Expression of Exogenous DNA in Mouse Embryos Surviving After In Vitro Selection with G-418

Abstract

This study was designed to determine whether preimplantation mouse embryos carrying the MT-neo/MT-β-gal transgene, which contains a neomycin resistance gene (neo) and E. coli β-galactosidase (β-gal) gene, can be selected by incubation in the presence of G-418 prior to transfer to recipients. Mouse 1-cell eggs were injected with MT-neo/MT-β-gal DNA, allowed to develop to the 4-cell stage and then treated for 3 days with 200 μg/ml of G-418, a concentration known to completely inhibit development of normal embryos in vitro. Twenty-eight (15.1%) of 186 4-cell embryos that had been microinjected developed to the blastocyst stage after culture with G-418. Histochemical staining of the resulting blastocysts for β-gal activity revealed that 28.6% (8 of 28) of G-418-resistant embryos were positive for β-gal activity. Of 158 control 4-cell eggs that had been injected with MT-neo/MT-β-gal DNA but not treated with G-418, 55 (34.8%) developed to the blastocyst stage. Four (7.3%) of these 55 blastocysts expressed the β-gal gene. These findings suggest that mouse preimplantation embryos with exogenous DNA after injection can be concentrated approximately 4-fold after selection in the presence of G-418.