Nuclear Transplantation of Mouse Inner Cell Mass and Trophectoderm Cells into Enucleated Two-Cell Embryos.

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. Trophectoderm (TE) and inner cell mass (ICM) cells from blastocytsts were compared for their ability to produce chimeric mice or conceptuses (pluripotency) using nuclear transplantation in which a single cell was transplanted into an enucleated blastomere of a 2-cell embryo. The developmental ability of the embryos reconstituted with TE and ICM cells was dependent on when the recipient 2-cell embryos were recovered after hCG administration. When 2-cell embryos obtained 38-42 and 43-46 h post hCG injection were used, cell division of the reconstituted embryos rarely progressed to the 4-cell stage. However, when embryos recovered 48-51 h post hCG were used, the proportion of cleaved embryos increased significantly, developing to blastocysts with several large blastomeres. When reconstituted embryos were treated with nocodazole after nuclear transplantation, the percentage of cleaved embryos significantly increased, with some developing to blastocysts. Such blastocysts were transferred to recipient females, and no donor nuclei were detected in the conceptuses at midgestation. The in vitro developmental ability of the chimeric 2-cell embryos reconstituted with TE and ICM cells from blastocysts was quite limited and no chimeric conceptuses were obtained.