Reprogramming roadblocks are system-dependent
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE70816 | GEO | 2015/08/08
SECONDARY ACCESSION(S): PRJNA289631
REPOSITORIES: GEO
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Project description:Since the first generation of induced Pluripotent Stem cells (iPSCs), several reprogramming systems have been used to study its molecular mechanisms. However, the system of choice largely affects the reprogramming efficiency, influencing our view on the mechanisms. Here we demonstrate that reprogramming triggered by less efficient polycistronic reprogramming cassettes not only highlights Mesenchymal-Epithelial Transition (MET) as a roadblock, but also faces more severe difficulties to attain a pluripotent state even post-MET. Also, in contrast to previous findings, more efficient cassettes can reprogram both wild type and Nanog-/- fibroblasts with comparable efficiencies, routes and kinetics, rebutting previous studies that Nanog is critical for iPSC generation. We revealed that the 9 amino acids in the N-terminus of Klf4 in polycistronic reprogramming cassettes are the dominant factor causing these critical differences. Our data establishes that some reprogramming roadblocks are system-dependent, highlighting the need to pursue mechanistic studies with close attention to the systems to better understand reprogramming. The aim of the experiment is to compare the reprogramming pathways driven by two different polycistronic cassettes (MKOS and OKMS). We have isolated cells at intermediate stages of both MKOS and OKMS reprogramming and analysed their gene expression profiles. 2N- are CD44- ICAM1-, Nanog-GFP-, 3N- are CD44- ICAM1+, Nanog-GFP-, 3N+ are CD44- ICAM1+, Nanog-GFP+, all from day 10 of reprogramming. MKOS/OKMS iPSCs are established iPSC clones, TNG an Embryonic Stem Cell line carrying a Nanog-GFP reporter published in Chambers et al. Cell, 113, 643-655, from this line TNG MKOS and OKMS Embryonic Stem Cells were generated after targeting the Sp3 locus with the MKOS or the OKMS cassette respectively,E14 a reference Embryonic Stem Cell line and MEF are Mouse Embryonic Fibroblasts either wild type or generaterd from TNG MKOS or OKMS ESCs. D6 is the D6s4B5 iPSC line published in O'Malley et al. Nature, 499, 88-91.
2015-08-08 | E-GEOD-70816 | biostudies-arrayexpress
Project description:It has been suggested that the transcription factor Nanog is essential for the establishment of pluripotency during the derivation of embryonic stem (ES) cells and induced pluripotent stem (iPS) cells. However, successful reprogramming to pluripotency with a growing list of divergent transcription factors, at ever increasing efficiencies, suggests that there may be many distinct routes to a pluripotent state. Here, we have investigated whether Nanog is necessary for reprogramming murine fibroblasts under highly efficient conditions using the canonical reprogramming factors Oct4, Sox2, Klf4 and cMyc. In agreement with prior results, the efficiency of reprogramming Nanog-/- fibroblasts was significantly lower than that of control fibroblasts. However, in contrast to previous findings, we were able to reproducibly generate iPS cells from Nanog-/- fibroblasts that effectively contributed to chimeric mice. Thus while Nanog may be an important mediator of reprogramming it is not required for establishing pluripotency in the mouse, even under standard conditions. In order to further evaluate the equivalency of Nanog null iPSC to nanog null ESCs, we have performed RNAseq on two independent nanog null iPSC lines, as well as Nanog Null ESC, WT ESC and iPSCs as well as MEFs. As a negativve control for reprogramming we have analyzed a partially reprogrammed iPSC line. 2-4 biological replicates each of 7 conditions (WT MEFs, WT ESC, WT iPSC, WT partially reprogrammed iPSC (piPS), Nanog null ESC, Nanog null iPSC clone G2 and Nanog null iPSC clone G5)
2014-01-01 | E-GEOD-53212 | biostudies-arrayexpress
Project description:During the reprogramming of mouse embryonic fibroblasts (MEFs) to induced pluripotent stem cells, the activation of pluripotency genes such as Nanog occurs after the mesenchymal to epithelial transition (MET). Here we report that both adult stem cells (neural stem cells- NSCs) and differentiated cells (astrocytes) of the neural lineage can activate Nanog in the absence of cadherin expression during reprogramming. Gene expression analysis revealed that only the Nanog+Ecadherin+ populations expressed stabilization markers and had upregulated several cell cycle genes; and were transgene independent. Inhibition of Dot1L activity, which has previously been shown to increase MET, enhanced both the numbers of Nanog+ and Nanog+E-cadherin+ colonies, suggesting a MET independent pathway for activation of Nanog in NSCs. Expressing Sox2 in MEFs prior to reprogramming does not alter the ratio of Nanog colonies that express E-cadherin obtained. Taken together these results provide a novel pathway for reprogramming taken by cells of the neural lineage. Neural Stem Cells (NSCs) were induced to reprogram by the induction of Oct4, Sox2, c-Myc and Klf4. Reprogramming colonies that expressed either Nanog alone (N+E-) or Nanog and E-cadherin (N+E+) were sorted by flow cytometry and used as input for RNA-sequencing. There are 3 replicates each for the N+E- and N+E+ samples.
