Identification of oestrogen-responsive transcripts in Potamopyrgus antipodarum

The freshwater caenogastropod Potamopyrgus antipodarum is a promising test species for partial life-cycle toxicity testing and also for studies of endocrine disruptors. However, endocrine signalling pathways and the genes/transcripts involved are barely identified and characterized in this snail. We therefore performed whole transcriptome sequencing (454 pyrosequencing), selected transcripts that are known to be hormone-responsive in vertebrates and determined their expression via quantitative real-time PCR after 24 h exposure to the oestrogens 17-ethinyloestradiol (EE2) and 17-oestradiol (E-2). Examined mRNAs were: nuclear receptors [oestrogen receptor (ER), chicken ovalbumin upstream promoter-transcription factor (COUP-TF), ecdysone-induced protein (E75)], repressors of oestrogen-induced activity [prohibitin-2 (PHB-2), striatin (STRN)] and the egg yolk precursor vitellogenin (VTG). Significantly increased expression by EE2 and E-2 treatment was detected for ER and VTG. E-2 induced significant upregulation of E75, PHB-2 and STRN, while EE2 did not. COUP-TF expression was unaffected by EE2 or by E-2. Variations between replicates were higher in snails exposed to EE2 than to E-2. The identification of these oestrogen-responsive transcripts contributes to a better characterization of the endocrine system of P. antipodarum and provides possible biomarkers for the detection of endocrine disruption.