Depletion of Sun1/2 Induces Heterochromatin Accrual in MSCs
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PROVIDER: PRJNA796421 | ENA |
REPOSITORIES: ENA
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Project description:Mesenchyal Stem Cells (MSCs) differentiation into multiple lineages, such as osteocytes and adipocytes, has been shown to be regulated by mechanical signals. The Linker of the Nucleoskeleton and Cytoskeleton (LINC) complex has been shown to be required for mechanical signal transduction, regulation of MSCs differentiation, and nuclear integrity. The LINC complex is made of Nesprins and Sun proteins. Nesprin proteins associate with the cytoskeleton on the outer nuclear membrane and Sun proteins are bound to the inner nuclear membrane where they bind to inner nuclear proteins and chromatin. We investigated the role of the Sun1/2 in regulating the inner nuclear functions of chromatin organization and adipogenic differentiation independently of the LINC complex function. We show that depletion of Sun1/2 increased nuclear area and perimeter, and decreased circularity. Expression of a dominant-negative KASH (dnKASH) domain targeting the SUN domain on Sun proteins inhibiting Nesprin-SUN association resulting a loss of Nesprin localization to the nuclear envelope decreased nuclear area and circularity. Adipogenesis was inhibited during Sun1/2 depletion while dnKASH expression accelerated adipgoenesis. RNA-seq data showed decreased adipogensis and increased immune response during Sun1/2 depletion. dnKASH responded oppositely with increased adipogenic gene expression and decreased immune response. We also observed increased H3K9me3 levels, increased H3K9me3 foci count, and enrichment on Adipoq during Sun1/2 depletion. No increase of H3K9me3 levels, foci count, or increased H3K9me3 enrichment on Adipoq was found during dnKASH expression. We conclude that physically decoupling of the LINC complex via dnKASH accelerates adipogenesis and that Sun1/2 regulates chromatin organization and adipogenesis independently of the LINC complex function.
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Project description:We describe the epigenetic profiling of the H3K9me2 and HP1a in Drosophila third instar larvae before and after CDK12 depletion by RNA interference (RNAi). Here we show that CDK12 regulates heterochromatin dynamics in Drosophila chromosomes. Depletion of CDK12 induces the increased HP1a and H3K9me2 binding profile on the coding region of euchromatic genes, with the X chromosome being the most affected. These results are consistent with the polytene chromosome immunostaining pattern of HP1a and H3K9me2 after CDK12 knockdown in our initial cytological observations, which show that CDK12 depletion induce heterochromatin spreading on euchromatic arms, especially on the X chromosome. This study describes a novel role of the CDK12 complex in controlling the epigenetic transition between euchromatin and heterochromatin. Examination of the genome-wide H3K9me2 and HP1a binding profile in wildtype larvae (WT) and CDK12-depleted larvae (CDK12-KD). Examination of the genome-wide CDK12 binding profile in wildtype larvae (WT). Twelve independent immunoprecipitations were conducted for each antibody. Two biological replicates were performed.
2015-11-02 | E-GEOD-63011 | biostudies-arrayexpress
Project description:We describe the epigenetic profiling of the H3K9me2 and HP1a in Drosophila third instar larvae before and after CDK12 depletion by RNA interference (RNAi). Here we show that CDK12 regulates heterochromatin dynamics in Drosophila chromosomes. Depletion of CDK12 induces the increased HP1a and H3K9me2 binding profile on the coding region of euchromatic genes, with the X chromosome being the most affected. These results are consistent with the polytene chromosome immunostaining pattern of HP1a and H3K9me2 after CDK12 knockdown in our initial cytological observations, which show that CDK12 depletion induce heterochromatin spreading on euchromatic arms, especially on the X chromosome. This study describes a novel role of the CDK12 complex in controlling the epigenetic transition between euchromatin and heterochromatin.
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Project description:Antigen Ki-67 is a nuclear protein expressed in proliferating mammalian cells. It is widely used in cancer histopathology but its functions remain unclear. Here, we show that Ki-67 controls heterochromatin organisation. Altering Ki-67 expression levels did not significantly affect cell proliferation in vivo. Ki-67 mutant mice developed normally and cells lacking Ki-67 proliferated efficiently. Conversely, upregulation of Ki-67 expression in differentiated tissues did not inhibit cell cycle arrest. Ki-67 interactors included proteins involved in nucleolar processes and chromatin regulators. Ki-67 depletion disrupted nucleologenesis but did not inhibit pre-rRNA processing. In contrast, it altered gene expression. Ki-67 silencing also had wide-ranging effects on chromatin organisation, disrupting heterochromatin compaction and long-range genomic interactions. Trimethylation of histone H3K9 and H4K20 at heterochromatin was strongly reduced. Overexpression of human or Xenopus Ki-67 induced ectopic heterochromatin formation. Altogether, our results suggest that Ki-67 expression in proliferating cells spatially organises heterochromatin, thereby controlling gene expression.
