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Project description:Generation of induced pluripotent stem cells from specialized cell types provides an excellent model to study how cells maintain their stability, and how they can change identity, especially in the context of disease. Previous studies have shown that chromatin safeguards cell identity by acting as a barrier to reprogramming. We investigated mechanisms by which the histone macroH2A variants inhibit reprogramming and discovered that they work as gate keepers of the mesenchymal cell state by blocking epithelial transition, a step required for reprogramming of mouse fibroblasts. More specifically, we found that individual macroH2A variants regulate the expression of defined sets of genes, whose overall function is to stabilize the mesenchymal gene expression program, thus resisting reprogramming. We identified a novel gene network (MSCN, mesenchymal network) composed of 63 macroH2A-regulated genes related to extracellular matrix, cell membrane, signaling and the transcriptional regulators Id2 and Snai2, all of which function as guardians of the mesenchymal phenotype. ChIP-seq and KD experiments revealed a macroH2A variant-specific combinatorial targeting of the genes reconstructing the MSCN, thus generating robustness in gene expression programs to resist cellular reprogramming.
| S-EPMC10335705 | biostudies-literature
Project description:The establishment and maintenance of cellular identity rely upon the precise coordination of regulatory pathways culminating to the proper execution of cell type-specific gene expression programs. Generation of induced pluripotent stem cells (iPSCs) from highly specialized cell types provides an excellent model system to study how cells maintain their stability through the functional interplay of transcription factors and chromatin structure, and how they can change identity, especially in the context of disease. Previous studies have shown that chromatin structure safeguards cell identity by acting as a barrier to reprogramming. Here, we investigated the mechanisms of how the histone variant macroH2A inhibits reprogramming by interfering with the mesenchyme to epithelial transition, a step that is a prerequisite for reprogramming of mouse embryonic fibroblasts. We found that each of the macroH2A isoforms regulates the expression of defined sets of genes, whose overall function is to stabilize the mesenchyme phenotype, thus resisting reprogramming. We identified a novel gene network (MSCN, mesenchyme network) composed of 63 macroH2A-regulated genes encoding proteins of the extracellular matrix, cell membrane, cytoplasmic signal integrators and the transcriptional regulators Id2 and Snai2, all of which can function as key controllers of the mesenchyme phenotype. Functional studies including ChIP-seq and KD experiments using any one of the individual macroH2A isoforms revealed an isoform-specific combinatorial targeting of the genes that reconstruct the MSCN. Our findings established that the combinatorial macroH2A targeting of the MSCN components safeguards cell identity and demonstrated its pivotal role in maintaining the differentiated cell phenotype by generating robustness in gene expression programs to resist cellular reprogramming.
2023-06-21 | GSE215884 | GEO
Project description:The establishment and maintenance of cellular identity rely upon the precise coordination of regulatory pathways culminating to the proper execution of cell type-specific gene expression programs. Generation of induced pluripotent stem cells (iPSCs) from highly specialized cell types provides an excellent model system to study how cells maintain their stability through the functional interplay of transcription factors and chromatin structure, and how they can change identity, especially in the context of disease. Previous studies have shown that chromatin structure safeguards cell identity by acting as a barrier to reprogramming. Here, we investigated the mechanisms of how the histone variant macroH2A inhibits reprogramming by interfering with the mesenchyme to epithelial transition, a step that is a prerequisite for reprogramming of mouse embryonic fibroblasts. We found that each of the macroH2A isoforms regulates the expression of defined sets of genes, whose overall function is to stabilize the mesenchyme phenotype, thus resisting reprogramming. We identified a novel gene network (MSCN, mesenchyme network) composed of 63 macroH2A-regulated genes encoding proteins of the extracellular matrix, cell membrane, cytoplasmic signal integrators and the transcriptional regulators Id2 and Snai2, all of which can function as key controllers of the mesenchyme phenotype. Functional studies including ChIP-seq and KD experiments using any one of the individual macroH2A isoforms revealed an isoform-specific combinatorial targeting of the genes that reconstruct the MSCN. Our findings established that the combinatorial macroH2A targeting of the MSCN components safeguards cell identity and demonstrated its pivotal role in maintaining the differentiated cell phenotype by generating robustness in gene expression programs to resist cellular reprogramming.
