We have been evolving for millions of years now. From primate to modern man, we had quite a bit of journey. We have lost and also gained evolutionary characters on our path. But carrying a viral element in our genome after being infected by a virus millions of years ago is a question to ask.
Human endogenous retroviruses, or HERVs for short, is the segment of DNA which Humans have been carrying for millions of years from a retrovirus after our ancestors got infected by this. These viral elements are not of any danger since it lost its ability to replicate and infect over the course of evolution. They are an integral part of our genome. In fact HERVs are seen 5 times more in non-coding regions than in coding regions in humans. Researchers are now focusing on the correlation of HERVs and even on the onset or history of the disease. Yet we don’t understand whether HERVs are the cause or the consequence of such disease.
Even though we know about HERVs for a long time, we couldn’t understand it better due to lack of technology. Recently, German virologist Michelle Vincendeau and her colleagues through modern technology tried to unlock the mechanism of these HERVs, by doing so they demonstrate the negative effects of HERVs on human brain cell development.
The researchers activated a specific group of HERVs in human embryonic stem cells using CRISPR technology and generated nerve cells (that is neurons). These viral elements in turn activate specific genes, which includes classical developmental factors involved in brain development. Hence, the nerve cells produced in our cerebral cortex lost their function entirely. They produced a much shorter axon(the nerve branching) compared to that of a healthy neuron, impairing the brain activity. The activation of one specific gene in HERVs would result in impairs cortical neuron development and ultimately brain development.
This discovery put us one step ahead of disorders such as neurodegenerative diseases. Since Neurodegenerative diseases are often associated with the activation of several HERV groups, the negative impact of HERV activation on cortical neuron development is an essential finding. Environmental factors such as bacteria, virus and UV light can activate these HERVs, therefore playing their role in affecting cortical neuron development. Thus this knowledge enhances the clinical application of such onset. Switching off this viral element in patients is the new field open to the researchers now, hence trying to cure the patients suffering from the onset from this viral element. Has a next step, the group at Helmholtz Zentrum München will study the impact of HERV deactivation in neurons in the context of disease.
All said, the research findings provide important details that these epigenetic mechanisms keep viral elements under controlled healthy brain development. It should also be looked at that our evolution doesn’t keep stuff which are unwanted, we have been carrying these elements for millions of years now. Even Michelle Vincendeau suspects that these controlled viral elements play a functional role in normal brain development. Further research would provide more functional detail of this HERNs.