Injection of Antisense RNA specific for E-cadherin demonstrates that E-cadherin facilitates compaction, the first differentiative step of the mammalian embryo.

We have investigated the effect of antisense E-cadherin RNA in the preimplantation mouse embryo. Antisense RNA was injected into each cell of two-cell embryos that were cultured for 2 days until the normal time of compaction and scored for abnormalities. Embryos injected with the antisense RNA showed delayed compaction compared to the embryos injected with control, or sense, RNA. Delayed cleavage was not the cause because nuclear staining with Hoechst dye 33258 showed about the same number of nuclei in both uncompacted embryos injected with antisense RNA compared with compacted embryos injected with sense RNA at the same hours post human chorionic gonadotropin (hCG). Immunofluorescence with a monoclonal antibody to E-cadherin was markedly diminished in embryos injected with antisense RNA compared with control, injected embryos, suggesting that the observed delayed compaction is due to the inhibition of E-cadherin gene expression by antisense RNA. Embryos injected with antisense RNA eventually compacted and then expressed E-cadherin, but at lower apparent levels than controls. Injection of a single blastomere at the two-cell stage created half-embryo abnormalities.