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Boshans LL, Factor DC, Singh V, Liu J, Zhao C, Mandoiu I, Lu QR, Casaccia P, Tesar PJ, Nishiyama A. The Chromatin Environment Around Interneuron Genes in Oligodendrocyte Precursor Cells and Their Potential for Interneuron Reprograming. Front Neurosci 2019; 13:829. [PMID: 31440130 PMCID: PMC6694778 DOI: 10.3389/fnins.2019.00829] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 07/25/2019] [Indexed: 12/13/2022] Open
Abstract
Oligodendrocyte precursor cells (OPCs), also known as NG2 glia, arise from neural progenitor cells in the embryonic ganglionic eminences that also generate inhibitory neurons. They are ubiquitously distributed in the central nervous system, remain proliferative through life, and generate oligodendrocytes in both gray and white matter. OPCs exhibit some lineage plasticity, and attempts have been made to reprogram them into neurons, with varying degrees of success. However, little is known about how epigenetic mechanisms affect the ability of OPCs to undergo fate switch and whether OPCs have a unique chromatin environment around neuronal genes that might contribute to their lineage plasticity. Our bioinformatic analysis of histone posttranslational modifications at interneuron genes in OPCs revealed that OPCs had significantly fewer bivalent and repressive histone marks at interneuron genes compared to astrocytes or fibroblasts. Conversely, OPCs had a greater degree of deposition of active histone modifications at bivalently marked interneuron genes than other cell types, and this was correlated with higher expression levels of these genes in OPCs. Furthermore, a significantly higher proportion of interneuron genes in OPCs than in other cell types lacked the histone posttranslational modifications examined. These genes had a moderately high level of expression, suggesting that the "no mark" interneuron genes could be in a transcriptionally "poised" or "transitional" state. Thus, our findings suggest that OPCs have a unique histone code at their interneuron genes that may obviate the need for erasure of repressive marks during their fate switch to inhibitory neurons.
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Affiliation(s)
- Linda L. Boshans
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
- Connecticut Institute for Brain and Cognitive Sciences, University of Connecticut, Storrs, CT, United States
| | - Daniel C. Factor
- Department of Genetics and Genome Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH, United States
| | - Vijender Singh
- Computational Biology Core, University of Connecticut, Storrs, CT, United States
| | - Jia Liu
- Advanced Science Research Center at the Graduate Center, Neuroscience Initiative, The City University of New York, New York, NY, United States
| | - Chuntao Zhao
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH, United States
| | - Ion Mandoiu
- Department of Computer Science and Engineering, University of Connecticut, Storrs, CT, United States
| | - Q. Richard Lu
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH, United States
| | - Patrizia Casaccia
- Advanced Science Research Center at the Graduate Center, Neuroscience Initiative, The City University of New York, New York, NY, United States
| | - Paul J. Tesar
- Department of Genetics and Genome Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH, United States
| | - Akiko Nishiyama
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
- Connecticut Institute for Brain and Cognitive Sciences, University of Connecticut, Storrs, CT, United States
- Institute for Systems Genomics, University of Connecticut, Storrs, CT, United States
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Mechanism of human somatic reprogramming to iPS cell. J Transl Med 2017; 97:1152-1157. [PMID: 28530648 DOI: 10.1038/labinvest.2017.56] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 04/10/2017] [Accepted: 04/17/2017] [Indexed: 01/09/2023] Open
Abstract
Somatic reprogramming to induced pluripotent stem cells (iPSC) was realized in the year 2006 in mice, and in 2007 in humans, by transiently forced expression of a combination of exogenous transcription factors. Human and mouse iPSCs are distinctly reprogrammed into a 'primed' and a 'naïve' state, respectively. In the last decade, puzzle pieces of somatic reprogramming have been collected with difficulty. Collectively, dissecting reprogramming events and identification of the hallmark of sequentially activated/silenced genes have revealed mouse somatic reprogramming in fragments, but there is a long way to go toward understanding the molecular mechanisms of human somatic reprogramming, even with developing technologies. Recently, an established human intermediately reprogrammed stem cell (iRSC) line, which has paused reprogramming at the endogenous OCT4-negative/exogenous transgene-positive pre-MET (mesenchymal-to-epithelial-transition) stage can resume reprogramming into endogenous OCT4-positive iPSCs only by change of culture conditions. Genome-editing-mediated visualization of endogenous OCT4 activity with GFP in living iRSCs demonstrates the timing of OCT4 activation and entry to MET in the reprogramming toward iPSCs. Applications of genome-editing technology to pluripotent stem cells will reshape our approaches for exploring molecular mechanisms.
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