Evidence for the existence of cytochrome P450 gene families (CYP1A, 3A, 4A, 11A) and modulation of gene expression (CYP1A) in the mussel Mytilus spp.

The presence and expression of four gene families of the cytochrome P450 multi-gene family (CYP450) was investigated in the digestive gland of M. edulis using Southern and Northern blot analysis. The cDNA probes employed were for CYP1A1 (pfP1450-3′, 1.5kb from rainbow trout), CYP3A (phPCN12, human), CYP4A1 (2.1kb, rat) and CYP1A1 (1.9kb, human). Single hybridising mRNAs of approximately 2.1kb were seen for all probes, indicating presence and expression of genes from or similar to the four families. Hybridisation on Southern blots was demonstrated for CYP3A and CYP11A, confirming the presence of related CYP genes. The former gave a strong band at about 4.5kb and a weak one at 7.3kb, and the latter a single band at 13kb. The detection of CYP3A-like sequences is consistent with the reported presence of testosterone 6-β-hydroxylase activity in M. edulis. Marked variation in levels of CYP1A-like mRNA were seen in mussels from several sites in the Venice area (UNESCO-MURST Venice Lagoon Project), indicating modulation of gene expression. Some correlation with contaminant exposure was seen, indicating potential for use of this measurement as a biomarker for organic pollution.