- Exponential increase in transposon activity identified in aging
- Scientists find low calorie diet suppresses transposon activity
and increases life span.
- Gene manipulation could lead to the over-expression of certain
genes that suppress the activity of transposons.
are genetic sequences that have become a
part of the genome as a result of evolutionary processes, but could play a
critical role in the lifespan of the individual.
The DNA material is held tightly within
heterochromatin material, when this heterochromatin loosens its grip during
aging, the 'rogue' elements or transposons shift position and could get
attached to important positions of the DNA sequence. Increased attachment of
these transposon elements restricts the expression of the genes to which they
are attached, leading to senescence or aging
‘Controlling calorie intake could control transposon activity and increase lifespan.’
Senior author Dr. Stephen Helfand from The
Brown University of Biology and colleagues have found that certain
interventions that include controlling calorie intake
and gene manipulations could
affect the activity of these transposons and increase lifespan.
The recent study published in the Journal
Proceedings of the National Academy of Sciences
provides evidence for
interventions that could increase lifespan. Dr. Stephen Helfand said " 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."
Mechanism of Action of the Transposable
Transposons are found to be
more active in somatic cells
than in germ line cells and this is
attributed to an evolutionary need to protect the germ line cells. However, the
underlying mechanism, according to a study by Sturm Á and colleagues titled "
The mechanism of ageing: primary role of transposable elements in genome
disintegration" and published in the Journal Cellular and Molecular Life
, attributes this to the presence of a Piwi-piRNA system in germ
The Piwi-piRNA system suppresses the
transposable elements which allow germ line cell proliferation with the
preservations of genomic integrity. This system is also found in
cells of organisms like hydra that displays immortality
The somatic cells that lack the presence of
this Piwi-piRNA system show a gradual disintegration and aging. The transposons
are thus pivotal for aging and controlling their movement could increase the
lifespan of the individual.
Proof of Movement of Transposons
Scientists from The Brown University studied
the movement of these transposons by inserting certain genetic segments, in
which the movement of specific transposable elements leads to a fluorescent
glow that could be viewed under the microscope, into the fat body cells of
fruit flies. These fat body cells in fruit flies were equivalent to human
As the age of the fruit flies increased there
was an increase in the movement of transposons and the increase was not steady
Low Calorie Diet and Transposon Activity
A low calorie diet
is considered important to
maintaining health and the right weight for an individual but the researchers
in this study found that a low calorie diet could delay the activity of
transposons. This can increase the lifespan of the individual.
Gene Manipulation and Transposon Activity
The scientists from Brown University
performed a series of experiments that involved the manipulation of genes in
lowering transposon activity
the gene Su(var)3-9 is over expressed it leads to the formation of heterochromatin
that restricts the activity of the transposable elements. This was found
to increase the lifespan of the fruit flies from 60 days to 80 days.
- Dicer-2: When the expression of
Dicer-2 is increased, it leads to the utilization of the small RNA pathway
to suppress the activity of the transposons. In mice with mutation in
Dicer-2 gene, there is a disruption in the ability to control the
transposons. When the HIV drug 3TC was introduced into such mice, there
was an increase in lifespan.
The scientists in the study have highlighted
the importance of the transposons in increasing the lifespan, however, as Dr.
Jason Wood who is a faculty investigator of the study said "There are lots
of potential mechanisms that influence the aging
There are a lot of things going on, but we think this is one of them."
The scientists aim to look at the
following factors to determine the importance of transposons in affecting the
activity will be increased in a living system and its effect on aging
editing tool CRISPR will be used to study the effect of
transposons on the lifespan.
interventions that affect the activity of the transposons will be studied.
The team of researchers received a $9.7
million grant from The University of Rochester and New York University to work
on transposons and aging.
The extensive studies that are being carried
out will provide a better insight into how these transposons can affect the
expression of our genes and how interventions could prevent the activity of
these rogue elements. However, the current study underlines the importance of a
low calorie diet, especially in controlling transposon activity.
- Transposable Elements in Aging - (https://www.fightaging.org/archives/2015/10/transposable-elements-in-aging/)
- The Mechanism of Aging - (http://www.ncbi.nlm.nih.gov/pubmed/25837999)