Transfection of mouse eggs and embryos using DNA combined to cationic liposomes

We have used plasmid DNA in combination with cationic liposomes to transfec t mouse eggs and embryos. The plasmid was rhodamine labeled, which allowed a direct visualization of the DNA uptake by the cells. Immature eggs, colle cted from the ovaries, were easily transfected, but once the egg was ovulat ed the zona pellucida (ZP) acted as a barrier and prevented transfection. P ermeabilization or removal of the ZP was therefore a requirement to allow t ransfection. Transfected eggs were capable of being fertilized in vitro giv ing raise to embryos that expressed the recombinant protein. Morulae and bl astocysts were also transfected when the ZP was permeabilized, but the effi ciency of transfection decreased and in some cases not all the blastomeres incorporated the plasmid. Pronuclear embryos were cultured and showed expre ssion of the transgene from the 2-cell stage. This indicates that liposome- transfection of oocytes or pronuclear embryos could be a simple and suitabl e method to introduce foreign genes in embryos and perhaps could be also us eful to generate transgenic animals. Mol. Reprod. Dev. 56:360-365, 2000. (C ) 2000 Wiley-Liss, Inc.