Fig. 3. Phenotype of LPP3-deficient embryos. (A,B) E9.5 wild-type embryo showing the vascularization of the yolk sac (A, arrows), and normal embryonic development at this stage (B); the embryo has turned and the allantois has contacted the chorion. In this individual the connection was lost because of the removal of the extra-embryonic membranes. (C,D) E9.5 homozygous null sibling of the embryo shown in (A,B). The extra-embryonic membranes appear thin, pale, with an anemic appearance and no indication of large blood vessel formation (C). The embryo was smaller and developmentally delayed. The most evident malformation is the abnormal development of the allantois (all). (E) A unique LPP3^-/- embryo (right) recovered at E10 showing an advanced developmental progression. Despite an almost normal appearance, the allantois (all) of this embryo formed a very compact mass of tissue. The differentiation of allantoic endothelial cells was demonstrated by the presence of the endothelial marker flk-1 (brown staining). A heterozygous sibling is shown on the left. (F) Semithin section through the allantois of an E9.5 mutant embryo showing blood vessels formation (arrows) and differentiation of hematopoietic cells (asterisk). Scale bars, 0.5 mm.

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