The Epigenetic Clock

Have you ever wondered, or at least once thought about when your last day to live is? To know the exact date when you will perhaps die? Although it may seem like a morbid thought, your time of death can now be roughly estimated. That sounds absolutely absurd, like something straight out of the film Back to the Future. How is that possible you may ask? The scientific world has been excelling in a field called epigenetics. Epigenetics is the study of changes in the environment of an organism that modifies gene expression and the change in a gene function altering physical characteristics. However, the DNA sequence itself is not changed.

Epigenetics transforms the way we think about genomes. Your time of death can now be estimated using the epigenetic clock, also known as the “Horvath’s Clock,” named after biostatician and geneticist Steve Horvath. The clock is a process where DNA goes through chemical changes similar to the rusting of objects like the Statue of Liberty. Gene expression related to epigenetics can be altered through reactions known as methylation and acetylation on the DNA or histones, a protein used to coil and compact DNA. Methylation ultimately tightens DNA around histones to lessen the expression of a gene while acetylation loosens the coils around the histones to upregulate or increase expression. Methylation, the addition of a methyl group, on the DNA base Cytosine over time is what is used to measure aging. The faster the methylation, the faster the aging.  

So far, the clock shows that although different tissues are methylated at different rates, a majority of our body organs have similar rates except for the female breasts, which methylates, faster and the cerebellum, the back part of the brain, which has a slower rate. Aging can potentially be reversed and this is the focus of another section of biology called stem cell biology where adult stem cells can be converted into pluripotent cells, cells that can produce any tissue.

Horvath’s clock may be the most accurate molecular biomarker of aging to date. The effects of epigenetics on our bodies is huge as it plays a role in the fate of our cells and its relation to figuring our causation of a disease and potentially finding a cure. However, as many more years pass and science begins to advance, who knows what better technology and knowledge will humanity obtain.


Elysium Health. (2018, June 28). Is Horvath's Clock the Smoking Gun of Biological Aging? Retrieved from 

Walida Ali