Sensitive and robust gene expression changes in fish exposed to estrogen--a microarray approach.
BACKGROUND
Vitellogenin is a well established biomarker for estrogenic exposure in fish. However, effects on gonadal differentiation at concentrations of estrogen not sufficient to give rise to a measurable vitellogenin response suggest that more sensitive biomarkers would be useful. Induction of zona pellucida genes may be more sensitive but their specificities are not as clear. The objective of this study was to find additional sensitive and robust candidate biomarkers of estrogenic exposure.


RESULTS
Hepatic mRNA expression profiles were characterized in juvenile rainbow trout exposed to a measured concentration of 0.87 and 10 ng ethinylestradiol/L using a salmonid cDNA microarray. The higher concentration was used to guide the subsequent identification of generally more subtle responses at the low concentration not sufficient to induce vitellogenin. A meta-analysis was performed with data from the present study and three similar microarray studies using different fish species and platforms. Within the generated list of presumably robust responses, several well-known estrogen-regulated genes were identified. Two genes, confirmed by quantitative RT-PCR (qPCR), fulfilled both the criteria of high sensitivity and robustness; the induction of the genes encoding zona pellucida protein 3 and a nucleoside diphosphate kinase (nm23).


CONCLUSIONS
The cross-species, cross-platform meta-analysis correctly identified several robust responses. This adds confidence to our approach used for identifying candidate biomarkers. Specifically, we propose that analyses of an nm23 gene together with zona pellucida genes may increase the possibilities to detect an exposure to low levels of estrogenic compounds in fish.
Gunnarsson
Lina
L
Department of Neuroscience and Physiology, the Sahlgrenska Academy at Göteborg University, Göteborg, Sweden. lina.gunnarsson@fysiologi.gu.se <lina.gunnarsson@fysiologi.gu.se>
Kristiansson
Erik
E
Förlin
Lars
L
Nerman
Olle
O
Larsson
D G Joakim
DG
D000818:Animals; D015415:Biomarkers; D017931:DNA Primers / Q000235:genetics; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism*; D004997:Ethinyl Estradiol / Q000633:toxicity*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D054778:NM23 Nucleoside Diphosphate Kinases / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000072216:Zona Pellucida Glycoproteins
D015415:Biomarkers; D017931:DNA Primers; D004527:Egg Proteins; D008562:Membrane Glycoproteins; D054778:NM23 Nucleoside Diphosphate Kinases; D011956:Receptors, Cell Surface; D000072216:Zona Pellucida Glycoproteins; D004997:Ethinyl Estradiol