The Expression Profile of Fibroblast Growth Factor 9 and Its Regulation Mechanism on Steroidogenesis in Mouse Testis.

Fibrobast growth factor 9 (FGF9) is a multifunctional polypeptide, and participates in bone formation, lens fiber differentiation, nerve development, gap junction formation and sex determination. Previously, Colvins JS et al. reported that the FGF9 knock out mouse has female phenomenon when it has Y chromosome. Fibroblast growth factor receptors (FGFRs), the members of transmembrane receptor tyrosine kinase, have three immunoglobulin-like domains to interact with FGF9 to pass on the serial signal into cells. In our previous study, we demonstrate that the FGF9 could up-regulate the testosterone production in mouse Leydig cells by protein kinase A pathway in time- and dose-dependent matters. In order to confirm the expression of FGF9, we used immunohistochemistry (IHC) to directly identify the location and expression level of FGF9 and FGFR in mouse testis. We found that the FGF9 would sustain and have higher expression level during the maturation of Leydig cells in postnatal mouse. FGFR1 and FGFR3 have higher expression levels from birth to adult. During the Leydig cell maturation, FGFR2 has the similar expression profile to FGF9. In addition to observe the effect of FGF9 and FGFRs in Leydig cells, we used FGF9 and protein kinase inhibitors to investigate the detail signal transduction pathway which activated by FGFRs. We found that the FGF9 could activate JNK, ERK1/2 and p38 of MAPK pathway and AKT of PI3K pathway at different time points in immature Leydig cells. According to these findings, we suggested that the FGF9 plays a role for testosterone production and Leydig cell maturation in mouse testis.

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