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Fig. 4. Defective placental labyrinth development in
Cdx2+/-/Cdx4-/0 compound mutant embryos.
(A-H) Hematoxylin and Eosin-stained sections of placentas from wild-type
(A,C,E,G; C is an enlargement of A; G is an enlargement of E) and
Cdx2+/-/Cdx4-/0 compound mutant littermates
(B,D,F,H; D is an enlargement of B; H is an enlargement of F). (A-D) At
E9.5, only some Cdx2+/-/Cdx4-/0 allantoic
vessels have started to penetrate the chorionic trophoblast layer without
overt signs of branching morphogenesis, whereas wild-type placentas show
branched vessels deeply penetrating the chorionic ectoderm. These vessels
intermingle with maternal blood sinuses, from which they are separated in many
places by only a thin haemotrichorial membrane (triangle in C) in the crucial
part of the labyrinth (la in A) that is concerned with the vital interchanges
between maternal and fetal circulation. (E-H) At E10.5, the defect
becomes more severe, as revealed by the complete separation of maternal and
embryonic blood flows (mrb and frb in H) and the virtual absence of the
labyrinth (F, compare with E). Scale bars: 100 µm. cp, chorionic plate;
mrb, maternal red blood cell; frb, fetal red blood cell; la, labyrinthine
trophoblast.
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