Expression of the hemophilic adhesion molecule, Ep-CAM, in the mammalian germ line

During normal embryonic development, mammalian germ cells use both cell mig ration and aggregation to form the primitive sex cords. Germ cells must be able to interact with their environment and each other to accomplish this; however, the molecular basis of early germ eel adhesion is not well charact erized. Differential adhesion is also thought to occur in the adult seminif erous tubules, since germ cells move from the periphery to the lumen as the y differentiate. Ln a screen for additional adhesion molecules expressed by the germ line, expression of the hemophilic adhesion molecule, Ep-CAM, was identified in embryonic, neonatal and adult germ cells using immunocytoche mistry and flow cytometry with an Ep-CAM-specific monoclonal antibody. At e mbryonic stages, germ cells were found to express Ep-CAM during migration a t embryonic day 10.5 and early gonad assembly at embryonic day 12.5. Expres sion of Ep-CAM was also found on neonatal male and female germ cells. Ln th e adult testis, Ep-CAM was detected only on spermatogonia, and was absent f rom more differentiated cells. Finally, embryonic stem cells were shown to express this receptor. It is proposed that Ep-CAM plays a role in the devel opment of the germ line and the behaviour of totipotent cells.