'Junk' DNA inherited from our ancient ancestors could be rewiring our brains and altering our behaviour and emotions, study finds


Some of our brain's activity could be being guided by so-called 'junk DNA' we inherited from our ancient ancestors, a new study has concluded. The human genome contains all the instructions needed to build and maintain our bodies — however half of it appears to be 'junk' that doesn't code for any proteins. Much of this mysterious extra DNA comes in the form of transposons — or 'jumping genes' — which can move around between people and appear in different places.

It is thought that transposons originated from ancient viruses — and can today be harmful if they have 'jumped' into a gene such as to disrupt cellular processes. However, recently experts have proposed that this 'junk' information may in fact play an active and beneficial role in our bodies. Working with flies, expert from the University of Oxford have found that transposons appear to be related to specific genes that control our behaviour and emotions.

At Oxford's Centre for Neural Circuits and Behaviour, researchers have been investigating transposon activity in unprecedented detail in the brains of fruit flies — which are used a model organism — by means of so-called single-cell sequencing. Their findings showed that transposons are not active across the whole fly brain, but instead operate in certain areas only, forming distinct patterns of expression.

Moreover, these patterns appeared to be linked to genes located near transposons — suggesting that this 'junk' DNA may in fact play a beneficial role in our bodies. To investigate further, molecular biologist Christoph Treiber and colleagues used software tools they developed to explore how transposons are expressed.

They found that transposons segments are often part of the messenger RNA sent from neural genes in the cell nucleus out to the cytoplasm where proteins are made. This suggests that transposons may be used to alter neural function — and act on genes that have roles in such brain activities as the formation of memories and the sleep-wake cycle.

'We know that animal genomes are selfish and changes that are not beneficial often don’t prevail,' said Dr Treiber. 'Since transposons are parts of hundreds of genes in every fly strain that we looked at, we think these physical links likely represent an advantage for the fly.' 'We now want to understand the impact of these new alleles on the behaviour of individual animals.'

'Transposons might broaden the range of neuronal function in a fly population, which in turn could enable a few individuals to react more creatively in challenging situations,' he added.

'Also, our preliminary analyses show that transposons might play a similar role in our brain,' said Dr Treiber. 'Since every person has a unique transposon "fingerprint", our findings could be relevant to the need to personalise pharmacological treatments for patients with neurological conditions.' The full findings of the study were published in the journal Genome Research.