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DamID: Loss of a heterochromatin anchor rescues altered genome organization and EDMD muscle defects triggered by a laminopathy mutation

ABSTRACT: Point mutations in nuclear structural protein laminA produce rare and generally tissue-specific diseases called laminopathies. The introduction of a human Emery Dreifuss Muscular Dystrophy (EDMD)-inducing mutation (laminA-Y45C) into C. elegans lamin (LMN-Y59C), recapitulates many EDMD phenotypes, and results in hyper-sequestration of heterochromatic arrays at the nuclear periphery. Using muscle-specific Emerin Dam-ID we show that the LMN-Y59C mutation also leads to misorganization of endogenous chromatin. We find increased perinuclear anchoring primarily along chromosome arms, and enhanced release of chromosomal cores. Coincidentally, Y59C worms have reduced locomotion and compromised sarcomere integrity. By coupling this mutation with deletion of the perinuclear chromodomain protein CEC-4, which tethers H3K9-methylated chromatin, we rescue the EDMD-like physiology and ultrastructural defects in sarcomeres. It further counteracts the altered spatial organization of chromosomal sequences, particularly along chromosomal arms. The data in this submission refer to the identification of chromatin enriched at the nuclear periphery (as measured by interaction with Dam::EMR-1) in muscle cells of L3/L4 control animals or cec-4 mutants expressing either GFP::LMN-1 (wild type lamin) or GFP::LMN-1(Y59C).

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE135850 | GEO | 2020/12/31

REPOSITORIES: GEO

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RNA-seq: Loss of a heterochromatin anchor rescues altered genome organization and EDMD muscle defects triggered by a laminopathy mutation

Project description:Point mutations in nuclear structural protein lamin A produce rare, tissue-specific diseases called laminopathies. The introduction of a human Emery Dreifuss Muscular Dystrophy (EDMD)-inducing mutation (lamin A-Y45C) into C. elegans lamin (LMN-Y59C), recapitulates many EDMD phenotypes, and correlates with hyper-sequestration of heterochromatic arrays at the nuclear periphery. Using muscle-specific emerin Dam-ID, we also document the misorganization of endogenous chromatin in the LMN-Y59C mutant. We score increased perinuclear positioning along chromosome arms, and enhanced release within chromosomal cores. Coincidentally, Y59C worms have reduced locomotion and compromised sarcomere integrity. By coupling the Y59C mutation with deletion of the perinuclear chromodomain protein CEC-4, which tethers H3K9-methylated chromatin, we rescue the EDMD-like physiology and ultrastructural defects in sarcomeres. Deletion of cec-4 also rescued the Y59C-induced changes in chromatin organization. The promoters of genes that change position in the LMN-Y59C mutant, are enriched for E2F (EFL-1/-2) binding sites, consistent with previous studies implicating the Rb-E2F interaction with lamin A in muscle dysfunction. Gene expression changes provoked by LMN-Y59C are also largely reversed by cec-4 deletion. In summary, the ablation of a perinuclear H3K9me-anchor can counteract the dominant muscle-specific defects provoked by a laminopathic mutation, implicating peripheral chromatin organization in the control of muscle integrity.

2020-12-31 | GSE136576 | GEO

LMN-1-DamID in N2 and set-25(n5021) met-2(n4256) mutant early C. elegans embryos

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DamID of Dam::LMN-1 and Dam::EMR-1 in Caenorhabditis elegans adult worms

Project description:Laminopathies are caused by mutations in components of the nuclear envelope (NE). While most NE components are widely expressed, laminopathies affect only a subset of tissues. However, the understanding of the molecular mechanisms that explain this phenomenon is still elusive. Here we have performed a genome wide DamID analysis in adult C. elegans nematodes comparing the DNA association profile of two components of the NE, Lamin/LMN-1 and Emerin/EMR-1. Although both proteins were associated to silent DNA, EMR-1 showed a predominant role in the anchoring of muscle and neuronal promoters to the nuclear periphery. Deletion of either EMR-1 or LEM-2, another integral NE protein, caused local changes in nuclear architecture with both increased and decreased LMN-1 association. Comparison of Dam::LMN-1 and Dam::EMR-1 DNA assotiation in wild type strains and Dam::LMN-1 DNA association in wild type, lem-2(tm1582) and emr-1(gk119) mutant backgrounds.

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LMN-1-DamID in N2 and set-25(n5021) met-2(n4256) mutant early C. elegans embryos

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Histone H3K9 methylation promotes formation of genome compartments in C. elegans via chromosome compaction and perinuclear anchoring (Hi-C)

Project description:Genomic regions preferentially associate with regions of similar transcriptional activity, partitioning genomes into active and inactive compartments within the nucleus. Here we explored mechanisms controlling genome compartment organization in C. elegans and investigated roles for compartments in regulating gene expression. The distal arms of C. elegans chromosomes, which are enriched for heterochromatic histone modifications including H3K9me, interact with each other both in cis and in trans, while interacting less frequently with central regions of chromosomes, leading to genome compartmentalization. Arms are anchored to the nuclear periphery via the nuclear envelope protein CEC-4, which binds to H3K9me. By performing genome-wide chromosome conformation capture experiments (Hi-C), we showed that eliminating H3K9me1/me2/me3 through mutations in the methyltransferase genes met-2 and set-25 significantly impaired formation of genome compartments. cec-4 mutations also impaired compartmentalization, but to a lesser extent. We found that H3K9me promotes compartmentalization through two distinct mechanisms: perinuclear anchoring of chromosome arms via CEC-4 to promote their cis association, and an anchoring-independent mechanism that compacts individual chromosome arms. In both met-2 set-25 and cec-4 mutants, no dramatic changes in gene expression were found for genes that switched compartments or for genes that remained in their original compartment, suggesting that compartment strength does not dictate gene expression levels. Furthermore, H3K9me, but not perinuclear anchoring, also contributes to formation of another prominent feature of chromosome organization, megabase-scale topologically associating domains on X that are established by the dosage-compensation condensin complex. Our results demonstrate that H3K9me plays crucial roles in regulating genome organization at multiple levels.

2020-04-21 | GSE144252 | GEO

Histone H3K9 methylation promotes formation of genome compartments in C. elegans via chromosome compaction and perinuclear anchoring (ChIP-seq)

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LEM-2 ChIP-seq to study chromatin anchoring

Project description:Chromatin Immunoprecipitation against the nuclear envelope protein LEM-2 to detect association to the nuclear periphery. LEM-2 ChIP was performed on early embryo fixed extracts for wild-type and two mutants that have altered position of a perinuclear chromatin reporter. LEM-2 ChIP on early embryo chromatin extracts of three different genotypes: wild-type, met-2 set-25_delta_delta and cec-4_delta, in two independent biological replicas

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DamID of Dam::EMR-1 in Caenorhabditis elegans L1 larvae

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Project description:DamID of Dam::LMN-1 and Dam::EMR-1 in Caenorhabditis elegans adult worms

| PRJNA189179 | ENA