Fibronectin localization in the mouse embryo from the two cell stage to the morula stage

Among the characters of fibronectin, the adhesiveness may play an important role in embryo implantation. It is concluded that, using the direct and indirect immunofluorescence techniques, fibronectin was not found on the zona pellucida, but on the embryo surface even from the two cell stage. The results imply that (i) fibronectin is not an initial differentiation marker for the stage of endoderm, which used to be postulated, (ii) the surface fibronectin which has been produced at least from the two cell stage is covered by the zona pellucida to mask its adhesiveness during the oviduct transport, and (iii) after hatching in the uterus cavity the surface fibronectin facilitates the embryo implantation.