Diverse epigenetic strategies interact to control epidermal differentiation [ChIP-Seq]
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ABSTRACT: It is becoming clear that interconnected functional gene networks, rather than single genes in isolation, govern stem cell self-renewal and differentiation. To identify potential epigenetic networks that impact on human epidermal stem cells we performed siRNA based genetic screens for 332 chromatin modifiers. We developed a Bayesian mixture model to predict putative functional interactions between those epigenetic modifiers that regulated differentiation. This allowed us to discover a network of genetic interactions involving EZH2, UHRF1 (both known to regulate epidermal self-renewal), ING5 (a MORF complex component), BPTF and SMARCA5 (NURF complex components). Genome-wide localisation and global mRNA expression analysis revealed that these factors impact two distinct but functionally related gene sets, including integrin extracellular matrix receptors that mediate anchorage of epidermal stem cells to their niche. Using a competitive epidermal reconstitution assay we confirmed that ING5, BPTF, SMARCA5, EZH2 and UHRF1 control differentiation under physiological conditions. Thus, regulation of distinct gene expression programs through the interplay between diverse epigenetic strategies protects epidermal stem cells from differentiation. Examination of genome-wide localisation of ING5 in primary human keratinocytes
Project description:It is becoming clear that interconnected functional gene networks, rather than single genes in isolation, govern stem cell self-renewal and differentiation. To identify potential epigenetic networks that impact on human epidermal stem cells we performed siRNA based genetic screens for 332 chromatin modifiers. We developed a Bayesian mixture model to predict putative functional interactions between those epigenetic modifiers that regulated differentiation. This allowed us to discover a network of genetic interactions involving EZH2, UHRF1 (both known to regulate epidermal self-renewal), ING5 (a MORF complex component), BPTF and SMARCA5 (NURF complex components). Genome-wide localisation and global mRNA expression analysis revealed that these factors impact two distinct but functionally related gene sets, including integrin extracellular matrix receptors that mediate anchorage of epidermal stem cells to their niche. Using a competitive epidermal reconstitution assay we confirmed that ING5, BPTF, SMARCA5, EZH2 and UHRF1 control differentiation under physiological conditions. Thus, regulation of distinct gene expression programs through the interplay between diverse epigenetic strategies protects epidermal stem cells from differentiation. Primary human keratinocytes (line Lka, passage 2) were cultured in Keratinocyte Serum Free Medium (KSFM) to 70% confluency in 10 cm dishes. Cells were treated with: vehicle (0.2% DMSO), the EGFR inhibitor AG1478 (10 uM), recombinant human BMP2/7 heterodimer (200 ng/ml) or a combination of AG1478+BMP2/7 (10 uM and 200 ng/ml, respectively) for 48 hours. RNA was extracted directly using a Qiagen RNeasy kit
Project description:It is becoming clear that interconnected functional gene networks, rather than single genes in isolation, govern stem cell self-renewal and differentiation. To identify potential epigenetic networks that impact on human epidermal stem cells we performed siRNA based genetic screens for 332 chromatin modifiers. We developed a Bayesian mixture model to predict putative functional interactions between those epigenetic modifiers that regulated differentiation. This allowed us to discover a network of genetic interactions involving EZH2, UHRF1 (both known to regulate epidermal self-renewal), ING5 (a MORF complex component), BPTF and SMARCA5 (NURF complex components). Genome-wide localisation and global mRNA expression analysis revealed that these factors impact two distinct but functionally related gene sets, including integrin extracellular matrix receptors that mediate anchorage of epidermal stem cells to their niche. Using a competitive epidermal reconstitution assay we confirmed that ING5, BPTF, SMARCA5, EZH2 and UHRF1 control differentiation under physiological conditions. Thus, regulation of distinct gene expression programs through the interplay between diverse epigenetic strategies protects epidermal stem cells from differentiation.
Project description:It is becoming clear that interconnected functional gene networks, rather than single genes in isolation, govern stem cell self-renewal and differentiation. To identify potential epigenetic networks that impact on human epidermal stem cells we performed siRNA based genetic screens for 332 chromatin modifiers. We developed a Bayesian mixture model to predict putative functional interactions between those epigenetic modifiers that regulated differentiation. This allowed us to discover a network of genetic interactions involving EZH2, UHRF1 (both known to regulate epidermal self-renewal), ING5 (a MORF complex component), BPTF and SMARCA5 (NURF complex components). Genome-wide localisation and global mRNA expression analysis revealed that these factors impact two distinct but functionally related gene sets, including integrin extracellular matrix receptors that mediate anchorage of epidermal stem cells to their niche. Using a competitive epidermal reconstitution assay we confirmed that ING5, BPTF, SMARCA5, EZH2 and UHRF1 control differentiation under physiological conditions. Thus, regulation of distinct gene expression programs through the interplay between diverse epigenetic strategies protects epidermal stem cells from differentiation.
