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Establishing and improving retroviral episome transfer of transcription factors to achieve cell fate conversion and reprogramming

ABSTRACT: Gene transfer of distinct cocktails of transcription factors enables the targeted modification of cell fate. Reprogramming somatic cells to induced pluripotent stem cells (iPSCs) via ectopic expression of the transcription factors Oct4, Sox2, Klf4 and c-Myc allows creation of pluripotent cells with the potential to differentiate into any cell type of the body. To achieve a high degree of biosafety for future application of converted cells, technologies are required to express the required transcription factors without affecting the target cell genome. Retroviral vectors are widely employed gene transfer vehicles and can be converted into transient gene delivery vehicles by mutation of the viral integrase, thus avoiding risks associated with retroviral integration. We improved the retroviral episome transfer system by identifying the most suitable vector architecture, by enhancing episomal expression and by tuning the activity of the transcription factor Oct4. Repeated episomal transductions allowed establishment of stable, fully reversible expression levels over time. Providing proof-of-principle in the reprogramming context, we were able to generate human iPSCs following retroviral episomal transfer of Oct4 in fibroblasts stably expressing Klf4, Sox2 and c-Myc, with a high percentage of clones not carrying residually integrated vector copies. RNA obtained from human embryonic stem cells, fibroblasts and induced pluripotent stem cell lines reprogrammed with the mentioned reprogramming protocol

ORGANISM(S): Homo sapiens

SUBMITTER: Franz-Josef Müller

PROVIDER: E-GEOD-57378 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Establishing and improving retroviral episome transfer of transcription factors to achieve cell fate conversion and reprogramming

Project description:Gene transfer of distinct cocktails of transcription factors enables the targeted modification of cell fate. Reprogramming somatic cells to induced pluripotent stem cells (iPSCs) via ectopic expression of the transcription factors Oct4, Sox2, Klf4 and c-Myc allows creation of pluripotent cells with the potential to differentiate into any cell type of the body. To achieve a high degree of biosafety for future application of converted cells, technologies are required to express the required transcription factors without affecting the target cell genome. Retroviral vectors are widely employed gene transfer vehicles and can be converted into transient gene delivery vehicles by mutation of the viral integrase, thus avoiding risks associated with retroviral integration. We improved the retroviral episome transfer system by identifying the most suitable vector architecture, by enhancing episomal expression and by tuning the activity of the transcription factor Oct4. Repeated episomal transductions allowed establishment of stable, fully reversible expression levels over time. Providing proof-of-principle in the reprogramming context, we were able to generate human iPSCs following retroviral episomal transfer of Oct4 in fibroblasts stably expressing Klf4, Sox2 and c-Myc, with a high percentage of clones not carrying residually integrated vector copies.

2015-05-06 | GSE57378 | GEO

Small molecules enable highly efficient neuronal conversion of human fibroblasts

Project description:Forced expression of pro-neural transcription factors was shown to mediate direct neuronal conversion of human fibroblasts. Since neurons are postmitotic, the conversion efficiency represents an important parameter. Here we present a minimalist approach combining two factor neuronal programming with small molecule-based inhibition of GSK3ß and SMAD signaling, which gives rise to functional neuron-like cells (iNs) of various neurotransmitter phenotypes with an overall yield of up to >200% and a final neuronal purity of up to >80%. Timcourse of reprogramming of fibroblasts towards an neuronal phenotype in two independent fibroblast lines

2012-04-07 | E-GEOD-36246 | biostudies-arrayexpress

Transcription profiling of human induced pluripotent stem cells signature and memory retention

