Ancient Viruses Influence Behavior

viruses influence behavior

Viruses influence behavior: A Retrovirus

Do we owe our complex brains to viruses? New research from Lund University in Sweden hints that viruses integrated into our DNA play an important role in our brain function. These ancient viruses influence behavior.

Endogenous retroviruses are pieces of genetic code originating from viruses making up a part of the human genome. These virus snippets actually make up as much as 8-10% of our DNA. This DNA comes from the retrovirus life cycle, when a retrovirus replicate it inserts its DNA into the DNA of the host organism pasting itself into our genome. In some cases the retroviruses can even infect germline cells like egg or sperm. When this happens the retrovirus DNA is “inherited” through generations. This process has occurred for millions of years, cutting and pasting new DNA pieces into our genome. Luckily the virus DNA have undergone mutations that prevent them from coming back to “life”. Today these ancient viruses simply are a part of us. Now new research find that these snippets of “junk” DNA might actually play an important part in brain function.

Ancient Viruses Influence Behavior

This new research were published in the journal Cell Reports

Remnants of viruses left in our genome have long been thought junk, a leftover from our development over millions of years. In this study Johan Jakobsson and colleagues find that these ancient DNA snippets actually might have a regulatory role in brain function affecting our behavior.

[pullquote]”We have been able to observe that these viruses are activated specifically in the brain cells and have an important regulatory role. We believe that the role of retroviruses can contribute to explaining why brain cells in particular are so dynamic and multifaceted in their function. It may also be the case that the viruses’ more or less complex functions in various species can help us to understand why we are so different” says Johan Jakobsson that led the research team.[/pullquote]

In this study performed on neural stem cells researchers found a molecular mechanism called TRIM28 regulates activation of  retrovirus DNA. Removing this molecule leads to high expression levels of “virus” DNA. Activating viral genes also turn on several nearby genes, changing gene expression in neural stem cells. Earlier studies have found that removing this regulator lead to complex changes in behavior similar to those seen in neurological and psychiatric disorders. The complex network virus DNA snippets might actually be influencing our behavior.

What does It Mean For us that Viruses influence behavior?

We are the result of millions of years of evolution and during that time DNA from other sources integrated into our own. Over this long time span they’ve developed function that we now depend on, “old” viruses might actually control a part of how our brain works. The next step for researchers is to find if these snippets of viral DNA still left in us are involved in diseases of the brain and if modifying the DNA might be a new way to understand brain diseases.

Do you feel comfortable knowing that ancient viruses influence behavior, maybe even controlling you?

Image credit: Standford

Fasching L et al. (2015). TRIM28 Represses Transcription of Endogenous Retroviruses in Neural Progenitor Cells. Cell reports, 10 (1), 20-8 PMID: 25543143