Daniel G Cyr

Department of Anatomy and Cell Biology




Research Interests

Our research focuses on the regulation of intercellular communication and effects of environmental contaminants on male reproduction in both mammalian and wildlife species. Intercellular communication between adjacent cells can be accomplished directly by the formation of intercellular junctions. In mammals, our studies have focused on the epididymis, a primary target of androgens, cellular interactions between epithelial principal cells lead to the formation of a blood-epididymal barrier which is crucial for providing the specific environment essential for the final stages of sperm maturation. Our studies have characterized the presence and regulation of the proteins that make up the epididymal junctional complex. More recently we have shown that these cellular interactions can be affected by environmental toxicants such as nonylphenol and tributyltin. While these chemicals are known endocrine disrupting chemicals, it is noteworthy that their effects on cellular junctions in the testis and epididymis are independent of their endocrine disrupting effects.

Our research has also focused on the effects of endocrine disrupting chemicals on the reproduction and thyroid function of fish and amphibians. Recently, we have shown that fish from the St. Lawrence River are exposed to estrogenic compounds resulting in delayed spermatogenesis and a high rate of intersex. Interestingly, when these fish are fed to lactating rats, their male offspring have impaired reproductive capacity when they reach adulthood. An effect that appears linked to a loss of intercellular communication in the testis. We have also studied the role of contaminants on thyroid function in fish. This is particularly important, as thyroid hormones are essential for initiating reproductive cycles in fish. Our studies have shown that contaminants such as PCBs can alter the metabolism of thyroid hormones thus resulting in the formation of inactive metabolites thereby decreasing thyroid function. Current studies focus at understanding the mechanism by which endocrine disrupting chemicals can alter reproduction in fish and mammalian species.