Antoine E. Simond, Véronique Lesage, Jonathan Verreault, Lisa Loseto, Magali Houde, Ashley Elliot, Marie Noël, Tanya M. Brown

The St. Lawrence Estuary (SLE) beluga whale (Delphinapterus leucas) population is endangered. It has been postulated that exposure to elevated concentrations of polychlorinated biphenyls (PCBs), chlorinated pesticides, polybrominated diphenyl ethers (PBDEs), and emerging halogenated flame retardants (HFR) contribute to the non-recovery of this population. Recently, concentrations of PCBs, chlorinated pesticides and emerging HFRs in SLE male beluga blubber were shown to correlate with skin transcript levels of genes coding for nuclear receptors and proteins involved in the regulation of thyroid and steroid hormones, as well as the metabolism of xenobiotics. A growing number of studies investigating contaminant-related effects in cetaceans rely on "omics" methods such as, transcriptomics or proteomics, as these approaches require small amounts of tissue and are amenable to multiple analyses. To improve our understanding of the impacts of contaminants on the health of SLE belugas and the mechanisms of toxicity involved, we assessed the transcriptomic and proteomic skin profiles of adult male belugas from the SLE and a reference population in Canada (Eastern Beaufort Sea). Total RNAs and proteins were isolated from skin samples of adult male belugas from the SLE (n = 39) and Eastern Beaufort Sea (n = 34), and PCBs, PBDEs and emerging HFRs were measured in blubber. RNA sequencing and proteomics analyses allowed the identification of 21,646 unique gene transcripts and 6,152 proteins. Ongoing work will characterize the functional profile of differentially expressed genes and proteins to help better understand the biological implications of contaminant exposure to the endangered SLE beluga population and to identify potential biomarkers to be used for future monitoring efforts. The combined use of transcriptomics and proteomics is a promising tool for marine mammal ecotoxicology research and has the potential to significantly improve the risk evaluation of contaminant exposure to this and other at-risk populations.