Biodiversity of Cytochrome P450 Genes and Biomarkers for Coastal Pollution in Mussels
John J. Stegeman and Jared V. Goldstone, Biology
We propose to develop molecular biomarkers for anthropogenic coastal pollution in environmentally and economically important mussels, focusing on the blue mussel Mytilus edulis (Bivalvia: Mytilinae), and on related Mytilus spp. (e.g., M. galloprovincialis). Global aquaculture production of mussels has at times exceeded 500,000 tons annually, and mussels are an important aquaculture species in New England. Like several other bivalves, Mytilus species have important characteristics of sentinel species useful in pollution biomonitoring. They are distributed in temperate waters in both pelagic ecosystems and brackish estuaries where runoff is at its highest, and are sessile filter feeders, which accumulate a wide range of contaminants. Studies over several decades have
consistently shown that contaminant levels in mussel tissues respond to ambient environmental levels and are integrated over a given area.
Despite the decades of chemical exposure data, few if any reliable biomolecular indicators of chemical exposure exist in Mytilus. This is in distinct contrast to marine vertebrates. We propose to develop a suite of molecular biomarkers for chemical exposure in mussels that will inform regulators of likely contamination problems, and will provide sentinel markers for chemical change that could affect coastal systems. The information would be useful to researchers around the world working to identify and establish monitoring programs incorporating biomarkers in mussels.
The studies will involve searching databases for Mytilus CYP genes, cloning and sequencing CYP genes that are candidates for regulation by chemicals to unambiguously establish relationships, and determining their response to exposure to chemicals experimentally and environmentally. The approach will include:
- Searching public databases using hidden Markov models for CYP genes, and similarly searching
private databases produced by collaborators.
- Annotating all CYP genes uncovered and cloning and sequencing selected genes to confirm
identity of full-length sequences and to confirm that the genes are expressed.
- Exposure of reference site mussels to chemicals (e.g., benzo[a]pyrene, polybrominated diphenyl
ether, ortho- and non-ortho-substituted polychlorinated biphenyls), including dose response and
time dependent variables, and measurement of the levels of expression of relevant CYP genes in
M. edulis tissues by quantitative PCR.
This grant, though small, would enable us to provide critical information to engage an international consortium to address molecular responses in mussels exposed to organic chemical contaminants, a longstanding question with implications for biomonitoring, seafood safety and public health, and molecular evolution of and biodiversity of xenobiotic response systems. Understanding the environmental effects of contaminant chemicals cannot be achieved without knowledge of the diversity of cytochrome P450 (CYP) genes and their expression, and eventually their function. A comprehensive knowledge of Mytilus CYP and their probable functional relationships to mammalian CYP will provide a lasting foundation, underpinning current or future toxicological research with mussels. The studies we propose will be the most complete and definitive to address molecular responses to chemicals in Mytilus.
*pdf of final report at right