Benzo[a]pyrene decreases global and gene specific DNA methylation during zebrafish development

DNA methylation is important for gene regulation and is vulnerable to early-life exposure to environmental contaminants. We found that direct waterborne benzo[a]pyrene (BaP) exposure at 24 μg/L from 2.5 to 96 hpf to zebrafish embryos significantly decreased global cytosine methylation by 44.8% and promoter methylation in vasa by 17%. Consequently, vasa expression was significantly increased by 33%. In contrast, BaP exposure at environmentally relevant concentrations did not change CpG island methylation or gene expression in cancer genes such as ras-association domain family member 1 (rassf1), telomerase reverse transcriptase (tert), c-jun, and c-myca. Similarly, BaP did not change gene expression of DNA methyltransferase 1 (dnmt1) and glycine N-methyltransferase (gnmt). While total DNMT activity was not affected, GNMT enzyme activity was moderately increased. In summary, BaP is an epigenetic modifier for global and gene specific DNA methylation status in zebrafish larvae.

► BaP decreased global DNA methylation in zebrafish larvae.
► BaP decreased vasa promoter methylation and increased vasa gene expression.
► BaP did not change methylation or gene expression of rassf1, tert, c-jun, or c-myca.
► GNMT, but not DNMT, enzyme activity was moderately increased by BaP.
► BaP is an epigenetic modifier of DNA methylation status in zebrafish larvae.