Everett C A, West J D
Department of Obstetrics and Gynaecology, University of Edinburgh, United Kingdom.
Genet Res. 1998 Dec;72(3):225-8. doi: 10.1017/s0016672398003498.
Tetraploid (4n) cells do not contribute equally to all tissues of midgestation mouse chimaeras and mosaics. Our previous studies of early blastocysts showed that 4n cells are preferentially allocated to the mural trophectoderm of the early blastocyst and this may contribute to the restricted distribution pattern seen at later stages. In this study of later-stage blastocysts we found evidence for selection against 4n cells. The contribution of 4n cells to 4n<-->2n chimaeric blastocysts decreased between E3.5 and E4.5 days, whereas the composition of 2n<-->2n controls changed little over this period. These results suggest that, prior to implantation, blastocysts have already lost some tetraploid cells from their embryonic and extra-embryonic lineages due to a combination of preferential allocation of 4n cells to the mural trophectoderm and selection against 4n cells throughout the embryo.
四倍体（4n）细胞对妊娠中期小鼠嵌合体和镶嵌体的所有组织的贡献并不相同。我们之前对早期囊胚的研究表明，4n细胞优先分配到早期囊胚的壁滋养外胚层，这可能导致了后期出现的受限分布模式。在这项对后期囊胚的研究中，我们发现了针对4n细胞进行选择的证据。在E3.5至E4.5天之间，4n细胞对4n<-->2n嵌合囊胚的贡献减少，而2n<-->2n对照在此期间的组成变化不大。这些结果表明，在着床前，由于4n细胞优先分配到壁滋养外胚层以及整个胚胎对4n细胞的选择，囊胚已经从其胚胎和胚外谱系中丢失了一些四倍体细胞。
