Chromosomes in the Porcine First Polar Body Possess Competence of Second Meiotic Division within Enucleated MII Stage Oocytes: e82766

• Published in: PloS one 2013-12, Vol.8 (12)
• Main Authors: Lin, Tao, Diao, Yun Fei, Kang, Jung Won, Lee, Jae Eun, Kim, Dong Kyo, Jin, Dong Il
• Format: Article
• Language: English
• Subjects: Chromosomes
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0082766

To determine whether chromosomes in the porcine first polar body (PB1) can complete the second meiotic division and subsequently undergo normal pre-implantation embryonic development, we examined the developmental competence of PB1 chromosomes injected into enucleated MII stage oocytes by nuclear transfer method (chromosome replacement group, CR group). After parthenogenetic activation (PA) or in vitro fertilization (IVF), the cleavage rate of reconstructed oocytes in the IVF group (CR-IVF group, 36.4 plus or minus 3.2%) and PA group (CR-PA group, 50.8 plus or minus 4.2%) were significantly lower than that of control groups in which normal MII oocytes were subjected to IVF (MII-IVF group, 75.8 plus or minus 1.5%) and PA (MII-PA group, 86.9 plus or minus 3.7%). Unfertilized rates was significantly higher in the CR-IVF group (48.6 plus or minus 3.3%) than in the MII-IVF group (13.1 plus or minus 3.4%). The blastocyst formation rate was 8.3 plus or minus 1.9% in the CR-PA group, whereas no blastocyst formation was observed in the CR-IVF group. To produce tetraploid parthenogenetic embryos, intact MII stage oocytes injected with PB1chromosomes were electrically stimulated, treated with 7.5 mu g/mL cytochalasin B for 3 h (MII oocyte + PB1 + CB group), and then cultured without cytochalasin B. The average cleavage rate of reconstructed oocytes was 72.5% (48 of 66), and the blastocyst formation rate was 18.7% (9 of 48). Chromosome analysis showed similar proportions of haploid and diploid cells in the control (normal MII oocytes) and CR groups after PA; overall, 23.6% of blastocysts were tetraploid in the MII oocyte + PB1 + CB group. These results demonstrate that chromosomes in PB1 can participate in normal pre-implantation embryonic development when injected into enucleated MII stage oocytes, and that tetraploid PA blastocysts are produced (although at a low proportion) when PB1 chromosomes are injected into intact MII stage oocytes.