T-Ag Inhibits Implantation by EC Cell Derived Embryoid Bodies

A Espinosa and LP Villarreal


When introduced into ES cells of a blastocyct, polyomavirus (Py)
T-Ag results in mice mosaic for T-Ag but otherwise essentially normal.  It
has been reported that SV40 T-Ag does not inhibit differentiation of F9 EC
cells, but did inhibit endogenous retrovirus (IAP) production.  We
therefore sought to determine if Py T-Ag had any affect on EC derived embryoid
body implantation onto placenta.  F9 EC cells were selected for T-Ag
maintenance.  Like the SV40 transformed cells, these Py T-Ag selected EC
cells no longer express IAP transcripts following differentiation into embryoid
bodies. Normal and Py T-Ag selected F9 cells were differentiated into embryoid
bodies then implanted into pseudopregnant mice.  We observe, that normal F9
derived embryoid bodies underwent the initial stages of implantation whereas the
Py T-Ag selected embryoid bodied did not implant.  The implications of this
observation with respect to trophectoderm and ERV function are discussed. 
We examine the idea that ERVs may be a required element for normal embryo