Nonylphenol modulates expression of androgen receptor and estrogen receptor genes differently in gender types of the hermaphroditic fish Rivulus marmoratus Jung Soo Seo a , Young-Mi Lee a , Sang-Oun Jung a , Il-Chan Kim b , Yong-Dal Yoon c , Jae-Seong Lee a, * a Department of Molecular and Environmental Bioscience, and The National Research Lab of Marine Molecular and Environmental Bioscience, Graduate School, Hanyang University, Seoul 133-791, South Korea b Polar BioCenter, Korea Polar Research Institute, Korea Ocean Research and Development Institute, Incheon 406-840, South Korea c Department of Life Science, College of Natural Sciences, Hanyang University, Seoul 133-791, South Korea Received 15 May 2006 Available online 30 May 2006 Abstract To uncover the effect of estrogenic chemicals [4-nonylphenol (NP) and bisphenol A (BisA)] on the expression of androgen receptor (AR) and estrogen receptors (ERa and ERb) in the hermaphroditic fish Rivulus marmoratus, we cloned the full length of the cDNAs encoding AR, ERa, and ERb 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, ERa, and ERb genes showed a high similarity to the relevant fish species on amino acid residues, respectively. Rm-ERa and Rm-ERb cDNAs included a serine-rich region when compared to other teleost fish ER genes. Tissue-specific expression of Rm-AR and Rm-ERb mRNAs in adult hermaphrodite R. marmoratus was high in the gonad, while Rm-ERa mRNA was high in the liver based on real-time RT-PCR. In addition, Rm-AR and Rm-ERa mRNAs increased along with developmental stage from stage 3 (5 dpf) to hatching, while Rm-ERb mRNA increased from stage 2 (2 dpf). To uncover the effect of estrogenic chemicals on R. marmoratus, we exposed the fish to NP (300 lg/l) and BisA (600 lg/l) for 96 h. Significant down-regulation of Rm-AR, Rm-ERa, and Rm-ERb 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-ERa, and Rm-ERb 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 poten- tial impact of estrogenic compounds using this species as a model system. Ó 2006 Elsevier Inc. All rights reserved. Keywords: Rivulus marmoratus; Androgen receptor; Estrogen receptor a; Estrogen receptor b; Nonylphenol; Bisphenol A; Modulation; Expression The molecular mechanism behind sex determination and differentiation in fish has yet to be well defined. Two research groups have independently isolated a sex-determi- nation gene (the DMY gene) from Japanese medaka (Oryz- ias latipes) [1,2], but determinants may vary according to fish species. Unlike mammals, fish may convert their gender naturally or in response to chemical exposure (e.g., steroid hormones). Steroid hormones derived from the gonads play crucial roles in sexual differentiation, mat- uration, and behavior in vertebrates [3]. In fact, many gonochoristic species can undergo gonad sex inversion in either direction following sex steroid treat- ment early in development. Although the actual mecha- nisms involved are still unclear, steroid hormones have been implicated in natural sex change in fish. In addition, steroid hormone receptors are activated by steroid ligands, 0006-291X/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2006.05.123 * Corresponding author. Fax: +82 2 2299 9450. E-mail address: jslee2@hanyang.ac.kr (J.-S. Lee). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 346 (2006) 213–223 BBRC