Difference between hESCs and NSC-Derived Integration-Free iPSCs

By introducing Oct4 and Nanog into human fetal neural progenitor cells, the Muotri lab at UCSD, in collaboration with colleagues from the Yeo and Gage labs of UCSD and Salk, was able to create induced pluripotent stem cells (iPS cells) using the oriP/EBNA1 episomal system to introduce the aforementioned Oct4 and Nanog. While it has been shown by others that with less differentiated cells, such as progenitor cells, it is relatively easy to reprogram using two, or sometimes even one, of the commonly used iPSC generating factors (Oct4, Sox2, Klf4, c-Myc, Nanog, or Lin28) as reported in the AlleleNews article “iPSC generated by using a single reprogramming factor” on August 3rd, 2009, the new publication in PLoS ONE analyzed in detail the differences between embryonic stem cells (ES cells) and iPS cells.



There were three groups of genes that changed significantly between hESC versus iPSC and iPSC versus NSC; genes that are important in early embryonic fate including iPSC-expressed factors that are not sufficiently repressed and genes that are upregulated in iPSCs but are silenced in both NSCs and hESCs which may be downstream to the reprogramming genes during dedifferentiation. Their conclusion is that iPSCs may retain the gene expression signature of donor cells in human reprogrammed cells, even with integration-free gene transfer vehicles such as oriP/EBNA1 element containing plasmids. It should be pointed out that this episomal vector system has been previously reported for iPS cell generation by the Thomson group, see:

(http://allelebiotech.com/blogs/2009/03/episomal-expression-of-ips-inducing-genes-no-trace-of-transgenes-afterwards/). In this paper it was also shown, not unexpectedly, that myc-immortalized cell lines can be efficiently reprogrammed.



Marchetto et al. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0007076



Note from Allele: Congratulations to Maria, Gene, Alysson and the Gage lab.