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.
OVOL1 Influences the Determination and Expansion of iPSC Reprogramming Intermediates.
Specimen part, Treatment
View SamplesSince 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. Overall design: 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.
Reprogramming Roadblocks Are System Dependent.
No sample metadata fields
View SamplesOct3/4, 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 Nos: 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.
KLF4 N-terminal variance modulates induced reprogramming to pluripotency.
Sex, Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
An EWS-FLI1-Induced Osteosarcoma Model Unveiled a Crucial Role of Impaired Osteogenic Differentiation on Osteosarcoma Development.
Specimen part, Cell line, Treatment
View SamplesEWS-FLI1, a multi-functional fusion oncogene, is exclusively detectable in Ewing sarcomas. However, previous studies reported that a subset of osteosarcomas also harbor EWS-ETS family fusion, suggesting that the fusion gene may be involved in the development of a particular type of osteosarcomas. Here using the doxycycline inducible EWS-FLI1 system, we established an EWS-FLI1-dependent osteosarcoma model from murine bone marrow stromal cells. We revealed that the withdrawal of EWS-FLI1 expression enhances the osteogenic differentiation of sarcoma cells, leading to mature bone formation. Taking advantage of induced pluripotent stem cell (iPSC) technology, we also showed that the sarcoma-derived iPSCs with cancer-related genetic abnormalities exhibited the impaired differentiation program of osteogenic lineage irrespective of the EWS-FLI1 expression. Finally, we demonstrated that EWS-FLI1 contributed to in vitro sarcoma development from the sarcoma-iPSCs after osteogenic differentiation. These findings demonstrated that modulating cellular differentiation is fundamental principle of the EWS-FLI1-induced osteosarcoma development. Furthermore, the in vitro cancer model using sarcoma-iPSCs should provide a novel platform for dissecting relationship between cancer genome and cellular differentiation.
An EWS-FLI1-Induced Osteosarcoma Model Unveiled a Crucial Role of Impaired Osteogenic Differentiation on Osteosarcoma Development.
Specimen part, Cell line, Treatment
View SamplesWe report that Zic family (Zic1/2/3) and orphan nuclear receptors family (Esrrb and Nr5a2) transcription factors (TFs) synergistically enhance the reprogramming efficiency when transduced with Oct4, Sox2 and Klf4 (OSK) into murine fibroblasts. To identify the molecular mechanisms underlying this synergy, we analyzed global gene expression at 6 days after introduction of reprogramming factors. As a result, we found that primary targets of these TFs are different when either of TFs was introduced with OSK, but a significant portion of genes including pluripotency makers such as Dppa2 was synergistically upregulated. Further analysis revealed that metabolic pathways are the important targets of these TFs for efficient reprogramming.
Hybrid Cellular Metabolism Coordinated by Zic3 and Esrrb Synergistically Enhances Induction of Naive Pluripotency.
No sample metadata fields
View SamplesWe analyzed the effects of cellular context on the function of the synovial sarcoma-specific fusion protein, SS18-SSX, using human pluripotent stem cells containing the drug-inducible SS18-SSX gene. To investigate the cell-type-dependent effecfts of SS18-SSX, we performed gene expression profiling experiments.
SS18-SSX, the Oncogenic Fusion Protein in Synovial Sarcoma, Is a Cellular Context-Dependent Epigenetic Modifier.
Specimen part
View SamplesThe spectrum of genetic mutations differs among cancers in different organs, implying a cellular context-dependent effect of the genetic aberrations. However, the extent to which the cellular context affects the consequences of oncogenic mutations remains to be fully elucidated. We reprogrammed colon tumor cells in an Apc Min/+ mouse model, in which the loss of the Apc gene plays a critical role in tumor development, and established reprogrammed tumor cells (RTCs) that exhibit pluripotent stem cell (PSC)-like signatures of gene expression. We show that the majority of the genes in the RTCs that were affected by the Apc mutations did not overlap with the genes that were affected in the intestine or those that were affected by the accumulation of beta-catenin in PSCs. The RTCs lacked pluripotency but exhibited the increased expression of Cdx2 and a differentiation propensity that was biased toward the trophectoderm cell lineage. The genetic rescue of the mutated Apc allele conferred pluripotency on the RTCs and enabled their differentiation into various cell types in vivo. The re-disruption of Apc in the RTC-derived differentiated cells resulted in neoplastic growth that was exclusive to the intestine, yet the majority of intestinal lesions remained pre-tumoral microadenomas. These results highlight the significant influence of the cellular context on gene regulation, cellular plasticity, and cellular behavior in response to the loss of the Apc function. Our results also imply that transition from microadenomas to macroscopic tumors is reprogrammable, which underscores the importance of epigenetic regulation on colon tumor promotion.
Cellular context-dependent consequences of Apc mutations on gene regulation and cellular behavior.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Srf destabilizes cellular identity by suppressing cell-type-specific gene expression programs.
Specimen part
View SamplesMulticellular organisms consist of multiple cell types, whose identities are maintained appropriately at locations where they are reside. The identity of each cell type is primarily maintained by cell-type-specific gene expression programs, but mechanisms that suppress these programs are poorly defined. Here we show that serum response factor (Srf), a transcription factor that is activated by various extracellular stimuli, can repress cell-type-specific genes and promote cellular reprogramming to pluripotency. Manipulations that decrease -actin monomer resulted in nuclear accumulation of Mkl1 and the activation of Srf, which downregulated cell-type-specific genes and altered epigenetics in enhancers and chromatin organization. Mice overexpressing Srf exhibited various pathologies including an ulcerative colitis-like symptom and a metaplasia-like phenotype in the pancreas. Our results demonstrate an unexpected function of Srf via a mechanism by which extracellular stimuli actively destabilize cell identity and suggest Srf involvement in a wide range of diseases.
Srf destabilizes cellular identity by suppressing cell-type-specific gene expression programs.
Specimen part
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