Environmental impacts on the endocrine system and molecular study of steroid hormone receptors in fish

A wide range of chemicals are now known to mimic hormones based on their structure or via their interference with hormone biosynthesis and/or degradation. Exposure to these so called endocrine disrupting chemicals (EDCs) can cause disruptions in development, alter sexual differentiation and function, and impact adversely on reproduction. Aquatic animals are especially vulnerable to the effects of EDCs, since exposures can be continuous and in some cases at high levels.

In assessments of the effects of EDCs, generally few studies have taken into consideration ’species diversity’ and/or the ‘genetic diversity’. A whole genome duplication event occurred coincident with the teleost radiation, resulting in duplicated paralogous genes and subsequently induced neo-functionalization (i.e. acquiring a new function), sub-functionalization (the original gene function is split and distributed to different paralogues) or inactivation/gene loss. As a consequence in teleosts, estrogen signaling is mediated through at least three ER subtypes (ERα, β1 and β2), and this complicates understanding of estrogen signaling pathways and the deleterious effects of the EDCs. We showed each subtype will likely show differential responses to EDCs. We also showed sensitivity to EDCs among ER subtypes is conserved between phylogenically different taxonomic groups.