Scientists discover new embryonic cell type that self-destructs to
protect the developing embryo

Date:
June 20, 2023
Source:
University of Bath
Summary:
Scientists have uncovered a new quality control system that removes
damaged cells from early developing embryos.


Facebook Twitter Pinterest LinkedIN Email

==========================================================================
FULL STORY ========================================================================== Scientists studying gene activity data of the early human embryo have discovered an overlooked type of cell which self-destructs within
days of forming, as part of a quality control process to protect the
developing foetus.

The findings give insights on what happens at the very first stages of
life after fertilisation which could in the future help improve IVF or regenerative medicine treatments.

A new study published on 20 June 2023 in PLoS Biology by an international
team of scientists including researchers at the University of Bath,
finds that our earliest development in the womb may be rather different
to what we have always assumed.

While human adults are made up of trillions of cells, we all started
out as just one cell, the fertilized egg. This divides to become 2 cells
which in turn divide to become four, which become 8 and so on. At some
point the cells then start to specialise in their function. Like trains
sent to different end stations, some will be shunted off to become the
placenta while others will become the embryo.

Self-destructing embryonic cell The team of scientists analysed previously published data on gene activity of each individual cell from 5-day old
embryos and discovered around a quarter of the cells didn't fit the
profile of any of the known cell types (pre-embryo, pre-placenta etc).

Investigating further, they discovered that these cells contained
so-called "Young transposable elements" or "jumping genes." These are
rogue elements of DNA that can copy themselves and insert themselves
back into our DNA, often causing damage in the process.

Staining of embryos by project collaborators in Spain confirmed the
existence of the cells with proteins derived from the jumping genes.

Looking a little further forward in time, the team found their descendants
both have DNA damage and undergo a process of programmed cell death.

Quality control mechanism This process, the researchers suggest, looks
like a form of quality control: selection between cells in favour of
the good ones.

Dr Zsuzsanna Izsva?k, co-senior author from the Max Delbru"ck Center
and an expert on mobile DNA, said: "Humans, like all organisms, fight
a never-ending game of cat and mouse with these harmful jumping genes.

"While we try and suppress these jumping genes by any means possible,
very early in development they are active in some cells, probably because
we cannot get our genetic defences in place fast enough." Co-lead author Professor Laurence Hurst, from the Milner Centre for Evolution at the University of Bath, said: "If a cell is damaged by the jumping genes - -
or any other sort 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.

"We are used to the idea of natural selection favouring one organism over another. What we are seeing within embryos also looks like survival of
the fittest but this time between almost identical cells. It looks like
we've uncovered a novel part of our arsenal against these harmful genetic components." Using old genetic enemies to fight new ones Conversely, the single-cell data showed that the key cells that will become the embryo
(the inner cell mass or ICM) don't contain jumping genes but instead
express a virus-like gene called human endogenous virus H. This helps
suppress the young jumping genes in the inner cell mass, fitting with
an emerging pattern that we use our old genetic enemies to fight our
new ones.

The authors suggest that if the quality control process is too sensitive,
the embryo as a whole may die. This might explain why some mutations
in our system to detect damage in early embryos are also associated
with infertility.

* RELATED_TOPICS
o Health_&_Medicine
# Stem_Cells # Genes # Brain_Tumor # Lymphoma
o Plants_&_Animals
# Developmental_Biology # Genetics # Biology #
Biotechnology
* RELATED_TERMS
o Marsupial o Mammalian_embryogenesis o BRCA1 o Prostate_cancer
o Stem_cell o Natural_killer_cell o White_blood_cell o
Endocrine_system

========================================================================== Story Source: Materials provided by University_of_Bath. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Manvendra Singh, Aleksandra M. Kondrashkina, Thomas J. Widmann,
Jose L.

Cortes, Vikas Bansal, Jichang Wang, Christine Ro"mer, Marta
Garcia- Canadas, Jose L. Garcia-Perez, Laurence D. Hurst,
Zsuzsanna Izsva'k. A new human embryonic cell type associated
with activity of young transposable elements allows definition
of the inner cell mass. PLOS Biology, 2023; 21 (6): e3002162 DOI:
10.1371/journal.pbio.3002162 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230620174450.htm

--- up 1 year, 16 weeks, 1 day, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)