Our Genes Are Not Our Own!

We've all heard the fun fact that we have more bacterial cells (by pure numbers) than human cells in our bodies. It makes us consider the symbiosis, between ourselves and the natural world, that is salient and essential to human existence. However, no one ever talks about the viruses that have embedded themselves into our genomes and our evolutionary pathways, and played an incredibly important role in the development of the human species as we know it today. Viral DNA makes up approximately 8% of the human genome, with over 100,000 pieces of this foreign DNA lodged into our own DNA. Most of this genetic material comes from retroviruses, which work by inserting their DNA into their host's DNA and then using the cellular machinery to further proliferate. If these retroviruses infect gametes (sperm or egg) their genetic information can potentially be passed on to the next generation, thus cementing them as a new addition to the human genome.

There is still much research to be done on the role of this viral genes in the human context. A virologist at Oxford University named Dr. Katzourakis says "It's not an either or - are these things good or bad? It's a lot more complicated than that." There has been evidence linking this residual retroviral genetic information to development of cancer cells in vitro. However, there are also some viral genes that produce proteins that are essential to reproductive processes. For example, viral genes are responsible for coding proteins called syncytins that play a crucial role in the assembly of the placenta. There is another very important protein called Hemo that is produced by the developing fetus and placenta. It has been hypothesized that Hemo acts as a signal from the developing fetus to the mother, suppressing the mother's immune system so that it does not target the fetus.

Ultimately, we are carrying viruses with us, in our genes and in our evolution. While it still unclear precisely what role they play, we know that there must be some reason this viral DNA has been allowed to persist in our genomes over all these hundreds of thousands of years of natural selection and evolution. This is a growing field of research and it will be exciting to see where it goes within our lifetimes.

-Emma Mathers :)

https://www.nytimes.com/2017/10/04/science/ancient-viruses-dna-genome.html