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

在卵裂阶段，第二极体（PB2）与其中一个卵裂球的融合被认为是人类二倍体-三倍体混合倍性的原因机制。在这项研究中，我们检测了小鼠PB2s的基因组稳定性以及PB2s是否可以参与混合倍体胚胎的产生。大多数PB2s在发射后70 h仍处于细胞周期的S期，未发生凋亡。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的混合倍体胚胎。3n卵裂球在受精后第11天具有分化为囊胚内细胞团和滋养层的能力，构成胚胎的胎盘组织。结果表明，PB2与卵裂球的融合是形成混合倍体胚胎的原因之一。

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.