HIGHLIGHTED TOPIC Epigenetics in Health and Disease Epigenetics: an emerging player in health and disease

mous opportunities to gain a greater understanding of the genetic intricacies underlying biological systems in both health and disease. Along with variations in the linear sequence of the genome that may predispose to certain pathologies, there is increasing evidence that epigenetic factors can profoundly influence gene expression and, in turn, resistance or suscepti-bility to disease (2, 10). The term “epigentics ” comes from the Greek word epigenesis and was coined by the developmental biologist Conrad Waddington (1905–1975) in the late 1940s. In recalling this, Waddington wrote, “Some years ago (e.g., 1947) I introduced the word ‘epigenetics, ’ derived from the Aristotelian word ‘epigenesis, ’ which had more or less passed into disuse, as a suitable name for the branch of biology which studies the causal interactions between genes and their prod-ucts which bring the phenotype into being ” (8, 12). In his seminal book, The Strategy of Genes, Waddington (13) de-scribed his epigenetic landscape theory. Waddington theorized, at a time when the function and regulation of genes was very poorly understood, that cellular development must be governed by a variety factors outside the scope of genetic inheritance. This novel and innovative theory provided the framework for modern epigenetics. Today, epigenetics is commonly defined as changes in gene expression that occur without a change in DNA sequence (4, 11). It can be viewed as a bridge between genotype and phenotype (5). Over the past decade, there has been mounting interest in the associations between epigenetic modifications and human conditions and diseases such as aging, cancer, lupus, schizophrenia, and cardiovascular disease. While many of these pathologies can be heavily influenced by heritable factors, environmental factors also play a role. Indeed, the impact of environmental factors (i.e., diet, smoking, physical activity, pollutants) on disease pathology is thought to b