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Fig. 3. Fate maps of the precursors of embryonic and extraembryonic endoderm and
the pattern of cell movement in the endoderm of the mid-streak stage
embryo. (A) The expression domain of Cer1 and
Sox17 in the endoderm of a mid-streak embryo (anterior to the left).
Cer1 expression overlaps in the distal, posterior-distal and
posterior-middle regions, which contribute to the gut endoderm, but is also
expressed in the endoderm immediately distal and lateral to the primitive
streak, and in the anterior proximal endoderm. Sox17 expression
overlaps in the posterior-middle region and is also expressed in the
extraembryonic visceral endoderm. Both genes are expressed in the anterior
visceral endoderm (asterisk, anterior proximal region). (B) Fate maps
of the endoderm of mid-streak-stage gastrula (left figures in B'
and B'') showing the localization of the precursors of embryonic
(gut) endoderm (B') and extraembryonic (yolk sac) endoderm (B'') of
the early-somite-stage embryo (right figures in B' and B'').
(C) Color coding of the seven sites in the mid-streak-stage embryo for
testing endodermal cell fates (see Fig.
1A). (D-G') The trajectories of the progenitors of the yolk
sac endoderm (D-E') and embryonic endoderm (F-G') during development from the
mid-streak to the mid- to late-streak stage (D,F) and then to the
early-head-fold stage (E,E',G,G'), showing the distribution of cells arising
from (E,G) anterior and distal sites and (E',G') posterior sites separately.
Cells originated from each of the seven sites are color-coded. In D and F, the
origin of the arrow shows the location of the cells at the mid-streak stage
and the head of the arrow marks the predicted position of these cells at the
mid- to late-streak stage, based on the cell-fate data. Double-headed arrows
indicate the expansion of the distal and posterior-distal endoderm. Red line
in the posterior region of the embryo (B,C) marks the primitive streak.
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