People with old viruses in their DNA are more susceptible to depression, research shows
Ancient viruses are still in human DNA, but a new discovery has found that some may contribute to psychiatric disorders.
Scientists from King’s College London identified five ‘fossil viruses’ linked to depression, schizophrenia and bipolar disorder.
The ancient viruses, called Human Endogenous Retroviruses (HERVs), were previously known but were seen without purpose as ‘junk DNA’ – but could now lead to new treatments for people suffering from such conditions.
Researchers said the sequences are hundreds of thousands of years old, meaning they could have come from Neanderthals.
Ancient viruses are still in human DNA, but a new discovery has found that some may contribute to psychiatric disorders. Scientists from King’s College London have identified five ‘fossil viruses’ linked to depression, schizophrenia and bipolar disorder
Dr. Timothy Powell, co-senior author, said: ‘This study uses a novel and robust approach to assess how genetic susceptibility to psychiatric disorders impacts on the expression of ancient viral sequences present in the modern human genome.
‘Our results suggest that these viral sequences likely play a more important role in the human brain than previously thought, with specific HERV expression profiles associated with increased susceptibility to some psychiatric disorders.’
The human genome consists of just over six billion individual letters of DNA β about the same number as other primates such as chimpanzees β spread across 23 pairs of chromosomes.
To read a genome, scientists first chop all that DNA into pieces hundreds to thousands of letters long.
Sequencing machines then read the individual letters in each piece, and scientists try to put the pieces together in the correct order, as if putting together a complicated puzzle.
The study analyzed data from large genetic studies involving tens of thousands of people, both with and without mental health conditions.
The team also used information from autopsy brain samples from 800 individuals to investigate how DNA variations associated with psychiatric disorders affect the expression of HERVs, which make up up to eight individuals of the human genome.
So researcher found that some genetic risk variants partially affected the expression of HERVs.
Once the five expressions were identified, the team found two associated with risk of schizophrenia, one associated with risk of both bipolar disorder and schizophrenia, and one associated with risk of depression.
The team noted that no HERV expressions associated with hyperactivity disorders and autism spectrum disorders were found.
Dr. Rodrigo Duarte, first author, said: ‘We know that psychiatric disorders have a substantial genetic component, with many parts of the genome contributing incrementally to susceptibility.
‘In our study we were able to examine parts of the genome corresponding to HERVs, leading to the identification of five sequences relevant to psychiatric disorders.
‘Although it is not yet clear how these HERVs affect brain cells and confer this increase in risk, our findings suggest that their expression regulation is important for brain function.’