What if we could turn off disease like a light switch? In the world of Dr. Stephen Wellinghoff of Southwest Research Institute (SwRI®) in San Antonio, Texas and Dr. Ranjan Perera of Memorial Health University Medical Center in Savannah, Georgia, flipping that switch is not only feasible, it’s achievable.
Many of us may remember from biology that every cell in our body contains a nucleus. Inside the nucleus sits the DNA, comprised of thousands of genes and organized into structures called chromosomes. We can think of DNA as the blueprint within each cell. This blueprint is transcribed into RNA, which is more like a working plan. The RNA serves as a template for the synthesis of proteins, which determine how each cell will function: what role it will play within the body and whether it’s healthy or unhealthy.
Classic genetics defined our DNA as fixed, passed down from our mothers and fathers and fully defined in the womb. But there’s a new kid on the biological block called epigenetics – a field that explores how our genes, the DNA they form, and the surrounding cellular microenvironment can be altered in fully developed cells. New evidence suggests that our DNA can be modified throughout our lifetime. According to Dr. Perera, epigenetics is one of the most promising scientific disciplines of post-genomic biology. “It is the missing piece in gene expression. We have known about genomics (the study of an organism's entire genome,) and we also know about proteomics (the study of an organism's complete complement of proteins), but in between, there has been a missing link of how these genes are regulated. And that’s where epigenetics comes into play. Let’s take an example: we know that certain phenotypical characteristics such as hair color or skin color are specified and controlled by certain genes or DNA sequences. Under this paradigm, two identical twins should have the exact same DNA footprints. Yet we often find genetically identical twins that are physiologically different. For example, one might be healthy while the other may be sick or have defects – and these differences can increase with age. How can we explain that? That is why we say there is a missing link; because the DNA is identical, something else must come into play. This missing link, epigenetics, is most likely the key to these differences.”
The differences between two twins or the changes in an individual throughout her lifetime may involve chemical modifications of the DNA itself, or modifications to proteins associated with the DNA that can induce the chain of genetic material to open or further fold onto itself. Acetylation, methylation, and ubiquitylation are all examples of DNA modification. At a high level, these each refer to some sort of alteration to the molecular structure of our DNA, in some cases remodeling some of the chromatin-associated proteins or transposing certain stretches of the DNA sequence. Any of these can lead to subtle changes in the way the genetic information is read or processed in the cell. Because DNA is transcribed into RNA and RNA translated into proteins, a fundamental change like this at the cell nucleus can be the equivalent of flipping a switch, turning a productive cell into a destructive cell. And because each new cell is essentially a duplicate of a prior one, any epigenetic modifications that occur in the nucleus can be passed to that cell’s offspring, spreading throughout the body.