Role of Postnatal Expression of Fgfr1 and Fgfr2 in Testicular Germ Cells on Spermatogenesis and Fertility in Mice

Background: Fibroblast growth factor (FGF) signaling is thought to play diverse roles in the male reproductive system. However, its role in testicular cells for spermatogenesis and fertility remains unclear. Methods: In this study, the expression and localization of Fgfr 1 (FGF Receptor) and Fgfr 2 in the postnatal mouse testes were examined by RT-PCR, Western blotting and immunohistochemistry. The in vivo function of each receptor in testicular germ cells was determined using germ cell-specific Fgfr mutant animals, Tex101- iCre;Fgfr flox/flox and Tex101-iCre;Fgfrflox/flox mice. The results were analyzed by Kruskal- Wallis test and Dunn's Post-test. Results: Both Fgfr1 and Fgfr2 were expressed in the testis throughout the entire postnatal development. Prominent immunostaining of these FGFRs was observed in interstitial and peritubular cells with little or no changes in all phases during postnatal development. Positive staining of these receptors was also detected in germ cells including elongated spermatids and spermatozoa. Germ cell-specific Fgfr1 or Fgfr2 mutant mice were viable with no developmental abnormalities in the testes and accessory sex organs. Fertility studies showed that the fecundity of both mutant mouse lines did not significantly differ from wild-type siblings (n=4, p>0.05). Further analysis indicated the presence of other Fgfrs in testicular germ cells including Fgfr 3, 4 and 5. Conclusion: The results demonstrated that Fgfr1 and 2 are expressed in all testicular cell types and that neither Fgfr1 nor Fgfr2 in testicular germ cells is essential for spermatogenesis and fertility. Future studies are needed to investigate the potential functional redundancy among five Fgfrs in male germ cells for spermatogenesis and fertility.