Requirement of preimplantation human embryos for extracellular calmodulin for development

: The objective of this study was to investigate the requirement for calmodulin in the cell division of the early human preimplantation embryo. Experiments using three agents capable of inhibiting calmodulin activity, N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W7), W7 linked to agarose beads (W7-agarose) and calmodulin antibody, showed that W7 and calmodulin antibody arrested division of embryos in a dose-dependent manner. As W7 is able to penetrate the zona pellucida and enter the cells, calmodulin antibody can traverse the zona but not enter the cells and W7-agarose cannot traverse the zona, we have deduced that the calmodulin which appears relevant to embryo division may be both intracellular and intrazonal but not extrazonal. We conclude that calmodulin is specifically required for cell division in the early human preimplantation embryo and that the concentration of calmodulin surrounding the embryo within the zona is particularly important to embryo development.