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A transcriptome study on temperature and estradiol effects on European sea bass (Dicentrarchus labrax) gonads

AuthorsDíaz, Noelia ; Piferrer, Francesc
Issue Date27-May-2014
Citation10th International Symposium on Reproductive Physiology of Fish, Expanding the khowledge base of reproductive success: from genes to the environment, Olhao, Portugal, 25-30 May 2014. Abstract book: 37 (2014)
AbstractIntroduction The European sea bass (Dicentrarchus labrax) is a gonochoristic species with a polygenic sex determination system with environmental influences. Elevated temperatures early in development alter sex ratios by masculinizing fish that otherwise would have developed as females. Furthermore, estradiol-17ß (E2) treatment when applied at the hormone sensitive period is known to feminize fish. Our aim was to analyze the effects of E2 at a whole transcriptomic level in fish exposed to high temperature. Methods European sea bass juveniles previously reared at 21°C from 20 to 90 dph, covering the early gonad formation period, were divided into two groups. One was fed with a diet containing E2 at 10 mg/kg of food prepared with the alcohol evaporation method during the hormone sensitive period (90-160 dph), while the other was treated with a food treated with the solvent alone. At the end of the experiment, biometric data and tissues were collected for further analysis, and the sex ratio was calculated. We collected 170 days post hatch (dph) gonads from putative females based on cyp19a1a mRNA expression levels and determined the transcriptomic profile using a custom-made sea bass microarray (GPL13443). Microarray data was normalized and analyzed using Bioconductor in R. Microarray results were validated by qRT-PCR of selected genes of interest. Results and Discussion Because of the temperature regime used, 80% males were found in the control group at 337 dph. In contrast, the E2-treated group had 100% females. Transcriptomic analysis of E2-treated versus control gonads showed 420 differentially expressed (DE) genes. Elevated temperature was responsible of the up-regulation of the genes related to the male pathway in controls. However, E2 treatment completely negated this masculinizing effect. Analysis of the transcriptomic results of the ovarian steroidogenesis-related genes showed a down-regulation of this pathway in the E2-treated group. In addition, screening of several epigenetic mechanisms-related genes present in the microarray also showed a tendency to down-regulation in the E2 group. Conclusion Together, these results corroborate the relationship between elevated temperature, the up-regulation of the male pathways and sex ratio bias. Moreover, the transcriptomic down-regulation of the ovarian steroid synthesis pathway after E2 administration is in agreement with what has been previously reported for E2 plasma levels in fish after E2 treatment. Although some of the genes related with epigenetic regulatory mechanisms were DE in the E2-treated group, it remains to be determined the possible causal relationship among these observations.
Description10th International Symposium on Reproductive Physiology of Fish (10th ISRPF), Expanding the khowledge base of reproductive success: from genes to the environment, 25-30 May 2014, Olhao, Portugal.-- 1 page
Appears in Collections:(ICM) Comunicaciones congresos
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