Single-nucleus transcriptomics reveals distinct myelin-enriched microglia and increased MSR1-mediated phagocytosis as common features across dementia subtypes
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PROVIDER: PRJNA1297732 | ENA |
REPOSITORIES: ENA
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Project description:Alzheimer’s disease (AD), dementia with Lewy bodies (DLB), and Parkinson’s disease dementia (PDD) collectively represent the majority of dementia cases worldwide. While these subtypes share clinical, genetic, and pathological features, their transcriptomic similarities and differences remain poorly understood. We applied single-nucleus RNA-sequencing (snRNA-seq) to prefrontal cortex samples from individuals with non-cognitive impairment control (NCI), and dementia subtypes (AD, DLB, and PDD) to investigate cell type-specific gene expression patterns and pathways underlying pathological similarities and differences across dementia subtypes. SnRNA-seq findings were validated through RNAscope, immunohistochemistry, and additional biochemical analyses in human tissues and cellular models. snRNA-seq analysis revealed elevated microglial proportions across all dementia subtypes compared to NCI. Further analysis of cell type-specific transcriptomes identified overlapping differentially expressed genes (DEGs) between microglia and oligodendrocytes across all dementia subtypes. While AD showed molecular similarities to NCI, PDD and DLB were clustered more closely together, sharing a greater number of DEGs and related pathways, predominantly associated with microglia. Investigation of interactions between microglia and oligodendrocytes revealed a distinct myelin-enriched microglia (MEM) subcluster in all dementia subtypes. MSR1, a gene encoding a scavenger receptor, was upregulated in microglia across all dementia subtypes, along with its associated gene HSPA1A in oligodendrocytes. RNAscope supported the potential interaction between microglia and oligodendrocytes, where these cells were in closer proximity to each other in human cortical tissues of PDD compared to NCI. MSR1 expression was significantly increased in cortical primary microglia from PD mice compared with non-transgenic (NTg) mice. Additionally, the expression of myelin-associated genes (MBP, MOBP and PLP1) was significantly upregulated in PD microglia compared to NTg, supporting the presence of MEM. Furthermore, MSR1-positive microglia colocalised with MBP in cortical tissue of PDD patients, suggesting a functional role of MSR1 in myelin debris clearance. Overexpression of MSR1 in microglial cells enhanced their phagocytic activity toward myelin, and reciprocally, myelin treatment upregulated MSR1 protein levels, indicating enhanced MSR1-mediated myelin phagocytosis.
2025-07-28 | GSE303823 | GEO
Project description:The efficiency of central nervous system (CNS) remyelination declines with age. This is in part due to an age-associated decline in the phagocytic removal of myelin debris, which contains inhibitors of oligodendrocyte progenitor cell differentiation. In this study we show that expression of genes involved in the retinoid X receptor (RXR) pathway are decreased with aging in myelin-phagocytosing cells. Loss of RXR function in young macrophages mimics aging by delaying remyelination after experimentally-induced demyelination, while RXR agonists partially restore myelin debris phagocytosis in aged macrophages. The FDA-approved RXR agonist bexarotene, when used in concentrations achievable in human subjects, caused a reversion of the gene expression profile in aging human monocytes to a more youthful profile. These results reveal the RXR pathway as a positive regulator of myelin debris clearance and a key player in the age-related decline in remyelination that may be targeted by available or newly-developed therapeutics. 24 Human CD14+ monocyte-sorted PBMC samples representing 4 Healthy Volunteers (HV) and 4 Multiple Sclerosis (MS) patients under 3 different treatment conditions. Condition 1 = (-) Phagocystosis (-) Bexarotene. Condition 2 = (+) Phagocystosis (-) Bexarotene. Condition 3 = (+) Phagocystosis (+) Bexarotene.
2015-11-04 | E-GEOD-66988 | biostudies-arrayexpress
Project description:The efficiency of central nervous system (CNS) remyelination declines with age. This is in part due to an age-associated decline in the phagocytic removal of myelin debris, which contains inhibitors of oligodendrocyte progenitor cell differentiation. In this study we show that expression of genes involved in the retinoid X receptor (RXR) pathway are decreased with aging in myelin-phagocytosing cells. Loss of RXR function in young macrophages mimics aging by delaying remyelination after experimentally-induced demyelination, while RXR agonists partially restore myelin debris phagocytosis in aged macrophages. The FDA-approved RXR agonist bexarotene, when used in concentrations achievable in human subjects, caused a reversion of the gene expression profile in aging human monocytes to a more youthful profile. These results reveal the RXR pathway as a positive regulator of myelin debris clearance and a key player in the age-related decline in remyelination that may be targeted by available or newly-developed therapeutics.
