Epigenetics and Cellular Memory

This is all part of what we now call " epigenetics ", a word composed of the Greek prefix " epi ", meaning beyond or above, and the word " genetics ". As a scientific discipline, epigenetics has captured the public imagination in recent years, particularly since we were first able to " glimpse " the sequence of the human genome just over ten years ago. As exciting as this step was, it was also a daunting one, as we came face to face with the reality - and perhaps the inevitability - of the genetics that make us up. This realization was accompanied by the realization that we would now be able to read, as if from a book, many of the traits that characterize us - our strengths, weaknesses, predispositions to disease, etc. - (with all the ethical and philosophical problems this implies). The idea that epigenetics - i.e. the way our genome is read - could give us hope that we are more than just the sum of our genes, has aroused great interest and curiosity in the public and the media. Are we somehow able to escape the inevitability of our genetic make-up ? Can what we eat, the air we breathe and even the emotions we feel influence not only the way our genes are expressed, but also the way our children's and grandchildren's genes will be expressed tomorrow ?

It's absolutely certain that the environment in which we live can influence the way our genes are expressed, and that this can sometimes lead to stable phenotype changes - and in some cases, disease. It's a different story, however, when it comes to the extent to which such changes can be passed on from one generation to the next. Over the last years, it has become clear that characteristics that are not due to changes in the DNA sequence can be passed on from one generation to the next in certain living organisms, particularly in the plant kingdom . So the question is : what role does the environment play ? And can this type of process occur in humans ? And if so, to what extent ? At present, we have no clear answers to these questions.

While it's clear that the subject of epigenetics has given rise to a veritable media frenzy, the amalgam of scientific facts and fantasies we're witnessing is dangerous and liable to undermine the progress of science and our understanding of it. Fortunately, scientific research is advancing rapidly in this field and should provide us with answers and clarifications in the years to come.

In the context of this Chair in Epigenetics and Cellular Memory, I propose to present the work and ideas that form the basis of this new field of research, while considering the hopes and fears it may raise. This is no easy task, since the word " epigenetics " itself was coined in 1942 by Conrad Hal Waddington, to describe the link between genotype and phenotype during development. In the 1990s, the word took on a definition that associated it with the notion of heritability. More recent definitions speak of the structural adaptation of chromosome regions to record, signal or perpetuate altered states of activity, via environmental influences on gene expression. This is why the title of this Chair includes the notion of " cellular memory ", as it is appropriate to include the notion of maintaining and propagating a particular state of gene activity, or protein coiling, or cellular structure, throughout the different temporal scales of life - including the cell cycle, the organism, or the passage from one generation to another. This cellular memory can be stable or transient - it can either be programmed in such a way that it is reversible, or accidentally disappear in the course of life. In some cases, such " amnesia " can lead to dysfunction and disease, while in others it can be an advantage, revealing new functions from which selection can be made. Here, in Abstract, are some of the concepts I hope to explore in the years to come.