2023-06-21 | GSE215883 | GEO
Project description:Combinatorial targeting of a novel MET/EMT network components by macroH2A variants safeguards cell identity.
| PRJNA891225 | ENA
Project description:Combinatorial targeting of a novel MET/EMT network components by macroH2A variants safeguards cell identity [RNA-seq]
| PRJNA891229 | ENA
Project description:Combinatorial targeting of a novel MET/EMT network components by macroH2A variants safeguards cell identity [ChIP-seq]
| PRJNA891232 | ENA
Project description:MacroH2A core histone variants have a unique structure that includes a C-terminal nonhistone domain. They are highly conserved in vertebrates and are thought to regulate gene expression. However, the nature of genes regulated by macroH2As and their biological significance remain unclear. Here, we examine macroH2A function in vivo by knocking out both macroH2A1 and macroH2A2 in the mouse. While macroH2As are not required for early development, the absence of macroH2As impairs prenatal and postnatal growth and can significantly reduce reproductive efficiency. The distributions of macroH2A.1- and macroH2A.2-containing nucleosomes show substantial overlap, as do their effects on gene expression. Our studies in fetal and adult liver indicate that macroH2As can exert large positive or negative effects on gene expression, with macroH2A.1 and macroH2A.2 acting synergistically on the expression of some genes and apparently having opposing effects on others. These effects are very specific and in the adult liver preferentially involve genes related to lipid metabolism, including the leptin receptor. MacroH2A-dependent gene regulation changes substantially in postnatal development and can be strongly affected by fasting. We propose that macroH2As produce adaptive changes to gene expression, which in the liver focus on metabolism.
| S-EPMC4248737 | biostudies-literature
Project description:Over the last years, microRNAs (miRs) have shown to be crucial for breast tumour establishment and progression. To understand the influence that miRs have over transcriptional regulation in breast cancer, we constructed mutual information networks from 86 TCGA matched breast invasive carcinoma and control tissue RNA-Seq and miRNA-Seq sequencing data. We show that miRs are determinant for tumour and control data network structure. In tumour data network, miR-200, miR-199 and neighbour miRs seem to cooperate on the regulation of the acquisition of epithelial and mesenchymal traits by the biological processes: Epithelial-Mesenchymal Transition (EMT) and Mesenchymal to Epithelial Transition (MET). Despite structural differences between tumour and control networks, we found a conserved set of associations between miR-200 family members and genes such as VIM, ZEB-1/2 and TWIST-1/2. Further, a large number of miRs observed in tumour network mapped to a specific chromosomal location in DLK1-DIO3 (Chr14q32); some of those miRs have also been associated with EMT and MET regulation. Pathways related to EMT and TGF-beta reinforce the relevance of miR-200, miR-199 and DLK1-DIO3 cluster in breast cancer. With this approach, we stress that miR inclusion in gene regulatory network construction improves our understanding of the regulatory mechanisms underlying breast cancer biology.
| S-EPMC5648819 | biostudies-literature
Project description:Cellular differentiation involves profound remodelling of chromatic landscapes, yet the mechanisms by which somatic cell identity is subsequently maintained remain incompletely understood. To further elucidate regulatory pathways that safeguard the somatic state, we performed two comprehensive RNA interference (RNAi) screens targeting chromatin factors during transcription-factor-mediated reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPS cells). Subunits of the chromatin assembly factor-1 (CAF-1) complex, including Chaf1a and Chaf1b, emerged as the most prominent hits from both screens, followed by modulators of lysine sumoylation and heterochromatin maintenance. Optimal modulation of both CAF-1 and transcription factor levels increased reprogramming efficiency by several orders of magnitude and facilitated iPS cell formation in as little as 4 days. Mechanistically, CAF-1 suppression led to a more accessible chromatin structure at enhancer elements early during reprogramming. These changes were accompanied by a decrease in somatic heterochromatin domains, increased binding of Sox2 to pluripotency-specific targets and activation of associated genes. Notably, suppression of CAF-1 also enhanced the direct conversion of B cells into macrophages and fibroblasts into neurons. Together, our findings reveal the histone chaperone CAF-1 to be a novel regulator of somatic cell identity during transcription-factor-induced cell-fate transitions and provide a potential strategy to modulate cellular plasticity in a regenerative setting.
| S-EPMC4866648 | biostudies-literature
Project description:The epigenome regulates gene expression and provides a molecular memory of cellular events. A growing body of evidence has highlighted the importance of epigenetic regulation in physiological tissue homeostasis and malignant transformation. Among epigenetic mechanisms, the replacement of replication-coupled histones with histone variants is the least understood. Due to differences in protein sequence and genomic distribution, histone variants contribute to the plasticity of the epigenome. Here, we focus on the family of macroH2A histone variants that are particular in having a tripartite structure consisting of a histone fold, an intrinsically disordered linker and a globular macrodomain. We discuss how these domains mediate different molecular functions related to chromatin architecture, transcription and DNA repair. Dysregulated expression of macroH2A histone variants has been observed in different subtypes of cancer and has variable prognostic impact, depending on cellular context and molecular background. We aim to provide a concise review regarding the context- and isoform-dependent contributions of macroH2A histone variants to cancer development and progression.
| S-EPMC8232725 | biostudies-literature