Gene transcription profiling in mussels (Mytilus sp.) exposed to the model compounds copper choloride and Benzo[a]pyrene

Abstract Environmental pollution is increasing in coastal areas and is responsible for adverse health effects in marine wild life. The oceans are vast and the sources of pollution are many, which make the effects of pollution difficult to assess in a reliable and valid way. Different toxic components have different mode of actions, leading to series of responses in organism. The first early responses to a toxicant, in most cases a system at the molecular level designed to target the specific toxicant, is important to identify. A series of biological marker (biomarker) analyses have thus been developed to assess the effects of exposure to single chemicals (metals and organic compounds) and complex pollution discharges. Single biomarkers are useful as indicators of the presence pollution as they reflect biochemical and physiological changes, but they may not necessary predict the effects on the whole organism. Several mussel species in the genus Mytilus has frequently been used to assess chemical pollution in the aquatic environment and with the availability of high-content molecular methods such as microarrays, makes this group of species highly interesting for use in toxicity assessment and environmental monitoring. The aim of this project was to evaluate the performance of a newly developed high-content Mytilus sp. oligonucleotide array (oligoarray) and to specifically assess the transcriptional effects in M. edulis digestive organ after exposure to the fundamentally different pollutants Copper chloride (CuCl2) and the Polycyclic Aromatic Hydrocarbon (PAH) Benzo[a]pyrene (BaP). The results showed that an oligoarray based on M. edilus and M. galloprovinciales could be used to study the differential expression in M. edulis digestive gland after exposure to Cu and BaP. There were also indentified different MoA for Cu and BaP, as well as several genes and pathways related to general stress responses of toxicity for both compounds. Further work on the development of the array includes inclusion of additional sequence information from other sequencing projects, redundancy reduction and further verification of the microarray results by Real Time quantitative Polymerase Chain Reaction (RT-qPCR) to assess the dynamic range and sequence specificity of the array. Keywords: Pollution, Environmental monitoring, biomarkers, common mussel (Mytilus sp.), BaP, Cu, microarray, gene expression.Norsk Institutt for Vannforskning (NIVA