Placenta is initiated first, as cells of a fertilized egg divide and specialize

Date:
September 24, 2020
Source:
The Francis Crick Institute
Summary:
The first stages of placental development take place days before the
embryo starts to form in human pregnancies. The finding highlights
the importance of healthy placental development in pregnancy,
and could lead to future improvements in fertility treatments such
as IVF, and a better understanding of placental-related diseases
in pregnancy.



FULL STORY ==========================================================================
The first stages of placental development take place days before the
embryo starts to form in human pregnancies. The finding highlights the importance of healthy placental development in pregnancy, and could lead
to future improvements in fertility treatments such as IVF, and a better understanding of placental-related diseases in pregnancy.


==========================================================================
In a study published in the journal Nature, researchers looked at
the biological pathways active in human embryos during their first few
days of development to understand how cells acquire different fates and functions within the early embryo.

They observed that shortly after fertilisation as cells start to divide,
some cells start to stick together. This triggers a cascade of molecular
events that initiate placental development. A subset of cells change
shape, or 'polarise', and this drives the change into a placental
progenitor cell -- the precursor to a specialised placenta cell --
that can be distinguished by differences in genes and proteins from
other cells in the embryo.

"This study highlights the critical importance of the placenta for
healthy human development," said Dr Kathy Niakan, group leader of the
Human Embryo and Stem Cell Laboratory at the Francis Crick Institute
and Professor of Reproductive Physiology at the University of Cambridge,
and senior author of the study.

Niakan added: "If the molecular mechanism we discovered for this first
cell decision in humans is not appropriately established, this will have significant negative consequences for the development of the embryo
and its ability to successfully implant in the womb." The team also
examined the same developmental pathways in mouse and cow embryos. They
found that while the mechanisms of later stages of development differ
between species, the placental progenitor is still the first cell to differentiate.

"We've shown that one of the earliest cell decisions during development
is widespread in mammals, and this will help form the basis of future developmental research. Next we must further interrogate these pathways
to identify biomarkers and facilitate healthy placental development in
people, and also cows or other domestic animals," said Claudia Gerri,
lead author of the study and postdoctoral training fellow in the Human
Embryo and Stem Cell Laboratory at the Francis Crick Institute.

During IVF, one of the most significant predictors of an embryo implanting
in the womb is the appearance of placental progenitor cells under the microscope.

If researchers could identify better markers of placental health or find
ways to improve it, this could make a difference for people struggling
to conceive.

"Understanding the process of early human development in the womb could
provide us with insights that may lead to improvements in IVF success
rates in the future. It could also allow us to understand early placental dysfunctions that can pose a risk to human health later in pregnancy,"
said Niakan.


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


========================================================================== Journal Reference:
1. Claudia Gerri, Afshan McCarthy, Gregorio Alanis-Lobato, Andrej
Demtschenko, Alexandre Bruneau, Sophie Loubersac, Norah
M. E. Fogarty, Daniel Hampshire, Kay Elder, Phil Snell, Leila
Christie, Laurent David, Hilde Van de Velde, Ali A. Fouladi-Nashta,
Kathy K. Niakan. Initiation of a conserved trophectoderm program
in human, cow and mouse embryos.

Nature, 2020; DOI: 10.1038/s41586-020-2759-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200924114141.htm

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