First published online May 23, 2008
Development 135, 1201e (2008)
© The Company of Biologists Limited
Secrets of the placental labyrinth unlocked
The inner compartment of the rodent placenta - the labyrinth - contains the
villi where nutrients pass from the maternal blood into the foetal blood.
These villi are covered with a layer of mononuclear sinusoidal trophoblast
giant cells (S-TGCs) and two layers of multinucleated syncytiotrophoblast
cells (SynT-I and SynT-II). Now, on
p. 2083, Simmons and
colleagues solve the long-standing mystery of the developmental origins of
this trilaminar structure. By examining gene expression in the mid-gestation
mouse labyrinth, the researchers identify specific markers for each layer.
They show that these markers are expressed in distinct layers in the chorion
(the embryo's outer membrane) before villous formation begins and that the
induction of the S-TGC and SynT-I precursors does not require the presence of
SynT-II precursors, the first of the precursors to appear. Thus, they
conclude, the three differentiated trophoblast cell types in the rodent
labyrinth arise from distinct, autonomous precursors in the chorion that are
patterned before its morphogenesis begins.

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Related articles in Development:
- Early patterning of the chorion leads to the trilaminar trophoblast cell structure in the placental labyrinth
- David G. Simmons, David R. C. Natale, Valerie Begay, Martha Hughes, Achim Leutz, and James C. Cross
Development 2008 135: 2083-2091.
[Abstract]
[Full Text]