GSE201140
Multigenerational DNA methylation responses to copper exposure in Daphnia: potential targets for epigenetic biomarkers?
Epigenetic mechanisms are moving to the forefront of environmental sciences, especially because environmentally induced epigenetic changes shape biological responses to contamination of chemicals. Moreover, such marks can be inherited by subsequent generations through epigenetic transgenerational inheritance, thus having long-term implications. In this work, we focused on Daphnia as a representative of the potentially threatened freshwater biota aiming to gain an insight on the involvement of epigenetic mechanisms in their response, eventually adaptation, to metal contamination. Copper induced DNA methylation changes, their potential transgenerational inheritance, and life-history traits were assessed. Organisms differing in their history of past exposure to copper were exposed to toxic levels of the element for one-generation (F0) and then monitored for three subsequent unexposed generations (F1, F2, and F3). Overall, methylation changes targeted important genes for counteracting the effects of metals and oxidative stress, including dynein light chain, ribosomal kinase and nuclear fragile X mental retardation-interacting protein. Also, contrasting overall and gene-specific methylation responses were observed in organisms differing in their history of exposure to copper, with different transgenerational methylation responses being also identified among the two groups, without apparent life-history costs. Taken together, these results demonstrate the capacity of copper to promote epigenetic transgenerational inheritance in a specific manner concerning past history of exposure, thereby supporting the potential of developing and incorporating epigenetic biomarkers in risk assessment frameworks. Overall design: Comparison of transgenerational - 4 generations; F0, F1, F2 and F3 - DNA methylation patterns among daphnids with different life-histories of exposure to copper: 15 sequenced samples, treatments corresponding to F0 non-naïve daphnids (acclimated and exposed in F0 to a copper enriched medium - 3 replicates), F0 naïve daphnids (acclimated in blank ASTM and exposed in F0 to a copper enriched medium - 3 replicates), F0 control daphnids (cultured in blank ASTM), F3 non-naïve dapnids (cultured in blank ASTM - 3 replicates) and F3 naïve daphnids (cultured in blank ASTM - 3 replicates).