Gene expression profiling in common cormorant liver with an oligo array: assessing the potential toxic effects of environmental contaminants.
To establish a monitoring system for gene expression profiles related to chemical contamination in wild common cormorants (Phalacrocorax carbo), the present study constructed an oligo array designed from expressed sequence tag (EST) sequences of the cormorant liver, where 1061 unique oligonucleotides were spotted. Common cormorants were collected from Lake Biwa, Japan in May 2001 and 2002. With the use of this oligo array, gene expression profiles in the liver of individual specimens were evaluated. To determine the expression patterns of genes altered by environmental contaminants, relationships between concentrations of persistent organochlorines including polychlorinated dibenzo-p-dioxins, furans, polychlorinated biphenyls, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane and its metabolites (DDTs), hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs), butyltins, and bisphenol A (BPA) and expression levels of each gene in the cormorant liver were examined using stepwise multiple regression analysis. The reliability of data obtained by the oligo array was further confirmed by quantifying the expression levels of certain genes using real-time RT-PCR. The 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent (TEQ) level was positively correlated with both cytochrome P4501A4 and 1A5 gene expression. In addition, the mRNA level of an antioxidant enzyme, Cu/Zn superoxide dismutase, was negatively correlated with hepatic total TEQ. Other antioxidant enzymes, glutathione peroxidase 3 and glutathione S-transferase class mu, were negatively correlated with HCHs and BPA levels, respectively. The mRNA expression level of a nonenzymatic antioxidant, haptoglobin, was negatively but not significantly correlated with CHLs. These results led to a hypothesis that wild cormorant population may suffer from oxidative stress due to chemically induced formation of reactive oxygen species and subsequent reduction of antioxidant resistance. Thus, the cormorant oligo array may be a useful monitoring tool to identify specific gene expression profiles altered by various environmental contaminants. Although further research is required to clarify a definitive cause-and-effect relationship, the current study provides valuable information on contaminant-responsive genes to predict potential effects on wildlife in a real environment.
Nakayama
Kei
K
Center for Marine Environmental Studies, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan.
Iwata
Hisato
H
Kim
Eun-Young
EY
Tashiro
Kosuke
K
Tanabe
Shinsuke
S
D000818:Animals; D001717:Birds / Q000235:genetics*; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics; D004784:Environmental Monitoring / Q000379:methods; D004785:Environmental Pollutants / Q000506:poisoning*; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D008099:Liver / Q000201:enzymology*; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction
D004785:Environmental Pollutants; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System