Demecolcine-assisted enucleation for bovine cloning.

The present study demonstrated that demecolcine treatment for at least 30 min produces a membrane protrusion in metaphase II-stage bovine oocytes. The maternal chromosome mass is condensed within the protrusion, which makes it easy to remove the maternal chromosomes for nuclear transfer (NT). Maturation promoting factor activity, but not mitogen-activated protein kinase activity, increased up to 30% in oocytes during demecolcine treatment. One normal healthy calf was obtained after transfer of four NT blastocysts produced following demecolcine treatment. Demecolcine treatment did not increase the potential of NT oocytes to develop into blastocysts. The present study demonstrated that chemically-assisted removal of chromosomes is effective for bovine cloning.