Recent study results have brought the “transposon theory of aging” to the forefront. Transposons are rogue elements of DNA that break free from aging cells and rewrite themselves into other areas of the genome. This process creates lifespan shortening turmoil in the tissues genetic makeup.
Previous studies have shown that as cells age, tightly-wound heterochromatin wrapping—which typically imprison transposons—becomes looser, causing them to slip out from their positions in chromosomes and allows new ones to move in, disrupting normal cell function. On the other hand, researchers and scientists have found that restricting calories or following low-calorie diets can lengthen lifespan in animal models.
Senior author of the study, Dr. Stephen Helfand, explained, “In this report the big step forward is towards the possibility of a true causal relationship. So far there have been associations and suggestions that to all of us make sense, but the difference in science is that you need the data to back up your opinion.”
The current findings stem from a combination of different studies that help solidify the connection between heterochromatin, transposon, aging, and lifespan.
In one experiment, the researchers inserted special genetic snippets into fat body cells of flies, which are similar to human liver and fat cells. These cells would glow green when specific transposable elements moved throughout the genome. Observation under a microscope revealed a clear pattern of how the glowing “traps” increased as the flies aged.
Lead investigator James wood explained, “Flies reach a certain age and then it takes off more exponentially.” Transposable element activity was correlated with the process of dying.
The researchers then began to manipulate genes responsible for heterochromatin repression, which are found in mammals and flies. They found that increasing gene expression of Su(var)3-9 prolonged the flies’ lifespan 20 days longer than their average lifespan (60 days to 80 days). Increasing gene expression of Dicer-2 was also found to increase lifespan.
Finally, the researchers found that an anti-HIV drug can restore some lifespan to flies if they had a mutation that disabled Dicer-2.
Additional research is required to better understand the effects of transposons and aging The researchers have outlined future experiments to help them to gain better knowledge on aging.
Orenstein, D., “Study results advance ‘transposon theory of aging,” Brown University, http://news.brown.edu/articles/2016/09/lifespan, last accessed September 13, 2016.
Wood, J. G., et. Al., “Chromatin-modifying genetic interventions suppress age-associated transposable element activation and extend life span in Drosophila,” Proceedings of the National Academy of Sciences of the United States of America, http://www.pnas.org/content/early/2016/09/07/1604621113, last accessed September 13, 2016.