DIFFERENTIAL EXPRESSION OF FIBROBLAST GROWTH-FACTOR RECEPTORS DURING RAT LENS MORPHOGENESIS AND GROWTH

Purpose, Fibroblast growth factors (FGF) play important roles in the d evelopmental biology of the lens. Recently, it was shown that the expr ession of one of the FGF receptors, FGFR1 (flg; fibroblast growth fact or receptor 1), was closely associated with the onset of lens fiber di fferentiation. In this study, the expression patterns of three other m embers of the FGF receptor family were analyzed and compared. Methods. The expression patterns of FGFR2 (bek and keratinocyte growth factor receptor [KGFR] variants) and FGFR3 were analyzed by in situ hybridiza tion during embryonic and postnatal lens development. Results, In the ocular primordia, both FGFR2 variants were detected on embryonic day 1 2 (E12) and FGFR3 was detected on E14. From E16 to E20, distinct spati al expression patterns became evident within the lens; FGFR3 showed an anteroposterior increase in expression, with strongest expression in the outer cortical fibers. In contrast, bek showed uniform expression throughout the lens epithelium (including the central and germinative zones) and the transitional zone, with a subsequent decline in maturin g fibers. The KGFR variant of FGFR2 showed strongest expression in the early fibers of the transitional zone; its expression in the epitheli um was weaker in the germinative zone of embryonic and neonatal rats. There was an age-related decline in expression of FGFRs after birth-an effect that was more marked for FGFR3 than for the FGFR2 variants. Co nclusions. Combined with those in a previous study, these results indi cate that the FGFR1, bek, KGFR, and FGFR3 genes exhibit different, yet overlapping, patterns of expression throughout lens development and d ifferentiation. The distinct spatiotemporal patterns of expression of FGF receptors may play an important role in regulating anteroposterior patterns of lens cell behavior.