The 8 percent of human DNA that is derived from viruses may cause the cell mutation behind psychiatric disorders such as schizophrenia and mood disorders, according to scientists at Osaka University in Japan.
Detailed in a recent article in the journal Nature by University of Texas at Arlington biology professor Cédric Feschotte, the study revealed that the genomes of mammals contain DNA derived from the insertion of bornaviruses, or RNA viruses whose replication takes place in the nucleus of cells.
Bornaviruses cause Borna disease, a neurological syndrome thought to play a role in some human neurological and psychiatric conditions such as bipolar disorder and depression. It infects only neurons and establishes a persistent infection in its host's brain.
Researchers have known since 2001 that 8 percent of human genetic material is derived from retroviruses. That assimilation of viral sequences into the host genome is called endogenization. Until now, retroviruses were the only viruses thought to generate endogenous copies in vertebrates.
But scientists were able to find spontaneous BDV insertions in the chromosomes of human cultured cells persistently infected by BVD. Feschotte siggests that the BDV insertions could be a source of mutations in the brain cells of infected individuals.
In other words, the bornavirus insertions could have medical and evolutionary implications in humans, such as schizophrenia and other mood disorders.