EXPRESSION OF A SPECIFIC MOUSE GERM-CELL NUCLEAR ANTIGEN (GCNA1) BY EARLY EMBRYONIC TESTICULAR TERATOMA CELLS IN 129 SV-SL/+ MICE/

Spontaneous testicular teratomas which develop at a high rate in 129/S v-Sl/+ mice are thought to be derived from germ cells. The teratomas p resent initially as groups of atypical germ-like cells within seminife rous cords of the 15.5 days post coitum (dpc) embryonic testes. These pluripotent teratoma stem cells are capable of differentiating into ma ny kinds of tissues in adult mice. In this immunohistochemical study, we have examined the testes of 129/Sv-Sl/+ mice to determine whether t he teratoma cells which developed in these gonads retain the nuclear a ntigen GCNA1. GCNA1 is a 110 kDa mouse Germ Cell Nuclear Antigen recog nized by a rat monoclonal antibody 10D9G11. GCNA1 is expressed in mous e germ cells after they migrate into the genital ridge (11.5 dpc), thr oughout embryonic development until postnatally germ cells arrive at t he diplotene/dictyate stage of the first meiotic division, when it is no longer expressed. Early foci (16.5 dpc) of teratoma stem cells in 1 29/Sv-Sl/+ mice strongly express GCNA1, but down regulate GCNA1 expres sion by 19.5 dpc. The loss of GCNA1 expression from teratoma stem cell s late in embryonic development is in contrast to embryonic gonocytes which retain GCNA1 expression throughout fetal development. All postna tal undifferentiated and differentiated teratoma cells did not appear to express GCNA1. The expression of the germ cell specific nuclear ant igen GCNA1 in early teratoma stem cells further demonstrated that the testicular teratomas originate from early germ cells. The stronger rea ction of monoclonal antibody 10D9G11 to GCNA1 within early teratoma ce lls compared to normal germ cells makes GCNA1 useful in identifying ea rly embryonic tumor foci.