Complementation of placental defects and embryonic lethality by trophoblast-specific lentiviral gene transfer.

Placental dysfunction underlies many complications during pregnancy, and better understanding of gene function during placentation could have considerable clinical relevance. However, the lack of a facile method for placenta-specific gene manipulation has hampered investigation of placental organogenesis and the treatment of placental dysfunction. We showed previously that transduction of fertilized mouse eggs with lentiviral vectors leads to transgene expression in both the fetus and the placenta. Here we report placenta-specific gene incorporation by lentiviral transduction of mouse blastocysts after removal of the zona pellucida. All of the placentas analyzed, but none of the fetuses, were transgenic. Application of this method substantially rescued mice deficient in Ets2, Mapk14 (also known as p38alpha) and Mapk1 (also known as Erk2) from embryonic lethality caused by placental defects. Ectopic expression of Mapk11 also complemented Mapk14 deficiency during placentation.

Targeted gene modification in mouse ES cells using integrase-defective lentiviral vectors.

Lentiviral vectors efficiently integrate into the host genome of both dividing and nondividing cells, and so they have been used for stable transgene expression in biological and biomedical studies. However, recent studies have highlighted the risk of insertional mutagenesis and subsequent oncogenesis. Here, we used an integrase-defective lentiviral (IDLV) vector to decrease the chance of random integration and examined the feasibility of lentiviral vector-mediated gene targeting into murine embryonic stem (ES) cells. After transduction with wild-type lentiviral vectors, none of the 512 G418 resistant clones were found to be homologous recombinant clones. Although the transduction efficiency was lower with the IDLV vectors (5.9% of wild-type), successful homologous recombination was observed in nine out of the 941 G418 resistant clones (0.83 +/- 1.32%). Pluripotency of the homologous recombinant ES cells was confirmed by the production of chimeric mice and subsequent germ line transmission. Because lentiviral vectors can efficiently transduce a variety of stem cell types, our strategy has potential relevance for secure gene-manipulation in therapeutic applications.