Ancient viruses still persist in human DNA, but a new discovery has found that some may contribute to psychiatric disorders.
Scientists of King’s College London identified five ‘fossil viruses’ associated with depression, schizophrenia and bipolar disorder.
Ancient viruses, called human endogenous retroviruses (HERVs), were previously known but considered “junk DNA” for no purpose, but could now lead to new treatments for those suffering from such conditions.
The researchers said the sequences are hundreds of thousands of years old, meaning they could have originated from Neanderthals.
Ancient viruses still persist in human DNA, but a new discovery has found that some may contribute to psychiatric disorders. Scientists at King’s College London identified five ‘fossil viruses’ associated with 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 imparts its effects on the expression of ancient viral sequences present in the modern human genome.
“Our results suggest that these viral sequences probably play a more important role in the human brain than originally thought, and that specific HERV expression profiles are associated with increased susceptibility to some psychiatric disorders.”
The human genome is made up of just over six billion individual letters of DNA (approximately the same number as that of other primates such as chimpanzees) spread across 23 pairs of chromosomes.
To read a genome, scientists first cut up all that DNA into pieces of hundreds to thousands of letters.
Sequencing machines then read the individual letters on each piece and scientists try to assemble the pieces in the correct order, like putting together an intricate puzzle.
The study analyzed data from large genetic studies involving tens of thousands of people, with and without mental health problems.
The team also used data from autopsy brain samples of 800 individuals to explore how DNA variations linked to psychiatric disorders affect the expression of HERVs, which make up up to eight individuals in the human genome.
researcher then discovered that some genetic risk variants partially affected HERV expression.
With the five expressions identified, the team found two associated with the risk of schizophrenia, one associated with the risk of bipolar disorder and schizophrenia, and one associated with the risk of depression.
The team noted that no HERV expressions were found associated with hyperactivity disorder and autism spectrum conditions.
Dr. Rodrigo Duarte, first author, said: “We know that psychiatric disorders have a substantial genetic component, and that many parts of the genome progressively contribute to susceptibility.”
‘In our study we were able to investigate parts of the genome corresponding to HERVs, which led to the identification of five sequences relevant to psychiatric disorders.
“Although it remains unclear how these HERVs affect brain cells to confer this increased risk, our findings suggest that their regulation of expression is important for brain function.”