Abstract
Both genetic and epigenetic responses of organisms to environmental factors, including chemical exposures, influence adaptation, susceptibility to toxicity and biodiversity. In model organisms, it is established that epigenetic alterations, including changes to the methylome, can create a memory of the received signal. This is partly evidenced through the analysis of epigenetic differences that develop between identical twins throughout their lifetime. The epigenetic marks induce alterations to the gene expression profile, which, in addition to mediating homeostatic responses, have the potential to promote an abnormal physiology either immediately or at a later stage of development, for example leading to an adult onset of disease. Although this has been well established, epigenetic mechanisms are not considered in chemical risk assessment or utilised in the monitoring of the exposure and effects of chemicals and environmental change. In this review, epigenetic factors, specifically DNA methylation, are highlighted as mechanisms of adaptation and response to environmental factors and which, if persistent, have the potential, retrospectively, to reflect previous stress exposures. Thus, it is proposed that epigenetic “foot-printing” of organisms could identify classes of chemical contaminants to which they have been exposed throughout their lifetime. In some cases, the potential for persistent transgenerational modification of the epigenome may also inform on parental germ cell exposures. It is recommended that epigenetic mechanisms, alongside genetic mechanisms, should eventually be considered in environmental toxicity safety assessments and in biomonitoring studies. This will assist in determining the mode of action of toxicants, no observed adverse effect level and identification of biomarkers of toxicity for early detection and risk assessment in toxicology but there are critical areas that remain to be explored before this can be achieved.
Highlights
Organisms have the ability to respond to environmental stressors such as toxic chemicals and adapt beneficially to new environments
It is becoming more evident that epigenetic mechanisms are involved in adaptive responses in individuals; they have a significant role in host-pathogen interactions as reviewed by Gomez-Diaz et al [13]
We explore the epigenetic responses of organisms to environmental stressors with a particular focus on the persistence or “memory” of such modifications and the ways in which this memory can usefully reflect the status of the environment in which humans and other organisms reside
Summary
Organisms have the ability to respond to environmental stressors such as toxic chemicals and adapt beneficially to new environments This is accomplished, in part, by altering their epigenomes and subsequently their transcription profiles. Chipman / Mutation Research xxx (2013) xxx–xxx environmental agents and we present examples of studies in a range of species showing how exposure to chemicals can promote persistent changes in the epigenome with phenotypic outcomes These studies lead to the concept of “epigenetic footprinting” for retrospective assessment of chemical exposures. These insights may shape the future of regulatory toxicology and environmental monitoring, especially where there are chronic exposures to pollutants
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