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Project description:The global loss of heterochromatin during aging has been observed in eukaryotes from yeast to humans, and this has been proposed to be one of the causes of aging. However, the cause of this age-associated loss of heterochromatin has remained enigmatic. Here we show that heterochromatin markers, including histone H3K9 di-/tri-methylation and HP1, decrease with age in murine muscle stem cells (MuSCs) as a consequence of the depletion of the methyl donor SAM. We find that restoration of intracellular SAM in aged MuSCs restores heterochromatin content to youthful levels and rejuvenates age-associated features including DNA damage accumulation, increased cell death, and defective muscle regeneration. SAM is not only a methyl group donor for transmethylation but it is also an aminopropyl donor for polyamine synthesis. Excessive consumption of SAM in polyamine synthesis may reduce its availability for transmethylation. Consistent with this premise, we observe that perturbation of increased polyamine synthesis by inhibiting spermidine synthase (Srm) restores the intracellular SAM content as well as heterochromatin formation, leading to improvements in aged MuSC function and regenerative capacity. Together, our studies demonstrate a direct causal link between polyamine metabolism and epigenetic dysregulation during MuSC aging.
2023-11-17 | GSE229851 | GEO
Project description:The global loss of heterochromatin during aging has been observed in eukaryotes from yeast to humans, and this has been proposed to be one of the causes of aging. However, the cause of this age-associated loss of heterochromatin has remained enigmatic. Here we show that heterochromatin markers, including histone H3K9 di-/tri-methylation and HP1, decrease with age in murine muscle stem cells (MuSCs) as a consequence of the depletion of the methyl donor SAM. We find that restoration of intracellular SAM in aged MuSCs restores heterochromatin content to youthful levels and rejuvenates age-associated features including DNA damage accumulation, increased cell death, and defective muscle regeneration. SAM is not only a methyl group donor for transmethylation but it is also an aminopropyl donor for polyamine synthesis. Excessive consumption of SAM in polyamine synthesis may reduce its availability for transmethylation. Consistent with this premise, we observe that perturbation of increased polyamine synthesis by inhibiting spermidine synthase (Srm) restores the intracellular SAM content as well as heterochromatin formation, leading to improvements in aged MuSC function and regenerative capacity. Together, our studies demonstrate a direct causal link between polyamine metabolism and epigenetic dysregulation during MuSC aging.
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Project description:Bone marrow mesenchymal stromal cells (MSCs) regulate homeostasis and trafficking of cells of the blood lineage. In response to traumatic injury or infection, MSCs are believed to mobilize from the bone marrow, but it is largely unknown how egress into circulation impacts MSC function. Here we show that biomechanical forces associated with trafficking of MSCs from the bone marrow into the vasculature contribute uniquely to genetic signaling that reinforces MSC repression of immune cell activation. Laminar wall shear stress (LSS) typical of fluid frictional forces present on the lumen of arterioles stimulates increases in antioxidant and anti-inflammatory mediators, as well as an array of chemokines capable of immune cell recruitment. Importantly, LSS promotes a signaling cascade through COX2 that elevates prostaglandin E2 (PGE2) biosynthesis, permitting MSCs to suppress immune cell activation in the presence of inflammatory cues. Pharmacological inhibition of COX2 depleted PGE2 and impaired the ability of MSCs to block tumor necrosis factor-α (TNF-α) production, supporting a key role for PGE2 in the MSC immunomodulatory response to LSS. Preconditioning of MSCs by LSS ex vivo was an effective means of enhancing therapeutic efficacy in a rat model of traumatic brain injury, as evidenced by decreased numbers of apoptotic and M1-type activated microglia in the hippocampus and by retention of endogenous MSCs in the bone marrow. We conclude that biomechanical forces provide critical cues to MSCs residing at the vascular interface which influence MSC immunomodulatory and paracrine functions, thus providing unique opportunities for functional enhancement of MSCs used in therapeutic applications.
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