According to new research published in Nature, depression, schizophrenia, and bipolar disorder are linked with ancient viral DNA known as HERVs in our genome.
Ancient viruses have left behind genetic sequences that makeup 8% of human DNA. These sequences are known as human endogenous retroviruses or Hervs, and they have been there for hundreds of thousands to millions of years—some of them even before Homo sapiens appeared on the scene.
According to the most recent research, there may be a connection between some old viral DNA sequences in the human genome and the vulnerability to mental illnesses like schizophrenia, bipolar disorder, and major depressive disorder.
The surviving retroviruses from these infections are known as hervs. Retroviruses are a type of virus that replicates its genetic material within the infected cells’ DNA. We were most likely infected by retroviruses more than once during our evolutionary history. Upon infection of sperm or egg cells that produced progeny, the genetic material of these retroviruses was transmitted to the next generations, so creating an enduring component of human ancestry.
Hervs were once thought to be “junk DNA,” or sections of our genome with no apparent purpose. However, as our knowledge of the human genome has grown, it has become clear that this so-called junk DNA serves more purposes than once thought.
First, scientists discovered that Hervs controls how other human genes are expressed. If a genetic feature’s DNA segment is utilized to make RNA (ribonucleic acid) molecules, it is referred to as “expressed.” These RNA molecules can then act as bridges to produce particular proteins or assist in controlling other regions of the genome.
According to preliminary studies, Hervs control the expression of nearby genes that play crucial roles in biology. A Herv that controls the expression of a gene involved in altering the connections between brain cells is one illustration of this.
In blood and brain samples, hervs have also been shown to generate RNAs and even proteins. Because these molecules can move across different cellular compartments to perform various activities, they can exert a wide range of actions.
Additionally, research has shown evidence that suggests some human genes are descended from Hervs. This suggests that Hervs were occasionally appropriated for specialized biological roles along the course of evolution. For example, syncytins 1 and 2 (human genes derived from Hervs) are essential for placental development.
HERVs in psychiatric disorders
We sought to learn more about whether variations in Herv expression were linked to genetic predisposition to certain psychiatric diseases, given the quantity of Hervs in the genome and their potentially wide range of roles.
We assessed Herv expression in about 800 autopsied brain samples in our investigation. This made it easier for us to pinpoint DNA changes that affected the expression of Herv in the brain.
We next compared the results of these data with those from extensive genetic studies that examined genetic variations among tens of thousands of individuals, both with and without mental health issues. These investigations found genetic variants linked to many psychiatric disorders.
It was discovered that there was a hereditary predisposition to major psychiatric diseases associated with the expression of four Hervs. Two of these Hervs were linked to depression, one to bipolar disorder and schizophrenia, and one to both conditions when expressed. These findings imply that Hervs might be more significant in the brain than previously believed.
Hervs is just one piece of the genetic mosaic that contributes to psychiatric disorders; there are many genes involved. Our discovery is the first to demonstrate that genetic vulnerability for a psychiatric condition also functions through these ancient viral DNA sequences, even though more research is needed to determine the specific impact of these Hervs on brain cells and an individual’s susceptibility to certain psychiatric disorders.
Determining the practical implications of our findings and their potential for therapeutic development is still premature. However, we have high hopes for this field of study. After being disregarded for years, our research highlights the significance of these enigmatic sequences in the human genome by connecting Herv expression in the brain with psychiatric diseases.
Last year, GreatGameIndia reported that according to a study published in the Lancet Psychiatry, researchers found that antipsychotic prescriptions to children and youth in England have doubled.
