No more lying about your age: your DNA chemistry will let the world know exactly how old your cells are.
One scientist has put together an enormous amount of available bioinformatic information to conclude that the modifications of methylation in each cell’s DNA, which are part of the epigenetics of the cell, can be used as predictors of age.
Steve Horvath, from the University of California Los Angeles (UCLA) has published a paper in the open access journal Genome Biology with a new approach to the information already published by different laboratories in the past years. Importantly, he collected and analyzed large databases of DNA sequences, that were independently compiled in the past, but that could all be compared because they were obtained using the same DNA sequencing technology. The author acknowledges the “ generosity of hundreds of researchers” that provided the “unprecedented collection of DNA methylation data” in publicly available databases.
In the genomes, DNA bases can suffer chemical alterations such as additions of methyl groups. These alterations can be “normal” or due to faulty cell metabolism. In the case of normal changes, the chemical marks introduced in the DNA function as signals that determine the fate of the cells. For example, a decision to activate or repress certain genes will depend on those chemical modifications, also known as epigenetic alterations (epigenetics: sometimes defined as “besides genetics”, for being a cellular code that works in addition to the genetic code). In the same way, cells may acquire abnormal behaviors due to altered epigenetic modifications. One of the epigenetic aspects already described relates to the fact that some genes, which are cancer-prone, may have abnormal activation due to epigenetic marks thus leading to cancer progression. For these reasons, Horvath has studied not only healthy tissues, but also cancer samples. In total, 8000 samples were analyzed. This complex bioinformatics study has led to a program that can be used as multi-tissue predictor of age, now freely available to the scientific community. Scientists have know for some time now that that epigenetics changes were among the many manifestations of ageing that cells develop, just like wrinkles in an old person’s face. However, nobody knew how accurately age could be estimated. Now, the predictor program has shown that the age of an healthy tissue can be determined by quantifying its DNA methyl marks, or epigenetic marks (DNA methylation is not the sole epigenetic mark characterized so far, but its functional relevance is particularly well-established).
But perhaps the most promising results, concerning human health, come from the fact that cancer tissues were found to be “older” that healthy tissues. In average, the “epigenetic age” of cancers was accelerated by 36 years. Also, the predictor determined that tissues in the proximity of cancer cells were already 12 years “older” compared to healthy tissues. From these results, one can envision a technical development whereby the predictor would be able to tell whether a particular tissue sample is healthy or not. Primary tumors, as well as metastasis, could be identified molecularly at very early stages of development, given that only a few cells would be required for the epigenetic analysis. The progression of the tumors could also be quantified according to their epigenetic age.
In the future, the Horvath predictor is expected to allow the accurate identification of age from a human cell sample, but also to contribute decisively to cancer early diagnosis, which is paramount for the successful management and treatment of several types of cancer.