Production of recombinant therapeutic proteins in the milk of transgenic dairy goats represents an excellent alternative to the high capital and operating costs associated with high-volume mammalian cell culture. However, generation of transgenic goats through pronuclear microinjection is somewhat inefficient and costly. Moreover, it would be ideal to clonally generate production animals of a given transgenic line. The combination of goat embryonic stem (ES) cells and goat nuclear transfer technologies would solve these two problems, as well as allow scale-up of production herds within one generation. We propose to use our combined expertise in preimplantation embryology, goat reproductive biology, and mammary gland expression molecular biology to apply these technologies to the transgenic dairy goat system. One aspect of the Phase I project will be to derive pluripotential goat ES cells from blastocyst-stage embryos following strategies recently used successfully in sheep. The second aspect of this Phase I project will be to study the architecture and the plasticity of goat oocytes, to optimize nuclear transfer protocols using goat oocytes as recipients and goat ES lines as donors. If time allows, embryo reconstitution experiments will be attempted, to evaluate the quality of the goat derived ES cells and the nuclear transfer methods. PROPOSED COMMERCIAL APPLICATIONS Transgenic goats represent a safe and affordable choice for the high-volume production of recombinant human therapeutic proteins that will constitute an increasing important part of the future pharmaceutical formulary. Goat embryonic stem cells will simplify the generation and scale up of commercially useful transgenic dairy goat herds.