What is Epigenetics?
A growing scientific discipline.
Epigenetics is relatively new, but rapidly growing, scientific discipline that investigates the effect developmental or environmental factors have on how genes are expressed or “turned on” in a way that does not change the underlying DNA sequence. The epigenome is a complex layer of regulatory information superimposed on the genome that includes chromosome structure and DNA methylation.
DNA is an organism’s instruction manual. It tells an organism’s cells how to construct tissues and organs. However, since every cell has the same genetic information, how do certain cells know, for example, to become neurons rather than skin cells? This is an area where epigenetics plays a major role. Epigenetic factors tell cells which pages of its instruction manual (which genes) to read at any given time. Although an organism’s cells have identical genomes each tissue has a unique epigenome (different epigenetic factors) controlling which genes are expressed (turned on). It is these epigenetic factors that instruct a neuron to develop the structure and characteristics it needs to function properly and differently from a skin cell, i.e. a neuron cell expresses genes that help it develop dendrites and axons. These same genes will be turned off in the skin cell. Epigenetic mechanisms are also effected by an organism’s environment. Environmental factors such as diet can alter where epigenetic marks are laid down on the DNA and thereby influence an organism’s long-term health.
Epigenetics is everywhere and happening all the time. The collection of epigenetic factors (epigenome) in your cells is affected by the environment, your lifestyle, aging, chemicals and toxins, and diseases. Epigenetic changes can be stable and last a lifetime, and even be passed on to your offspring. These changes can affect your health and wellbeing. However, your epigenome is dynamic and is constantly being affected by your environment, therefore epigenetic changes can be reversed by lifestyle changes or medications. Studies of identical twins, whom have identical DNA, start life with fairly similar epigenomes, but their epigenomes become increasingly different with age (see figure). Because the different environments and lifestyles each are exposed to provide them with unique epigenomes, it is possible for one twin to develop a disease like diabetes or cancer while the other does not.
Biological Molecular Mechanisms
Epigenetics is the study of the biochemical factors or signals that regulate gene expression without changing the underlying sequence of the DNA. The epigenetics factors are often characterized by chemical modifications to DNA (DNA methylation), to the proteins that package DNA (histones), or RNA molecules.
Epigenetics is relevant to the following areas:
- early poor nutrition with adult obesity and diabetes,
- tobacco smoke and air pollution with asthma and developmental delay,
- toxins like BPA (Bisphenol A) with infertility and cancer risk,
- PAHs (Polycyclic aromatic hydrocarbons) with neurodevelopmental effects,
- and childhood stress with anxiety disorders.
Understanding the links between environmental factors and epigenetic changes can help ensure that children into healthy adults.
While the child is in utero, environmental factors can affect three generations: the mother, the child and the child’s reproductive cells (his or her offspring). Reprod Toxicol. Apr 2011; 31(3): 363–373.