Fig. 3. Junctional PtdIns(3,4,5)P₃ synthesis is due to E-cadherin signalling. (A) Junctional PtdIns(3,4,5)P₃ synthesis in a 16-cell morula (left) is inhibited upon removal of extracellular Ca²⁺ (middle; note the decompaction of the embryo). Readmission of extracellular Ca²⁺ allowed for PtdIns(3,4,5)P₃ re-synthesis at cell-cell contacts (right; note embryo re-compaction). (B) Two-cell embryo (from a low-density culture; top) and 16-cell embryo (bottom) cultured in the presence of ECCD-1. The anti-E-cadherin antibody prevented junctional PtdIns(3,4,5)P₃ synthesis and embryo compaction. (C) PtdIns(3,4,5)P₃ synthesis upon embryo aggregation. The arrowhead points to the new contact region between two aggregated two-cell embryos. PtdIns(3,4,5)P₃ was monitored with GFP-PH_GRP1 (A,B) or GFP-PH_Akt (C). Confocal images are representative of at least 12 similar observations.