Protocol matters – reproducibility and rigor of DNA methylation data sets [BiSulfite-seq]

While epigenetics continues to be a burgeoning research area in neuroscience, unaddressed issues related to data reproducibility across laboratories remain. Indeed, separating meaningful experimental changes from background variability is a challenge in epigenomic studies. Genome-wide DNA methylation analysis of hippocampal tissues from wild-type rats across three independent laboratories revealed that seemingly minor protocol differences resulted in significant epigenome profile changes, even in the absence of experimental intervention. Difficult-to-match factors such as animal vendors and a subset of husbandry and tissue extraction procedures produced quantifiable variations between wild-type animals across the three laboratories. To enhance scientific rigor, we conclude that strict adherence to protocols is necessary for the execution and interpretation of epigenetic studies and that protocol-sensitive epigenetic changes, amongst naive animals, may confound experimental results.