Study on chromosomal stability and developmental potential of mouse second polar bodies

第二极体(PB2)与一个卵裂球在卵裂期的融合被认为是人类二倍体-三倍体混合倍体的原因机制。在这项研究中，我们检测了小鼠PB2的基因组稳定性，以及PB2是否参与了混合倍体胚胎的产生。大部分PB2在排出后70h仍处于细胞周期的S期，未发生细胞凋亡。当PB2与其中一个2-细胞卵裂球融合时，PB2的染色体被整合到卵裂球的有丝分裂纺锤体中，形成2n/3n混倍体胚胎。受精后11d，3n卵裂球具有分化为胚泡内细胞团和滋养层的能力，形成胚胎的胎盘组织。结果表明，PB2与卵裂球的融合是导致混倍体胚胎形成的原因之一。

The fusion of a second polar body (PB2) with one of the blastomeres during the cleavage stage has been considered as a causal mechanism underlying diploid-triploid mixoploidy in humans. In this study, we examined the genomic stability of mouse PB2s and whether the PB2s can participate in the generation of mixoploid embryos. Majority of the PB2s remained in the S phase of the cell cycle until 70 h after being emitted without undergoing apoptosis. When the PB2 was fused with one of the 2-cell blastomeres, the chromosomes of the PB2 were incorporated in the mitotic spindle of the blastomere, resulting in the formation of the 2n/3n mixoploid embryo. The 3n blastomeres had the ability to differentiate into the inner cell mass and the trophectderm of blastocysts, and constituted the placenta tissue of the embryo at 11 days after fertilization. The findings suggest that the fusion of the PB2 with a blastomere is one of the causative factors of the formation of the mixoploid embryos.