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() Developmental toxicity of mercury in zebrafish (Danio rerio): alterations in behavior and gene expression.

Carvan, III, Michael1, Rise, Matthew1, Wimpee, Barbara1, Weber, Daniel1, 1 University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, USA

ABSTRACT- Mercury is a known neurotoxicant that is primarily introduced into the environment by coal-fired power plants and accumulates in aquatic systems. Fish consumption advisories have been posted in nearly every state in the United States and are most prevalent in the upper midwestern states of Minnesota, Wisconsin, and Michigan. Mercury affects the developing nervous system and fish from these water bodies may be neurologically impaired as a result of the developmental exposure. We are investigating the effects of organic and inorganic mercury exposure on developing zebrafish by analyzing changes in the startle reflex response, and identifying changes in gene expression by microarray analysis. The goal of this project is to identify neural and molecular biomarkers as predictors of mercury exposure and deficits in specific behavioral endpoints. We exposed zebrafish embryos and/or larvae to varying concentrations of mercury during specific developmental periods. Immediately following exposure, a sample of the population was used to determine mercury uptake by ICP-MS, another sample was used to analyze gene expression on an 8,000 element zebrafish cDNA microarray, and the remainder were raised to seven days post-fertilization (five days post-hatch) for analysis of startle reflex responses. Mortality and behavioral alterations were shown to be dose-dependent and to vary with the time of exposure. Preliminary microarray analysis following mercury exposure reveals changes in the expression of a number of genes primarily associated with neurological structure and function, mitochondrial function, and immune system function. The results of this project will contribute to a more complete mechanistic understanding of the connection between gene expression and behavioral dysfunction resulting from developmental mercury exposure. The results of this study have implications for both human biomedicine and for recruitment in wild fish populations from mercury contaminated water bodies.

Key words: neurotoxicity, mercury, microarray, behavior

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