Spatially restricted position-dependent implications of lamin A promoter occupancy on gene activity (ChIPs and MeDips)
ABSTRACT: Interactions between the nuclear lamina (NL) and chromatin are thought to occur through large lamin association domains (LADs) and correlate with gene repression in these domains. We show that binding of lamin A/C (LMNA) to promoters occurs on discrete domains that are associated with distinct transcriptional outputs. Chromatin immunoprecipitation identifies thousands of LMNA-bound promoters, primarily linked to signaling functions. LMNA often occupies narrow domains on promoters, yet LMNA-bound promoters are often contiguous. LMNA-bound genes are overall repressed, but repression correlates with co-enrichment in repressive histone marks rather than LMNA occupancy per se. Genes marked by LMNA and H3K4me3 escape LMNA-associated repression in the absence of repressive histone marks. Positioning of LMNA on promoters relative to the TSS correlates with distinct transcriptional outputs: whereas upstream-distal binding can be transcriptionally permissive, TSS occupancy is associated with promoter inactivity. Perturbation in NL organization causes reorganization of lamin promoter occupancy and uncouples LMNA binding from promoter inactivity. Our results show the existence of many spatially restricted LMNA binding events on promoter regions, with distinct position-dependent transcriptional outputs. ChIPs were done from cultured untreated and LMNA-downregulated adipose stem cell (ASC) chromatin. MeDIPs were done from LMNA-downregulated ASCs. ChIP and MeDIP DNA was hybridized onto the aforementioned HG-18 Nimbegen promoter arrays.
Project description:Interactions between the nuclear lamina (NL) and chromatin are thought to occur through large lamin association domains (LADs) and correlate with gene repression in these domains. We show that binding of lamin A/C (LMNA) to promoters occurs on discrete domains that are associated with distinct transcriptional outputs. Chromatin immunoprecipitation identifies thousands of LMNA-bound promoters, primarily linked to signaling functions. LMNA often occupies narrow domains on promoters, yet LMNA-bound promoters are often contiguous. LMNA-bound genes are overall repressed, but repression correlates with co-enrichment in repressive histone marks rather than LMNA occupancy per se. Genes marked by LMNA and H3K4me3 escape LMNA-associated repression in the absence of repressive histone marks. Positioning of LMNA on promoters relative to the TSS correlates with distinct transcriptional outputs: whereas upstream-distal binding can be transcriptionally permissive, TSS occupancy is associated with promoter inactivity. Perturbation in NL organization causes reorganization of lamin promoter occupancy and uncouples LMNA binding from promoter inactivity. Our results show the existence of many spatially restricted LMNA binding events on promoter regions, with distinct position-dependent transcriptional outputs. Total RNA obtained from ASCs and ASCs depleted of LMNA (LMNA-KD) and processed for microarray hybridization.
Project description:The nuclear lamina interacts with the genome through megabase-size lamina-associated domains (LADs). LADs have been identified in proximity labeling assays and recently by chromatin immunoprecipitation-sequencing (ChIP-seq) of A- and B-type lamins. LADs localize mainly to the nuclear periphery, they are gene-poor and largely heterochromatic. Here, we show that the mode of chromatin fragmentation for ChIP, namely either bath sonication (used to date for ChIP of nuclear lamins) or digestion with micrococcal nuclease (MNase) leads to the discovery of distinct sets of lamin-interacting domains (which we refer to as LiDs) with distinct gene content, histone composition enrichment and relationship to lamin B1-interacting domains. We find that total genome coverage by lamin A/C ('LMNA') LiDs identified in sonicated or MNase-digested chromatin is similar (~730 megabases). Over half of these domains, however, are uniquely detected in sonicated or MNase-digested chromatin. Whereas sonication-specific LMNA LiDs are gene-poor and devoid of a broad panel of histone modifications, MNase-specific LMNA LiDs are of higher gene density and are enriched in H3K9me3, H3K27me3 and in histone variant H2A.Z. Analysis of published LMNB1 LADs and of LMNB1 LiDs identified by ChIP-seq further shows that LMNA can associate with 'open' chromatin domains displaying euchromatin features which are not associated with LMNB1. The differential genetic and epigenetic properties of lamin-interacting chromatin domains indicate the existence of distinct LiD populations identifiable in different chromatin contexts, including nuclease-accessible 'open' regions presumably localized in the nuclear interior. Overall design: There are two experiments of two samples each for LMNA ChIPs (ChIP and Input), and one LMNB1 ChIP sample, so 5 samples in total. The difference between the experiments are the chromatin fragmentation method (see extract protocols 1 and 2). One uses sonication while the other uses micrococcal nuclease (MNase).
