Techniques for nuclear transfer to mouse embryonic stem cells.
In this chapter, methods are described that permit the enucleation of mouse embryonic stem (ES) cells and the transfer of donor nuclei to these cells before or after enucleation has taken place. The small size and high nucleus-to-cytoplasm volume ratio of ES cells poses a challenge to their enucleation. The first step describes the production of lines of larger, polyploid ES cells, which are more suited to enucleation than diploid ES cells. In a second step, a simple centrifugal enucleation technique is described that allows efficient bulk production of ES cell cytoplasts and karyoplasts. Finally, techniques for nuclear transfer to ES cells are described, involving either transfer of karyoplasts to cytoplasts or the formation of heterokaryons between donor and recipient cells followed by the selective elimination of the polyploid nucleus. These methods have potential applications in the generation of autologous, diploid pluripotent cells from donor somatic cells. Also, they provide a novel dynamic model for studying nucleocytoplasmic interactions in ES cells.