Methylate for Males

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Science  13 Jan 2012:
Vol. 335, Issue 6065, pp. 147
DOI: 10.1126/science.335.6065.147-d

For some fish and reptiles, the genetic sex of an individual can be overridden by extreme temperature shifts, an effect that results in skewed sex ratios. One such species, the European sea bass, shows a male-biased sex ratio in response to high temperatures experienced before gonad development. How temperature affects sex ratios at a molecular level, however, is not well understood. Navarro-Martín et al. investigated this and found enhanced methylation of the promoter of the cyp19a gene in males as compared to females. cyp19a encodes gonadal aromatase, the enzyme that converts male hormones into the female hormones that are required for ovarian development. Increased methylation of the aromatase promoter was associated with reduced expression of the aromatase enzyme in males. Temperature increases resulted in increased methylation of the aromatase promoter in females, which was accompanied by a decrease in gene expression. On the basis of these results, the authors conclude that aromatase probably controls temperature sex determination in the European sea bass. Whether these results have implications for sex determination in other species remains to be determined.

PLoS Genet. 7, e1002447 (2011).

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