Project description:Transient expression of two factors, or from Oct4 alone, resulted in efficient generation of human iPSCs. The reprogramming strategy described revealed a potential transcriptional signature for human iPSCs yet retaining the gene expression of donor cells in human reprogrammed cells free of viral and transgene interference. Genetic reprogramming of somatic cells to a pluripotent state (induced pluripotent stem cells or iPSCs) by over-expression of specific genes has been accomplished using mouse and human cells. However, it is still unclear how similar human iPSCs are to human Embryonic Stem Cells (hESCs). Here, we describe the transcriptional profile of human iPSCs generated without viral vectors or genomic insertions, revealing that these cells are in general similar to hESCs but with significant differences. For the generation of human iPSCs without viral vectors or genomic insertions, pluripotent factors Oct4 and Nanog were cloned in episomal vectors and transfected into human fetal neural progenitor cells. The transient expression of these two factors, or from Oct4 alone, resulted in efficient generation of human iPSCs. The reprogramming strategy described here revealed a potential transcriptional signature for human iPSCs yet retaining the gene expression of donor cells in human reprogrammed cells free of viral and transgene interference. Moreover, the episomal reprogramming strategy represents a safe way to generate human iPSCs for clinical purposes and basic research. Experiment Overall Design: Gene expression profiles measured using human genome Affymetrix Gene Chip arrays were grouped by hierarchical clustering, and correlation coefficients were computed for all pair-wise comparisons

2009-12-19 | E-GEOD-18618 | biostudies-arrayexpress

Excluding Oct4 from Yamanaka cocktail unleashes the developmental potential of iPSCs

Project description:Oct4 is widely considered the most important among the four Yamanaka reprogramming factors. Here we show that the combination of Sox2, Klf4, and cMyc (SKM) suffices for reprogramming mouse somatic cells to induced pluripotent stem cells (iPSCs). Simultaneous induction of Sox2 and cMyc in fibroblasts triggers immediate retroviral silencing, which explains the discrepancy with previous studies that attempted but failed to generate iPSCs without Oct4 using retroviral vectors. SKM induction could partially activate the pluripotency network even in Oct4-knockout fibroblasts. Importantly, reprogramming in the absence of exogenous Oct4 results in greatly improved developmental potential of iPSCs, determined by their ability to give rise to all-iPSC mice in the tetraploid complementation assay. Our data suggest that overexpression of Oct4 during reprogramming leads to off-target gene activation during reprogramming and epigenetic aberrations in resulting iPSCs, and thereby bear major implications for further development and application of iPSC technology.

2019-11-06 | GSE137001 | GEO

Influence of ATM-mediated DNA damage response on genomic variation in human induced pluripotent stem cells (Affymetrix CNV)

Project description:Genome instability is a potential limitation to the research and therapeutic application of induced pluripotent stem cells (iPSCs). Observed genomic variations reflect the combined activities of DNA damage, cellular DNA damage response (DDR), and selection pressure in culture. To understand the contribution of DDR on the distribution of copy number variations (CNVs) in iPSCs, we mapped CNVs of iPSCs with mutations in the central DDR gene ATM onto genome organization landscapes defined by genome-wide replication timing profiles. We show that following reprogramming the early and late replicating genome is differentially affected by CNVs in ATM deficient iPSCs relative to wild type iPSCs. Specifically, the early replicating regions had increased CNV losses during retroviral reprogramming. This differential CNV distribution was not present after later passage or after episomal reprogramming. Comparison of different reprogramming methods in the setting of defective DNA damage response reveals unique vulnerability of early replicating open chromatin to retroviral vectors. We isolated genomic DNA from Ataxia-telangiectasia (A-T) iPSC cells derived from patient fibroblasts virus and episomal vectors, coresponding fibroblasts, normal human fibroblast derived iPSCcells, for hybridization to the Affymetrix Genome-Wide Human SNP 6.0 Array.

2016-03-29 | E-GEOD-78715 | biostudies-arrayexpress

Transcriptional Signature and Memory Retention of Human-induced Pluripotent Stem Cells

2009-10-20 | GSE18618 | GEO

Influence of ATM-mediated DNA damage response on genomic variation in human induced pluripotent stem cells (NimbleGen CNV)

2016-03-29 | E-GEOD-78717 | biostudies-arrayexpress

Comparisons between fully and partially reprogrammed iPS cells induced by pMX-Klf4, pMX-Oct4 and pMX-Sox2 retroviruses

