FIG. 2.
Phenotype of the Erf-deficient mouse embryos. (A) Gross morphology of 9.5-dpc wild-type (a) and Erfdl1/dl1 (b) embryos and 10.5-dpc wild-type (c) and Erfdl1/dl1 (d) embryos. (B) Yolk sac morphology of a wild-type (a) and an Erfdl1/dl1 (b) embryo at 9.5 dpc. A highly organized vascular network is formed in wild-type yolk sacs, whereas in Erfdl1/dl1 embryos the yolk sacs are pale and exhibit only the primary capillary plexus without further reorganization. Whole-mount staining of wild-type (c) and Erfdl1/dl1 (d) yolk sacs with hematoxylin are also shown. Large collecting vessels are formed in both wild-type and Erfdl1/dl1 yolk sacs (arrowheads), but in Erfdl1/dl1 they are enlarged and do not form secondary branches (arrows) as in the wild-type littermates. (C) Hematoxylin- and eosin-stained paraffin sections from wild-type (a, c, c′, and e) and Erfdl1/dl1 (b, d, d′, and f) littermates. At 8.5 dpc the allantois is attached throughout the chorion layer in the wild-type placentas (panel a, arrowheads) but not in Erfdl1/dl1 placentas, where the ectoplacemmtal cone cavity is still open (panel b, asterisk). At 9.5 dpc allantoic blood vessels invade the chorion layer in wild-type placentas (arrowheads in panels c, c′), but in the Erfdl1/dl1 placentas the chorion retains a compact structure, the labyrinth is totally absent (d′), and the ectoplacental cone cavity is still present (panel d, asterisk). At 10.5 dpc in wild-type placentas, maternal and embryonic blood vessels (panel e, arrow and arrowhead, respectively) intermingle and come to close apposition. In contrast, Erfdl1/dl1 placentas appear degenerative, with extensive hemorrhagic sites (panel f, arrows). al, allantois; ch, chorion; dec, decidua; gc, giant cells; lb, labyrinth; sp, spongiotrophoblast; uc, umbilical cord. Yellow dotted lines indicate the boundaries of the placenta.