Project description:Epigenetic environment of histone H3.3 on promoters revealed by integration of imaging and genome-scale chromatin and methyl-DNA immunoprecipitation information. Chromatin regions with different transcriptional outputs are distinguished by the deposition of histone variants. Histone H3.3 is incorporated into chromatin in a replication-independent manner; yet the relationship between H3.3 deposition, chromatin environment is incompletely understood. We have integrated imaging and genome-scale chromatin and methyl-DNA immunoprecipitation approaches to investigate the genomic distribution of epitope-tagged H3.3 in relation to histone modifications, DNA methylation and transcription. Results: Imaging shows that H3.3, in contrast to replicative H3.1 or H2B, is enriched in chromatin marked by histone modifications of active genes. A genome-wide survey identifies 1,649 H3.3-enriched promoters, only a subset of which is co-enriched in H3K4me3, H3K9me3 and/or H3K27me3, with a preference for H3K4me3, corroborating imaging data. H3.3-enriched promoters are depleted of H3.3 at the TSS in a transcription-independent manner. H3.3 is found predominantly on CpG-rich unmethylated promoters, creating a condition favourable for transcription. In undifferentiated mesenchymal stem cells, H3.3 target genes are linked to signaling and mesodermal differentiation, suggesting that H3.3 may be a mark of lineage priming. Conclusions: A minor fraction of H3.3 is targeted to promoters, which are predominantly CpG-rich, DNA unmethylated and devoid of detectable trimethylated H3K4, K9 and K27. Among H3.3 target promoters co-marked by methylated H3, H4K4me3 is preferred, with or without H3K27me3, arguing that in mesenchymal stem cells H3.3 marks transcriptionally active or potentially active promoters. Key words: Imaging, ChIP-chip, MeDIP-chip, histone H3.3, mesenchymal stem cells ChIP-chip and MeDIP-chip experiments: Performed with two independent biological replicates. Gene expression profiling experiments: Total RNA obtained from H3.3-EGFP transfected or empty-EGFP transfected mesenchymal stem cells compared to untransfected mesenchymal stem cells. Raw expression data linked below as supplementary file (GSE17053_Illumina_non-normalized_data.txt).
Project description:We surveyed DNA methylation profiles of all human RefSeq promoters in relation to gene expression and differentiation in adipose tissue, bone marrow and muscle mesenchymal progenitors, as well as in bone marrow-derived hematopoietic progenitors. We unravel strongly overlapping DNA methylation profiles between adipose stem cells (ASCs), bone marrow mesenchymal stem cells (BMMSCs) and muscle progenitor cells (MPCs), while hematopoietic progenitor cells (HPCs) are more epigenetically distant from MSCs seen as a whole. Differentiation resolves a fraction of methylation patterns common to MSCs, generating epigenetic divergence. DNA was isolated from MSCs isolated from various tissues and from differentiated cells, immunoprecipitated using antibodies to 5-methylcytosine, and co-hybridized onto Nimblegen promoter arrays together with input DNA.
Project description:Nuclear lamins contact the genome at the nuclear periphery through large domains and are involved in chromatin organization. Among broad peak calling algorithms available to date, none are suited for mapping lamin-genome interactions genome-wide. We disclose a novel algorithm, Enriched Domain Detector (EDD), for analysis of broad enrichment domains from ChIP-seq data. EDD enables discovery of genomic domains interacting with broadly distributed chromatin-associated proteins such as lamins. The main advantage of EDD over existing broad peak callers is sensitivity to domain width rather than enrichment strength at a particular site, and robustness against local variations. EDD is downloadable from http://github.com/eivindgl/edd. LMNA ChIP-seq experiments in human normal dermal fibroblasts (Lonza CC-2511; LDFs) and human normal primary dermal fibroblasts (Norwegian Stem Cell Center AD04DFs).
