A serial screen for roadblocks to reprogramming identifies the sumoylation effector protein Sumo2
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE76699 | GEO | 2016/03/03
SECONDARY ACCESSION(S): PRJNA308368
REPOSITORIES: GEO
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Project description:The generation of induced pluripotent stem cells (iPSCs) from differentiated cells following forced expression of Oct4, Klf4, Sox2 and c-Myc (OKSM) is slow and inefficient, suggesting that transcription factors have to overcome somatic barriers that resist cell fate change. Here, we performed an ubiased serial shRNA enrichment screen to identify novel repressors of somatic cell reprogramming into iPSCs. This effort uncovered the sumoylation effector protein Sumo2 as one of the strongest roadblocks to iPSC formation. Depletion of Sumo2 both enhances and accelerates reprogramming, yielding transgene-independent, chimera-competent iPSCs after as little as 36 hours of OKSM expression. We further show that the Sumo2 pathway acts independently of exogenous c-Myc expression and in parallel with small molecule enhancers of reprogramming. Critically, suppression of SUMO2 also promotes the generation of human iPSCs. Together, our results reveal sumoylation as a crucial post-transcriptional mechanism that resists the acquisition of pluripotency from fibroblasts using defined factors. Microarray analysis was performed during reprogramming or of iPSC lines derived upon Sumo2 knockdown Total RNA was isolated from day 6 reprogramming fibroblasts with or without Sumo2 knockdown; as well as stable iPSC clones derived from Sumo2 knockdown fibroblasts.
2016-03-03 | E-GEOD-76699 | biostudies-arrayexpress
Project description:The reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) upon overexpression of OCT4, KLF4, SOX2 and c-MYC (OKSM) provides a powerful system to interrogate basic mechanisms of cell fate change. However, iPSC formation with standard methods is typically protracted and inefficient, resulting in heterogeneous cell populations. We show that exposure of OKSM-expressing cells to both ascorbic acid and a GSK3-β inhibitor (AGi) facilitates more synchronous and rapid iPSC formation from several mouse cell types. AGi treatment restored the ability of refractory cell populations to yield iPSC colonies, and it attenuated the activation of developmental regulators commonly observed during the reprogramming process. Moreover, AGi supplementation gave rise to chimera-competent iPSCs after as little as 48 h of OKSM expression. Our results offer a simple modification to the reprogramming protocol, facilitating iPSC induction at unparalleled efficiencies and enabling dissection of the underlying mechanisms in more homogeneous cell populations. 18 samples were analyzed in total, samples represent bulk cultures of reprogrammable-MEFs (Rep-MEFs) that express OKSM and were supplemented with ascorbic acid and GSK3i during iPS cell induction. Control samples represent similar bulk cultures of reprogrammable-MEFs that express OKSM but were not supplemented with ascorbic acid and GSK3i during iPS cell induction. GMP-iPSCs were generated using 48 hours of OKSM+AGi induction. Fibroblast-iPSCs were generated using 96 hours of OKSM+AGi induction.
2014-09-23 | E-GEOD-57774 | biostudies-arrayexpress
Project description:The reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) upon overexpression of OCT4, KLF4, SOX2 and c-MYC (OKSM) provides a powerful system to interrogate basic mechanisms of cell fate change. However, iPSC formation with standard methods is typically protracted and inefficient, resulting in heterogeneous cell populations. We show that exposure of OKSM-expressing cells to both ascorbic acid and a GSK3-β inhibitor (AGi) facilitates more synchronous and rapid iPSC formation from several mouse cell types. AGi treatment restored the ability of refractory cell populations to yield iPSC colonies, and it attenuated the activation of developmental regulators commonly observed during the reprogramming process. Moreover, AGi supplementation gave rise to chimera-competent iPSCs after as little as 48 h of OKSM expression. Our results offer a simple modification to the reprogramming protocol, facilitating iPSC induction at unparalleled efficiencies and enabling dissection of the underlying mechanisms in more homogeneous cell populations.
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Project description:Factor-induced reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) is inefficient, complicating mechanistic studies. Here, we examined defined intermediate cell populations poised to becoming iPSCs by genome-wide analyses. We show that induced pluripotency elicits two transcriptional waves, which are driven by c-Myc/Klf4 (first wave) and Oct4/Sox2/Klf4 (second wave). Cells that become refractory to reprogramming activate the first but fail to initiate the second transcriptional wave and can be rescued by elevated expression of all four factors. The establishment of bivalent domains occurs gradually after the first wave, whereas changes in DNA methylation take place after the second wave when cells acquire stable pluripotency. This integrative analysis allowed us to identify genes that act as roadblocks during reprogramming and surface markers that further enrich for cells prone to forming iPSCs. Collectively, our data offer new mechanistic insights into the nature and sequence of molecular events inherent to cellular reprogramming. DNA methylation profiles obtained at different timepoints during reprogramming of somatic cells: Day 0, +3, +6, +9 and iPSC
2013-03-18 | E-GEOD-45248 | biostudies-arrayexpress
Project description:Cellular reprogramming from somatic cells to induced pluripotent stem cells (iPSCs) can be achieved through forced expression of the transcription factors Oct4, Klf4, Sox2 and c-Myc (OKSM). These factors, in combination with environmental cues, induce a stable intrinsic pluripotency network that confers indefinite self-renewal capacity on iPSCs. In addition to Oct4 and Sox2, the homeodomain-containing transcription factor Nanog is an integral part of the pluripotency network. Although Nanog expression is not required for the maintenance of pluripotent stem cells, it has been reported to be essential for the establishment of both embryonic stem cells (ESCs) from blastocysts and iPSCs from somatic cells. Here we revisit the role of Nanog in direct reprogramming. Surprisingly, we find that Nanog is dispensable for iPSC formation under optimized culture conditions. We further document that Nanog-deficient iPSCs are transcriptionally highly similar to wild-type iPSCs and support the generation of teratomas and chimeric mice. Lastly, we provide evidence that the presence of ascorbic acid in the culture media is critical for overcoming the previously observed reprogramming block of Nanog knockout cells. Comparison of Nanog KO iPSCs to WT pluripotent cells.
