Samenvatting

Hox genes are important genes patterning and giving identity to all tissues along the Anteroposterior axis of the developing embryo. Hox genes are positively regulated by the Caudal related homeobox genes Cdx. Cdx is important in axial extension and patterning certain tissues. To find out if Cdx and Hox cooperate in the developing embryo and if Hox is involved in axial extension, Cdx4-/-;HoxA; compound mutant mouse embryos are generated and analyzed. E10.5 Cdx4-/-;HoxA;embryos did not reveal an abnormal phenotype. Breeding heterozygous compound mutants was difficult because passing the HoxA; allele occurred at low frequencies. This could be due to synergy between Cdx4 and the HoxA cluster. To find out if Hox defects resemble the defects of Cdx mutants in derivates of the allantois, HoxA-13-/- mutant embryo placental labyrinths are analyzed for morphological differences. HoxA-13-/- shows a mild morphological difference of the placental labyrinth at E14.5 compared to Wild-type litters and dies around E14.5. HoxA-13-/- defects arise later in the placental labyrinth than Cdx defects. HoxA-13 therefore plays no crucial role in formation of the placental labyrinth.