2016-02-18 | E-GEOD-76130 | biostudies-arrayexpress
Project description:During the reprogramming of mouse embryonic fibroblasts (MEFs) to induced pluripotent stem cells, the activation of pluripotency genes such as Nanog occurs after the mesenchymal to epithelial transition (MET). Here we report that both adult stem cells (neural stem cells- NSCs) and differentiated cells (astrocytes) of the neural lineage can activate Nanog in the absence of cadherin expression during reprogramming. Gene expression analysis revealed that only the Nanog+Ecadherin+ populations expressed stabilization markers and had upregulated several cell cycle genes; and were transgene independent. Inhibition of Dot1L activity, which has previously been shown to increase MET, enhanced both the numbers of Nanog+ and Nanog+E-cadherin+ colonies, suggesting a MET independent pathway for activation of Nanog in NSCs. Expressing Sox2 in MEFs prior to reprogramming does not alter the ratio of Nanog colonies that express E-cadherin obtained. Taken together these results provide a novel pathway for reprogramming taken by cells of the neural lineage.
2016-02-18 | GSE76130 | GEO
Project description:Oct3/4, Sox2, Klf4, and c-Myc re-wire somatic cells to achieve induced pluripotency (iPS cells). However, subtle differences in reprogramming methodology may confound comparative studies of reprogramming-induced gene expression changes. We specifically focused on the design of polycistronic reprogramming constructs, which encode all four factors linked with 2A peptides. Notably, publically available cassettes were found to employ one of two Klf4 variants (Klf4S and Klf4L; GenBank Accession No’s: AAC52939.1 and AAC04892.1), differing only by nine N-terminal amino acids. In a polycistronic context, these two variants generated dissimilar protein stoichiometry, where Klf4L vectors produced more Klf4 protein than those encoding Klf4S. Employing piggyBac transposons, we systematically assessed gene expression changes during mouse embryonic fibroblast (MEF) reprogramming using a panel of novel and publically available polycistronic cassettes (Klf4S: OKMS, STEMCCA, EB-C5, WTSI; Klf4L: OSKM, MKOS, OK+9MS, OKN-HAMS). Strikingly, global gene expression patterns elicited by the panel of polycistronic cassettes at an intermediate stage of reprogramming (day6) diverged according to the Klf4 variant they encoded. Klf4L expressing vectors induced gene expression changes in MEFs similar to over-expression of Klf4 alone. Moreover, we found that these gene expression clusters were associated with differences in reprogramming hallmarks, including colony formation frequencies and the stabilization of transgene-independent pluripotency. Our data exposes a Klf4 reference cDNA variation that alters polycistronic factor stoichiometry, implicating a threshold in determining reprogramming outcomes. We hope this study will help to guide the comparison of compatible public gene expression data sets.