Project description:This SuperSeries is composed of the following subset Series: GSE34556: Diverse epigenetic strategies interact to control epidermal differentiation [ChIP-Seq] GSE34557: Diverse epigenetic strategies interact to control epidermal differentiation [Illumina bead array] Refer to individual Series
Project description:The vitamin D receptor (VDR) regulates cell proliferation and differentiation including epidermal keratinocytes by modulating transcription of its target genes. We are investigating the role of VDR in epidermal stem cells and their progenies in the regeneration process of epidermis and hair in the skin. VDR null mice are utilized in which VDR is specifically deleted in keratin 14 (K14) expressing keratinocytes by Cre-lox strategy. The impact of VDR deletion was evaluated by comparison of VDR null mice with no cre littermate control mice. The VDR was abundantly expressed in potential epidermal stem cells including basal cells in interfollicular epidermis (IFE), and in CD34 expressing bulge keratinocytes in hair follicles. Gene expression profiles and subsequent pathway analysis of stem cell enriched keratinocyte populations revealed that the VDR deletion significantly suppressed β-catenin signaling as well as VDR signaling. The role of VDR in epidermal stem cells was studied during hair follicle cycling and wound healing processes. The epidermal stem cells were not appropriately stimulated by hair depilation, and did not reinitiate anagen in the hair follicles resulting in a failure of hair regrowth. In addition, the stem cells were not fully activated after full thickness wounds were generated in VDR null skin under a low calcium diet to suppress compensation pathways. Cell proliferation was not fully induced in potential stem cells located in both IFE and hair follicles near the wounding edges, and re-epithelialization rate was delayed in VDR null skin. Gene expression profiling of the wounded skin (3 days after injury) indicated that β-catenin signaling was not fully induced in VDR null skin comparable to that observed in β-catenin null mice. The β-catenin target genes including Axin2 and cell cycle regulators involved in epidermal stem cell function were not induced in the edges of the wound of VDR null skin. These results demonstrated that VDR plays an essential role in hair cycling and wound healing processes through regulation of β-catenin signaling in epidermal stem cells and their progenies. n=3 CON and KO (each sample contain RNA extracted from keratinocytes, which is isolated from VDR KO and littermate control skins excised from 3 mice)
Project description:Progenitor cells maintain self-renewing tissues throughout life by sustaining their capacity for proliferation while suppressing cell cycle exit and terminal differentiation. DNA methylation provides a potential epigenetic mechanism for the cellular memory needed to preserve the somatic progenitor state through repeated cell divisions. DNA methyltransferase 1 (DNMT1) maintains DNA methylation patterns after cellular replication. Although dispensable for embryonic stem cell maintenance, a clear role for DNMT1 in maintaining the progenitor state in constantly replenished somatic tissues, such as mammalian epidermis, is uncharacterized. Here we show that DNMT1 is essential for supporting epidermal progenitor cell function. DNMT1 protein was found enriched in undifferentiated cells, where it was required to retain proliferative stamina and suppress differentiation. In tissue, DNMT1 depletion led to exit from the progenitor cell compartment, premature differentiation and eventual tissue loss. These effects correlated with DNA methylation as genome-wide analysis revealed that a significant portion of epidermal differentiation gene promoters were methylated in self-renewing conditions but were subsequently demethylated during differentiation. Gene expression analysis: To establish a differentiation signature for primary human keratinocytes, total RNA was isolated in biologic duplicate from cells cultured in growth conditions and high calcium differentiation conditions and hybridized to Affymetrix HG-U133 2.0 Plus arrays. This gene signature was also compared to DNMT1 deficient cells cultured in growth conditions. Methylated DNA profiling: To globally characterize DNA methylation in primary human keratinocytes, genomic DNA was immunoprecipitated using a 5-methylcytidine antibody, amplified, and hybridized to NimbleGen HG18 promoter tiling arrays. Profiling was done using DNA isolated in growth conditions as well as differentiation conditions.
