A Surprising Link Between 8% of our DNA and Mental Illness from Ancient Virus

Our DNA holds a vast library of instructions, not just for building our bodies, but also for shaping our health and susceptibility to disease.  Recent research has uncovered a surprising link between snippets of ancient viral DNA embedded within our genome and an increased risk for certain mental illnesses.

Fossil Virus in Our DNA: Unveiling the Role of HERVs

Around 8% of human DNA is made up of leftover genetic material from ancient viruses known as Human Endogenous Retroviruses (HERVs). These viral remnants date back millions of years, with some even predating the emergence of Homo sapiens. Initially dismissed as “junk DNA,” scientists are now discovering that this virus may play a more significant role than previously thought, particularly in brain function and mental health.

Imagine viruses from millions of years ago infecting our ancestors and leaving a copy of their genetic material behind. This genetic material got incorporated into our genome and passed down through generations. These remnants are the HERVs. There are different families and types of HERVs, some potentially more active than others.

From Silent Passengers to Active Players: How HERVs Influence Our Genes

Earlier research suggested HERVs might regulate the activity of other human genes. Gene expression refers to the process where a specific DNA segment is used to create RNA molecules, which in turn can be translated into proteins or help control other parts of the genome. Interestingly, some HERVs seem to influence neighboring genes with important biological functions, like regulating connections between brain cells.

Potential Impact on Health:

Regulation of Other Genes: This virus can influence the activity of other genes through a process called gene expression. They might act like switches, turning genes on or off, potentially affecting various biological functions.

Protein and RNA Production: Some HERVs might produce their own proteins and RNA molecules which could influence cellular processes in various ways. Evolutionary Benefits:  Some of this virus insertions might have been beneficial in the past, providing resistance to future viral infections.

Furthermore, scientists have found evidence that the virus can produce their own RNA molecules and even proteins within our blood and brain tissues. These molecules have the potential to exert diverse effects on cellular function. In some cases, these ancient viruses may have even been repurposed for beneficial roles during evolution. For example, the syncytin genes involved in placental development are actually derived from HERVs.

The HERV-Mental Illness Connection: Unraveling a Complex Puzzle

Given the abundance and potential functions of this virus, researchers investigated whether these ancient viral sequences might be linked to susceptibility for certain mental illnesses.

A recent study profiled HERV expression in nearly 800 postmortem brain samples. This analysis helped identify specific DNA variations influencing HERV activity within the brain.  The researchers then compared this data with findings from large genetic studies that examined genetic differences between tens of thousands of individuals with and without mental health conditions. These studies had already identified DNA variations associated with various psychiatric disorders.

The combined analysis revealed a fascinating connection: the expression of four specific HERVs was linked to an increased risk for major psychiatric disorders. Two HERVs were associated with schizophrenia, one with both schizophrenia and bipolar disorder, and another with depression. This suggests that HERVs may play a more crucial role in brain function than previously thought.

Looking Ahead: The Potential Impact of This Discovery

Mental health disorders are complex conditions with multiple contributing factors, and HERVs are just one piece of the puzzle. While the exact impact of these specific HERVs on brain cells and susceptibility to mental illness remains unclear, this study is the first to demonstrate a link between genetic risk for psychiatric disorders and the activity of these ancient viral sequences.

Although the practical applications of these findings are still under exploration, the potential for future treatments is exciting. By recognizing the importance of HERVs in the brain and their connection to mental health, this research opens doors for further investigation and potentially new avenues for therapeutic development.

This discovery highlights the ongoing process of scientific exploration. What was once considered “junk DNA” is now revealing itself to be a dynamic player in our health and well-being.  Further research on HERVs and their influence on brain function holds immense promise for a deeper understanding of mental illness and the development of more effective treatments.