Guest Post by Charles Dupras & Vardit Ravitsky

Re: The ambiguous nature of epigenetic responsibility

Epigenetics is a recent yet promising field of scientific research. It explores the influence of the biochemical environment (food, toxic pollutants) and the social environment (stress, child abuse, socio-economic status) on the expression of genes, i.e. on whether and how they will switch ‘on’ or ‘off’. Epigenetic modifications can have a significant impact on health and disease later in life. Most surprisingly, it was suggested that some epigenetic variants (or ‘epi-mutations’) acquired during one’s life could be transmitted to offspring, thus having long-term effects on the health of future generations.

Epigenetics is increasingly capturing the attention of social scientists and ethicists, because it brings attention to the importance of environmental exposure for the developing foetus and child as a risk factor for common diseases such as cardiovascular, diabetes, obesity, allergies and cancers. Scholars such as Hannah Landecker, Mark Rothstein and Maurizio Meloni have argued that epigenetics may be used to promote various arguments in ongoing debates on environmental and social justice, as well as intergenerational equity. Some even suggested that epigenetics could lead to novel ways of thinking about moral responsibilities for health.

Is it fair that disadvantaged populations are exposed to an inequitable share of harmful environments – such as polluted areas – that are epigenetically-detrimental to their health? Who should be held responsible for protecting children and future generations from epigenetic harm induced by their environments? Should we hold the parents accountable for detrimental epigenetic impact of their behavior on their children? And how should we manage the possible risks of stigmatization and discrimination of people that we consider blameworthy of inflicting epigenetic harm on others? These sensitive questions call for a nuanced investigation of the impact epigenetics can have on our understanding of moral responsibility.

In our paper “The ambiguous nature of epigenetic responsibility”, recently published in the Journal of Medical Ethics, we “caution the bioethics community against adopting a simplistic approach toward the notion of ‘epigenetic responsibility’”. We argue that “it is over-simplistic to understand epigenetic responsibility as a monolithic concept emerging solely from comparisons between epigenetics and genetics”. We demonstrate how the complexity of epigenetics – as a field composed of a variety of molecular mechanisms with distinct biological features – forces us to refine our conceptual debate regarding the responsibilities that emerge from it.

To exemplify the diversity of these features, we focused on two important biological ambiguities that are inherent to epigenetics and that may, we argue, impact the ascription of moral epigenetic responsibilities to different actors in our society (e.g. previous generations, parents, individuals, governments, corporations, international agencies). We therefore discuss epigenetic normality and epigenetic plasticity and we call these features ‘ambiguous’ because they seem to involve internal contradictions.

Epigenetic normality refers to the notion that there is a ‘normal’ or ‘typical’ epigenome, and that deviations from it may be seen as problematic. We discuss the very challenging task of identifying such a ‘reference epigenome’ or, in other words, defining “epigenetic normality”. Unlike the genome, the epigenome is not ubiquitous. It differs among cell types and tissues, and depends on the developmental stage of the living organism. Moreover, under various circumstances the epigenome may be ‘programmed’ to best respond to its surrounding environment. Thus, an epigenetic modification cannot be treated a priori as a burden or a health risk. To know whether it is indeed detrimental, one should also consider the living environment of the individual and the possibly adaptive character of this modification. When our perception of the ‘normal’ or even ‘ideal’ epigenome changes, our understanding of moral epigenetic responsibilities changes with it.

Epigenetic plasticity refers to the notion that epigenetic modifications are acknowledged to be simultaneously dynamic (and potentially reversible) and stable (and potentially heritable). How can these chemical reactions be malleable and permanent at the same time? This ambiguity regarding “epigenetic plasticity”, we argue, means that we should understand epigenetic variants as placed on a ‘spectrum of plasticity’. In certain cases they are reversible – which would entail moral responsibilities to cure disease by reversing them. In other cases, they may be stable enough to become heritable – which raises issues related to moral obligations of inter-generational justice. Epigenetic plasticity therefore affects the nature and level of moral responsibility actors carry in specific contexts for specific actions.

Finally, ascribing moral epigenetic responsibilities to different actors in society should take into account the increasingly blurred line between the concepts of ‘nature’ and ‘nurture’, which may impact theories of justice themselves. We should also acknowledge important limitations in the amount and scope of scientific evidence that has been accumulated so far, in relation for instance to potential transmission of epigenetic variants to future generations, or the premature extrapolation from animal models to humans. Our article thus presents important scientific nuances and demonstrates how they should be incorporated into the debate about moral epigenetic responsibilities. This is an interesting case study of how sound scientific understanding should inform and sharpen conceptual bioethical debates.