Devlopment of chimaeric two‐cell mouse embryos produced by allogenic exchange of single nucleus from two‐ and eight‐cell embryos

Abstract

Synchronous or asynchronous chimaeras were produced by transplanting a single nucleus of two- and eight-cell embryos from CD-1xCD-1 or BALB/CxBALB/C albino strains into one enucleated blastomere of a late F1 (C57/BLxCBA) x F1 two-cell embryo. The cytoplasmic volume of the blastomere was reduced in some instances by 50%. These chimaeric embryos were cultured in vitro and transferred to pseudopregnant recipients. The distribution of each component to the pups and to the day-10 embryos after transfer to recipients was determined by examining their coat color and by glucose phosphate isomerase analysis, respectively. The contribution of progeny of the nuclear-transplanted cell with nonreduced cytoplast to the pups was 83% when synchronous; this proportion decreased to 43% when asynchronous because the progeny tended to migrate to the trophoblast and/or to the primitive endoderm. When the recipient cytoplast was reduced by 50%, the contribution of the nuclear-transplanted cell progeny to the pups was 79% when synchronous and 80% when asynchronous. This shows that allogenic exchange of a single nucleus at the two-cell stage by nuclear transfer is an effective procedure for producing highly asynchronous mouse chimaeras and suggests that larger and advanced blastomeres tend to be excluded from the inner cell mass of the embryo, but smaller, advanced blastomeres do not.

Synchronous division of mouse two-cell embryos with nocodazole in vitro

“…Synchronization of the cell cycle between a donor nucleus and recipient cytoplasm is important for pronuclear and nuclear exchange (Smith et al, 1988(Smith et al, , 1990, nuclear transplantation of fetal germ cells (Kato & Tsunoda, in press) and the production of chimaeric embryos (Kono et al, 1989). The observation that nocodazole can synchronize cell division of two-cell mouse embryos up to the four-cell stage may be applicable to such studies.…”

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

“…However, no chimeric conceptuses were obtained from embryos reconstituted with TE cells or ICM cells. Chimeric mice were produced by nuclear transplantation of single nuclei from 8-cell embryos into an enucleated blastomere of a 2-cell embryo [8]. Failure to demonstrate pluripotecy of ICM cells with this procedure may have been due to too large a difference in developmental stage between the donor cell and recipient 2-cell embryo.…”

“…Nakamura and Tsunoda [6] have reported that mouse chimeras were produced by synchronous allogenic exchange of a single nucleus at the 2-cell stage. This procedure has also produced chimeraes from asynchronous embryos up to the 8-cell stage [7,8]. …”