Epigenetic traits related to vitellogenin gene expression reveal clues for organismal response to estrogen in Cyprinus carpio

Epigenetic mechanisms orchestrate gene expression during development and lifelong adaptation to changing environments. In adult male fish estrogen exposure leads to feminization where vitellogenin (vtg) expression serves as robust marker for exposure to estrogenic endocrine disruptor compounds. With the aim to reveal related epigenetic traits and novel blood markers, we analyzed response of male carp to 17-estrogen (E2). After three-day E2 treatment, DNA methylation bisulfite analysis of 8 CpGs in the vtg gene promoter in liver revealed diminished C-methylation in E2- relative to control carp, which correlated with increased vtg mRNA levels. We further studied male carp with high and low vtg expression in liver characterizing blood extracellular vesicles (EV), which seem to be released from different cells playing regulatory roles in an intricate communication network coordinating whole organism response. Small RNA libraries were prepared from EV enriched blood serum of male carp, presenting 50.1% miRNAs, 42.9% piRNAs, 7% snoRNA and snRNAs. From high versus low vtg carp, a set of 18 miRNAs differentially present in serum EVs was determined and target genes predicted. Comparison with in silico processed data sets from liver mRNAs of estrogen treated male zebrafish revealed 121 differentially expressed genes in liver in response to E2 in male fish. Finally, the integrative analyses of experimental and in silico data visualized a network of miRNAs and target genes involved in oxidoreductase pathways, response to chemical stimulus and small molecule and lipid biosynthetic processes. These epigenetic markers might help to better understand organismal responses to potential harmful exposure to endocrine disruptors in the aquatic environment. Acknowledgement: Conicyt 21130511 GV, 21150665 FS. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska Curie grant agreement No 722634.