Role of FGF9 in sheep testis steroidogenesis during sexual maturation

Fibroblast growth factor 9 (FGF9) is an important signaling molecule in early gonadal development. Hu sheep are noted for reproductive precociousness and fertility. The present study was conducted to investigate the gene expression and functions of FGF9 in ovine testis steroidogenesis during sexual maturity. A 874 bp cDNA fragment of FGF9 was detected that included a 627 bp coding sequence, encoding 208 amino acids. The FGF9 amino acid sequence of sheep had high homology with this molecule of other mammalian species. Additionally, the abundance of FGF9 in ovine testis was greater (P <  0.05) at 9 months (M) and 24 M of age compared with those at 3 M. Immunohistochemistry further revealed that FGF9 mainly localized in the Leydig cells and that there were small amounts in elongating spermatids. The functions of FGF9 in sheep Leydig cells was investigated using a siRNA-FGF9. Secretion of T and abundance of testosterone synthesis-related enzymes in Leydig cells were inhibited (P <  0.05) by siRNA-FGF9. Thus, these results demonstrated FGF9 is an important regulator of testosterone biosynthesis in rams. Results of the present research provide a new perspective for genetic and molecular research on modulation of physiological mechanisms during sexual maturity in male sheep.