2011 (SBTE) 25th Annual Meeting Proceedings - International ...

R.C. Cheb
hebel.
el. 2011. Use of Applied Reproductive Technologies (FTAI, FTET) to Improve the Reproductive Efficiency in
Dairy Cattle. Acta Scientiae Veterinariae. 39(Suppl 1): s203 - s221.
bryonic disc, but it is dislocated about one third of its
diameter anteriorly as compared with the epiblast of
the embryonic disc (Figure 6; [13,46]). It is likely
that this dense hypoblast region emits signals to the
epiblast which suppress mesoderm-formation in the
anterior epiblast regions [13]. In this sense, the hypoblast
may carry the blue-print for the specification of
the epiblast.
During Days 11 to 12, the embryonic disc
develops into an oval shape, and a crescent-shaped
accumulation of cells are found in the posterior region
of the disc [43]. This crescent includes mesodermal
progenitors which express the mesodermal markers,
T (BRACHYURY) and GOOSECOID [3,45], and
apparently ingression of BRACHYURY-expressing
extra-embryonic mesoderm is initiated from this
crescent even before the “true” gastrulation starts with
the appearance of the primitive streak (see later; [45]).
A porcine embryo displaying BRACHYURY expression
in the posterior epiblast is displayed in Figure 6.
With the development of the embryonic disc,
a very peculiar pattern of OCT4 and NANOG expression
develops in the porcine epiblast: The majority of
epiblast cells express OCT4, but small groups or
islands of cells are OCT4 negative [46]. The latter
cells, on the other hand, express NANOG resulting in
a mutually exclusive expression pattern (Figure 7).
Subsequently, NANOG expression is lost in almost
the entire epiblast, except for a few cell in the most
posterior region of the embryonic disc, in which OCT4
is also expressed [46]. The latter cells are believed to
be the primordial germ cells (PGCs).
N
Figure 5. Confocal laser scanning micrographs of Day 9-10 hatched porcine blastocyst displaying OCT4 and NANOG expression in the
epiblast.
Figure 6. Confocal laser scanning micrographs of Day 10-11 porcine blastocyst displaying expression of T (BRACHYURY) in the posterior
portion of the epiblast and of FOXA2 in the hypoblast. The open arrowheads in mark the periphery of the elongated embryonic disc. The
asterisks mark the hypoblast area with higher cell density, which is about one third dislocated anteriorly as compared with the embryonic disc.
A: Anterior; P: Posterior. Modified from Wolf et al. (2011b)[45].
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