De novo transcriptome sequencing and analysis of freshwater snail (Radix balthica) to discover genes and pathways affected by exposure to oxazepam
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Pharmaceuticals are increasingly found in aquatic ecosystems due to the non-efficiency of waste water treatment plants. Therefore, aquatic organisms are frequently exposed to a broad diversity of pharmaceuticals. Freshwater snail Radix balthica has been chosen as model to study the effects of oxazepam (psychotropic drug) on developmental stages ranging from trochophore to hatching. In order to provide a global insight of these effects, a transcriptome deep sequencing has been performed on exposed embryos. Eighteen libraries were sequenced, six libraries for three conditions: control, exposed to the lowest oxazepam concentration with a phenotypic effect (delayed hatching) (TA) and exposed to oxazepam concentration found in freshwater (TB). A total of 39,759,772 filtered raw reads were assembled into 56,435 contigs having a mean length of 1579.68 bp and mean depth of 378.96 reads. 44.91% of the contigs have at least one annotation. The differential expression analysis between the control condition and the two exposure conditions revealed 146 contigs differentially expressed of which 144 for TA and two for TB. 34.0% were annotated with biological function. There were four mainly impacted processes: two cellular signalling systems (Notch and JNK) and two biosynthesis pathways (Polyamine and Catecholamine pathways). This work reports a large-scale analysis of differentially transcribed genes of R. balthica exposed to oxazepam during egg development until hatching. In addition, these results enriched the de novo database of potential ecotoxicological models.
KeywordsEcotoxicology RNA sequencing Pharmaceutical Differential analysis Radix balthica
The authors thank Olivier Bouchez and all Get-PlaGe operators, INRA of Castanet-Tolosan for the perfect processing of our unusual samples. Funding for this work was provided to J-YM by a grant from the Region Midi-Pyrénées, Toulouse (France) for 70% and from Jean-François Champollion University Institute, Albi (France) for 30%. We thank also Jean-Michel MALGOUYRES operator for his help in organism collection and in maintain rearing of R. balthica.
The project was conceived and planned by FG, EB and J-YM. J-YM exposed, grinded and extracted the RNA. CK and FE performed the bioinformatics analysis and J-YM performed the differential analysis and the annotation of differential expressed contigs. J-YM wrote the manuscript and FG and EB proofread it.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
All procedures performed in this study were in accordance with the ethical standards of the institution at which the study was conducted and was in compliance with current French laws.
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