Brain Defects May Relate to Amount of Jumping Genes

In the article 'Jumping
Genes' May Contribute to Aging-Related Brain Defects, scientists found that
the number of transposons in the brains of fruit flies increases as they get
older. Transposons are also called jumping genes because they transpose
themselves into another part of the genome. This can cause fatal defects.
Another article on transposons called Rare
Form of Active 'Jumping Genes' Found in Mammals states that:

[caption id="attachment_7872" align="alignright" width="346" caption="Transposons"][/caption]

Many organisms have developed systems to decrease the
frequency at which jumping genes move, Craig says. Such systems are a component
of immunity, protecting mammals from retroviruses, as well as from the risk
that jumping genes will wreak havoc by interrupting an important gene.

It is believed that transposons have a role in brain development,
but can cause harm later on. Transposons accumulate as flies grow older.  In fruit flies, Ago2 protects against transposon
activity. When scientists blocked the Ago2 in young flies, they found that the
young flies had the same amount of transposons as much older flies. The young
flies were then found to have defects in long-term memory that are usually
found in much older flies. The young flies also had shorter life spans as
a result of the increase in active transposons. Scientists believe that transposons
may be accountable for age-related neurodegeneration. This is an important
discovery because it can lead to an understanding of aging, brain development,
and brain defects.