Nonylphenol modulates expression of androgen receptor and estrogen receptor genes differently in gender types of the hermaphroditic fish Rivulus marmoratus

To uncover the effect of estrogenic chemicals [4-nonylphenol (NP) and bisphenol A (BisA)] on the expression of androgen receptor (AR) and estrogen receptors (ERα and ERβ) in the hermaphroditic fish Rivulus marmoratus, we cloned the full length of the cDNAs encoding AR, ERα, and ERβ from gonadal tissue of R. marmoratus and analyzed the modulation of expression of these genes following exposure to estrogenic chemicals using real-time RT-PCR. R. marmoratus AR, ERα, and ERβ genes showed a high similarity to the relevant fish species on amino acid residues, respectively. Rm-ERα and Rm-ERβ cDNAs included a serine-rich region when compared to other teleost fish ER genes. Tissue-specific expression of Rm-AR and Rm-ERβ mRNAs in adult hermaphrodite R. marmoratus was high in the gonad, while Rm-ERα mRNA was high in the liver based on real-time RT-PCR. In addition, Rm-AR and Rm-ERα mRNAs increased along with developmental stage from stage 3 (5 dpf) to hatching, while Rm-ERβ mRNA increased from stage 2 (2 dpf). To uncover the effect of estrogenic chemicals on R. marmoratus, we exposed the fish to NP (300 μg/l) and BisA (600 μg/l) for 96 h. Significant down-regulation of Rm-AR, Rm-ERα, and Rm-ERβ mRNA was observed in gonadal tissue after exposure to NP but not BisA. In the liver, there were gender differences in gene expression after EDC exposure. These results demonstrate that expression patterns of the Rm-AR, Rm-ERα, and Rm-ERβ genes in the hermaphroditic fish, R. marmoratus, vary according to tissue and developmental stage as well as the specificity of environmental estrogenic chemicals. These genes can be useful as molecular biomarkers in assessing the potential impact of estrogenic compounds using this species as a model system.