By Stuart P. Atkinson
When induced pluripotent stem cell (iPSC) technology broke onto the scene in 2007, the attainment of a practical and ethical source of patient specific pluripotent stem cells seemed to be within our grasp. The use of somatic cell nuclear transfer (SCNT) for the derivation of human embryonic stem cells (hESCs) was all but relegated to the past, along with its ethical and technical difficulties. Further, as noted in an editorial in Nature, previous fraudulent claims in this field had added a degree of unwarranted scepticism to research undertaken in this field. However, iPSC derivation and its detailed analysis has shown that iPSC may have only a limited use in a therapeutic context due to differences between blastocyst-derived stem cells at the level of gene expression, epigenetic patterning, differentiation potential and genomic integrity. It is suggested that these differences may lead to dysfunctionality and/or tumorigenicity and have led some groups to return to SCNT-mediated techniques. The group of Dieter Egli from the The New York Stem Cell Foundation Laboratory, New York initiated a rigorous study designed to understand the obstacles to blastocyst development in SCNT in order that we can use this process to generate bona fide patient-specific hESCs. In their paper, published in Nature (Noggle et al), the group found that transfer of the somatic genome into an enucleated oocyte failed to develop and this was associated with an apparent arrest of developmentally-associated gene expression. They found however, that if the oocyte genome is left in place upon somatic genome transfer, the embryo can develop to the blastocyst stage and hESCs can be derived.