2015-11-04 | GSE66988 | GEO
Project description:Multiple sclerosis is a chronic, inflammatory, demyelinating disease of the central nervous system in which macrophages and microglia play a central role. During active multiple sclerosis foamy macrophages and microglia, containing degenerated myelin, are abundantly found in demyelinated areas. Recent studies have described an altered macrophage phenotype after myelin internalization. However, by which mechanisms myelin affects the phenotype of macrophages and how this phenotype can influence lesion progression is unclear. Here we demonstrate, by using genome wide gene expression analysis, that myelin-phagocytosing macrophages have an enhanced expression of genes in pathways involved in migration, phagocytosis and inflammation. More interestingly, we show that myelin internalization induces the expression of genes involved in liver X receptor signaling and cholesterol efflux. In vitro validation shows that myelin-phagocytosing macrophages indeed have an increased capacity to dispose intracellular cholesterol. Additionally, myelin suppresses the production of pro-inflammatory mediators, like nitric oxide and IL-6, by macrophages in a similar manner as a liver X receptor agonist. Our data show that myelin modulates the phenotype of macrophages by nuclear receptor activation, which may subsequently affect lesion progression in multiple sclerosis. Rat peritoneal macrophages were left untreated (n=5) or treated with isolated myelin (n=5) for 3 days. Both untreated and myelin-treated macrophages were subsequently stimulated with IFNM-RM-/ and IL1-M-NM-2 for 9 hours.
2012-08-20 | E-GEOD-34811 | biostudies-arrayexpress
Project description:Transcriptome of human primary macrophages from healthy controls after long-term myelin phagocytosis
| PRJNA1026622 | ENA
Project description:Background: The risk for dementia increases exponentially from the seventh decade of life. Identifying and understanding the biochemical changes that sensitize the ageing brain to neurodegeneration will provide new opportunities for dementia prevention and treatment. This study aimed to determine how ageing and major genetic risk factors for dementia affect the hippocampal proteome and lipidome of neurologically-normal humans over the age of 65. The hippocampus was chosen as it is highly susceptible to atrophy with ageing and in several neurodegenerative diseases. Methods: Mass spectrometry-based proteomic and lipidomic analysis of CA1 hippocampus samples from 74 neurologically normal human donors, aged 66 – 104, was used in combination with multiple regression models and gene set enrichment analysis to identify age-dependent changes in the proteome and lipidome. ANOVA was used to test the effect of major dementia risk alleles in the TMEM106B and APOE genes on the hippocampal proteome and lipidome, adjusting for age, gender, and post-mortem interval. Fibrillar C-terminal TMEM106B fragments were isolated using sarkosyl fractionation and quantified by immunoblotting. Results: Forty proteins were associated with age at false discovery rate-corrected P<0.05, including proteins that regulate cell adhesion, the cytoskeleton, amino acid and lipid metabolism, and ribosomal subunits. TMEM106B, a regulator of lysosomal and oligodendrocyte function, was regulated with greatest effect size. The increase in TMEM106B levels with ageing was specific to carriers of the rs1990622-A allele in the TMEM106B gene that increases risk for frontotemporal dementia, Alzheimer’s disease, Parkinson’s disease, and hippocampal sclerosis with ageing. Rs1990622-A was also associated with higher TMEM106B fibril content. Hippocampal lipids were not significantly affected by APOE genotype, however levels of myelin-enriched sulfatides and hexosylceramides were significantly lower, and polyunsaturated phospholipids were higher, in rs1990622-A carriers after controlling for APOE genotype. Conclusions: Our study demonstrates that TMEM106B protein abundance is increased with brain ageing in humans, establishes that dementia risk allele rs1990622-A predisposes to TMEM106B fibril formation in the hippocampus, and provides the first evidence that rs1990622-A affects brain lipid homeostasis, particularly myelin lipids. Our data suggests that TMEM106B is one of a growing list of major dementia risk genes that affect glial lipid metabolism.
