Characterization of CYP1A and gene expression profiling in three mysticete species

The Cytochrome P450 1A (CYP1A) gene of the three balenopterids Balaenoptera edeni (Bryde's whale), B. musculus (blue whale) and B. physalus (fin whale) has been characterized in this work to compare significant differences in the gene sequence related to its function and to compare the gene expression profile in the three species. CYP1A is of the most important enzyme involved in the bioactivation of exogenous compounds and its activity is well known to be induced after contaminants' exposure, in particular to persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) which can be bioaccumulated in the whales' blubber. We used non-lethal sampling methods to obtain skin biopsies from the specimens in the Gulf of California (Mexico). Since the cetacean's CYP is poorly investigated, we fully amplified, cloned and sequenced the gene in these very closely related specieswhich, however, differs in feeding habits (zooplanktonic vs fish-eating species) and migratory behavior (resident vs. migratoryspecies). Once obtained the full sequences of the CYPs in all the three species, mRNA levels were quantified by quantitative Real-Time PCR. Interestingly, the highest up-regulation of the gene was found in the fish-eating species Bryde'swhale, that also presents regionswith higher homology to the odontocetes species thanmysticetes. The lowestmRNA values were found in the resident species fin whale and the blue whale showed intermediate values. On this regard, the blue whale (zooplanktonic species) accumulates high concentration of POPs during the migration southwards to the Gulf of California while the fin whale (zooplanktonic species) is resident in the Gulf. Moreover the fish-eating species Bryde's whale, resident in the Gulf, showed the lowest levels of POPs in blubber. In conclusion, the diet and the migratory behavior and the evolution of CYP1A gene of the three species investigated could explain the different responses of CYP1A in metabolism of POPs.