187 EXPRESSION AND REGULATION OF THE FIBROBLAST GROWTH FACTOR GENE FAMILY DURING MOUSE FOLLICULAR DEVELOPMENT

Abstract

Recent studies have shown the critical roles of fibroblast growth factors (FGFs), including FGF8 produced by oocytes, in regulating follicular development. However, the expression and regulation of the FGF gene family, which consists of 22 ligands and 4 receptors, in the mouse ovary have not been well understood. The aim of the present study was to assess the expression and regulation of FGF ligands and receptors in the mouse ovary. Transcript levels of FGF ligands and receptors in immature (3-week-old) and adult (7- to 8-week-old) ovaries as well as other tissues of B6/DBA2F1 mice were analysed with RT-PCR. Furthermore, expression levels of FGF receptors in cumulus cells (CC) and mural granulosa cells (MG) before and after equine chorionic gonadotropin (eCG) treatment were determined with RT-quantitative PCR. Among 21 FGF ligands examined, 12 and 9 transcripts were detectable in immature and adult ovaries, respectively. More FGF ligands were detected in ovary, testis, heart, and brain compared to other tissues, including liver and spleen. Transcripts of all 4 FGF receptors (Fgfr1–4) were detectable in both immature and adult ovaries. Expression levels of Fgfr1 and Fgfr2 were significantly higher in MG compared with CC before and after the eCG treatment. Levels of Fgfr4 were comparable between MG and CC before the eCG treatment, but became significantly different with higher expression levels in MG after the eCG treatment. Fgfr3 transcripts were barely detectable in CC and MG. Overall levels of Fgfr1 in granulosa cells (CC and MG) were downregulated by eCG treatment, whereas those of Fgfr2 and Fgfr4 were upregulated. In summary, many FGF ligands are expressed, at least in mRNA levels, in mouse ovaries. Moreover, the expression levels of Fgfr transcripts in granulosa cells are dynamically regulated during follicular development.