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Project description:Acquisition of Pluripotency by HAG1-mediated Epigenetic Reprogramming of Key Potency Factor-encoding Loci in Arabidopsis
| PRJNA393553 | ENA
Project description:Shoot regeneration can be achieved in vitro through a two-step process involving the acquisition of pluripotency on callus-induction media (CIM) and the formation of shoots on shoot-induction media. Although the induction of root-meristem genes in callus has been noted recently, the mechanisms underlying their induction and their roles in de novo shoot regeneration remain unanswered. Here, we show that the histone acetyltransferase HAG1/AtGCN5 is essential for de novo shoot regeneration. In developing callus, it catalyzes histone acetylation at several root meristem-gene loci including WOX5, WOX14, SCR, PLT1, and PLT2, providing an epigenetic platform for their transcriptional activation. In turn, we demonstrate that the transcription factors encoded by these loci act as key potency factors conferring regeneration potential to callus and establishing competence for de novo shoot regeneration. Thus, our study uncovers key epigenetic and potency factors regulating plant-cell pluripotency. These factors might be useful in reprogramming lineage-specified plant cells to pluripotency.
| S-SCDT-EMBOJ-2017-98726 | biostudies-other
Project description:Shoot regeneration can be achieved in vitro through a two-step process involving the acquisition of pluripotency on callus-induction media (CIM) and the formation of shoots on shoot-induction media. Although the induction of root-meristem genes in callus has been noted recently, the mechanisms underlying their induction and their roles in de novo shoot regeneration remain unanswered. Here, we show that the histone acetyltransferase HAG1/AtGCN5 is essential for de novo shoot regeneration. In developing callus, it catalyzes histone acetylation at several root-meristem gene loci including WOX5, WOX14, SCR, PLT1, and PLT2, providing an epigenetic platform for their transcriptional activation. In turn, we demonstrate that the transcription factors encoded by these loci act as key potency factors conferring regeneration potential to callus and establishing competence for de novo shoot regeneration. Thus, our study uncovers key epigenetic and potency factors regulating plant-cell pluripotency. These factors might be useful in reprogramming lineage-specified plant cells to pluripotency.
| S-EPMC6187204 | biostudies-literature
Project description:In plants, multiple detached tissues are capable of forming a pluripotent cell mass, termed callus, when cultured on media containing appropriate plant hormones. Recent studies demonstrated that callus resembles the root-tip meristem, even if it is derived from aerial organs. This finding improves our understanding of the regeneration process of plant cells; however, the molecular mechanism that guides cells of different tissue types to form a callus still remains elusive. Here, we show that genome-wide reprogramming of histone H3 lysine 27 trimethylation (H3K27me3) is a critical step in the leaf-to-callus transition. The Polycomb Repressive Complex 2 (PRC2) is known to function in establishing H3K27me3. By analyzing callus formation of mutants corresponding to different histone modification pathways, we found that leaf blades and/or cotyledons of the PRC2 mutants curly leaf swinger (clf swn) and embryonic flower2 (emf2) were defective in callus formation. We identified the H3K27me3-covered loci in leaves and calli by a ChIP-chip assay, and we found that in the callus H3K27me3 levels decreased first at certain auxin-pathway genes. The levels were then increased at specific leaf genes but decreased at a number of root-regulatory genes. Changes in H3K27me3 levels were negatively correlated with expression levels of the corresponding genes. One possible role of PRC2-mediated H3K27me3 in the leaf-to-callus transition might relate to elimination of leaf features by silencing leaf-regulatory genes, as most leaf-preferentially expressed regulatory genes could not be silenced in the leaf explants of clf swn. In contrast to the leaf explants, the root explants of both clf swn and emf2 formed calli normally, possibly because the root-to-callus transition bypasses the leaf gene silencing process. Furthermore, our data show that PRC2-mediated H3K27me3 and H3K27 demethylation act in parallel in the reprogramming of H3K27me3 during the leaf-to-callus transition, suggesting a general mechanism for cell fate transition in plants.
| S-EPMC3426549 | biostudies-literature
Project description:In 2006, the "wall came down" that limited the experimental conversion of differentiated cells into the pluripotent state. In a landmark report, Shinya Yamanaka's group described that a handful of transcription factors (Oct4, Sox2, Klf4 and c-Myc) can convert a differentiated cell back to pluripotency over the course of a few weeks, thus reprograming them into induced pluripotent stem (iPS) cells. The birth of iPS cells started off a rush among researchers to increase the efficiency of the reprogramming process, to reveal the underlying mechanistic events, and allowed the generation of patient- and disease-specific human iPS cells, which have the potential to be converted into relevant specialized cell types for replacement therapies and disease modeling. This review addresses the steps involved in resetting the epigenetic landscape during reprogramming. Apparently, defined events occur during the course of the reprogramming process. Immediately, upon expression of the reprogramming factors, some cells start to divide faster and quickly begin to lose their differentiated cell characteristics with robust downregulation of somatic genes. Only a subset of cells continue to upregulate the embryonic expression program, and finally, pluripotency genes are upregulated establishing an embryonic stem cell-like transcriptome and epigenome with pluripotent capabilities. Understanding reprogramming to pluripotency will inform mechanistic studies of lineage switching, in which differentiated cells from one lineage can be directly reprogrammed into another without going through a pluripotent intermediate.
