Comparative Analyses of Aryl Hydrocarbon Receptor Structure, Function and Evolution in Marine Mammals

Joy M. Lapseritis, Ph.D., 2007
Mark Hahn, Advisor

Marine mammals possess high body burdens of persistent organic pollutants, including PCBs and dioxin-like compounds (DLC). Chronic environmental or dietary exposure to these chemicals can disrupt the function of reproductive and immune systems in laboratory animals. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor, mediating the expression of a suite of genes in response to exposure to DLC and structurally related chemicals. Species-specific differences in AHR structure can affect an organism’s susceptibility to the effects of DLC. The structures and functions of several cetacean AHRs were investigated using in vitro molecular cloning and biochemical techniques. Using remote biopsy and molecular cloning methods, RNA was extracted from small integument samples from living North Atlantic right whales to identify the AHR cDNA sequence and other genes. Molecular and biochemical characteristics for North Atlantic right whale and humpback whale AHR cDNAs were determined using in vitro and cell culture methods. The properties of these AHRs were compared with those from other model and marine mammalian species using biochemical, phylogenetic, and homology modeling analyses. Additional studies are necessary to link exposure to environmental contaminants with potential reproductive effects in marine mammals, especially via interactions with steroid hormone receptor pathways.