Embryo development arose from ancient viruses

Scientists at the Spanish National Cancer Research Center have found that certain viruses that infected the first multicellular organisms played an important role in the emergence of embryonic development. Research results published in the journal Science Advances.

It is known that the genetic material of endogenous retroviruses was integrated into the genomes of organisms, likely leading to the Cambrian explosion more than 500 million years ago, when there was a dramatic increase in biodiversity. Genetic sequences from ancient viruses make up at least 8-10 percent of the human genome, and until recently these remnants were considered junk DNA.

The new work showed that the endogenous retrovirus MERVL is involved in embryo development, especially at a certain stage of the transition from totipotency to pluripotency. The fragment embedded in the DNA is closely related to the operation of the URI gene, the removal of which blocks the formation of the embryo. If the URI does not work, then the cell remains in a state of totipotency, when it can give rise to any cell in the body. However, normal development requires a transition to pluripotency—the ability to transform only into cells of embryonic tissues.

During the totipotency phase, when there are only two cells in the oocyte, the expression of the viral MERVL-gag protein is at a high level. This protein binds to the URI and blocks its action. However, the level of the viral MERVL-gag protein gradually decreases and URI promotes the emergence of pluripotency. Both genetic factors are necessary for the transition to be smooth and stable.

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