EXPERIMENTAL MANIPULATIONS OF COMPACTION AND THEIR EFFECTS ON THE PHOSPHORYLATION OF UVOMORULIN

Compaction of the eight-cell stage mouse embryo is a critical event in the generation of different cell types within the preimplantation emb ryo. Uvomorulin, a member of the cadherin family of cell adhesion mole cules, is important during compaction and its phosphorylation increase s early in the eight-cell stage, suggesting that this posttranslationa l modification may be important for compaction to proceed. We have ass essed the importance of the phosphorylation of uvomorulin during compa ction by preventing, reversing, or inducing adhesion prematurely. The only condition that affected the overall level of uvomorulin phosphory lation was the prevention of compaction through prolonged exposure of four-cell embryos to low Ca2+. This treatment reduced the level of uvo morulin phosphorylation in eight-cell embryos, and perturbed its local ization to regions of cell-cell contact. Thus, whilst the phosphorylat ion of uvomorulin does not appear to regulate directly uvomorulin's ad hesive function, it may be associated with the redistribution of uvomo rulin during compaction. (C) 1996 Wiley-Liss, Inc.