Expression Analysis of Sex-Specific and Endocrine-Disruptors-Responsive Genes in Japanese Medaka, Oryzias latipes , using Oligonucleotide Microarrays

Gene profiling of Japanese medaka (Oryzias latipes) was performed using an oligonucleotide DNA microarray representing 26,689 TIGR Oryzias latipes Gene Indices (OLGIs). We first confirmed the high correlation coefficients (>0.94) of gene expression in individual medaka grown under the standard procedures. Secondly, we exposed male medaka to estrogenic compounds [17β-estradiol (E2), 17α-ethynylestradiol (EE2), nonylphenol (NP), octylphenol (OP), and bisphenol A (BpA)], and assessed estrogenic compounds-induced changes in mRNA expression with the medaka microarray. Histological analysis showed the production of testisova in the testes of male medaka exposed to the estrogenic chemicals. Microarray analysis of the chemical-treated male medaka identified estrogenic compoundsresponsive OLGIs, although many of those OLGIs were not sex-specific. Based on the mRNA expression profiles, assessment of the degree of feminization/demasculinization using the combination of Pearson correlation coefficient (CC) and Euclidean distances was also attempted in order to estimate the impact of hormonally active chemicals. The calculated feminization factors indicate that E2 and EE2 treatment “weakly feminized” male medaka (∼50%), while NP, OP, or BpA treatment did not significantly feminize male medaka (<6%). On the other hand, the calculated male-dysfunction factors suggest that male physiological functions were disrupted by the EE2 exposure (∼50%), but not significantly by E2, NP, OP, or BpA treatments (<16%). Results demonstrate the possibility of using medaka microarrays to estimate the overall effects of hormonally active chemicals. 1 Japan Pulp & Paper Research Institute, Inc., Tokodai 5-13-11, Tsukuba, Ibaraki, 300-2635; Japan; Tel: +81-29-847-4321, Fax: +81-29-847-8923 2 Human Stress Signal Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba West, Onogawa 16-1, Tsukuba 305-8569, Japan 3 GeneFrontie, Corp., Nihonbashi Kayabacho 3-2-10, Chuo-ku, Tokyo, 103-0025, Japan