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An epigenetic mechanism mediating temperature effects on fish sex ratios

AuthorsNavarro-Martín, Laia ; Viñas, Jordi ; Gutiérrez, Arantxa; Díaz, Noelia ; Ribas, Laia ; Vanezis, Konstantinos; Di Croce, Luciano; Piferrer, Francesc
Issue DateMar-2010
CitationI Jornada de Cromatina i Epigenètica (2010)
AbstractMany reptiles and fish have temperature-dependent sex determination (TSD), where the temperature experienced during early development determines gonadal sex. However, the underlying mechanism has remained elusive. In the developing gonads of non-mammalian vertebrates, expression of cyp19a, the gene coding for aromatase, is essential for female development. In ectothermic vertebrates, exposure to female-promoting temperatures is associated with cyp19a upregulation, whereas exposure to male-producing temperatures is associated with cyp19a suppression. The European sea bass has a sex determination mechanism influenced by temperature. Water temperatures 3–4°C higher than normal masculine about 50% of genetic females. The period of highest temperature sensitivity, 0–15 days post fertilization (dpf), is located not only before sex differentiation (150 dpf) but also before the formation of the gonadal ridges (35 dpf), and even before the migration of the primordial germ cells (25 dpf). How, then, temperature can determine the fate of an organ that is still not formed, not even in a rudimentary manner? This suggested the possibility of an epigenetic mechanism by which increased temperature could silence the expression of genes essential for female development. Analysis of a ~500 bp region of the sea bass cyp19a promoter showed the presence of seven CpGs. Males had double DNA methylation levels than females. Further, we also found an inverse relationship between cyp19a promoter DNA methylation and cyp19a gene expression levels. Induced methylation of the cyp19a promoter suppressed transcription in vitro. Finally, a CpG differentially methylated by temperature was found to be conserved across species. We have suggested that DNA methylation of the aromatase promoter most likely is the long-sought after mechanism connecting environmental temperature and sex ratios in species with TSD, including fish and reptiles. Currently, we are investigating the appearance of the sex-related differences in cyp19a promoter methylation and testing the effects of DNA methylation inhibitors
DescriptionI Jornada de Cromatina i Epigenètica Organitzada per la Secció de Biologia Molecular de la Societat Catalana de Biologia. Institut d'Estudis Catalans, 5 de març 2010, Barcelona
Appears in Collections:(ICM) Comunicaciones congresos
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