Is “100% Conversion” No Longer a Taboo Phrase in the iPSC Field?

“By removing a single protein called Mbd3, a team at the Weizmann Institute of Science in Rehovot, Israel, was able to increase the conversion rate to almost 100%”. A staggering statement written by Monya Baker for Nature News, after her journal’s online publication by Rais et al. reported their discovery. This discovery displays that by removing the expression of nucleosome remodeling and deacetylation repressor complex member Mbd3, all cells can be reprogrammed with the OSKM Yamanaka factors. What we have described last September in Nature’s Scientific Reports (Warren et al. 2012) that by fusing Oct4 with strong transcription activation domain, we achieved essentially the same results which we call “bulk conversion”. One can imagine that the strong transcription activation domain very likely effects such strong reprogramming through some type of chromosomal remodeling indirectly.

As we later learned, people in the field believe that reprogramming is a stochastic event and it is impossible to achieve something like “bulk conversion”. We are happy to see that sea change now that a separate group also demonstrated “bulk conversion”. Recently we have shown that instead of 2 weeks or more, as required when mRNA reprogramming was first reported or commonly practiced, we could start taking up iPSCs around a week without doing any traditional transfection—just change the medium everyday as for all stem cell cultures, with mRNA complex as a supplement to be added together with bFGF.

Knocking-down Mbd3 is potentially useful, especially in situations where we have difficulty reprogramming a particular line, and it could make reprogramming more successful in more demanding conditions such as leaving out B18R as we recently established. However one needs to be cautious about the unavoidable off-target effects of siRNAs when including siRNA against Mbd3 in their RNA mix.

Rais et al. Nature (2013)

Warren et al. Scientific Reports (2012)

Tags: 100% reprogramming, bulk conversion, iPSC 101, Mbd3, Nature, R-iPSC, Rais et al., RNA transfection, siRNA-Mbd3

Picture Blog — Human mRNA-Induced Pluripotent Stem Cells Generated in Days

R-iPS Cell FAQ 1:
What phenotypic changes can be observed during a successful reprogramming trial?

About one week out, target fibroblasts should show an involution of fibroblastic processes, and foci or clusters of epitheliod cells—ideally with small nuclei, minimal cytoplasm, and signs of ongoing mitosis—should appear. Colonies with hESC morphology typically start emerging in ~10-14 days.

Tags: Episomal plasmids, footprint free, human ESCs, human iPSCs, Luigi Warren, mRNA transfection, R-iPSC