Expression of N-CAM in Fertilized Pre- and Periimplantation and Parthenogenetically Activated Mouse Embryos

The expression of the cell adhesion molecule of the immunoglobulin family, neural cell adhesion molecule (N-CAM), in the pre- and periimplantation embryo was examined by immunocytochemistry. N-CAM is expressed on unfertilized ovulated oocytes, fertilized preimplantation embryos at all stages of development and parthenogenetically activated eggs and embryos. In fertilized embryos, expression from the 4-cell stage can be partially inhibited by blocking embryonic transcription before 38 h post human chorionic gonadotropin (hCG). Expression of N-CAM was reduced on the trophoblast of day 6 blastocysts in culture, weak on the trophoblast of embryonic outgrowths and disappears from invading trophoblast in utero. An antibody against alpha(2-8) linked polysialic acid, mAb2-2B, reacted with embryos from the 8-cell stage, and staining was similarly reduced on the trophoblast of blastocysts at the time of implantation. These results suggest a role for N-CAM in the interactions of cells of the preimplantation mammalian embryo which requires further investigation.