Inhibition of Dab2 expression with antisense oligodeoxynucleotides in mouse embryos

Background: Dab2, 1 of the 2 mammalian orthologs of the Disabled protein in Drosophila, is a mitogen-responsive phosphoprotein and a cytoplasmic adaptor involved in several signal transduction pathways. Deficiency in Dab2 affects endodermal cell positioning and is embryonically lethal. Aims and Results: In the present study, the Dab2 expression pattern in mouse embryos from embryonic day (E)7.5 to E9.5 was first determined by specific immunohistochemical staining. Dab2 protein was expressed exclusively in the extraembryonic endoderm at E7.5 and was detected within the cranial mesenchyme, heart and foregut epithelium at E8.5. By E9.5, the protein was also localized in the roof plate of the hindbrain neural tube and within the branchial arch mesenchyme and epithelium. Next, to help define the role of Dab2 protein in early embryonic development, antisense oligodeoxynucleotides (ODNs) were microinjected into mouse embryos to inhibit Dab2 expression. The protein expression within the neural tube and cranial mesenchyme was greatly reduced following microinjection at E8.5 and culturing embryos intact with a whole-embryo culture system for 8 h in vitro. Moreover, 26.7% of the injected embryos exhibited a twisted neural tube or an unturned body axis. Twenty-four hours following microinjection of antisense ODNs, 70% of the injected embryos showed structural abnormalities mainly affecting the body axis, otic placode, forelimb buds, branchial arches and neural tube. Excessive cell death was detected histologically in the ventral part of the neural tube, although the expression of Dab2 protein had resumed by this stage (24 h following microinjection). Conclusion: We conclude that Dab2 plays an important role in mouse embryonic development between E8.5 and E9.5, as a reduction in Dab2 expression during this period was found to disturb normal development.