Cytoplasts from two-cell embryos for nuclear transplantation in the mouse

Cytoplasts for nuclear transplantation were prepared by microsurgical enucleation of one or both blastomeres of C57BL/6J and 129/Sv-ter 2-cell embryos. The survival of cytoplasts was high (85 to 97%) in both inbred strains. When cytoplasts with a "doubled" amount of cytoplasm were prepared by electrofusion of enucleated blastomeres in individual embryos, the fusion rate in C57BL/6J embryos was 93% while in 129/Sv-ter only 2%. Similar fusion rates were obtained for C57BL/6J (100%) and 129/Sv-ter (7%) embryos when enucleated and intact blastomeres were fused. The live foetuses and young born after transfer of manipulated embryos into day-1 recipients showed that enucleation and electrofusion were compatible with normal pre- and post-natal development.