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Recruitment to the nuclear periphery enhances repression of H3K9me2-marked genes and transposons to shape cell fate [RNAseq_shLBR]

ABSTRACT: Heterochromatic loci marked by histone H3 lysine 9 dimethylation (H3K9me2) are enriched at the nuclear periphery in metazoans, but the functional importance of this organization is unknown. Both the nuclear lamins and the nuclear membrane protein lamin B receptor (LBR) have been linked to heterochromatin positioning in mammals, yet embryonic stem cells (mESCs) lacking all lamins retain both LBR and H3K9me2 at the nuclear periphery. We ablated LBR in this context and show that heterochromatin detaches from the nuclear periphery in lamin + LBR quadruple knockout (QKO) cells. QKO mESCs sustain naïve pluripotency and maintain H3K9me2 at normal levels across the genome but cannot repress H3K9me2-marked genes or transposons. Further, their capacity to differentiate into epiblast-like cells (EpiLCs) is impaired. While normal EpiLCs expand H3K9me2 across the genome, QKO EpiLCs exhibit abnormal patterning of this mark. QKO cells can exit naïve pluripotency and activate epiblast-stage genes but also express markers of alternative fates including the primitive endoderm. These results establish that recruitment of H3K9me2 to the nuclear periphery controls the spatial position, dynamic remodeling, and repressive capacity of this mark to shape cell fate decisions.

ORGANISM(S): Mus musculus

PROVIDER: GSE264602 | GEO | 2024/08/09

REPOSITORIES: GEO

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Project description:Purpose: to qualify and quantify the rearrangement of interactions of nuclear lamins A/C and B with the genome, in relation to nuclearradial repositioning of loci and changes in gene expression, in HepG2 cells exposed to cyclosporin A. .To compare HepG2 cell line transcriptome profiling (RNA-seq) with radially positioning of the chromatin anchored at the nuclear periphery before and after CsA treatment. Methods: To this end, we mapped lamin A and lamin B lamina-associated domains (LADs) by chromatin immunoprecipitation-sequencing (ChIP-seq) of lamin A/C (antibody sc7292x, Santa Cruz Biotechnology) and lamin B1 (antibody ab16048, Abcam), respectively. HepG2 cells were either cultured under proliferative conditions (controls) or exposed for 3 days to 10 uM cyclosporin A. We also assesed the transcriptome by RNA-seq under each condition in duplicate cultures. Results: CsA elicits accumulation of pre-lamin A in HepG2 cells, raising the hypothesis of a global rearrangement of lamin-chromatin interactions. We show here the existence of overlapping and distinct lamin A and B lamina-associated domains (which we refer to as A- and B-LADs, respectively). Whereas B-LADs largely remain constitutive, CsA elicits the formation of facultative A-LADs. Re-localization of A-LADs occur mainly on preexisting B-LADs. However, LAD rearrangement does not correlate with systematic changes in gene expression within LADs. We find a reorganization of A- and B-LADs after CsA treatment, entailing distinct contributions of A- and B- type lamins. to genome organization. Indeed, classification of lamin A LADs and lamin B LADs into properties of ‘A-only’, ‘B-only’ and ‘A-B’ LADs show an overall loss of A-only LADs after CsA treatment. A- only and B-only LADs are highly dynamic with A-B LADs being more stable.The rearrangement of lamin association after CsA treatment correlates with repositioning of loci in the nuclear space with, notably, a loss of lamin B associated with a re-localization of loci towards the nuclear center and conversely, a gain of lamin B linked to a repositioning of loci towards the nuclear periphery. Predictions on radial repositioning of LADs, and of loci within, from 3D structural models of the genome were supported by fluorescence in situ hybridization (FISH) analyses. Conclusions: We show that, while they amply co-localize on well-conserved LADs, lamins A and B also interact with distinct genomic regions that can interchange (switch) between lamin A and B upon CsA treatment. We unveil distinct lamin A and B interactions with chromatin, suggesting complementary contributions to genome conformation. Our data suggest that and lamins A and B may differentially modulate genome organization.

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Recruitment to the nuclear periphery enhances repression of H3K9me2-marked genes and transposons to shape cell fate [RNAseq_shLBR]

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