Mutation-induced DNMT1 cleavage drives neurodegenerative disease.
Ontology highlight
ABSTRACT:
SUBMITTER: Wang W
PROVIDER: S-EPMC8442919 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:DNA methyltransferase 1 (DNMT1) is the enzyme primarily responsible for propagation of the methylation pattern in cells. Mutations in DNMT1 have been linked to the development of adult-onset neurodegenerative disorders; these disease-associated mutations occur in the regulatory replication foci-targeting sequence (RFTS) domain of the protein. The RFTS domain is an endogenous inhibitor of DNMT1 activity that binds to the active site and prevents DNA binding. Here, we examine the impact of the disease-associated mutation A554V on normal RFTS-mediated inhibition of DNMT1. Wild-type and mutant proteins were expressed and purified to homogeneity for biochemical characterization. The mutation increased DNA binding affinity ~8-fold. In addition, the mutant enzyme exhibited increased DNA methylation activity. Circular dichroism (CD) spectroscopy revealed that the mutation does not significantly impact the secondary structure or relative thermal stability of the isolated RFTS domain. However, the mutation resulted in changes in the CD spectrum in the context of the larger protein; a decrease in relative thermal stability was also observed. Collectively, this evidence suggests that A554V disrupts normal RFTS-mediated autoinhibition of DNMT1, resulting in a hyperactive mutant enzyme. While the disease-associated mutation does not significantly impact the isolated RFTS domain, the mutation results in a weakening of the interdomain stabilizing interactions generating a more open, active conformation of DNMT1. Hyperactive mutant DNMT1 could be responsible for the increased DNA methylation observed in affected individuals.
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Project description:Frontotemporal lobar degeneration is a progressive neurodegenerative syndrome that is the second most common cause of early-onset dementia. Mutations in the progranulin gene are a major cause of familial frontotemporal lobar degeneration [Baker M, et al. (2006) Nature 442:916-919 and Cruts M, et al. (2006) Nature 442:920-924]. Although progranulin is involved in wound healing, inflammation, and tumor growth, its role in the nervous system and the mechanism by which insufficient levels result in neurodegeneration are poorly understood [Eriksen and Mackenzie (2008) J Neurochem 104:287-297]. We have characterized the normal function of progranulin in the nematode Caenorhabditis elegans. We found that mutants lacking pgrn-1 appear grossly normal, but exhibit fewer apoptotic cell corpses during development. This reduction in corpse number is not caused by reduced apoptosis, but instead by more rapid clearance of dying cells. Likewise, we found that macrophages cultured from progranulin KO mice displayed enhanced rates of apoptotic-cell phagocytosis. Although most neurodegenerative diseases are thought to be caused by the toxic effects of aggregated proteins, our findings suggest that susceptibility to neurodegeneration may be increased by a change in the kinetics of programmed cell death. We propose that cells that might otherwise recover from damage or injury are destroyed in progranulin mutants, which in turn facilitates disease progression.
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Project description:In two brothers born to consanguineous parents, we identified an unusual neurological disease that manifested with ataxia, psychomotor retardation, cerebellar and cerebral atrophy, and leukodystrophy. Via linkage analysis and exome sequencing, we identified homozygous c.2801C>T (p.(Ser934Leu)) in POLR1A (encoding RPA194, largest subunit of RNA polymerase I) and c.511C>T (p.(Arg171Trp)) in OSBPL11 (encoding oxysterol-binding protein-like protein 11). Although in silico analysis, histopathologic evidence and functional verification indicated that both variants were deleterious, segregation with the patient phenotype established that the POLR1A defect underlies the disease, as a clinically unaffected sister also was homozygous for the OSBPL11 variant. Decreased nucleolar RPA194 was observed in the skin fibroblasts of only the affected brothers, whereas intracellular cholesterol accumulation was observed in the skin biopsies of the patients and the sister homozygous for the OSBPL11 variant. Our findings provide the first report showing a complex leukodystrophy associated with POLR1A. Variants in three other RNA polymerase subunits, POLR1C, POLR3A and POLR3B, are known to cause recessive leukodystrophy similar to the disease afflicting the present family but with a later onset. Of those, POLR1C is also implicated in a mandibulofacial dysostosis syndrome without leukodystrophy as POLR1A is. This syndrome is absent in the family we present.