Project description:Dynamic interactions of nuclear lamins with chromatin through so-called lamin-associated domains (LADs) contribute to spatial arrangements of the genome. Here, we provide evidence for pre-patterning of differentiation-driven formation of lamin A/C LADs by domains of histone H2B modified by the nutrient sensor O-linked N-acetylglucosamine (H2BGlcNAc), which we term GADs. We demonstrate a two-step process of lamin A/C LAD formation during in vitro adipogenesis, involving (i) a spreading of lamin A/C-chromatin interactions during the transition from progenitor cell proliferation to cell cycle arrest, and (ii) a genome-scale redistribution these interactions through a process of LAD ‘exchange’ within hours of adipogenic induction. Chromatin state modeling reveals that lamin A/C LADs can be found both in active and repressive chromatin contexts which can be influenced by cell differentiation status. De novo formation of adipogenic lamin A/C LADs occurs non-randomly on GADs, consisting of megabase-size intergenic and repressive chromatin domains. Accordingly, while pre-differentiation lamin A/C LADs are gene-rich, post-differentiation LADs harbor repressive features reminiscent of lamin B1 LADs. Moreover, release of lamin A/C from genes directly involved in glycolysis concurs with their transcriptional upregulation after adipogenic induction, and with concordant downstream elevations in H2BGlcNAc levels and O-GlcNAc cycling. Our results unveil an epigenetic pre-patterning of adipogenic LADs by GADs, suggesting a coupling of developmentally regulated lamin A/C-genome interactions to a metabolically sensitive chromatin modification. Examination of LMNA and H2BGlcNAc binding in ASCs across differentiation
Project description:The human liver contains multiple cell types whose epigenetic patterns are undetermined. We examined the promoter methylome of purified and uncultured hepatic stellate cells (HSCs), hepatocytes (HEPs) and liver sinusoidal endothelial cells (LSECs), by methylated DNA immunoprecipitation (MeDIP) and array hybridization. Uncultured HSCs, LSECs and Heps show ~7000-8000 methylated promoters, with 60-70% similarity between all cell types. GO analysis for commonly methylated genes reveals involvement in germ cell development, segregating germ-line from somatic lineage methylation. HSCs, LSECs and HEPs also contain ~500-1000 uniquely methylated promoters; these are implicated in signaling and biosynthetic processes (HSCs), lipid transport and metabolism (LSECs), and chromatin assembly (HEPs). The promoter methylome of culture-activated HSCs deviates from that of their uncultured (quiescent) counterparts. HSC culture-induced activation also enhances methylation differences between individual donors; however this does not necessarily relate to changes in gene expression. HSc activation results in a net gain of promoter DNA methylation, despite the demethylation and de novo methylation of thousands of promoters. Our data provide to our knowledge the first genome-wide maps of promoter DNA methylation in human purified and uncultured liver cell types. Although methylation profiles are largely similar between HSCs, LSECs and hepatocytes, the detection of cell type-specific methylation patterns suggests a differential epigenetic programming of these cell types in the liver. Determine the promoter DNA methylation pattern of 3 uncultured, reshly isolated, human healthy liver cell types (hepatocytes (HEPs), liver sinusoidal endothelial cells (LSECs) and haptic stellate cells (HSCs), and of HSCs after a 24-h culture-induced activation.
