Molecular characterization of an estrogen receptor and estrogen-related receptor and their autoregulatory capabilities in two Mytilus species

Vertebrate-like sex steroid hormones have been widely detected in mollusks, and numerous experiments have shown the importance of steroids in gonad development. Nevertheless, their signaling pathways in invertebrates have not been uncovered yet. Steroid receptors are an ancient class of transcription factors with multiple roles in not only vertebrates but also invertebrates. Estrogen signaling is thought to have major roles in mollusk physiology, but the full repertoire of estrogen receptors is unknown. We presented the successful cloning of two novel forms of estrogen receptor-like genes. These receptors are present in two closely related species of Mytilus: Mytilus edulis and Mytilus galloprovincialis, commonly known and widely distributed sentinel species. Our phylogenetic analysis revealed that one of these receptors is an estrogen receptor (ER) and the other one is an estrogen-related receptor (ERR). Studies of expression analysis showed that both receptor mRNAs were localized in the oocytes and follicle cells in contact with developing oocytes in the ovary and Sertoli cells in the testis, and in the ciliated cells of the gill. In addition, we have evidence that one (ER) of these may have a capacity to autoregulate its own expression in the gonadal cells by estrogen (E2) and that this gene is responsive to estrogenic compounds

Estrogens disrupt serotonin receptor and cyclooxygenase mRNA expression in the gonads of mussels (Mytilus edulis)

Estrogenic contaminants in the aquatic environment are associated with feminisation of male fish, however their effects on some invertebrate species, such as bivalve molluscs, have yet to be characterised. Gametogenesis represents a critical step in the reproductive process and is subjected to hormonal control by serotonin (5-HT), prostaglandins (synthesised by cyclooxygenases-COX) and steroids such as 17 beta-estradiol (E2). Here, we examine the responses of 5-HT receptor and COX mRNA expression in mussels, Mytilus edulis, exposed to estrogenic compounds during different stages of their reproductive cycle. In mature mussels, 5-HT receptor mRNA expression decreased following E2 exposure. The opposite trend was observed in mussels at early gametogenesis stages. COX mRNA expression levels at both stages were generally decreased by E2 exposure. Mussels at early gametogenesis stages were also exposed to ethynylestradiol (EE2) and estradiol benzoate (EB) and a significant increase in 5-HT receptor mRNA expression was observed with both xeno-estrogens. COX expression levels were increased with EB exposure but no significant effects were found with EE2 exposure. These results show that the natural estrogen, E2, as well as the synthetic estrogen, EE2, induce alterations, dependent on reproductive stage, in the mRNA expression levels of 5-HT receptor and/or COX in the marine bivalve M. edulis. (C) 2010 Elsevier B.V. All rights reserved

Estrogens disrupt serotonin receptor and cyclooxygenase mRNA expression in the gonads of mussels (Mytilus edulis)

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