| S-EPMC5334463 | biostudies-literature
Project description:The pathophysiology of neurodegenerative diseases is poorly understood and there are few therapeutic options. Neurodegenerative diseases are characterized by progressive neuronal dysfunction and loss, and chronic glial activation. Whether microglial activation, which is generally viewed as a secondary process, is harmful or protective in neurodegeneration remains unclear. Late-onset neurodegenerative disease observed in patients with histiocytoses, which are clonal myeloid diseases associated with somatic mutations in the RAS-MEK-ERK pathway such as BRAF(V600E), suggests a possible role of somatic mutations in myeloid cells in neurodegeneration. Yet the expression of BRAF(V600E) in the haematopoietic stem cell lineage causes leukaemic and tumoural diseases but not neurodegenerative disease. Microglia belong to a lineage of adult tissue-resident myeloid cells that develop during organogenesis from yolk-sac erythro-myeloid progenitors (EMPs) distinct from haematopoietic stem cells. We therefore hypothesized that a somatic BRAF(V600E) mutation in the EMP lineage may cause neurodegeneration. Here we show that mosaic expression of BRAF(V600E) in mouse EMPs results in clonal expansion of tissue-resident macrophages and a severe late-onset neurodegenerative disorder. This is associated with accumulation of ERK-activated amoeboid microglia in mice, and is also observed in human patients with histiocytoses. In the mouse model, neurobehavioural signs, astrogliosis, deposition of amyloid precursor protein, synaptic loss and neuronal death were driven by ERK-activated microglia and were preventable by BRAF inhibition. These results identify the fetal precursors of tissue-resident macrophages as a potential cell-of-origin for histiocytoses and demonstrate that a somatic mutation in the EMP lineage in mice can drive late-onset neurodegeneration. Moreover, these data identify activation of the MAP kinase pathway in microglia as a cause of neurodegeneration and this offers opportunities for therapeutic intervention aimed at the prevention of neuronal death in neurodegenerative diseases.
| S-EPMC6047345 | biostudies-literature
Project description:The pathophysiology of neurodegenerative diseases is poorly understood, and therapeutic options are few. Neurodegenerative diseases are hallmarked by progressive neuronal dysfunction and loss, associated with chronic glial and immune activation1. Microglia are the resident macrophages of the nervous system thought to be important for the clearance of debris after neuronal damage and aid to repair and regeneration. Their activation is viewed in general as a reactive process in neurodegeneration1-3. Whether microglia itself may be causative of neurodegenerative diseases is unclear. Late-onset neurodegenerative disease is frequently observed in patients with histiocytoses4-10, which are clonal myeloid diseases associated with somatic mutations in the RAS/MEK/ERK pathway such as BRAFV600E 5,11,12, suggesting a possible role of somatic mutations in neurodegeneration. Yet, expression of BRAFV600E in the hematopoietic stem cell (HSC) lineage does not cause neurodegeneration13,14. However, recent works from our laboratories and other have revealed that microglia belong to a lineage of adult tissue-resident myeloid cells that develop during organogenesis from yolk sac erythro-myeloid progenitors (EMP) distinct from HSC15-18. We thus hypothesized that somatic BRAFV600E mutations in the resident macrophage lineage may cause neurodegeneration. We found that while BRAFV600E expression in the HSC lineage causes leukemic and tumoral diseases13,14, its expression in the EMP lineage instead results in a severe late-onset neurodegenerative disorder. Neurological symptoms, neuronal death, astrogliosis, immune activation, and amyloid precursor protein deposition were driven by ERK-activated microglia clones and preventable by RAF inhibition. These results identify the fetal precursors of tissue-resident macrophages as a potential cell-of-origin for histiocytoses, and demonstrate that a somatic mutation in the EMP lineage can drive late-onset neurodegeneration. Moreover, these data identify activation of the MAP kinase pathway in microglia as a cause of neurodegenerative disease, and provide opportunities for therapeutic intervention aimed at preventing neuronal death in neurodegenerative diseases
2017-09-21 | GSE95734 | GEO
Project description:While, transcriptional and epigenetic changes associated senescence processes are well studied, the 3D chromatin changes associated with it remains elusive. In this study, we have generated genome wide chromatin interaction maps (Hi-C), epigenetic (ChIP-Seq), replication-timing and gene expression (RNA-Seq) profiles from replication induced (RS) and oncogene induced (OIS) senescent cells. As senescence associated heterochromatin foci (SAHFs) differentiates both RS and OIS nuclei, we identified the regions that constitute SAHFs and called them Senescence Associated Heterochromatin Domains (SAHDs). Further, screening of candidate factors for SAHF induction allowed us to identify DNMT1 as a novel component that induces SAHFs by stimulation of HMGA2 expression. DNMT1 depletion does not reverse the senescence process, however, instead, depleted cells transition to a 3D genome conformation akin to that of cells in replicative senescence, suggesting that acute senescence induction (OIS) involves SAHF formation in addition to the RS-dependent 3D genome rewiring.
