This virus has been lurking in the human genome for thousands of years, and it is the first to prove that it affects the brain...

Since our ancestors were infected with retroviruses millions of years ago, a type of virus called "human endogenous retrovirus (HERV)" has been lurking in our genome.

What impact these virus fragments will have on humans and what their relationship with human diseases have attracted the attention of scientists for a long time, but in the past, due to limited technical means, people did not know.

Recently, scientists have used advanced technology to successfully prove for the first time that a group of HERV will have a negative impact on human brain development after activation.

The researchers pointed out that neurodegenerative diseases are usually related to the activation of some HERV, so it is an important discovery that HERV activation can interfere with neuron development and function.

Using CRISPR gene editing technology, researchers activated a specific set of HERVs in human embryonic stem cells, namely HERV-K (HML-2), and allowed the stem cells to differentiate to produce neurons.

▲The neuron (right) after activating HERV loses its normal function, and its shape is different from the normal neuron (left) (Image source: Reference [2]; Credit: Helmholtz Zentrum München / Michelle Vincendeau)

The experiment also revealed that the interference of this group of HERV on the development of cortical neurons is only for specific cell types, for example, dopaminergic neurons are not affected.

In addition, experimental results on cultured forebrain organoids also showed that the transcription of the HERV-K (HML-2) sequence altered the formation of the cortical layer.

▲Schematic diagram of the mechanism of the study: activation of HERV-K (HML-2) leads to excessive activation of genes such as NTRK3, impairing the differentiation of cerebral cortex neurons and cortical development (picture source: reference [1])

This study also suggests that during healthy brain development, epigenetic mechanisms keep HERV under control.

Reference materials:

[1] Padmanabhan Nair, V.