Usp22−/− placental failure is not due to aberrant chorioallantoic fusion or cardiovascular defects. (A) Bright-field images (left) of wild-type and Usp22 mutant embryos and placentas at E8.5-E9. Histological analysis (right) of E9 wild-type and Usp22 placentas stained with VCAM1. Black arrowheads depict points of chorioallantoic fusion. Scale bars: 1 mm in bright-field images; 100 μm in histological analysis. (B) Histological analysis of E9 wild-type and Usp22 placentas stained with H&E, TPBPA, proliferin, KI67 and TUNEL assay. Similar levels of proliferation and apoptosis were observed in both wild-type (red arrows) and Usp22 mutant placentas (red arrowheads). Asterisks depict clusters of enucleated fetal red blood cells. Scale bars: 100μm. (C) Bright-field images of wild-type and Usp22 mutant embryos at E9-E10. Scale bars: 1 mm. (D) Immunofluorescence for phalloidin (PHA) and PECAM1 markers on wild-type and Usp22 mutant embryonic heart cryo sections (8 μm thick) at E11. Scale bar 200 μm. al, allantois; alf, allantoic fusion; br, brain; cp, chorionic plate; fb, forebrain; h, heart; hb, hindbrain; jz, junctional zone; l, labyrinth; la, left atrium; lv, left ventricle; nf, neural fold; ra, right atrium; rv, right ventricle; s, somites; sp, spongiotrophoblasts; tgc, trophoblast giant cells; uc, umbilical cord.