Chairman : Sonia Garel
A central theme in biology is that the characteristics of an organism - the phenotype - are controlled by the nucleotide sequence of its genome. Understanding how the information encoded by the genome contributes to phenotypic variation remains one of the great challenges in the life sciences. It is now accepted that the cells of an organism all contain essentially the same DNA, and that differential gene expression explains different cellular identities and states.
However, even within an individual, there can be phenotypic variation between cells of the same type, or between genetically identical individuals such as twins. Are these differences due to epigenetic changes ? The term epigenetics was coined by Waddington to designate the processes by which a genotype gives rise to a phenotype during embryogenesis.
A more recent operational definition of epigenetics is the study of molecules and mechanisms that can perpetuate alternative states of gene activity within the context of the same DNA sequence, during cell divisions or even across generations. Certain modifications of chromatin, the physiological support of the genome, or associated molecules (proteins and RNA), can be propagated during genome duplication. We also realize that some epigenetic changes can be induced by the environment, although their propagation is often unclear.
A major question is whether there is an epigenetic code, in addition to the genetic code, that enables cells to receive and remember environmentally-induced signals to create a more stable state that can be passed on when cells divide, or even from one generation to the next. The advent of new technologies, notably the era of " omics " and advanced molecular genetic tools, have begun to reveal how, when and where combinations of epigenetic changes are induced, as well as their roles in activating or propagating variations in gene expression and the resulting phenotypes. I'll talk about deciphering epigenetic marks and how they can contribute to phenotypic variation during development or across generations.
