A team from the Institute of Molecular Genetics of the Czech Academy of Sciences (IMG) has succeeded in describing the loss of an antiviral gene called tetherin in several avian species, including the wild turkey, which is widely bred on farms. The finding is surprising because it is the first description of the evolutionary loss of this important antiviral mechanism in vertebrates.
The antiviral genes of living organisms encode proteins whose main function is to prevent viral infection. They block the multiplication of the virus at various levels. During evolution, these genes change and sometimes new ones are formed, causing evolutionary pressure from ever-changing viruses. There are also recorded cases when a particular animal specie quite surprisingly loses the antiviral genes.
A team from the IMG led by Daniel Elleder has previously described the antiviral gene tetherin in birds, including the domestic chicken. “The work fits into our long-term research on avian gene sequences,” says Daniel Elleder.
Tetherin is specific for its antiviral mechanism, which is found in the membrane of the cell producing the viral particles. It bonds these to the membrane during their production and prevents them from infecting other, previously unaffected cells. Since tetherin only needs to capture the viral membrane to function, it is able to block a wide range of so-called enveloped viruses.
Screening of avian genomes revealed several independent evolutionary losses of tetherin in multiple species. Turkey cells have been experimentally shown to be more sensitive to avian retroviruses as a result of this loss.
“Although almost everything is sequenced today, including viruses and their hosts, it turns out that some avian genes have a particular type of difficult sequences. These are almost insurmountable even for today’s advanced sequencing technologies. We try to classify avian genes into two categories: genes with almost illegible sequence but which actually exist, these we call hidden genes. Then the genes that have actually faded away during evolution, or lost genes. Tetherin therefore belongs to the second category, and subsequent research should find the reasons why the loss occurred,” says Daniel Elleder.
The study was published in the Journal of Virology and was also co-authored by researchers from the University of Tubingen in Germany.
Krchlíková V, Lotke R, Haußmann I, Reinišová M, Kučerová D, Pecnová Ľ, Ungrová L, Hejnar J, Sauter D, Elleder D: Independent loss events of a functional gene in galliform birds. J Virol 2023, e0080323. [pubmed] [doi]