Source: The post is based on the article “Discovered: A mechanism that quietly removes unfit cells before you’re born” published in The Hindu on 26th July 2023.
What is the News?
Scientists have found that cells that don’t express a particular gene are destroyed before an embryo starts to develop.
What are non committed cells?
In the early stages of the human embryo, before it has implanted in the mother’s womb, the cells arrange themselves in a particular way.
A blob of cells gathers towards one side of the embryo and the other cells arrange themselves around this blob. This blob is called the inner cell mass. It contains cells with the ability to make all the other types of cells in the human body – i.e. the cells in this blob are pluripotent.
Within the inner cell mass, researchers in 2016 had discovered a novel group of cells called non-committed cells.
These non-committed cells did not participate in the later stages of embryo development and appeared to be eliminated early on compared to the other inner cell mass cells, which contributed to forming the developing embryo.
Why do these non committed cells die so young?
A study has found that human embryonic stem cells express a gene called HERVH, a virus-like gene that’s important in maintaining pluripotency.
Most of the inner cell mass cells also express HERVH – but not the non-committed cells that eventually die.
The non committed cells actually express transposons also called “jumping genes”. These jumping genes are dangerous little pieces of DNA that can insert themselves into different regions of the genome, damaging it and leading to cell death. The DNA damage caused by the transposons leads to these cells dying out early
On the other hand, HERVH actually ends up protecting the cells from the damage inflicted by the jumping genes, kickstarting a protective mechanism that prevents the transposons from getting expressed in most cells.
But the non-committed cells that don’t express HERVH are killed off by the uncontrolled transposon activity.
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