Ma, H. et al. Nature 511, 177–183 (2014).

Somatic cells can be rendered pluripotent by transfer into an enucleated oocyte or by the forced expression of reprogramming factors. Which of these processes is more faithful remains unknown. With recent successful embryonic stem (ES) cell derivation from zygotes generated by somatic cell nuclear transfer (SCNT), it has become possible to compare otherwise isogenic pluripotent cells derived by these different processes. Ma et al. compared human SCNT-ES cells and induced pluripotent stem cells (iPSCs) generated using the same source of dermal fibroblasts as donor cells. These were further compared to ES cells derived from in vitro fertilization (IVF) of oocytes from the same donor used for SCNT. The researchers found that copy-number variations are comparable between iPSCs and SCNT-ES cells but that SCNT yields more complete epigenetic reprogramming than IVF controls.