Effects of sexual steroids on the expression of foxl2 in Gobiocypris rarus.

Gobiocypris rarus is an emerging fish model for aquatic toxicology in China as it is sensitive to environmental hormone disruptors. Exogenous sex steroids can affect sex differentiation and the expression of sex-related genes. Foxl2, a member of forkhead-box transcription factor family, is the key gene for ovary development and its mutation causes the blepharophimosis ptosis epicanthus inversus syndrome in human. We find that two foxl2 genes exist in fish genome, one is foxl2, and the other is foxl2b. Here, we reported the isolation and expression of foxl2 in G. rarus. G. rarus foxl2 cDNA is 1700bp in length with a 921bp of open reading frame encoding 306 amino acids containing the typical FH-domain. Semi-quantitative RT-PCR revealed its predominant expression in the eye, brain, gill and gonads. Moreover, the expression level in the ovary was significantly higher than that in the testis. Quantitative RT-PCR showed that foxl2 was up regulated after treatment with estradiol and was down regulated with 2-methyl-testosterone. These results suggested that Foxl2 plays an important role in female development of G. rarus, foxl2 mRNA expression is regulated by downstream sex hormones, and foxl2 can be used as a molecular indicator monitoring the environmental endocrine disruptors.