DNA methylation regulates gene expression and traits in the Pacific oyster. Researchers characterized DNA methylation in oysters using methylation sensitive PCR and bisulfite sequencing, finding that stress genes and genes with different regulatory needs have varying methylation levels. They are now using MBD-isolated genome sequencing to analyze methylation genome-wide and evaluate previous predictions of methylation status. Understanding DNA methylation's role in gene expression could improve selective breeding and hybrid vigor in oysters.