Project description:Somatic progenitors suppress differentiation to maintain tissue self-renewal. While epigenetic regulators of DNA and histone modifications can support such repression, a role for nuclear actin-like proteins is unclear. In epidermis, ACTL6a/BAF53A was found enriched in progenitors and down-regulated during differentiation. Conditional ACTL6a deletion abolished epidermal self-renewal and induced terminal differentiation, whereas ectopically expressed ACTL6a suppressed differentiation. Among known activators of epidermal differentiation, KLF4 was found to control 227 genes also regulated by ACTL6a. ACTL6a loss upregulated KLF4 and its target genes, effects that were blocked by KLF4 depletion. Among multiple ACTL6a-interacting epigenetic regulators, the SWI/SNF complex was required for KLF4 activation and differentiation. In progenitors, ACTL6a loss led to enhanced SWI/SNF binding to the promoters of KLF4 and other differentiation genes. ACTL6a thus maintains the undifferentiated progenitor state, in part by suppressing SWI/SNF complex-enabled induction of KLF4. Gene expression analysis: To identify the gene set controlled by ACTL6a in human keratinocyte. Total RNA was isolated in biologic duplicate from cells with ACTL6a loss as compared to controls, and hybridized to Affymetrix HG-U133 2.0 Plus arrays.
Project description:Numerous long non-coding RNAs (lncRNAs) were shown to have functional impact on cellular processes, such as human epidermal homeostasis, but for only a few the mode of action has been elucidated. Here, we report that lncRNA LINC00941 controls keratinocyte differentiation on a global level through association with the MTA2/NuRD complex, one of the major chromatin remodelers in cells. LINC00941 was found to interact with NuRD-associated MTA2, suppressing the expression of the transcription factor EGR3, a regulator of epidermal differentiation. Both LINC00941 and the MTA2/NuRD complex are enriched in non-differentiated keratinocytes and repress the expression of differentiation genes through epigenetic silencing of EGR3, consequentially preventing premature differentiation of human progenitor cells.
Project description:Transcriptional coactivator Mediator complex facilitates transcription of various transcription factors. Previously, we have generated Med1 conditional null mice, where a critical subunit of Mediator, Med1, is removed from keratinocytes. Here we present evidence that ablation of Med1 accelerated epidermal regeneration after injury. As bulge keratinocyte stem cells are important contributors to regenerate epidermis, we first analyzed properties of stem cells in Med1 null mice. BrdU long retaining analysis revealed that deletion of Med1 still maintained quiescence of bulge keratinocyte stem cells, despite of general hyperplasia observed in Med1 deficient keratinocytes. Gene expression analysis demonstrated that a series of niche matrix proteins decreased in Med1 deficient keratinocytes. In contrast, the expression of stem cell marker Sox9 was not altered, suggesting stem cells are present but activated because of abnormal niche surrounding stem cells. In addition, Med1 deletion suppressed injury induced inflammatory reaction, which indirectly regulates epidermal regeneration. We also indicated that TGFβ1 significantly decreased in both bulge and epidermal keratinocytes upon Med1 deletion. Our study demonstrates that coactivator Med1 has a critical role to maintain bulge stem cells and epidermal regeneration presumably through regulation in TGFβ signaling. n=3 WT and KO (each group contains keratinocytes isolated from adult skins excised from 2 mice)
Project description:Progenitor cells at the basal layer of skin epidermis play an essential role in maintaining tissue homeostasis and enhancing wound repair in skin. The proliferation, differentiation, and cell death of epidermal progenitor cells have to be delicately regulated, as deregulation of this process can lead to many skin diseases, including skin cancers. However, the underlying molecular mechanisms involved in skin homeostasis remain poorly defined. In this study, with quantitative proteomics approach, we identified an important interaction between KDF1 (Keratinocyte Differentiation Factor 1) and IKKα (IκB kinase α) in differentiating skin keratinocytes. Ablation of either KDF1 or IKKα in mice leads to similar but striking abnormalities in skin development, particularly in skin epidermal differentiation. With biochemical and mouse genetics approach, we further demonstrate that the interaction of IKKα and KDF1 is essential for epidermal differentiation. To probe deeper into the mechanisms, we find that KDF1 associates with a deubiquitinating protease, USP7 (Ubiquitin Specific Peptidase 7), and KDF1 can regulate skin differentiation through deubiquitination and stabilization of IKKα. Taken together, our study unravels an important molecular mechanism underlying skin tissue homeostasis and epidermal differentiation.