Project description:To investigate the molecular basis for male-specific steatohepatitis in Lamin A/C-deficient livers, microarray gene expression analysis was performed on total liver RNA isolated from 26- to 39-week-old, male LMNA+/+, LMNA flx/+, and LMNA flx/flx; Alb-Cre+ C57BL/6 mice fed either normal chow (NC) or high fat diet plus carbohydrate-supplemented water (HFD). Lamins are nuclear intermediate filament proteins that comprise the major components of the nuclear lamina in metazoan cells. Mutations in LMNA, which encodes lamins A/C, cause diseases termed laminopathies, including lipodystrophy, cardiomyopathy, and premature aging. The lamin A/C mutation-associated Dunnigan familial partial lipodystrophy is typically accompanied by fatty liver disease. The role of lamins in the liver is unknown, and it is unclear whether laminopathy-associated liver disease is due to primary hepatocyte defects or systemic alterations. To address these questions, mice carrying a hepatocyte-specific deletion of Lmna (KO mice) were generated. KO hepatocytes manifested abnormal nuclear morphology, and KO mice developed spontaneous male-selective hepatosteatosis, with increased susceptibility to high fat diet-induced steatohepatitis and fibrosis. The molecular mechanism by which liver-specific Lamin A/C deficiency induces male-specific steatohepatitis is unknown. The microarray data presented here demonstrates that hepatic Lmna deficiency is associated with upregulated expression of fatty acid transporters, lipid biosynthetic enzymes, lipid-droplet associated proteins, and interferon-regulated genes and other pro-inflammatory mediators. Overall design: Global gene expression profiling of liver RNA isolated from 26- to 39-week-old LMNA+/+, LMNA flx/+, and LMNA flx/flx; Alb-Cre+ C57BL/6 mice fed either normal chow (NC) or high fat diet plus carbohydrate-supplemented water (HFD). The following mouse livers were used in gene expression profiling: LMNA+/+; Alb-Cre+, NC-fed (n=2); LMNA flx/+; Alb-Cre+, NC-fed (n=3); LMNA flx/flx; Alb-Cre+, NC-fed (n=3); LMNA flx/+; Alb-Cre+, HFD-fed (n=3); and LMNA flx/flx; Alb-Cre+, HFD-fed (n=3).
Project description:The p.R482W hotspot mutation in A-type nuclear lamins causes familial partial lipodystrophy of Dunnigantype (FPLD2), a lipodystrophic syndrome complicated by early-onset atherosclerosis. Molecular mechanisms underlying endothelial cell dysfunction conferred by the lamin A mutation remain elusive. However, lamin A regulates epigenetic developmental pathways and mutations could perturb these functions. Here, we demonstrate that lamin A R482W elicits endothelial differentiation defects in a developmental model of FPLD2. Genome modeling in fibroblasts from patients with FPLD2 caused by the lamin A R482W mutation reveals repositioning of the mesodermal regulator T/Brachyury locus towards the nuclear center relative to normal fibroblasts, suggesting enhanced activation propensity of the locus in a developmental model of FPLD2. Addressing this issue, we report phenotypic and transcriptional alterations in mesodermal and endothelial differentiation of induced pluripotent stem cells we generated from a patient with R482Wassociated FPLD2. Correction of the LMNA mutation ameliorates R482W-associated phenotypes and gene expression. Transcriptomics links endothelial differentiation defects to decreased Polycomb-mediated repression of the T/Brachyury locus and over-activation of T target genes. Binding of the Polycomb repressor complex PRC2 to T/Brachyury is impaired by the mutated lamin A network, which is unable to properly associate with the locus. This leads to a deregulation of vascular gene expression over time. By connecting a lipodystrophic hotspot lamin A mutation to a disruption of early mesodermal gene expression and defective endothelial differentiation, we propose that the mutation rewires the fate of several lineages, resulting in multitissue pathogenic phenotypes. Overall design: RNA-seq data pertain to examination of expression profiles of 1) iPS cells derived from patients with Familial Partial Lipodystrophy of Dunnigan-type (FPLD2) with the LMNA p.R482W mutation and 2) FPLD2 patient-derived iPS cells in which the LMNA mutation has been repaired -- both during mesodermal differentiation from day 0 to day 4. ChIP-seq data pertain to ChIP of lamin A/C (LMNA) and lamin B1 (LMNB1) from cultured FPLD2 patient fibroblasts.
Project description:The main scientific objective of the project was to investigate whether Lamin A/C could be involved in neuroblastoma differentiation. Moreover, taking into account the significance of differentiation stage in the neuroblastoma tumor progression we have also studied a possible role of Lamin A/C in the tumorigenesis of this neuronal cancer. As differentiating stimulus we used the all-trans retinoic acid (RA), the most effective compound which has been shown to induce differentiation in neuroblastoma cells. To get insight into the impairment of cell differentiation produced by the LMNA (Lamin A/C) silencing in SHSY5Y cells, we compared the gene expression profile of control and silenced cells both in Retinoic Acid treated and untreated samples, using the one-color Agilent microarray platform. Four condition experiment: cells infected with a mock vector (Mock cells), treated and untreated with retinoic acid (RA); cells infected with a silencing vector for LMNA (LMNA-KD cells), treated and untreated with retinoic acid.