Tetraploid cells of enhanced green fluorescent protein transgenic mice in tetraploid/diploid-chimeric embryos

We succeeded in noninvasively analyzing the distribution of tetraploid (4n) cells in tetraploid <-> diploid (4n <-> 2n) chimeric embryos by using enhanced green fluorescent protein (EGFP) transgenic (Tg) mouse embryos. We also evaluated whether this technique of analyzing 4n-cells in EGFP Tg 4nk <-> 2n chimeric embryos could be used to determine which characteristics of 4n-cells cause the death of 4n-embryos and restricted distribution of 4n-cells in 4n <-> 2n-chimeric embryos after implantation. In our experiments, the distribution of 4n-cells in 4n <-> 2n-embryos was normal until an embryonic age of 3.5 days (E3.5). With respect to morphological development, there were no differences between 4n-, diploid (2n), 4n <-> 2n-, and diploid/diploid (2n <-> 2n) chimeric embryos, but the number of cells in the tetraploid (4n) blastocyst was smaller than expected. This decrease in the number of cells may have caused cell death or reduced the rate of cell division in 4n-cells, and may have restricted the distribution of 4n-cells in 4n <-> 2n-chimeric embryos. This study demonstrated the utility of EGFP transgenic mouse embryos for relatively easy and noninvasive study of the sequential distribution of cells in chimeric embryos.