2014-01-28 | E-GEOD-53832 | biostudies-arrayexpress
Project description:Cellular differentiation involves profound changes in the chromatic landscape, yet the mechanisms by which somatic cell identity is subsequently maintained remain incompletely understood. To further elucidate regulatory pathways that safeguard the somatic state, we performed two comprehensive RNAi screens targeting chromatin factors during transcription factor-mediated reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPSCs). Remarkably, subunits of the chromatin assembly factor-1 (CAF-1) complex emerged as the most prominent hits from both screens, followed by modulators of lysine sumoylation and heterochromatin maintenance. Suppression of CAF-1 increased reprogramming efficiency by several orders of magnitude and facilitated iPSC formation in as little as 4 days. Mechanistically, CAF-1 suppression led to a more accessible chromatin structure at enhancer elements early during reprogramming. These changes were accompanied by a decrease in somatic heterochromatin domains, increased binding of Sox2 to pluripotency-specific targets and activation of associated genes. Notably, suppression of CAF-1 also enhanced the direct conversion of B cells into macrophages and fibroblasts into neurons. Together, our findings reveal the histone chaperone CAF-1 as a novel regulator of somatic cell identity during transcription factor-induced cell fate transitions and provide a potential strategy to modulate cellular plasticity in a regenerative setting. Gene expression analysis in CAF-1 knockdown and Renilla control during early OKSM-induced reprogramming by microarray
2015-12-10 | E-GEOD-72741 | biostudies-arrayexpress
Project description:Cellular reprogramming from somatic cells to induced pluripotent stem cells (iPSCs) can be achieved through forced expression of the transcription factors Oct4, Klf4, Sox2 and c-Myc (OKSM). These factors, in combination with environmental cues, induce a stable intrinsic pluripotency network that confers indefinite self-renewal capacity on iPSCs. In addition to Oct4 and Sox2, the homeodomain-containing transcription factor Nanog is an integral part of the pluripotency network. Although Nanog expression is not required for the maintenance of pluripotent stem cells, it has been reported to be essential for the establishment of both embryonic stem cells (ESCs) from blastocysts and iPSCs from somatic cells. Here we revisit the role of Nanog in direct reprogramming. Surprisingly, we find that Nanog is dispensable for iPSC formation under optimized culture conditions. We further document that Nanog-deficient iPSCs are transcriptionally highly similar to wild-type iPSCs and support the generation of teratomas and chimeric mice. Lastly, we provide evidence that the presence of ascorbic acid in the culture media is critical for overcoming the previously observed reprogramming block of Nanog knockout cells.
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Project description:Heat shock induces rapid modification of proteins with SUMO2/3. This study concentrated in charaterizing how these changes are reflected on SUMOylation of chromatin bound proteins, trancsription, and chromatin binding of SUMO ligase PIAS1. Comparison of chromatin SUMO2/3 modification pattern in non-stressed and heat shocked K562 and VCaP cells. All samples were done as biological replicates. In K562 cells, SUMO2/3 ChIP-seq was done in non-stressed (37C) and heat shocked (30min at 43C) cells. The effect of heat shock factor 1 (HSF1) to chromatin SUMOylation in HS was studied in HSF1 silenced (shHSF1) K562 cells (non-stressed vs. heat shocked) using scramble shRNA transfected cells as control (shSCR). SUMO2/3, SUMO ligase PIAS1,and RNA polymerase II binding in HS (30 min at 43C) and recovery from HS (1h at 37C after HS) was studied using ChIP-seq. Effect of PIAS1 for chromatin SUMOylation was studied in PIAS1 silenced (siRNA for PIAS1, siPIAS1) cells (non-stressed or heat shocked) using non-targeting siRNA transfected cells as a control (siNON). Effect of SUMOylation to chromatin binding of RNA polymerase II was studied in UBE2I silenced (siRNA for UBE2I) and control (non-targeting siRNA transfected, siNON) VCaP cells (non-stressed or heat shocked). Effect of transtription inhibition for chromatin SUMOylation was studied in TRP (triptolide; 1 micromolar, 3h) and DRB (5,6-Dichlorobenzimidazole 1-beta-D-ribofuranosidase; 100 micromolar, 3h) treated VCaP cells. GRO-seq was used to determine HS-induced changes in nascent transcription in K562 cells.
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