Unexpected Snippets of Genetic Material From Viruses Found Lurking in Our DNA

Dark DNA Double Helix

Unexpected Diversity in Virus-Derived Sequences in the Human Genome

Powerful genetic analysis tools reveal that people exhibit a surprising level of variation in virus-derived genetic sequences.

Three RIKEN geneticists have discovered previously undetected snippets of genetic material from viruses lurking in our

Human Herpesviruses 6

Figure 1: A false-colored electron micrograph showing human herpesviruses 6 (HHV6; red circles) infecting a cell. RIKEN researchers have discovered new heritable structural variants derived from HHV6 in human genomes. Credit: © Callista Images/Cultura/Science Photo Library

Roughly 8% of the human genome can be traced backed to retroviruses—viruses that reverse the normal order of genetic transcription, having an

Shohei Kojima

Shohei Kojima and two RIKEN co-workers have discovered a surprisingly high level of variation between people in human endogenous viruses. Credit: © 2021 RIKEN

Now, Kojima, Anselmo Kamada and Nicholas Parrish, all at RIKEN IMS, have investigated virus-derived variations in 3,332 people from diverse populations using bioinformatic tools specially designed for the task.

They discovered that viruses are responsible for unexpected structural variations in the human genome. They also found rare variants in the germline that can be traced back to human herpesvirus 6 (Figure 1).

Not all the viral genetic material they found had ancient origins, however. The trio discovered that some commonly used cell lines had been infected by viruses. “We think these sequences are likely caused by infection of the subject who donated their blood for human genetics research,” says Parrish. “Strangely, the viruses don’t usually infect B cells, which were used to make the cell lines we used, and so we don’t fully understand how those viruses infected the cells.”

The team intends to explore the possible functions of the sequences they have identified. Some studies have suggested associations between viral genetic sequences and a higher risk of certain diseases, Parrish notes. “If that’s true, how and why are they maintained in the human population?” he asks. “We want to see if they provide some benefit in addition to the cost.”

Reference: “Virus-derived variation in diverse human genomes” by Shohei Kojima, Anselmo Jiro Kamada and Nicholas F. Parrish, 26 April 2021, PLoS Genetics.

DOI: 10.1371/journal.pgen.1009324