Efficient Creation of Transgenic Sheep: The Challenge for the Cell Biologist

Summary

Transgenic sheep are now being created in several centres throughout the world using microinjection of the transgene into the pronuclei of one cell zygotes to establish germ line transmission. Of the lambs born, about 8% are transgenic, a success rate which is comparable to the 15–35% success achieved with mice and pigs. However, this simple comparison fails to adequately highlight the considerable extra effort and cost required to create transgenic sheep through limitations such as the low reproductive capacity of this species. Low embryo numbers preclude adoption of many techniques for DNA transfer widely used for somatic cells. These constraints could be largely overcome if methods for the establishment of totipotent embryonic cell lines and methods to allow recreation of viable embryos from selected genetically transformed embryonic cells could be established. This approach is feasible as has been recently demonstrated in mice and there is a clear challenge to the cell biologist to establish similar technology for the sheep.