How nanomolar doses of combined metal salts (Cd, Cu, Hg) induce DNA damage and transcriptional changes in the gills of Mytilus galloprovincialis.. Mytilus galloprovincialis

We used a cDNA microarray previously defined for the marine sentinel organism Mytilus galloprovincialis (MytArray1.0) to evaluate the effects of nanomolar doses of combined metal salts (50, 100 and 200 nM mixtures of Cd, Cu and Hg) after 48 hours of mussel exposure. Pointing to the mussel gills, first target of toxic water contaminants and actively proliferating tissue, we found significant dose-related increases of cells with micronuclei and other nuclear abnormalities in the treated mussels, with differences in the bioconcentration of the three metals determined in the mussel pulp by atomic absorption spectrometry. Following gill RNA purification and DNA microarray analysis, individual gene expression profiles revealed some transcriptional changes at the 50 nM dose, and substantial increases of differentially expressed genes at the 100 and 200 nM doses with roughly similar amounts of up- and down-regulated signals. The functional annotation of transcripts with consistent expression trends and significantly altered at least in one dose point disclosed the complexity of the induced cell response. Overall design: Three-condition experiment (50, 100 and 200 nM doses), individual treated mussel vs. pooled control mussels (N=5), 3 biological replicates with dye-swap competitive hybridization (array A and B, 2 technical replicates/array).