Gonadal expression profiles of sex-specific genes during early sexual differentiation in Japanese eel Anguilla japonica

The Japanese eel Anguilla japonica is a prominent and highly valued species in the aquaculture industry in Japan. Sex determination and sex differentiation in eels are significantly affected by environmental factors; however, the molecular mechanisms involved in sex differentiation in eels are largely unknown. In this study, to investigate the gonadal expression profiles of sex-specific genes during and after sexual differentiation in Japanese eel, we induced elvers into predominantly phenotypic males or females by rearing on a control diet or estradiol-17 beta-treated diet, respectively, during the sex differentiation period. Quantitative real-time PCR showed that forkhead box L2A (foxl2a) and cytochrome P450 aromatase (cyp19a1) were more highly expressed in ovaries than in testes, whereas the expression levels of anti-Mullerian hormone (amh) and gonadal soma-derived factor (gsdf) were significantly higher in testes than in ovaries. Furthermore, foxl2a and cyp19a1 displayed female-specific expression early in the sex differentiation process, while after slightly more growth amh and gsdf displayed male-specific expression during sex differentiation. Together, these results suggest that these genes have important roles in sexual differentiation and development in this species.

Automated summary

The study revealed the essential role of estrogen in sex determination in Japanese eels, and provided the expression profiles of sex-specific genes (foxl2a, cyp19a1, amh, gsdf) during sexual differentiation, highlighting their importance in the process of sexual differentiation and development in the Japanese eel species.