Here’s a startling thought: the human genome contains ancient viruses. Researchers recently detected a 100-million-year-old virus called a human endogenous retrovirus (HERV) in the blood of pregnant women. The virus is old enough to have infected our ancestors when dinosaurs roamed the Earth – and scientists are still puzzling over how retroviruses might affect us in the long term.
Eight percent of the human genome is made up of ancient viruses and scientists are still trying to puzzle out their function. Three scientists, led by Gkikas Magiorkinis of the National and Kapodistrian University of Athens, wrote an article available online the end of September for Trends in Microbiology, delving into the mystery behind HERVs. They said, “Are they merely fossils that, like mosquitoes in amber, were stuck and preserved in large host genomes while their functions decayed?” They noted the 100-million-year-old retrovirus, first detected by another research group, “became a human gene that is expressed in embryos and cancers, and can be detected in the blood of pregnant women.”
Retroviruses insert a DNA copy of their RNA into a genome, according to IFLScience – this has devastating consequences with the human immunodeficiency virus, or HIV, for example. The 100-million-year-old HERV looks to be inactive during most stages, with low expression in many normal tissues, but it is expressed in the placenta, some stem cells, and cancer tissues like those of ovarian cancer, according to the scientists. The expression pattern “suggests potential roles for manipulation of stem cells and early life events, which could have very important impacts on adult diseases.”
IFLScience points out the find has raised more questions than it solves – the three researchers suggest a hypothesis at the end of their paper, but no definitive conclusions. They say scientists should explore the roles of endogenous retroviruses to pin down potential anticancer treatments.