Fig. 5. Altered branching of allantoic vessels, and similar endothelial and trophoblast marker expression in Cdx mutant and control embryos. (A,B) Morphometric analysis of embryonic placental vessels reveals more vessels with smaller average diameter in wild-type placentas than in mutant placentas. (C,D) Immunohistochemical staining for Pecam marks endothelial cells (in brown) in the developing labyrinth. At E9.5, wild-type embryonic vessels have penetrated the chorionic ectoderm and branched extensively (arrowheads in C) while Cdx2^+/-/Cdx4^-/0 mutant endothelial cells can only be detected on one side of the chorionic plate (arrowhead in D). (E,F) A well-established labyrinth is present at E10.5 in wild types (la in E), whereas in Cdx2^+/-/Cdx4^-/0 mutant placentas, embryonic vessels are present only in the allantoic mesoderm (F). (G-N) Expression of trophoblast markers at E9.5 in Cdx2^+/-/Cdx4^-/0 compound mutant placentas and controls. (G,H) In situ hybridization of Cdx2 shows expression in the ectoplacental cone and spongiotrophoblast. Expression is absent in the labyrinthine trophoblasts in both mutants and controls. (I,J) In situ hybridization of Mash2 shows expression in the ectoplacental cone, spongiotrophoblasts and labyrinthine trophoblasts. The morphology of the labyrinthine trophoblast differs between mutant and control, owing to the absence of an extensively intermingled labyrinth in the compound mutant. (K,L) In situ hybridization of Hand1 (eHAND) shows expression in the spongiotrophoblast and labyrinthine trophoblasts in wild-type and compound mutant placentas. (M,N) The ectoplacental cone and spongiotrophoblast marker Tpbp is expressed in wild-type and Cdx2^+/-/Cdx4^-/0 compound mutant placentas. epc, ectoplacental cone; sp, spongiotrophoblasts; tr, labyrinthine trophoblasts; cp, chorionic plate; la, placental labyrinth; mbs, maternal blood sinus; fbv, fetal blood vessel; Cdx mutant, Cdx2^+/-/Cdx4^-/0. Scale bars: 100 µm C-F; 500 µm in G-N.