VISUALIZATION AND CYTOGENETIC ANALYSIS OF 2ND POLAR BODY CHROMOSOMES FOLLOWING ITS FUSION WITH A ONE-CELL MOUSE EMBRYO

Purpose: This study was designed to visualize the second polar body (2 PB) chromosomes using its electrofusion with a one-cell-stage mouse em bryo to approach preconception diagnosis of chromosomal disorders. Res ults: Eighty to 90% hybridization efficiency has been achieved by elec trofusion of 2PB with mouse zygotes. 2PB chromosomes were visualized i n 40-50% of hybrids. Sixty-five percent of 2PB chromosomes were visual ized when fused with the cytoplast obtained microsurgically by removin g pronuclei from a one-cell embryo. As much as 33-43% of these resulti ng metaphases appeared to contain chromosomal aberrations. The follow- up of the development of the reconstructed one cell-stage hybrids in v itro revealed a significant decrease in their viability. The hybrid em bryos resulting from 2PB electrofusion with enucleated zygotes did not develop beyond the two-cell stage. Conclusion: Electrofusion is an ef ficient approach for hybridization of 2PB with a one-cell mouse embryo and may be useful for visualization and cytogenetic analysis of 2PB c hromosomes. The visualization rate of 2PB chromosomes is higher if 2PB is fused with enucleated zygotes. However, the method induces over 30 % of chromosomal aberrations and may lead to a significant decrease in the viability of the resulting one-cell embryos.