MP7 Toxicogenomics in Environmental Studies
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall

(SOE-1117-805257) Energy metabolism, molting and reproduction related microarray as a tool for toxicant evaluation in Daphnia magna.

Soetaert, A¹, Vandenbrouck, T¹, Moens, L¹, van der Ven, K¹, Van Leemput, K², Blust, R¹, De Coen, W¹, ¹ Laboratory for Ecophysiology, Biochemistry and Toxicology, Department of Biology, University of Antwerp, Antwerp, Belgium² Intelligent System Lab, Department of Mathematics and Informatics, University of Antwerp, Antwerp, Belgium

ABSTRACT- Since decades Daphnia magna has been the organism of choice for aquatic toxicity testing. Presently, molecular tools are emerging which enable environmental toxicologists to monitor gene expression changes resulting from toxicant exposure in animal species whose genome is not fully known, like Daphnia magna. In this study we applied a combination of genomics technologies to evaluate differential gene expression in Daphnia magna after toxicant exposure. Since chemical stress reduces the amount of energy that is allocated to growth and reproduction we have investigated the expression of genes related to energy metabolism, growth (molting) and reproduction (age-specific) for toxicant characterization. Energy metabolism, molting and reproduction specific cDNA libraries were created using the Suppression Subtractive Hybridization PCR and applied for construction of a custom cDNA array. An important fraction of the genes in these libraries are related to glycolysis, the electron transport chain, protein, carbohydrate and lipid metabolism (energy metabolism), cuticle and protein degradation (molting) and embryo development (reproduction). To evaluate this custom cDNA array exposure experiments were conducted with different chemicals (propiconazole, fenarimol, Cd and Pb) and adverse effects were studied at higher levels of biological organization. Exposure to propiconazole (a fungicide causing developmental deformities in Daphnia offspring) was used as an initial case study. Microarray analysis of freshwater fleas exposed for short periods to this compound clearly caused important effects in genes related to embryo development, energy metabolism, molting and cell cycle. One of the major affected genes was vitellogenin which plays a crucial role in the embryonic development. The downregulation of vitellogenin was also found after exposure to another embryotoxicant namely fenarimol. Organismal effects confirmed the major molecular findings. Presently, we have demonstrated the potential of microarray analysis in toxicity screening with Daphnia magna. Future applications of these molecular techniques will be discussed.

Key words: Toxicogenomics, Microarray, Daphnia magna, Embryotoxicants