2020-03-27 | GSE130306 | GEO
Project description:Background & aimsIntrahepatic cholangiocarcinoma (ICC) is a devastating liver cancer with extremely high intra- and inter-tumoral molecular heterogeneity, partly due to its diverse cellular origins. We investigated clinical relevance and the molecular mechanisms underlying hepatocyte (HC)-driven ICC development.MethodsExpression of ICC driver genes in human diseased livers at risk for ICC development were examined. The sleeping beauty and hydrodynamic tail vein injection based Akt-NICD/YAP1 ICC model was used to investigate pathogenetic roles of SRY-box transcription factor 9 (SOX9) and yes-associated protein 1 (YAP1) in HC-driven ICC. We identified DNA methyltransferase 1 (DNMT1) as a YAP1 target, which was validated by loss- and gain-of-function studies, and its mechanism addressed by chromatin immunoprecipitation sequencing.ResultsCo-expression of AKT and Notch intracellular domain (NICD)/YAP1 in HC yielded ICC that represents 13% to 29% of clinical ICC. NICD independently regulates SOX9 and YAP1 and deletion of either, significantly delays ICC development. Yap1 or TEAD inhibition, but not Sox9 deletion, impairs HC-to-biliary epithelial cell (BEC) reprogramming. DNMT1 was discovered as a novel downstream effector of YAP1-TEAD complex that directs HC-to-BEC/ICC fate switch through the repression of HC-specific genes regulated by master regulators for HC differentiation, including hepatocyte nuclear factor 4 alpha, hepatocyte nuclear factor 1 alpha, and CCAAT/enhancer-binding protein alpha/beta. DNMT1 loss prevented NOTCH/YAP1-dependent HC-driven cholangiocarcinogenesis, and DNMT1 re-expression restored ICC development following TEAD repression. Co-expression of DNMT1 with AKT was sufficient to induce tumor development including ICC. DNMT1 was detected in a subset of HCs and dysplastic BECs in cholestatic human livers prone to ICC development.ConclusionWe identified a novel NOTCH-YAP1/TEAD-DNMT1 axis essential for HC-to-BEC/ICC conversion, which may be relevant in cholestasis-to-ICC pathogenesis in the clinic.
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Project description:PH20 is a member of the human hyaluronidase family that degrades hyaluronan in the extracellular matrix and controls tumor progression. Inhibition of DNA methyltransferases (DNMTs) leads to elevated hyaluronan levels; however, whether DNMT inhibitors control PH20 remains unclear. Here, we report that the DNMT1 inhibitor, decitabine, suppresses PH20 expression by activating the long non-coding RNA PHACTR2-AS1 (PAS1). PAS1 forms a tripartite complex with the RNA-binding protein vigilin and histone methyltransferase SUV39H1. The interaction between PAS1 and vigilin maintains the stability of PAS1. Meanwhile, PAS1 recruits SUV39H1 to trigger the H3K9 methylation of PH20, resulting in its silencing. Functionally, PAS1 inhibits breast cancer growth and metastasis, at least partially, by suppressing PH20. Combination therapy of decitabine and PAS1-30nt-RNA, which directly binds to SUV39H1, effectively blocked breast cancer growth and metastasis in mice. Taken together, DNMT1, PAS1, and PH20 comprise a regulatory axis to control breast cancer growth and metastasis. These findings reveal that the DNMT1-PAS1-PH20 axis is a potential therapeutic target for breast cancer.
| S-EPMC8934873 | biostudies-literature
Project description:RNA was purified from fusiform gyrus tissue sections of autopsy-confirmed Alzheimer's cases and neurologically normal age-matched controls. The "SAM.ID" sample characteristic is a sample identifier internal to Genentech. The ID of this project in Genentech's ExpressionPlot database is PRJ0007261
2017-12-20 | GSE95587 | GEO
Project description:Mitochondrial diseases have been shown to result from mutations in mitochondrial genes located in either the nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). Mitochondrial OXPHOS complex I has 45 subunits encoded by 38 nuclear and 7 mitochondrial genes. Two male patients in a putative X-linked pedigree exhibiting a progressive neurodegenerative disorder and a severe muscle complex I enzyme defect were analyzed for mutations in the 38 nDNA and seven mtDNA encoded complex I subunits. The nDNA X-linked NDUFA1 gene (MWFE polypeptide) was discovered to harbor a novel missense mutation which changed a highly conserved glycine at position 32 to an arginine, shown to segregate with the disease. When this mutation was introduced into a NDUFA1 null hamster cell line, a substantial decrease in the complex I assembly and activity was observed. When the mtDNA of the patient was analyzed, potentially relevant missense mutations were observed in the complex I genes. Transmitochondrial cybrids containing the patient's mtDNA resulted in a mild complex I deficiency. Interestingly enough, the nDNA encoded MWFE polypeptide has been shown to interact with various mtDNA encoded complex I subunits. Therefore, we hypothesize that the novel G32R mutation in NDUFA1 is causing complex I deficiency either by itself or in synergy with additional mtDNA variants.
| S-EPMC2693342 | biostudies-literature