Scientific Finding: 100 Million Year Old Virus Found In Blood Of Pr...

Yes you read that right! 100 million year old virus .. living inside our genome. This virus has been around way before us humans on planet Earth, way back to the age of the Dinosaurs, and to make things weirder, it is part of our genes.

In fact, a recent study conducted by Heidmann, O., et al., was able to find traces of a human endogenous retrovirus called HEMO (human endogenous MER34 [medium-reiteration-frequency-family-34] ORF), essentially identified in fetuses, stem cells, tumors, as well as blood of pregnant women.

What is a human endogenous retrovirus (HERV)?

First, a retrovirus is basically a virus, that just acts Backwards. While a virus' normal transcription occurs from DNA to RNA, yet retroviruses utilize their reverse transcriptase (a process first identified in 1970) enzyme to produce DNA from RNA, so it's the other way around. Hence the term retro.
The way they generate their protein is then formulated as RNA → DNA → RNA → polypeptide.

And a well-known example of a retrovirus is actually the HIV. You can basically see its transcription process in the illustration below

You can also check out this cool animation out about Retrovirus reverse transcription

Now, human endogenous retroviruses are hence those retroviruses, that are present in the human genome.
Surprisingly, those viruses actually compromise up to 8% of the human genome.
While they no longer act as viruses, and constitute a portion of our genome (or at times partial sequences of those viruses), they essentially get passed throughout generations and to our children.
And for many years it was unclear what role they play, if any, yet there were some findings to a functionality some HERVs contribute in the human placenta.

First, they promote fusion of cells in placentas, which is important for the anatomy of the syncytiotrophoblast (hence the name syncytins). Second, they protect the embryo from the mother’s immunity (fetomaternal immunotolerance). (Reference 2 below)

Why is this important?

HEMO was identified in the recent study in the process of being produced from the embryo, and then into the pregnant mother's blood. Its expression pattern is high in placenta, cancer and stem cells, where the relevant protein can be easily detected.
While the role that this virus plays is still unclear, yet it is one of the recently identified HERVs that actually sheds extracellularly (similarly though to Ebola), and could potentially carry a big role in stem cells due to its shedding pattern occurring extensively at embryo level.
Add to that, being preserved for over 100 million years is a big evolutionary indicator for a potential key role it plays.

This strong purifying selection, combined with the expression pattern, suggests an important functional role for HEMO in stem cells and early life events in primates

More importantly, several hypotheses had been presented since 1990 and which link, for instance, breast cancer back to "in utero" origins, as well as the count of stem cells with cardiovascular disease. And hence, HEMO could be a key factor in figuring out missing links in womb-to-adulthood diseases.

HEMO’s expression pattern suggests potential roles for manipulation of stem cells and early life events, which could have very important effects on adult diseases

On the other hand, several theories are at play now. One is that HEMO production could be a communication stream from embryo to mother to protect the child from the mother's immune system, a role that, as highlighted above, is played by other HERVs at the moment.
At the other end of the spectrum, the other speculation is that this is simply the virus playing its role in survival, in simply utilizing the host for replication and continuity and keeping stem cells available the longer possible, stem cells being the best environment for it to replicate. While this is definitely true, would this be its only role?

Future work

While identifying this HERV was a key scientific finding, yet its implications could be immense in the future, as further findings emerge into the pattern of its work, as well as the potential for utilizing this info we have at the moment, along with future findings, to come up with potential advances in the fields of immuno therapy as well as oncology.

...the identified protein could constitute a "stemness marker" of the normal cell and a possible target for immunotherapeutic approaches in tumors.

Thank you for reading through!

@mcfarhat

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Scientific Finding: 100 Million Year Old Virus Found In Blood Of Pregnant Women

What is a human endogenous retrovirus (HERV)?

Why is this important?

Future work

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