Differentiation of murine premigratory primordial germ cells in culture

In the mouse embryo, primordial germ cells first appear in the extraembryon ic mesoderm and divide rapidly while migrating to the fetal gonad. Shortly after their arrival in the gonad, germ cells sexually differentiate as prol iferation ceases. Previous studies have established that primordial germ ce lls proliferate and migrate in feeder layer culture. To explore cellular re gulation of fetal germ cell development, we have used germ cell nuclear ant igen 1 (GCNA1), a marker normally expressed only in postmigratory germ cell s, to investigate the developmental potency of both pre- and postmigratory cells in this culture system. We found that explanted premigratory germ cel ls will initiate expression of this marker and are, therefore, capable of u ndertaking some aspects of gonocyte differentiation without intimate exposu re to the fetal gonad. We have also tested whether postmigratory gonocytes are stable in culture. As detected by either alkaline phosphatase or GCNA1, we did not detect longterm survival of either prospermatogonia or oogonia under conditions that support the survival, proliferation, and differentiat ion of earlier premigratory cells. These observations are consistent with a n autonomous cellular mechanism governing the initial stages of gonocyte di fferentiation, and suggest that differentiation towards gonocytes is accomp anied by a change in requirements for cell survival.