In vivo gene transfer into the blastoderm of early developmental stage of chicken.

An attempt was made to improve gene transfer into chick embryos in order to produce transgenic chickens. The beta-actin-lacZ/MiwZ, a marker gene in transfection reagent, was injected into the blastodisc of either unincubated fertilized eggs (stage X) or eggs induced from the shell gland by treating the hens intravenously with oxytocin or arginine vasotocin (stages IV-VI). All the manipulated embryos were incubated to reach stage XIV, the period at which primordial germ cells (PGCs) migrate from the germinal crescent to the gonadal anlage via the blood stream. MiwZ was detected in the embryos, extraembryonic tissues and blood by the histochemical staining method of beta-galactosidase. The MiwZ DNA was detected in 57% (127/221) of the survival embryos and in 9% (12/127) of the embryonic tissues. The expression was observed mosaically in the epidermis, heart and neural tube. The PGCs in the blood collected from the vitelline artery or dorsal aorta also showed a positive histochemical staining. However, the expression of MiwZ using the soft shelled eggs was more intense in the extraembryonic tissues, although it did not emerge in the embryos. Thus, it is possible to introduce an exogenous gene into the embryonic tissues using incubated fertilized eggs without sacrificing the hens. This technique for successive genetic operations should facilitate the production of transgenic chickens.