Ancient DNA found in the brain is linked to psychiatric disorders

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A new study suggests that ancient viral DNA still present in the human genome may be linked to major psychiatric disorders.

The study, conducted by King's College London, found that thousands of DNA sequences arising from ancient viral infections have been found in the brain, some of which contribute to susceptibility to mental disorders such as schizophrenia, bipolar disorder, and depression.

About 8% of the genome (the complete set of DNA) consists of sequences called human endogenous retrovirus (HERV), the product of an ancient viral infection that occurred hundreds of thousands of years ago.

It was thought that these "fossil" viruses had no important function and were merely DNA waste. However, scientists have discovered where these 'fossil' viruses are located in our DNA, which has helped them understand what functions they may perform.

This study is the first to show that a specific set of human endogenous retroviruses expressed in the human brain contributes to susceptibility to psychiatric disorders.

Dr Timothy Powell, co-lead author of the study and senior lecturer at the Institute of Psychiatry, Psychology and Neuroscience (IoPPN), from King's College London, said: “This study uses a new and powerful approach to assess genetic predisposition to psychiatric disorders. It has implications for the expression of "Our results suggest that these viral sequences may play a more important role in the human brain than originally thought, with specific expression of human endogenous retroviruses being associated with increased susceptibility to some psychiatric disorders."

The researchers looked at data from large studies involving tens of thousands of people, with and without mental illness, as well as information from autopsy brain samples from 800 people.

They found that certain genes preferentially affected the expression of human endogenous retroviruses.

The researchers reported five strong endogenous retroviral expression signatures associated with psychiatric disorders, including two associated with risk of schizophrenia, one associated with risk of both bipolar disorder and schizophrenia, and one associated with risk of depression.

“We know that psychiatric disorders have a significant genetic component, with many parts of the genome increasingly contributing to susceptibility,” said Dr. Rodrigo Duarte, first author and research fellow at the Institute of Psychiatry, Psychology and Neuroscience (IoPPN). of parts of the genome corresponding to endogenous retroviruses, leading to the identification of five sequences relevant to psychiatric disorders. While it is not yet clear how these viruses affect brain cells to cause this increase in risk, our findings suggest that their expression is regulated. "It is important for brain function."

“More research is needed to understand the exact function of most endogenous retroviruses, including those identified in our study,” noted Dr. Douglas Nixon, co-lead author of the study and a researcher at the Feinstein Institutes for Medical Research at Northwell Health, USA. “We believe that “A better understanding of these ancient viruses, and the known genes involved in psychiatric disorders, has the potential to revolutionize mental health research and lead to new ways of treating or diagnosing these conditions.”