The importance of validating the demethylating effect of 5-aza-dC in model species

The use of DNA demethylating agents has been popular in epigenetic studies. Recently, Cook et al. (2015), claimed an effect of 5-aza-2’-deoxycytidine (5-aza-dC) on the sex ratio of a parasitoid wasp without verifying its effect on DNA methylation. We repeated the 5-aza-dC feeding treatment to test its effectiveness. We used bisulfite amplicon sequencing of ten genes that were either heavily methylated, previously showed a response to 5-aza-dC or suggested to regulate fatty acid synthesis epigenetically, and demonstrate that wasps fed 5-aza-dC did not show reduced DNA methylation at these loci. Therefore, the conclusion that demethylation shifts sex ratios upwards needs reconsideration.