A new study is providing insights into how transposons affect aging processes. These pieces of DNA, capable of breaking off and moving to other parts of the genome, were believed to become more active with increasing age. For the first time, researchers have gathered hard evidence by using fruit flies as model organisms. The findings are in a paper that was just published in the journal Proceedings of the National Academy of Sciences.
Transposons are segments of DNA that can break off, replicate, and move around the genome. Normally, transposon movement is limited by cell mechanisms. One such mechanism is the formation of heterochromatin, dense chromosomal material that represses transposons and blocks them from moving around. Based on previous research, scientists have speculated that increased transposon movement is related to aging processes.
A team of researchers studied transposon activity in fruit flies (Drosophila melanogaster). By using fluorescence techniques, the team was able to observe how the transposons moved around. As the flies aged, the transposons began jumping around to different parts of the genome. Once the flies were close to dying, transposon activity increased significantly.
Calorie-restricted diets have already been shown to increase fruit fly lifespans. When the team put their flies on a low-calorie diet, transposon activity slowed. The diet also repressed the activity of certain genes associated with transposons and heterochromatin.
The team then tried activating genes that help improve heterochromatin repression. Activating a gene called Su(var)3-9 restricted transposon activity, extending the maximum lifespan of the flies by 20 days. Increasing the activity of a similar gene, called Dicer-2, had the same effect. An anti-HIV drug, 3TC, also increased lifespan by inhibiting the activity of transposons.
The findings provide substantial evidence for the theory that transposon movement is closely linked to aging. The research team already has more experiments planned, including one to investigate the effect of increasing, rather than repressing, transposon activity. The team will also be using CRISPR techniques to edit the genomes of the flies. If the team can prevent the movement of transposons through gene editing, they may be able to artificially increase lifespan. All of these studies will help scientists better understand the aging process in both flies and humans.
Jason G. Wood 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 (2016).