Transgenic cloned mice expressing enhanced green fluorescent protein generated by activation stimuli combined with 6-dimethylaminopurine

Generation of human lactoferrin transgenic cloned goats using donor cells with dual markers and a modified selection procedure

The objective was to use dual markers to accurately select genetically modified donor cells and ensure that the resulting somatic cell nuclear transfer kids born were transgenic. Fetal fibroblast cells were transfected with dual marking gene vector (pCNLF-ng) that contained the red-shifted variant of the jellyfish green fluorescent protein (LGFP) and neomycin resistance (Neo) markers. Cell clones that were G418-resistant and polymerase chain reaction-positive were subcultured for several passages; individual cells of the clones were examined with fluorescence microscopy to confirm transgenic integration. Clones in which every cell had bright green fluorescence were used as donor cells for nuclear transfer. In total, 86.7% (26/30) cell clones were confirmed to have transgenic integration of the markers by polymerase chain reaction, 76.7% (23/30) exhibited fluorescence, but only 40% (12/30) of these fluorescent cell clones had fluorescence in all cell populations. Moreover, through several cell passages, only 20% (6/30) of the cell clones exhibited stable LGFP expression. Seven transgenic cloned offspring were produced from these cells by nuclear transfer. Overall, the reconstructed embryo fusion rate was 76.6%, pregnancy rates at 35 and 60 days were 39.1% and 21.7%, respectively, and the offspring birth rate was 1.4%. There were no significant differences between nuclear transfer with dual versus a single (Neo) marker (overall, 73.8% embryo fusion rate, 53.8% and 26.9% pregnancy rates, and 1.9% birth rate with five offspring). In conclusion, the use of LGFP/Neo dual markers and an optimized selection procedure reliably screened genetically modified donor cells, excluded pseudotransgenic cells, and led to production of human lactoferrin transgenic goats. Furthermore, the LGFP/Neo markers had no adverse effects on the efficiency of somatic cell nuclear transfer.

Production of cloned sei whale (Balaenoptera borealis) embryos by interspecies somatic cell nuclear transfer using enucleated pig oocytes

In this study, we examined the feasibility of using subzonal cell injection with electrofusion for interspecies somatic cell nuclear transfer (iSCNT) to produce sei whale embryos and to improve their developmental capacity by investigating the effect of osmolarity and macromolecules in the culture medium on the in vitro developmental capacity. Hybrid embryos produced by the electrofusion of fetal whale fibroblasts with enucleated porcine oocytes were cultured in modified porcine zygote medium-3 to examine the effects of osmolarity and fetal serum on their in vitro developmental capacity. More than 66% of the whale somatic cells successfully fused with the porcine oocytes following electrofusion. A portion (60~81%) of the iSCNT whale embryos developed to the two- to four-cell stages, but no embryos were able to reach the blastocyst stage. This developmental arrest was not overcome by increasing the osmolarity of the medium to 360 mOsm or by the addition of fetal bovine or fetal whale serum. Our results demonstrate that sei whale-porcine hybrid embryos may be produced by SCNT using subzonal injection and electrofusion. The pig oocytes partly supported the remodeling and reprogramming of the sei whale somatic cell nuclei, but they were unable to support the development of iSCNT whale embryos to the blastocyst stage.