Ancient viruses are embedded everywhere in the human genome. Estimates range, but it's thought that about eight percent of the human genome could be made up of these ancient retroviruses, which are also known as transposable elements. It's thought that the action of many of of these sequences has stopped, though some research has shown they may still affect human biology. And now, scientists have shown that transposable elements also play crucial roles in the development of human embryos. The findings have been reported in Cell.
There are transposable elements in the human genome that are active in the earliest stages of human embryo development, when there is significant molecular flexibility and plasticity. But the regulation of that plasticity is unclear.
In this study, the researchers developed a new method to analyze the activity of transposable elements. They used multiple mammalian species including mouse, non-human primates and rabbit to assemble an atlas of gene transcription during early developmental stages.
This showed that there are ancient viral elements that were thought to be inactive at work in mammalian embryos. There are unique sets of elements expressed by various species. Transposable elements do not only appear to be active in some cases, but that action is also seen in different species. These elements can orchestrate the expression of thousands of genes in one cell at the same time. This process can also be manipulated.
"This approach offers a novel way to influence cell fate, such as directing stem cell differentiation, which typically requires the simultaneous manipulation of hundreds of genes," explained co-first study author Dr. Marlies Oomen of Helmholtz Munich. "Our work highlights the importance of understanding the regulatory principles behind transposable elements."
The cells of early embryos can create any cell type in the body, and the activation of transposable elements is a critical part of early embryos, noted corresponding study author Professor Maria-Elena Torres-Padilla of Helmholtz Munich.
"By understanding how these cells regulate ancient viral elements, we gain crucial insights into the mechanisms of cellular plasticity. This study sets the stage for future research into specific regulatory elements, with broad implications for health, disease, and how manipulating these elements could impact cellular processes."
This research has opened up a new understanding of transposable element activity during development, as well as illuminating a new process that could be studied and used in various ways.
Sources: Helmholtz Association of German Research Centres, Cell
