Transient transmission of a transgene in mouse offspring following in vivo transfection of male germ cells.

Sperm-mediated gene transfer in vertebrates has undergone various developments over the last few years, in different laboratories. In the present study, we microinjected a circular plasmid, carrying the lacZ reporter gene mixed with noncommercial cationic lipids, into the seminiferous tubules of anesthetized adult mice. Histochemical analysis was used to estimate the transfection efficiency 48-96 hr and 40 days after injection. As early as 48-96 hr post-injection, an efficient transfection was revealed by a beta-galactosidase expression within both immature and differentiated germ cells. By 40 days post-injection, the specific LacZ expression was restricted to the most immature germ cells in the basal portion of the seminiferous tubules. At this time, some injected males were mated with wild-type females and the progeny were analyzed by PCR and Southern blot. We showed that the transgene was transmitted to the offspring but remained episomal, as it was found in the tail of the young animals but not at adulthood. Therefore, the plasmid seemed to be lost during the numerous germ cells divisions. This plasmid stayed in some tissues, such as skeletal muscle and cardiac muscle. No integrative forms have yet been found with the use of a circular DNA.