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A mechanism that quietly removes unfit cells before you’re born

 

Source: TH

 Context: Research on the early stages of human embryonic development and the role of specific cells known as the inner cell mass has gained importance recently.

  • The inner cell mass contains pluripotent cells, meaning they have the potential to differentiate into all the different cell types that make up the human body. These cells are of great interest to scientists as they are responsible for shaping the entire human body.
  • In a study conducted in 2016, researchers discovered a subset of non-committed cells within the inner cell mass. Unlike the majority of cells in the inner cell mass that go on to contribute to the developing embryo, these non-committed cells seem to die off early in the development process.
  • Further investigation revealed that the non-committed cells lack the expression of a gene called HERVH, which is critical for maintaining pluripotency in human embryonic stem cells.
  • Instead, these cells express transposons, also known as “jumping genes,” which can insert themselves into different parts of the genome, potentially causing DNA damage and leading to cell death.

 

HERVH, despite being a type of transposon itself, appears to protect the pluripotent cells from the harmful effects of other transposons. By the end of this early developmental stage, the cells that express HERVH survive and become the “good” cells that will form the embryo, while the non-committed cells that lack HERVH expression die through cell death.

The study refers to the early human embryo as a “selection arena,” where cells compete to survive based on their gene expression patterns.