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/Sv-Sl/+ mice are thought to be derived from germ cells. The teratomas present initially as groups of atypical germ-like cells within seminiferous cords of the 15.5 days post coitum (dpc) embryonic testes. These pluripotent teratoma stem cells are capable of differentiating into many kinds of tissues in adult mice. In this immunohistochemical study, we have examined the testes of 129/Sv-Sl/+ mice to determine whether the teratoma cells which developed in these gonads retain the nuclear antigen GCNA1. GCNA1 is a 110 kDa mouse Germ Cell Nuclear Antigen recognized by a rat monoclonal antibody 10D9G11. GCNA1 is expressed in mouse germ cells after they migrate into the genital ridge (11.5 dpc), throughout embryonic development until postnatally germ cells arrive at the diplotene/dictyate stage of the first meiotic division, when it is no longer expressed. Early foci (16.5 dpc) of teratoma stem cells in 129/Sv-Sl/+ mice strongly express GCNA1, but down regulate GCNA1 expression by 19.5 dpc. The loss of GCNA1 expression from teratoma stem cells late in embryonic development is in contrast to embryonic gonocytes which retain GCNA1 expression throughout fetal development. All postnatal undifferentiated and differentiated teratoma cells did not appear to express GCNA1. The expression of the germ cell specific nuclear antigen GCNA1 in early teratoma stem cells further demonstrated that the testicular teratomas originate from early germ cells. The stronger reaction of monoclonal antibody 10D9G11 to GCNA1 within early teratoma cells compared to normal germ cells makes GCNA1 useful in identifying early embryonic tumor foci.