Ancient viral infections may lurk in DNA and cause mental disorders

Have you ever wondered if there’s something hidden deep inside that is influencing our mental well-being? What if I told you the answer might lie not in our present experiences, but in remnants of ancient viral infections buried within our DNA?

A new study from King’s College London has unearthed a fascinating connection between these “fossil viruses” and mental disorders like schizophrenia, bipolar disorder, and depression.

Viral code for mental disorders in DNA

Imagine our ancient ancestors, facing viral infections hundreds of thousands of years ago. While their bodies fought these infections, tiny fragments of the viruses’ genetic code became embedded within their DNA.

These fragments, called Human Endogenous Retroviruses (HERVs), were passed down through generations and now make up a significant portion of our own genetic makeup.

For a long time, scientists believed that these HERVs were merely remnants of past infections, serving no purpose in our bodies.

However, recent advancements in the field of genomics have allowed us to explore these sequences in greater detail, revealing potential links between HERV activity and certain psychiatric disorders.

This research suggests that HERVs, once dismissed as “junk DNA,” may actually play a role in influencing our mental health.

Rewriting the “junk DNA” narrative

“This study uses a novel and robust approach to assess how genetic susceptibility for psychiatric disorders imparts its effects on the expression of ancient viral sequences present in the modern human genome,” explains Dr. Timothy Powell, a senior author of the study.

“Our results suggest that these viral sequences probably play a more important role in the human brain than originally thought, with specific HERV expression profiles being associated with an increased susceptibility for some psychiatric disorders.”

In other words, these ancient viral remnants might be actively influencing our brains and potentially increasing our risk for certain mental illnesses.

Viral genes in mental disorders

To unravel this mystery, the researchers analyzed genetic data from tens of thousands of individuals, both with and without mental health conditions.

They also examined brain samples from 800 individuals to see how variations in DNA associated with psychiatric disorders affected HERV expression.

What they discovered was remarkable: while most genetic risk factors for mental illness impacted genes with known functions, some specifically targeted the expression of HERVs.

The team identified five distinct HERV expression patterns linked to psychiatric disorders:

• Two associated with schizophrenia
• One associated with both schizophrenia and bipolar disorder
• One associated with depression

“We know that psychiatric disorders have a substantial genetic component, with many parts of the genome incrementally contributing to susceptibility,” notes Dr. Rodrigo Duarte, the study’s first author.

According to Duarte, they were able to investigate parts of the genome corresponding to HERVs, which led to the identification of five sequences that are relevant to psychiatric disorders.

“Whilst it is not clear yet how these HERVs affect brain cells to confer this increase in risk, our findings suggest that their expression regulation is important for brain function,” Duarte concluded.

Viral frontier in mental disorders research

While we don’t yet know exactly how these ancient viruses affect brain cells or contribute to mental illness, this research opens a whole new avenue for exploration. It suggests that these “fossil viruses” could play a more significant role in human health than we ever imagined.

“Further research is needed to understand the exact function of most HERVs, including those identified in our study,” notes Dr. Douglas Nixon, another senior author.

Nixon believes that a better understanding of these ancient viruses, and the known genes implicated in psychiatric disorders, have the potential to revolutionize mental health research and lead to novel ways to treat or diagnose these conditions.

Could these ancient viral sequences hold the key to developing new treatments or diagnostic tools for mental disorders? It’s a tantalizing possibility.

Imagine being able to pinpoint individuals at higher risk for certain mental illnesses based on their unique HERV expression profiles. Or even developing therapies that target these viral remnants to alleviate symptoms.

The research is still in its early stages, but the implications are profound. By delving into our evolutionary past, we may unlock a deeper understanding of our mental health present and future.

The study is published in the journal Nature Communications.

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