Epigenetics—New Frontier for Alcohol Research

T he term " epigenetics " is rapidly becoming one of the more important watchwords in the field of alcohol research. Put simply, epigenetics is the study of changes in gene function that occur without a change in the body's genetic code, instead relying on epigenetic markers on, among others, the DNA and certain nuclear proteins to turn genes " on " and " off. " Epigenetic changes also are brought about by histone modifications , as well as by the role that noncoding RNA (ncRNA) plays. By acting on these epigenetic markers, environmental factors such as diet, stress, and prenatal nutrition can make an imprint on the genes that are active in different tissues and at various stages of life. Even more importantly, these alterations may be passed along from one generation to the next. The result is that the influences from harmful environmental factors can be extended beyond the individual and passed to his or her offspring. This issue of Alcohol Research: Current Reviews explores the concept of epigenetics and the role it plays—not only in shaping the key characteristics that ensure normal functioning but also which may lead to disease. In particular, the issue looks at how epigenetics influences the body's response to alcohol and the development of alcohol use disorders and various disease states. The concept of epigenetics is not new, originating in the 1940s (Waddington 1942). The idea was put forth to explain alterations in an organism's phenotype that could not be attributed to modifications in its genotype. Or, in more modern terms, epigenetic modifications are the reason that identical DNA sequences can lead to different gene expression profiles. The specific nature of these modifications, however, has come to light only in recent years. These findings have painted a fascinating and complex picture involving the coordinated interplay of numerous regulatory epigenetic mechanisms that help ensure the organism's normal development and function as well as adaptability to changes in environmental conditions. Importantly, epigenetic modifications of both DNA and histones are time-and tissue-or organ-specific; as a result, disruptions of the epigenome can have vastly diverse consequences, depending on the developmental stage and tissue or organ affected. One crucial epigenetic mechanism involves methylation of the DNA, particularly in regulatory regions, which typically results in the silencing of genes. Other modifications center on the histone proteins that help package the DNA in the cell nucleus and which determine how …