2015-03-13 | GSE65468 | GEO
Project description:It has been suggested that the transcription factor Nanog is essential for the establishment of pluripotency during the derivation of embryonic stem (ES) cells and induced pluripotent stem (iPS) cells. However, successful reprogramming to pluripotency with a growing list of divergent transcription factors, at ever increasing efficiencies, suggests that there may be many distinct routes to a pluripotent state. Here, we have investigated whether Nanog is necessary for reprogramming murine fibroblasts under highly efficient conditions using the canonical reprogramming factors Oct4, Sox2, Klf4 and cMyc. In agreement with prior results, the efficiency of reprogramming Nanog-/- fibroblasts was significantly lower than that of control fibroblasts. However, in contrast to previous findings, we were able to reproducibly generate iPS cells from Nanog-/- fibroblasts that effectively contributed to chimeric mice. Thus while Nanog may be an important mediator of reprogramming it is not required for establishing pluripotency in the mouse, even under standard conditions. In order to further evaluate the equivalency of Nanog null iPSC to nanog null ESCs, we have performed RNAseq on two independent nanog null iPSC lines, as well as Nanog Null ESC, WT ESC and iPSCs as well as MEFs. As a negativve control for reprogramming we have analyzed a partially reprogrammed iPSC line.
2014-01-01 | GSE53212 | GEO
Project description:Differentiated somatic cells can be reprogrammed into induced pluripotent stem cells by ectopic expression of transcription factors Oct4, Sox2, Klf4, and c-Myc, but the mechanisms are still to be dissected. The stoichiometry of factors influences the efficiency of induced pluripotent stem cells, and previous studies emphasized the requirement of high levels of overexpressed Oct4. In this study, we showed that, with appropriate stoichiometry achieved by polycistronic cassettes, Sox2 and Klf4 were sufficient to initiate and establish pluripotency in differentiated cells efficiently without Oct4 overexpression.
2020-01-01 | GSE98280 | GEO
Project description:Many of the structural and mechanistic requirements of oocyte-mediated nuclear reprogramming remain elusive. Previous accounts that transcriptional reprogramming of somatic nuclei in mouse zygotes may be complete in 24-36 hours, far more rapidly than in other reprogramming systems, raise the question of whether the mere exposure to the activated mouse ooplasm is sufficient to enact reprogramming in a nucleus. We therefore prevented DNA replication and cytokinesis, which ensue after nuclear transfer, in order to assess their requirement for transcriptional reprogramming of the key pluripotency genes Oct4 (Pou5f1) and Nanog in cloned mouse embryos. Using transcriptome and allele-specific analysis, we observed that hundreds of mRNAs, but not Oct4 and Nanog, became elevated in nucleus-transplanted oocytes without DNA replication. Progression through the first round of DNA replication was essential but not sufficient for transcriptional reprogramming of Oct4 and Nanog, whereas cytokinesis and thereby cell-cell interactions were dispensable for transcriptional reprogramming. Responses similar to clones also were observed in embryos produced by fertilization in vitro. Our results link the occurrence of reprogramming to a previously unappreciated requirement of oocyte-mediated nuclear reprogramming, namely DNA replication. Nuclear transfer alone affords no immediate transition from a somatic to a pluripotent gene expression pattern unless DNA replication is also in place. This study is therefore a resource to appreciate that the quest for always faster reprogramming methods may collide with a limit that is dictated by the cell cycle.
2016-12-17 | GSE53497 | GEO
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:The forced expression of Yamanaka factors (Oct3/4, Sox2, Klf4, and c-Myc) reprograms cells into induced pluripotent stem cells (iPSCs) through a series of sequential cell fate conversions. The order and robustness of gene expression changes are highly depended on the Yamanaka factor stoichiometry. We specifically focused on two different reprogramming paths induced by high- and low-Klf4 stoichiometry, which were accomplished by introducing OK+9MS or OKMS polycistronic cassettes, respectively, into mouse embryonic fibroblasts. By comparing these reprograming intermediates with embryonic stem cells (ESCs) and primary keratinocytes, we identified high-Klf4 specific, transiently up-regulated epithelial genes. We found that expression of these epithelial genes was enriched in a TROP2-positive cell population. Moreover, we identified a set of transcription factors which are candidates for the regulation of transiently expressed epithelial genes, and revealed their connection to high-Klf4-specific reprogramming hallmarks.
2019-01-10 | GSE116309 | GEO