Gene Nuclear transplantation

Figure 4. Demonstration of the development of a transcriptionally repressive state by nuclear transplantation. In the first experimental protocol, the injected nucleus was transplanted to an S-phase-arrested, one-cell embryo that was then analyzed at a time that corresponded to the mid-late two-cell stage. In the second protocol, the injected nucleus was transplanted to an S-phase-arrested, two-cell embryo that was analyzed at a time that corresponded to the four-cell stage, whereas in the third protocol the injected nucleus was transplanted to a two-cell blastomere that divided. In the last protocol, the injected two-cell blastomere in G2 was transplanted to an S-phase-arrested, one-cell embryo that was then at a time that corresponded to the mid-late two-cell stage. The data are expressed relative to the amount of activity observed for the tk promoter-containing reporter gene in the S-phase-arrested one-cell embryos, and were taken from Henery et al., 1995.

Nuclear transplantation experiments also indicated that the repression of expression from a plasmid-bome reporter gene that was observed following injection of the plasmid into a two-cell blastomere nucleus was essentially irreversible (Henery et al., 1995)(Figure 4). Transfer of a two-cell blastomere nucleus that was injected in G2 with the enhancerless promoter to an enucleated S-phase-arrested, one-cell embryo resulted in only 5% the level of expression when compared to S-phase-arrested, one-cell embryos, and this expression was ineffectively stimulated by the presence of an enhancer. This irreversible repression seemingly contradicted a previous report that transplantation of a nucleus from an eight-cell embryo or nuclei from differentiated cells to an enucleated one-cell embryo resulted in the re-expression of theTRC when examined at the two-cell stage (Latham et al., 1991) the TRC is apparently irreversibly repressed since its expression is not observed in... 

Rideout W M, 3rd, Hochedlinger K, Kyba M, et al. (2002). Correction of a genetic defect by nuclear transplantation and combined cell and gene therapy. Cell. 109 17-27. 

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