Handmade somatic cell cloning in cattle.

Apart from the biological and ethical problems, technical difficulties also hamper the improvement and widespread application of somatic cell nuclear transfer (NT). Recently introduced zona-free procedures may offer a solution for the latter problem. The most radical approach of these techniques is the so-called handmade cloning (HMC). It does not require micromanipulators because the manipulations required for both enucleation and nucleus transfer are performed by hand. The HMC technique includes manual bisection of zona-free oocytes, selection of cytoplasts by staining, and the simultaneous fusion of the somatic cell with two cytoplasts to produce a cloned embryo. HMC is a rapid and efficient technique that suits large-scale NT programs. It requires less expertise and time than traditional NT methods and the cost of equipment is significantly less. Production efficiency is high and embryo quality, in terms of pregnancy rates and live births, is not compromised. Although HMC has been developed particularly for bovine NT, the technique is applicable to other species. The method may become a useful tool for both experimental and commercial somatic cell cloning because it allows for standardization of procedures and provides the possibility of automation.