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Expression of fibroblast growth factor‐8 and its cognate receptors, fibroblast growth factor receptor (FGFR)‐3c and‐4, in fetal bovine preantral follicles

Paracrine cell signaling is thought to be important for ovarian follicle development, and a role for some members of the fibroblast growth factor (FGF) family have been suggested. In the present study, we tested the hypothesis that FGF‐8 and its cognate receptors (FGFR‐3c and FGFR‐4) are expressed in bovine preantral follicles. Reverse transcription‐polymerase chain reaction was used to amplify bovine FGF‐8, FGFR‐3c, and FGFR‐4 from preantral follicle samples and a variety of fetal and adult tissues. All three genes were widely expressed in fetal tissues, with a restricted expression pattern in adult tissues. FGF‐8 and FGFR‐3c were expressed in secondary follicles in 70% of fetuses examined, whereas FGFR‐4 expression was significantly less frequent (20%). FGFR‐3c expression frequency was significantly lower in primordial compared to secondary follicles, and FGF‐8 expression showed a similar trend. FGFR‐4 was only observed when all follicle classes of an individual were expressing both FGF‐8 and FGFR‐3c. We conclude that FGF‐8 and its receptors are expressed in preantral follicles in a developmentally regulated manner. Mol. Reprod. Dev. 70: 255–261, 2005. © 2005 Wiley‐Liss, Inc.