Mechanistic Insights into Reprogramming to Induced Pluripotency

Department of Biological Chemistry, David Geffen School of Medicine, Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California 90024, USA.
Journal of Cellular Physiology (Impact Factor: 3.84). 04/2011; 226(4):868-78. DOI: 10.1002/jcp.22450
Source: PubMed


Induced pluripotent stem (iPS) cells can be generated from various embryonic and adult cell types upon expression of a set of few transcription factors, most commonly consisting of Oct4, Sox2, cMyc, and Klf4, following a strategy originally published by Takahashi and Yamanaka (Takahashi and Yamanaka, 2006, Cell 126: 663-676). Since iPS cells are molecularly and functionally similar to embryonic stem (ES) cells, they provide a source of patient-specific pluripotent cells for regenerative medicine and disease modeling, and therefore have generated enormous scientific and public interest. The generation of iPS cells also presents a powerful tool for dissecting mechanisms that stabilize the differentiated state and are required for the establishment of pluripotency. In this review, we discuss our current view of the molecular mechanisms underlying transcription factor-mediated reprogramming to induced pluripotency.

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Available from: Constantinos Chronis
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    • "Thanks to the recent research accomplishments in cellular reprogramming, previous studies have shown that cells are highly plastic [Hanna et al., 2011]. This plasticity is subject to the influence of critical transcription factors whose enforced expression can directly cause phenotypic changes in cells, including differentiation [Lavon et al., 2006; Liew et al., 2008], trans‐differentiation [Ho et al., 2011; Huang et al., 2011; Murry and Pu, 2011; Sekiya and Suzuki, 2011], and de‐differentiation [Hanna et al., 2008]. Therefore, it can be speculated that there are certain specific transcription factors, or a combination of transcription factors, that can facilitate the differentiation of ESCs, or even direct reprogram ESCs, into hepatocyte‐like cells. "
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    ABSTRACT: Hepatocytes can be generated from embryonic stem cells (ESCs) using inducers such as chemical compounds and cytokines, but issues related to low differentiation efficiencies remain to be resolved. Recent work has shown that overexpression of lineage-specific transcription factors can directly cause cells phenotypic changes, including differentiation, trans-differentiation, and de-differentiation. We hypothesized that lentivirus-mediated constitutive expression of forkhead box A2 (Foxa2) and hepatocyte nuclear factor 4 alpha (Hnf4a) could promote inducing mouse ESCs to hepatocyte-likes cells. First, ESC lines that stably expressed Foxa2, Hnf4a or Foxa2/Hnf4a were constructed via lentiviral expression vectors. Second, observations of cell morphology changes were made during the cell culture process, followed by experiments examining teratoma formation. Then, the effects of constitutive expression of Foxa2 and Hnf4a on hepatic differentiation and maturation were determined by measuring the marker gene expression levels of Albumin, α-fetoprotein, Cytokeratin18, and α1-antitrypsin. The results indicate that constitutive expression of Foxa2 and Hnf4a does not affect ESCs culture, teratoma formation, or the expression levels of the specific hepatocyte genes under autonomous differentiation. However, with some assistance from inducing factors, Foxa2 significantly increased the hepatic differentiation of ESCs, whereas the expression of Hnf4a alone or Foxa2/Hnf4a could not. Differentiated CCE-Foxa2 cells were more superior in expressing several liver-specific markers and protein, storing glycogen than differentiated CCE cells. Therefore, our method employing the transduction of Foxa2 would be a valuable tool for the efficient generation of functional hepatocytes derived from ESCs. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.
    Full-text · Article · Nov 2013 · Journal of Cellular Biochemistry
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    • "Potency can be defined as the disposition of a cell to transition into another cell phenotype; pluripotency is the ability of a cell to transition naturally into any of the cell phenotypes of an organism (where a transition is natural if it is not triggered by a technical intervention). Since Takahashi and Yamanaka described cell reprogramming of fibroblasts back to pluripotency (also known as generation of iPS, induced pluripotent stem cells) [1], hundreds of papers have dissected the reprogramming process and the cellular disposition of pluripotency at an ever-increasing resolution, reviewed in, e.g., [2] and [3]. This corpus is currently underused as there is no formal representation of the reported findings. "
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    ABSTRACT: Understanding, modelling and influencing the transition between different states of cells, be it reprogramming of somatic cells to pluripotency or trans-differentiation between cells, is a hot topic in current biomedical and cell-biological research. Nevertheless, the large body of published knowledge in this area is underused, as most results are only represented in natural language, impeding their finding, comparison, aggregation, and usage. Scientific understanding of the complex molecular mechanisms underlying cell transitions could be improved by making essential pieces of knowledge available in a formal (and thus computable) manner. We describe the outline of two ontologies for cell phenotypes and for cellular mechanisms which together enable the representation of data curated from the literature or obtained by bioinformatics analyses and thus for building a knowledge base on mechanisms involved in cellular reprogramming. In particular, we discuss how comprehensive ontologies of cell phenotypes and of changes in mechanisms can be designed using the entity-quality (EQ) model. We show that the principles for building cellular ontologies published in this work allow deeper insights into the relations between the continuants (cell phenotypes) and the occurrents (cell mechanism changes) involved in cellular reprogramming, although implementation remains for future work. Further, our design principles lead to ontologies that allow the meaningful application of similarity searches in the spaces of cell phenotypes and of mechanisms, and, especially, of changes of mechanisms during cellular transitions.
    Full-text · Article · Oct 2013 · Journal of Biomedical Semantics
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    • "Since Yamanaka and coworkers published their technique of deriving iPSCs from somatic cells using the four TFs (i.e. POU5F1, SOX2, KLF4 and MYC, OSKM) [3], [4], several variations on the original combination of ingredients (including TFs, small molecules, and cytokines) have been developed to improve the efficiency of induced pluripotency [27]. Of these, POU5F1 is currently the only non-replaceable factor for human iPSCs [2], [5], [6], [28]. "
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    ABSTRACT: POU5F1 is essential for maintaining pluripotency in embryonic stem cells (ESCs). It has been reported that the constitutive activation of POU5F1 is sustained by the core transcriptional regulatory circuitry in ESCs; however, the means by which POU5F1 is epigenetically regulated remains enigmatic. In this study a fluorescence-based reporter system was used to monitor the interplay of 5 reprogramming-associated TFs and 17 chromatin regulators in the transcription of POU5F1. We show the existence of a stoichiometric effect for SOX2, POU5F1, NANOG, MYC and KLF4, in regulating POU5F1 transcription. Chromatin regulators EP300, KDM5A, KDM6A and KDM6B cooperate with KLF4 in promoting the transcription of POU5F1. Moreover, inhibiting HDAC activities induced the expression of Pou5f1 in mouse neural stem cells (NSCs) in a spatial- and temporal- dependent manner. Quantitative chromatin immunoprecipitation-PCR (ChIP-qPCR) shows that treatment with valproic acid (VPA) increases the recruitment of Kdm5a and Kdm6a to proximal promoter (PP) and proximal enhancer (PE) of Pou5f1 whereas enrichment of Ep300 and Kdm6b was seen in PP but not PE of Pou5f1 promoter. These findings reveal the interplay between the chromatin regulators and histone modifications in the expression of POU5F1.
    Full-text · Article · Dec 2012 · PLoS ONE
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