Biomedical Engineering Reference
In-Depth Information
Fig. 1.1
Schematic representation of the specification of germ cells in the mouse embryo.
Primordial germ cells form in the embryo between 5.0 and 6.25 dpc. In the early embryo (
upper
panel
), the expression of Wnt3 makes the cells of the epiblast (
Epi
) responsive to BMP4 signals
(blue = BMP4 responsiveness) emanating from the extraembryonic ectoderm (
ExE
) (
large arrows
).
Inhibitory signals from the distal visceral endoderm (
DVE
) and later the anterior visceral endoderm
(
AV E
) (
yellow
) indicated by
small arrows
restrict BMP4 signals from posteriorizing cells of the
epiblast. Consequently, only cells at the posterior end of the epiblast receive sufficient BMP4 signal-
ing to begin to express Prdm1 and Prdm14 and to form primordial germ cells (
red circles
). The
circled area is shown in detail in the
lower panel
with the model of PGC specification. Ectoplacental
cone (
EC
). Anterior posterior axis (
A
↔
P
) is indicated by the
arrows
above the embryo on the left
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