What is Epigenetics?

“Epigenetics” refers to covalent modification of DNA, protein, or RNA, resulting in changes to the function and/or regulation of these molecules, without altering their primary sequences. In some cases, epigenetic modifications are stable and passed on to future generations, but in other instances they are dynamic and change in response to environmental stimuli. Nearly every aspect of biology is influenced by epigenetics, making it one of the most important fields in science.

Epigenetics and Me

Why do some foods cause health problems and others make us healthy? How does stress impact our long-term well-being? Why is it that the older we get, the more likely it is that age-related illness will strike us? Unlocking the secrets behind these and other questions has the potential to revolutionize life as we know it. The emerging field of epigenetics is aiming to do just that.

The importance of nature versus nurture has long been disputed. It cannot be denied that environment greatly influences how a child grows and develops, nor can it be denied that our DNA is the blueprint that makes us who we are. Epigenetics merges these two seemingly contradictory lines of thought to explain how environmental factors cause physical modifications to DNA and its associated structures, which result in altered functions.

The most commonly known epigenetic modification is DNA methylation. Although many technologies have been developed in the past to characterize genomic DNA methylation, none of them has been able to efficiently determine DNA methylation patterns on a genomic scale. Until now.

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Many cellular processes, including gene expression and DNA replication, are often regulated by mechanisms that fall into the category of “classical genetics”. This generally means that they are controlled by elements such as promoters, enhancers, or binding sites for repressor proteins, that are present or absent in the DNA sequence.  An example of this type of regulation is the control of expression of a cellular oncogene.  In normal (non-cancer) cells, this gene would not be expressed. However, in a cancer cell, this gene could have aquired a mutation, which is a change to the DNA sequence, that allows the oncogene to be expressed, and thus can contribute to the progression of cancer.

In addition to the regulatory mechanisms of classical genetics, nearly all cellular processes can also be regulated by epigenetic mechanisms.  Epigenetic mechanisms can be just as important to biological events as genetic mechanisms, and can also result in stable and heritable changes. However, the big difference between genetic and epigenetic regulation is that epigenetic mechanisms do not involve a change to the DNA sequence, whereas genetic mechanisms involve the primary DNA sequence and changes or mutations to this sequence.  Epigenetic regulation involves the modification of DNA and the proteins associated with DNA, which results in changes to the conformation of DNA and accessibility of other factors to DNA, without a change to the sequence of the DNA.

The Greek prefix “epi” means “on top of” or “over”, so the term “Epigenetics” literally describes regulation at a level above, or in addition to, those of genetic mechanisms. Common types of epigenetic regulation are DNA methylation and hydroxymethylation, histone modification, chromatin remodeling, and regulation by small and large non-coding RNAs. The field of epigenetics was given its name and a vague definition only ~50 years ago, but is now a dynamic and rapidly expanding discipline, challenging and revising traditional paradigms of inheritance.

Through epigenetics, the classic works of Charles Darwin, Gregor Mendel, and Jean-Baptiste Lamarck and others are now seen in different ways. As more factors influencing heredity are discovered, today’s scientists are using epigenetics to decipher the roles of DNA, RNA, proteins, and environment in inheritance. The future of epigenetics will reveal the complexities of cellular differentiation, embryology, the regulation of gene expression, aging, cancer, and other diseases.