Epigenetics and phenotype construction, a challenge for livestock production ?

Abstract

Epigenetics refers to the inheritable changes of genomic activities that do not alter DNA sequences. It deals with the molecular me-chanisms orchestrating chromatin remodelling, which leads to gene transcription or silencing. Here, we provide evidence from the published scientific literature that the epigenetic marks are apposed onto the genome in a sequential, reversible and/or inheritable manner. These marks can be finely measured to characterise the epigenome. The functional analysis of the epigenetic processes provides support to the two associated concepts of genome flexibility and robustness. Genome flexibility is involved in the acquisition of cell identity during differentiation (Why do not the various cellular types of an organism use the same genetic information in a similar manner ?), and in the adaptation to environmental cues as illustrated by the mechanism underlying the fate of honeybees that become fertile queens or sterile workers. But the epigenome is also crucial for the development of individuals that requires the robustness of epigenetic marks as exemplified from parental imprinting studies. The flexibility of epigenetic marks is associated with transitory adaptation to environmental changes while robustness reveals long term processes associated with more stable marks that in some instances can pass over several generations. This review points to the importance of epigenetic processes for genome functions and proposes that the integration of the molecular data describing the epigenomic states could be considered as new variables in selection to preserve the sustainability of animal breeding.