Epigenetics: A New Aspect of Classical Genetics

The central role of DNA as the genetic information of a living being is unquestionable; whether you understand the intricacies of genetic transmission or not. One of the fundamental principles of biology is the Central Dogma Theory of DNA inheritance, which states that DNA is made up of specific patterns of nucleotide base pairs, which are replicated and translated into proteins. Recently, however, scientists have become fascinated by other factors that affect DNA transmission, factors that seem to somewhat contradict aspects of the Central Dogma. The study of epigenetics has elucidated that certain environmental factors can chemically alter DNA, and that altered DNA is transmitted to offspring.

Researcher Georgia Dias at Emory University has been conducting experiments to study the extent of epigenetic inheritance. Dias conducted an experiment in which he exposed mice that he electrically-shocked to acetophenone, a chemical which is characterized by its “sweet, almond like smell”. Consistent with Pavolv’s famous theory of classical conditioning, the mice literally froze from fear when acetophenone was introduced to them again in the absence of the electric shock. What is notable about this is the effect on the offspring of the original mice. According to the Central Dogma, the offspring of the mice should not be affected by their parent’s aversion to acetophenone because there is no alteration of the germ cells, or the DNA that is inherited by offspring. Dias however noticed that the offspring, who had not been conceived during the experiment, were indeed more sensitive to acetophenone than other smells that they were exposed to. The third generation of mice were friskier and more sensitive upon exposure to acetphenone than mice that descended from the control group. Even more interestingly is that all three generations of experimental mic had above-average sized M71 glomeruli structures, the structures that act to connect acetophenone sensitive neurons in the nose to the olfactory bulbs. This study shows the strong role that epigenetics plays in determining the protein expression of offspring.

Another study of epigenetics was conducted by a research team from Kings College London. The team studied the role of epigenetics specifically as it relates to Autism Spectrum Disorder (ASD), which is a highly heritable disease. The research team focused specifically on the epigenetic changes in which the environment affects the expression and doesn’t change the underlying DNA. The subject of the study was identical twins. If one twin was diagnosed with Autism and the identical twin was not, then epigenetic factors were considered to have a role is the development of Autism. The researchers specifically focused on DNA methylation patterns in which genes are not expressed or “silenced”. DNA methylation at over 27,000 genome sites was examined and the studies reported the following results: Out of 50 pairs of identical twins, 34 pairs had one twin with ASD and one without; five pairs had ASD in both twins; and 11 pairs had no characteristics of ASD. Researchers noticed that at specific loci of the genome there was a consistent pattern of altered methylation for those who were diagnosed with ASD. Again, this indicates the important role of epigenetics. The base pair sequence of DNA could be identical yet certain environmental factors can affect DNA expression causing only one twin to be diagnosed with ASD.

Overall, research studying the role of epigenetics in our bodies is vitally important. So much so that in 2008, the National Institute of Health recognized this importance and allotted $190 million for epigenetics research. Government officials noted that epigenetics could explain mechanisms of aging, human development, and the origins of cancer, heart disease, and mental illness. Some scientists, like Dr. Randy Jirtle of Duke University Medical Center, think epigenetics may play a greater role in disease than genetics. Current research shows that epigenetic pharmaceuticals could replace or be used in conjunction with commonly accepted cancer treatments such as radiation and chemotherapy. Epigenetic control of the tumor suppressor genes directly affects the formation and progression of cancer, which is important because epigenetics has the factor of reversibility.  According to Dr. Jonathan Mill, the head of the Psychiatric Epigenetics laboratory at the Institute of Psychiatry at Kings College London, “Research into the intersection between genetic and environmental influences is crucial because risky environmental conditions can sometimes be avoided or changed.” While this is a relatively new field of biology, study and research involving epigenetics has become prevalent because of the possible benefits it can have on the future of medicine.