Global transcriptome analysis reveals specific signatures of pollutants in wild Atlantic eels. Anguilla

We used RNA-seq technology on two threatened species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), to test whether changes in transcriptome profiles in wild fish may be used to detect and unravel the toxicity of pollutants in a context of in situ exposure. Wild eels were sampled in 8 sites (4 Canadian and 4 French sites) presenting a contamination gradient. The hepatic transcriptome of 6 eels per sampling site was determined by high throughput RNA sequencing using Illumina Hiseq2000 technology. The liver was selected for our analysis due to its wide range of functions, including detoxification and energy metabolism. In parallel, the contamination levels of fish in 8 metals were determined in kidneys, i.e. in a main site of metal bioaccumulation. Twenty five persistent organic pollutants (POPs) known to be bioaccumulated in lipid-rich tissues were determined in muscle. A statistical analysis was then carried out to analyze the relationships between hepatic transcriptomic profiles and the contamination levels of fish. Such an approach was used to get out genes for which their transcription levels could be related to a single contaminant. In order to identify genes and by extension potential biomarkers of exposure that could be extrapolated across species, the transcriptome of all sampled eels (n=48), i.e. both European and American eels, were combined before carrying out analyses.