Literally meaning “above the genome,” the epigenome refers to differences in gene expression that are inherited without changing the sequence of DNA.  New research on environmental influences on health and disease has begun to shed light on why genetically identical individuals demonstrate different characteristics, such as susceptibility to disease.  Scientists have found that environmental exposure to nutritional, chemical and physical factors can alter the epigenome.   Several studies have been published involving metastable epialleles, which are alternate forms of a gene that are expressed due to epigenetic modifications linked to maternal nutrition and environmental exposure during very early development. Simple dietary changes have been shown to protect against the negative effects of environmental toxins on the fetal epigenome.  Embryos are vulnerable to environmentally-induced epigenetic alterations early in their development thus it is necessary to analyze the timing of exposure in order to fully understand environmental epigenomics.

The advent of bioinformatics has allowed researchers to more readily search the entire mouse genome for imprinted genes, but the real power of this approach has been recently demonstrated in its application to the human genome. While 2.5 percent of the mouse genome contains potentially imprinted genes, only 0.75 percent of the human genome is predicted to be imprinted. This means that the mouse genome may not be a suitable model for assessing human disease risk due to epigenetic mutations in imprinted genes.  It is necessary to develop bioinformatic models that can identify metastable epialleles in order to characterize all of the genes susceptible to environmental influences.

With the identification of epigenetically unstable locations in the human genome, it will be possible to screen individuals at an early age for epigenetically susceptible diseases, allowing for closer monitoring and more frequent follow-up. In addition, unlike genetic mutation, epigenetic profiles are potentially reversible. Therefore, epigenetic approaches for prevention and treatment, such as nutritional supplementation and/or pharmaceutical therapies may be developed to counteract negative epigenomic profiles.  The future of epigenomics therapy holds tremendous potential for not only individualized health care but also for population-wide disease diagnostic, screening, and prevention strategies.