As part of a quality control procedure to safeguard the developing fetus, researchers who examined gene activity data from the early stages of the human embryo discovered an overlooked type of cell that self-destructs within days of formation. The discoveries give experiences on what occurs at the absolute first phases of life after preparation, which might later on help at any point further develop IVF or regenerative medication medicines.
Our early development in the womb may be quite different from what we have always assumed, according to a new study that was published on June 20, 2023, in PLoS Biology by a global team of scientists, including researchers from the University of Bath.
Although the adult human body is comprised of trillions of cells, we all began as a single cell, the fertilized egg. This partitions to become two cells, which thusly separate to become four, which then become eight, etc. The cells then begin to specialize in their function at some point. Some will be shunted off to become the placenta, while others will become the embryo, analogous to trains sent to various end stations.
“If a cell is harmed by jumping genes—or any other type of error, such as having too few or too many chromosomes—the embryo is better off removing these cells and not allowing them to become part of the developing baby.”
Co-lead author Professor Laurence Hurst,
Self-destructive embryonic cell The researchers looked at data that had been published on the gene activity of each individual cell from 5-day-old embryos. They found that about a quarter of the cells didn’t fit the description of any of the known cell types (pre-embryo, pre-placenta, etc.).
They continued their investigation and discovered that these cells contained “jumping genes,” also known as “young transposable elements.” These are errant DNA components that are capable of self-copying and re-insertion into our DNA, frequently causing damage.
The presence of cells containing proteins derived from the jumping genes was confirmed through the staining of embryos by project collaborators in Spain.
The team discovered that both their ancestors have DNA damage and go through a process of programmed cell death when they look back a little bit further in time.
Mechanisms for quality control The researchers propose this procedure to resemble a type of quality control: the selection of the best cells from among them.
“Humans, like all organisms, fight a never-ending game of cat and mouse with these harmful jumping genes,” stated Dr. Zsuzsanna Izsvák, co-senior author and expert on mobile DNA.
“While we attempt to suppress these jumping genes in any way we can, they are active in some cells very early in development, probably because we cannot establish our genetic defenses quickly enough.”
“If a cell is damaged by the jumping genes—or any other kind of error such as having too few or too many chromosomes—then the embryo is better off removing these cells and not allowing them to become part of the developing baby,” co-lead author Professor Laurence Hurst, from the Milner Centre for Evolution at the University of Bath, stated.
We are accustomed to the idea that one organism will prevail over another through natural selection. Similarly, what we observe in embryos resembles survival of the fittest, but this time between cells that are nearly identical. It appears as though we have discovered a novel weapon against these harmful genetic components.”
In contrast, the single-cell data demonstrated that the key cells that will become the embryo—the inner cell mass, or ICM—do not contain jumping genes but rather express a virus-like gene known as human endogenous virus H. This helps suppress the young jumping genes in the inner cell mass, which fits with an emerging pattern that we use our old genetic enemies to fight our new ones.
That’s what the creators propose on the off chance that the quality control process is too delicate and the undeveloped organism all in all might bite the dust. This could be why some mutations in our system for detecting damage in early embryos are linked to infertility as well.
More information: Manvendra Singh et al, A new human embryonic cell type associated with activity of young transposable elements allows definition of the inner cell mass, PLOS Biology (2023). DOI: 10.1371/journal.pbio.3002162
