Do epigenomic factors influence twin bulls performances?

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With the development of tools for genomic evaluation, it is now possible to estimate breeding values at birth. To increase the rate of genetic improvement, there is a recent trend to use young animals as soon as possible and, in order to increase the rate of dissemination of their high merit genetic background, embryo splitting is becoming increasingly used. Twins share an identical DNA makeup and should, in all logic, lead to similar if not identical performances in regards to their genetic evaluations. In fact, recent data have shown that differences in breeding values can arise between twins. These differences may pertain to the evaluation itself or may arise from other sources. At the molecular level, phenotypes are the resulting from gene activity and it has been shown that the epigenome can largely influence gene expression. By definition, the epigenome represents all reversible modifications that induce changes in the DNA conformation and that will influence gene expression. A good example of an epigenomic modification is DNA methylation, which drives cell specific gene expression by shutting down genes that are irrelevant or dangerous to a cell type. So far, very little attention was given to the impact of the epigenome as it was deemed to be transient. However, it is now well accepted that epigenetic marks can be carried through at least 2 generations. The objective of the present project is to determine whether the sperm of twin bulls harbour similar, identical or divergent DNA methylation marks. These initial results are of importance to dairy producers because manipulating the source of these potential divergences, through adaptation of the uterine environment or post natal conditions, could influence how elite animals are produced.