blots and its cellular distribution was analyzed by in situ hybridization studies using DIG–labelled sense or antisense probes. Protein analysis were done by western blotting where FGF9 antibody against the N–terminal, polyclonal FGFR1, FGFR2 or FGFR3 antibodies were raised against the C–terminal regions were used. Signal was detected by chemiluminecense. Same primary antibodies were utilized in immunohistochemical studies on sections prepared from PN0, PN8, PN16 and adults. In control experiments neutralization was done by pre–incubation of the polyclonal antibody with appropriate blocking peptide. Primary antibody binding was revealed by using Alexa 488 conjugated secondary antibody where DAPI was also included. Results: The presence of FGF9 transcripts in adult rat retina was detected by RT–PCR and Northern blots revealed transcripts of 3.2 kb and 4.0 kb. Western blotting showed FGF9–immunoreactive bands at 30 and 55 kDa. FGF9 in situ hybridisation showed detectable signal in inner retina. Immunohistochemical studies indicated the presence of FGF9 in all cellular and plexiform layers throughout postnatal days examined. FGF9 mRNA demonstrated a biphasic expression profile, elevated at birth and adulthood, but relatively decreased during PN4–PN14. FGFR2–IIIc and R3–IIIc were detected by RT–PCR, and western blotting showed both FGFR existed as multiple forms between ∼100–200 kDa. FGFR2 and R3 antibodies showed prominent labelling in the inner retina. Conclusions: The widespread distribution of FGF9 as well as its preferred FGFR isoforms suggest these molecules may perform important functions during retinal development and maintenance. Since FGF9 is efficiently secreted, it is plausible that retinal neurons release the factor to act in an autocrine or paracrine manner.
Keywords: growth factors/growth factor receptors • gene/expression • retinal development