Recent studies show that induced pluripotent stem cells (iPSCs) generated through ectopic expression of transcription factors retain an epigenetic memory of their original somatic cells (Kim et al., 2010; Polo et al., 2010) or aberrant silencing of a single imprinted gene cluster (Liu et al., 2010; Stadtfeld et al., 2010), which affects their developmental and differentiation potentials. In contrast, nuclear transfer can more faithfully reprogramme somatic cells into embryonic stem (ES) cells (nuclear transfer ES cells, ntESCs) (Brambrink et al., 2006; Wakayama et al., 2006). However, it is still controversial whether reprogramming method per se determines the pluripotency of resulting cells. Here, using genetically identical donor cells, we generated three kinds of mouse reprogrammed cells: iPSCs, ntESCs, and iPSC-nt-ESCs, after successively reprogramming of iPSCs by nuclear transfer. We found that ntESCs had better developmental potential compared with iPSCs, and following nuclear transfer can not rescue, but deteriorate the developmental deficiency of iPSCs, resulting in the worst developmental ability in iPSC-nt-ESCs.
