Effect of environmental stressors on the mRNA expression of ecdysone cascade genes in Chironomus riparius

ABSTRACT: Chemical compounds produced by humans are continuously reaching the environment. In this work, we characterised the expression patterns of important endocrine-related genes involved in the ecdysone pathway in the fourth larval instar of the model species Chironomus riparius after exposure to three chemicals: ethinyl oestradiol (EE), nonylphenol (NP) and bis(tributyltin) oxide (TBTO). We used real-time PCR to analyse the gene expression levels of ecdysone receptor (EcR) and ultraspiracle (usp), two genes that encode the dimerising partners of the functional ecdysone receptor; the orphan receptor ERR (oestrogen-related receptor), with an unknown function in invertebrates; and E74, an early response gene induced by ecdysteroids. We estimated the bioaccumulation potential, bioavailability and physicochemical properties of these chemicals, together with a number of other exogenous agents known to interfere with the hormonal system. We also provide a review of previous transcriptional studies showing the effect of all these chemicals on ecdysone cascade genes. This analysis provides useful data for future ecotoxicological studies involving invertebrate species. CAPSULE: Changes in transcriptional activities of EcR, E74, usp and ERR genes after exposure to endocrine-disrupting chemicals would be useful as molecular bioindicators of endocrine disruption in Chironomus riparius.