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J Assist Reprod Genet (2013) 30:10551058 DOI 10.1007/s10815-013-0053-7
REVIEW
The ups and downs of somatic cell nucleus transfer (SCNT) in humans
Josef Fulka Jr. & Alena Langerova & Pasqualino Loi &
Grazyna Ptak & David Albertini & Helena Fulka
Received: 2 April 2013 /Accepted: 8 July 2013 /Published online: 24 July 2013 # Springer Science+Business Media New York 2013
Abstract Achieving successful somatic cell nuclear transfer (SCNT) in the human and subhuman primate relative to other mammals has been questioned for a variety of technical and logistical issues. Here we summarize the gradual evolution of SCNT technology from the perspective of oocyte quality and cell cycle status that has recently led to the demonstration of feasibility in the human for deriving chromosomally normal stem cells lines. With these advances in hand, prospects for therapeutic cloning must be entertained in a conscientious, rigorous, and timely fashion before broad spectrum clinical applications are undertaken.
Keywords Nucleus . Oocyte . Nucleus transfer
Simply stated, SCNT in mammals should in practice be a very straightforward technique. First, cytoplasts are prepared by enucleating the metaphase II stage oocytes, i.e. metaphase II chromosomes are removed from the oocyte. Second, the selected nucleus is introduced into the cytoplast either by direct injection or by induced cell fusion. The reconstructed SCNT products are then activated in ways mimicking fertilization and if everything goes well cloned embryos develop [6].
Logically, since following the birth of Dolly [7], and the production of additional clones in other mammalian species, there is ample confirmation that Dolly was not an exceptional case, prompting widespread discussion regarding the pros and cons of human SCNT. Given this prospect, it has been commonly accepted and broadly emphasized that the production of cloned human individuals must be banned (reproductive cloning). On the other hand, the production of embryos from which patient compatible embryonic stem cells could be obtained seemed to be acceptable, at least in some countries (therapeutic cloning). However, once the discovery of induced pluripotent stem cell production (iPSC) was realized by the work of Takahashi and Yamanaka [see 8 for review], illustrating that differentiated or even terminally differentiated cells can be converted (dedifferentiated) into a pluripotent state by induced overexpression of four factors (Oct 4, Sox 2, Klf 4, c-Myc;...