Cellular Reprogramming Picks Up Speed

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• published: 22 Sep 2013
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Video: Video 1: Highly enhanced ES-like colony formation by OSKM upon Mbd3 depletion Live imaging of reprogramming in equivalent regions (5*6 mosaic) and phase contrast, after plating 150 cells per well. Video was prepared from time-lapse measurements taken every 8 hours for 6.5 days at 50X magnification (5X objective lens), time from DOX induction is indicated in the upper title. Note the accelerated ES-like colony formation in Mbd3flox/- cells in comparison to Mbd3+/+ donor MEFs. (n=4 independent experiments). Video 2: Time-lapse microscopic imaging of deterministic reprogramming Live imaging of Mbd3flox/- and control Mbd3+/+ full well mosaics with fluorescent mCherry and Oct4-GFP markers. Measurements were taken every 12 hours for 6 days at 50X magnification. In house automated segmentation protocol was run over time-lapse data tracking Oct4-GFP activation dynamic. Right upper image show Mbd3+/+ and left upper image show Mbd3flox/- full well mosaics. Time from DOX induction is given in the upper title. Lower left graph indicates cumulative Oct4-GFP+ colonies for Mbd3flox/- (red graph) and Mbd3+/+ (blue graph). Lower right graph indicates the average fraction of Oct4-GFP+ cells within single colonies. (n=4 independent experiments). Video 3: Time-lapse imaging of reprogramming dynamics of Mbd3flox/- cells with single colony view Live imaging of Mbd3flox/- full well mosaics with fluorescent mCherry and Oct4-GFP markers. Measurements were taken every 12 hours for 6 days at 50X magnification. For each time point full well mosaic (upper image) and up to 40 representative single colony images (two lower images) are shown. The two white rectangles on the full well mosaic represent the bounding box of the two single colonies that are shown in the lower images. In addition, lower left graph indicates cumulative Oct4-GFP+ colonies and lower right graph indicates the average fraction of Oct4-GFP+ cells within single colonies for Mbd3flox/-. (n=4 independent experiments). Video 4: Time-lapse imaging of reprogramming dynamics of Mbd3+/+ cells with single colony view As in supplementary Video 3, live imaging of Mbd3+/+ full well mosaics with fluorescent mCherry and Oct4-GFP markers, measurements were taken every 12h for 6 days at 50X magnification. (n=4 independent experiments). - Cellular Reprogramming Picks Up Speed http://news.sciencemag.org/biology/2013/09/cellular-reprogramming-picks-speed Reference Deterministic direct reprogramming of somatic cells to pluripotency Nature (2013) doi:10.1038/nature12587 http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12587.html#videos Abstract Somatic cells can be inefficiently and stochastically reprogrammed into induced pluripotent stem (iPS) cells by exogenous expression of Oct4 (also called Pou5f1), Sox2, Klf4 and Myc (hereafter referred to as OSKM). The nature of the predominant rate-limiting barrier(s) preventing the majority of cells to successfully and synchronously reprogram remains to be defined. Here we show that depleting Mbd3, a core member of the Mbd3/NuRD (nucleosome remodelling and deacetylation) repressor complex, together with OSKM transduction and reprogramming in naive pluripotency promoting conditions, result in deterministic and synchronized iPS cell reprogramming (near 100% efficiency within seven days from mouse and human cells). Our findings uncover a dichotomous molecular function for the reprogramming factors, serving to reactivate endogenous pluripotency networks while simultaneously directly recruiting the Mbd3/NuRD repressor complex that potently restrains the reactivation of OSKM downstream target genes. Subsequently, the latter interactions, which are largely depleted during early pre-implantation development in vivo, lead to a stochastic and protracted reprogramming trajectory towards pluripotency in vitro. The deterministic reprogramming approach devised here offers a novel platform for the dissection of molecular dynamics leading to establishing pluripotency at unprecedented flexibility and resolution.