Nuclear transfer in goats using in vitro matured oocytes recovered by laparoscopic ovum pick-up.

THE PRODUCTION of the first transgenic mouse by pronuclear injection in 1981 (Gordon and Ruddle, 1981) stimulated the interest of animal scientists working with domestic livestock, since the potential of transgenic domestic livestock as bioreactors for the production of valuable biopharmaceuticals was immediately recognized. Relatively soon, transgenic sheep, pigs, and goats were produced (Wall et al., 1992); however, efficiencies of transgenic animal production in livestock were lower than that obtained in mice. Following pronuclear microinjection of in vivo derived goat zygotes, only two of 29 goats born were transgenic (Ebert et al., 1991). This rate of production has not changed despite improvements in techniques (Baldassarre et al., 2003). Cloning using nuclear transfer (NT) provides a much more efficient system than DNA microinjection for the production of transgenic goats as the donor cells can be screened for transgene incorporation into the genome, copy number, and integration sites prior to its use in NT (Keefer et al., 2001). This selection of the transgenic donor cell ensures that nearly all the progeny produced will be transgenic (Baldassarre et al., 2002). Cloning can also be used to propagate transgenic animals produced by DNA microinjection (Baguisi et al., 1999; Keefer et al., 2002a). Successful production of transgenic goats not only requires care and skill in preparation of the transgenic donor cell (Lazaris et al., in press), but also in the management of the oocyte donors and the embryo recipients. Reproductive management is important in maximizing the number and quality of the oocytes recovered from donors, as well as in the ability of the recipients to allow development to term of the NT embryos. In addition, excellent health status and animal husbandry practices are required to maximize the reproductive results and ensure compliance with regulatory guidelines and animal welfare recommendations.