Exogastrula formation in Xenopus laevis embryos depleted with maternal XmN-cadherin mRNA by antisense S-oligo DNA.

Xenopus XmN-cadherin gene appears to have dual functions, since its mRNA is maternally provided in unfertilized eggs, once disappears almost completely during gastrula stage, then accumulates again specifically in neural tissues in later stage embryos. In the present experiment, we first followed the change in XmN-cadherin mRNA level during oogenesis by RT-PCR and showed that this mRNA exists from the earliest stage of oogenesis and at least one third of it is inherited as a maternal mRNA. We then carried out an experiment to deplete the maternal XmN-cadherin mRNA by injecting its antisense S-oligo DNA into full grown oocytes. When mRNA-depleted oocytes were matured in vitro and fertilized eggs obtained therefrom by host transfer technique were allowed to develop, embryos cleaved normally and developed until blastula stage. Such XmN-cadherin mRNA-depleted blastulae initiated invagination, but further involution did not take place, and exogastrulae were formed. These results suggest that the main function of maternally provided XmN-cadherin mRNA is to support cell movement or rearrangement required later during gastrulation, rather than to maintain adhesion of blastomeres during cleavage and blastula formation.