| S-EPMC3193418 | biostudies-other
Project description:Mouse embryonic stem cells (mESCs) cultured under serum/LIF conditions exhibit heterogeneous expression of pluripotency-associated factors that can be overcome by two inhibitors (2i) of the MEK and GSK3 pathways. Several studies have shown that the "ground state" induced by 2i is characterized by global hypomethylation and specific transcriptional profiles, but little is known about the contributing effectors. Here we show that 2i conditions rapidly alter the global binding landscape of OCT4, SOX2, and NANOG. The dynamic binding influences enhancer activity and shows enrichment for regulators linked to Wnt and Erk signaling. Epigenomic characterization provided limited insights to the immediate transcriptional dynamics, suggesting that these are likely more secondary effects. Likewise, loss of the PRC2 component EED to prevent H3K27me3 deposition had minimal effect on the transcriptome, implying that it is largely dispensable for continued repression of bivalent genes and de novo silencing in 2i.
| S-EPMC4592414 | biostudies-literature
Project description:As somatic cells are converted into induced pluripotent stem cells (iPSCs), their chromatin is remodeled to a pluripotent configuration with unique euchromatin-to-heterochromatin ratios, DNA methylation patterns, and enhancer and promoter status. The molecular machinery underlying this process is largely unknown. Here, we show that embryonic stem cell (ESC)-specific factors Dppa2 and Dppa4 play a key role in resetting the epigenome to a pluripotent state. They are induced in reprogramming intermediates, function as a heterodimer, and are required for efficient reprogramming of mouse and human cells. When co-expressed with Oct4, Klf4, Sox2, and Myc (OKSM) factors, Dppa2/4 yield reprogramming efficiencies that exceed 80% and accelerate reprogramming kinetics, generating iPSCs in 2 to 4 days. When bound to chromatin, Dppa2/4 initiate global chromatin decompaction via the DNA damage response pathway and contribute to downregulation of somatic genes and activation of ESC enhancers, all of which enables an efficient transition to pluripotency. Our work provides critical insights into how the epigenome is remodeled during acquisition of pluripotency.
| S-EPMC6128737 | biostudies-literature
Project description:Enforced ectopic expression of a cocktail of pluripotency-associated genes such as Oct4, Sox2, Klf4 and c-Myc can reprogram somatic cells into induced pluripotent stem cells (iPSCs). The remarkable proliferation ability of iPSCs and their aptitude to redifferentiate into any cell lineage makes these cells a promising tool for generating a variety of human tissue in vitro. Yet, pluripotency induction is an inefficient process, as cells undergoing reprogramming need to overcome developmentally imposed epigenetic barriers. Recent work has shed new light on the molecular mechanisms that drive the reprogramming of somatic cells to iPSCs. Here, we present current knowledge on the transcriptional and epigenetic regulation of pluripotency induction and discuss how variability in epigenetic states impacts iPSCs' inherent biological properties.
| S-EPMC5514980 | biostudies-literature
Project description:Somatic cell nuclear transfer (SCNT)-mediated reprogramming is a rapid, efficient, and sophisticated process that reprograms differentiated somatic cells to a pluripotent state. However, many factors in this elaborate reprogramming process remain largely unknown. Here, we report that the microRNA (miR) miR-125b is an important component of SCNT-mediated reprogramming. Luciferase reporter assay, quantitative PCR, and Western blotting demonstrated that miR-125b directly binds the 3'-untranslated region of SUV39H1, encoding the histone-lysine N-methyltransferase SUV39H1, to down-regulate histone H3 lysine-9 tri-methylation (H3K9me3) in SCNT embryos. Furthermore, the miR-125b/SUV39H1 interaction induced loss of SUV39H1-mediated H3K9me3, caused heterochromatin relaxation, and promoted the development of SCNT embryos. Transcriptome analyses of SCNT blastomeres indicated that HNF1 homeobox B (HNF1B), a gene encoding a transcription factor downstream of and controlled by the miR-125b/SUV39H1 axis, is important for conferring developmental competence on preimplantation embryos. We conclude that miR-125b promotes SCNT-mediated nuclear reprogramming by targeting SUV39H1 to decrease the deposition of repressive H3K9me3 modifications.
| S-EPMC5612121 | biostudies-literature
Project description:Somatic cells can be transdifferentiated to other cell types without passing through a pluripotent state by ectopic expression of appropriate transcription factors. Recent reports have proposed an alternative transdifferentiation method in which fibroblasts are directly converted to various mature somatic cell types by brief expression of the induced pluripotent stem cell (iPSC) reprogramming factors Oct4, Sox2, Klf4 and c-Myc (OSKM) followed by cell expansion in media that promote lineage differentiation. Here we test this method using genetic lineage tracing for expression of endogenous Nanog and Oct4 and for X chromosome reactivation, as these events mark acquisition of pluripotency. We show that the vast majority of reprogrammed cardiomyocytes or neural stem cells obtained from mouse fibroblasts by OSKM-induced 'transdifferentiation' pass through a transient pluripotent state, and that their derivation is molecularly coupled to iPSC formation mechanisms. Our findings underscore the importance of defining trajectories during cell reprogramming by various methods.
| S-EPMC4500825 | biostudies-literature