A comparative study of the expression of CYP1A and CYP4 genes in aquatic invertebrate (freshwater mussel, Unio tumidus) and vertebrate (rainbow trout, Oncorhynchus mykiss).

CYP1A1 induction has been widely studied in vertebrates and is used as an indicator of exposure to persistent pollutants like dioxins, polychlorobiphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), especially in fish. Little work on this enzyme has been carried out in invertebrates, and results have suggested enzymatic or gene differences with the vertebrate isozyme. To date, a CYP4 isozyme has been characterized and sequenced in the marine mussel, Mytilus galloprovincialis, but no CYP1A invertebrate sequence has been found. The aim of this study was to identify CYP1A and CYP4 transcripts in the freshwater bivalve, Unio tumidus, and to compare their expression with those of the rainbow trout, Oncorhynchus mykiss, after treatment with the specific CYP1A1 and CYP4 vertebrate inducers, Aroclor 1254 and diethylhexylphthalate (DEHP), respectively. In spite of numerous amplification conditions and primer combinations tested, which had been successful in fish, no CYP1A sequence was amplified on cDNA of the digestive gland from either control and Aroclor-treated mussels. On the other hand, CYP4 transcripts were amplified in digestive glands from control and DEHP-treated mussels. As opposed to fish, no induction of this isozyme was obtained in mussels after phthalate treatment. Copyright 2004 Elsevier B.V.