Gene Transfer into Sheep

Gene transfer into animals has considerable potential for livestock improvement. If this potential is to be realized, the ease of generation of transgenic livestock will be of major importance. We report here the production of six transgenic sheep by microinjection of DNA into early embryos (1.2% of embryos transferred). Three different gene constructs were injected and transgenic sheep were obtained with each. The transgenic animals have all incorporated the DNA without detectable rearrangement, and where multiple copies were integrated, they are present in arrays of tandem repeats. Transmission of transferred genes to progeny of three of the sheep has been demonstrated. Five founder transgenic sheep described carry genes designed to direct the production of human clotting factor IX or human αl–antitrypsin in milk. Transgenic animals carrying such genes may ultimately provide a new source of these and other therapeutic proteins.