Effect of Demecolcine-Assisted Enucleation on the MPF Level and Cyclin B1 Distribution in Porcine Oocytes

Demecolcine (DEM) treatment of oocytes induces formation of a membrane protrusion containing a mass of condensed maternal chromosomes, which can be removed with minimal damage prior to somatic cell nuclear transfer (SCNT). However, the effect of this method on the distribution of maturation-promoting factor (MPF) in porcine oocytes has not been reported. Here, the level of MPF and the distribution of cyclin B1 were assessed in porcine oocytes following DEM treatment. In addition, the efficiencies of DEM-assisted and mechanical enucleation were compared, as were the development (in vitro and in vivo) of these oocytes following SCNT. MPF was uniformly distributed in oocytes that had been treated with 0.4 μg/ml DEM for 1 h. Immunofluorescence microscopy showed that in untreated oocytes, cyclin B1, the regulatory subunit of MPF, accumulated around the spindle, and was lowly detected in the cytoplasm. DEM treatment disrupted spindle microtubules, induced chromosome condensation, and reduced the level of cyclin B1 in the nuclear region. Cyclin B1 was uniformly distributed in DEM-treated oocytes and the level of MPF was increased. The potential of embryos generated from DEM-treated oocytes to develop in vivo was significantly greater than that of embryos generated from mechanically enucleated oocytes. This is the first study to report the effects of DEM-assisted enucleation of porcine oocytes on the distribution of cyclin B1. MPF in mature oocytes is important for the development of reconstructed embryos and for efficient SCNT.