Project description:Induced pluripotent stem (iPS) cell reprogramming is a gradual epigenetic process that reactivates the pluripotent transcriptional network by erasing and establishing heterochromatin marks. Here, we characterize the physical structure of heterochromatin domains in full and partial mouse iPS cells by correlative Electron Spectroscopic Imaging (ESI). In somatic and partial iPS cells, constitutive heterochromatin marked by H3K9me3 is highly compartmentalized into chromocenter structures of densely packed 10 nm chromatin fibers. In contrast, chromocenter boundaries are poorly defined in pluripotent ES and full iPS cells, and are characterized by unusually dispersed 10 nm heterochromatin fibers in high Nanog-expressing cells, including pluripotent cells of the mouse blastocyst prior to differentiation. This heterochromatin reorganization accompanies retroviral silencing during conversion of partial iPS cells by Mek/Gsk3 2i inhibitor treatment. Thus, constitutive heterochromatin reorganization serves as a novel biomarker with retroviral silencing for identifying iPS cells in the very late stages of reprogramming. We compared the expression profiles of partially and fully reprogrammed iPS cell lines derived from CD1 mouse embryonic fibroblasts (MEFSs) by retroviral reprogramming (pMX-Oct4, pMX-Klf4 and pMX-Sox2). to the differentiated MEFS and the J1 embryonic stem cell line. We also studied the effect of a 2i cocktail treatment in partially reprogrammed iPS cells.

2011-09-21 | E-GEOD-21595 | biostudies-arrayexpress

Influence of ATM-mediated DNA damage response on genomic variation in human induced pluripotent stem cells (Affymetrix expression)

Project description:Genome instability is a potential limitation to the research and therapeutic application of induced pluripotent stem cells (iPSCs). Observed genomic variations reflect the combined activities of DNA damage, cellular DNA damage response (DDR), and selection pressure in culture. To understand the contribution of DDR on the distribution of copy number variations (CNVs) in iPSCs, we mapped CNVs of iPSCs with mutations in the central DDR gene ATM onto genome organization landscapes defined by genome-wide replication timing profiles. We show that following reprogramming the early and late replicating genome is differentially affected by CNVs in ATM deficient iPSCs relative to wild type iPSCs. Specifically, the early replicating regions had increased CNV losses during retroviral reprogramming. This differential CNV distribution was not present after later passage or after episomal reprogramming. Comparison of different reprogramming methods in the setting of defective DNA damage response reveals unique vulnerability of early replicating open chromatin to retroviral vectors. We isolated RNA from Ataxia-telangiectasia (A-T) patient fibroblast derived iPS cells and A-T patient fibroblasts for hybridization to the Affymetrix gene expression microarrays.

2016-03-29 | E-GEOD-78716 | biostudies-arrayexpress

Pluripotency factor-induced lineage conversion involves transient passage through an iPS cell stage

Project description:Brief expression of pluripotency-associated factors such as OCT4, KLF4, SOX2 and c-MYC (OKSM), in combination with differentiation-inducing signals, was reported to trigger transdifferentiation of fibroblasts into alternative cell types. Here, we show that OKSM expression gives rise to both induced pluripotent stem cells (iPSCs) and iNSCs under conditions that were previously shown to induce only NSC transdifferentiation. Fibroblast-derived iNSC colonies silenced retroviral transgenes and reactivated silenced X chromosomes, both hallmarks of pluripotent stem cells. Moreover, lineage tracing via an Oct4-CreER labeling system demonstrated that virtually all iNSC colonies originate from cells transiently expressing Oct4, whereas ablation of Oct4-positive cells prevented iNSC formation. Lastly, use of an alternative transdifferentiation cocktail that lacks OCT4 and was reportedly unable to support induced pluripotency, yielded iPSCs and iNSCs carrying the Oct4-CreER-derived lineage label. Together, these data suggest that iNSC generation using OKSM and related reprogramming factors requires passage through a transient iPSC state. 5 samples were anlyzed in total, 2 induced pluripotent stem cells (iPSCs), 1 neural stem cells (NSCs) and 2 induced NSCs (iNSCs)

2015-04-30 | E-GEOD-65951 | biostudies-arrayexpress

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