Short communication Expression profiles of 4-nonylphenol-exposed medaka (Oryzias latipes) analyzed with a 3.4 K microarray Il-Chan Kim a , Young-Mi Lee b , Chulwoo Lee c , Hyun-Mi Kim c , Shoji Oda d , Yong-Sung Lee e , Hiroshi Mitani d , Jae-Seong Lee b, * a Polar BioCenter, Korea Polar Research Institute, Korean Ocean Research & Development Institute, Ansan 426-744, South Korea b Department of Molecular and Environmental Bioscience, Graduate School, Hanyang University, Seoul 133-791, South Korea c Environmental Risk Research Department, National Institute of Environmental Research, Incheon 404-170, South Korea d Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8562, Japan e Department of Biochemistry, College of Medicine, Hanyang University, Seoul 133-791, South Korea Abstract Changes in gene expression in liver of medaka in response to 4-nonylphenol (4-NP) were inves- tigated with a microarray consisting of 3.4 K medaka-specific cDNA probes. Upon exposure to 4- NP at two different concentrations (20 and 100 lg/L) for 24 h, we found 44 different genes that were up- or downregulated with statistically significant changes. Digestive enzyme genes were downregu- lated but vitellogenin, choriogenin and novel biomarker genes were upregulated. Additionally an analysis of the changes of gene expression with respect to time was conducted at 100 lg/L of 4- NP with samples at 0, 24, 48 and 96 h. The expression of 75 genes was altered and these were cat- egorized into four different clusters. The validity of the results was checked by semi-quantitative PCR with 12 representative genes and this confirmed the microarray data. Therefore, we suggest that this medaka 3.4 K chip would be useful in generating gene expression profiles for studies of ecotox- icogenomics in medaka. Ó 2006 Elsevier Ltd. All rights reserved. 0141-1136/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.marenvres.2006.04.051 * Corresponding author. Tel.: +82 2 2220 0769; fax: +82 2 2299 9450. E-mail address: jslee2@hanyang.ac.kr (J.-S. Lee). Marine Environmental Research 62 (2006) S141–S146 www.elsevier.com/locate/marenvrev MARINE ENVIRONMENTAL RESEARCH