They hope to use this protein, syncytin-1, to eventually develop a blood test to identify pregnancies at risk of miscarriage or pre-eclampsia.
'Until now we didn't know this protein was expressed so early in the embryo,' said Professor Harry Moore of the University of Sheffield, lead author of the study. 'Interestingly, the syncytin-1 protein was mainly secreted in the cells of the embryo, called polar trophoblast cells, which will first stick to the cells of the womb.'
The researchers found that the cells secreting syncytin-1 also secrete nanovesicles called exosomes. Professor Moore explained: 'These exosomes may communicate with cells in other areas of the mother to prepare her for pregnancy. If this doesn't happen properly at the earliest stages it may cause problems throughout pregnancy.'
They found that the syncytin-1 gene is expressed in the embryo before it implants and might therefore play a role in implantation. The syncytin-1 protein might also play a role in pregnancy complications such as recurrent miscarriage, fetal growth restriction and pre-eclampsia, according to the study authors.
Professor Janet Rossant, a developmental biologist at the University of Toronto in Ontario, Canada, who was not involved in the study, told New Scientist that the study does not prove the role of syncytin-1 in implantation. But she added that the syncytin-1 gene has been known for some time to be important for the development of the placenta and is a potential target for conditions such as pre-eclampsia.
The study, published in Human Reproduction, acknowledges the need for further functional studies of the role of syncytin-1 in implantation and early placental development. 'Eventually we may be able to develop blood tests based on our results to identify pregnancies that might be at risk and also develop appropriate therapies,' added Professor Moore.
The syncytin-1 gene is thought to have arisen from an ancient virus. 'Amazingly, the syncytin-1 gene is the result of a viral infection of our primate ancestors 25 million years ago. The viral DNA got into our ancestors' genome and was passed on through heredity, and the gene involved in the fusion of the virus with cells for infection was co-opted and became syncytin-1. Without it, humans probably would not have evolved,' said Professor Moore.