Differential Expression of Duplicate Insulin-like Growth Factor-1 Receptors () in Medaka Gonads.

Insulin-like growth factor-1 receptors () play important roles in regulating development, differentiation, and proliferation in diverse organisms. In the present study, subtypes of medaka , , and were isolated and characterized. RT-PCR results showed that and mRNA were expressed in all tissues and throughout embryogenesis. Using real-time PCR, the differential expression of and mRNA during folliculogenesis was observed. The results of in situ hybridization (ISH) revealed that both of them were expressed in ovarian follicles at different stages, and was also expressed in theca cells and granulosa cells. In the testis, both and mRNA were highly expressed in sperm, while mRNA was also obviously detected in spermatogonia. In addition, mRNA was also present in Leydig cells in contrast to the distribution of mRNA in Sertoli cells. Collectively, we demonstrated that differential RNA expression identifies medaka meiotic germ cells and somatic cells of both sexes. These findings highlight the importance of the system in the development of fish gonads.