2023-09-21 | PXD043880 | Pride
Project description:Multiple sclerosis is a chronic, inflammatory, demyelinating disease of the central nervous system in which macrophages and microglia play a central role. During active multiple sclerosis foamy macrophages and microglia, containing degenerated myelin, are abundantly found in demyelinated areas. Recent studies have described an altered macrophage phenotype after myelin internalization. However, by which mechanisms myelin affects the phenotype of macrophages and how this phenotype can influence lesion progression is unclear. Here we demonstrate, by using genome wide gene expression analysis, that myelin-phagocytosing macrophages have an enhanced expression of genes in pathways involved in migration, phagocytosis and inflammation. More interestingly, we show that myelin internalization induces the expression of genes involved in liver X receptor signaling and cholesterol efflux. In vitro validation shows that myelin-phagocytosing macrophages indeed have an increased capacity to dispose intracellular cholesterol. Additionally, myelin suppresses the production of pro-inflammatory mediators, like nitric oxide and IL-6, by macrophages in a similar manner as a liver X receptor agonist. Our data show that myelin modulates the phenotype of macrophages by nuclear receptor activation, which may subsequently affect lesion progression in multiple sclerosis.
2012-08-20 | GSE34811 | GEO
Project description:There are many subtypes of dementia, and identification of diagnostic biomarkers that are minimally-invasive, low-cost, and efficient is desired. Circulating microRNAs (miRNAs) have recently gained attention as easily accessible and non-invasive biomarkers. We conducted a comprehensive miRNA expression analysis of serum samples from 1348 Japanese dementia patients, composed of four subtypes—Alzheimer’s disease (AD), vascular dementia, dementia with Lewy bodies (DLB), and normal pressure hydrocephalus—and 246 control subjects. We used this data to construct dementia subtype prediction models based on penalized regression models with the multiclass classification. We constructed a final prediction model using 46 miRNAs, which classified dementia patients from an independent validation set into four subtypes of dementia. Network analysis of miRNA target genes revealed important hub genes, SRC and CHD3, associated with the AD pathogenesis. Moreover, MCU and CASP3, which are known to be associated with DLB pathogenesis, were identified from our DLB-specific target genes. Our study demonstrates the potential of blood-based biomarkers for use in dementia-subtype prediction models. We believe that further investigation using larger sample sizes will contribute to the accurate classification of subtypes of dementia.
2021-10-22 | GSE167559 | GEO
Project description:Vitamin D deficiency is a major environmental risk factor for the development of multiple sclerosis (MS). The major circulating metabolite of vitamin D (25OHD) is converted to the active form (calcitriol) by the hydroxylase enzyme CYP27B1. In MS lesions the tyrosine kinase MerTK expressed by microglia and macrophages regulates phagocytosis of myelin debris and apoptotic cells that can accumulate and inhibit tissue repair and remyelination. We show that calcitriol downregulates MerTK mRNA and protein expression in primary adult human microglia and monocyte-derived macrophages, thereby inhibiting myelin phagocytosis and apoptotic cell clearance. Proinflammatory myeloid cells express high levels of CYP27B1 compared to homeostatic (TGFb-treated) myeloid cells. Only proinflammatory cells in the presence of TNF-a generate calcitriol from 25OHD, resulting in repression of MerTK expression and function. The selective production of calcitriol in proinflammatory myeloid cells leading to downregulation of MerTK-mediated phagocytosis has the potential to reduce the risk for auto-antigen presentation while retaining the phagocytic ability of homeostatic myeloid cells, thereby contributing to inflammation reduction and enhanced tissue repair.
2020-04-21 | GSE148986 | GEO
Project description:Understanding the molecular mechanisms underlying frontotemporal dementia (FTD) is essential for the development of successful therapies. Systematic studies on human post-mortem brain tissue of patients with genetic subtypes of FTD are currently lacking. The Risk and Modyfing Factors of Frontotemporal Dementia (RiMod-FTD) consortium therefore has generated multi-omics datasets for genetic subtypes of FTD to identify common and distinct molecular mechanisms disturbed in disease. This experiment contains data from smRNA-sequencing of human post-mortem brain tissue of the frontal lobe from patients with FTD caused by mutations in GRN, MAPT or C9orf72 and healthy controls.
2023-02-26 | E-MTAB-12731 | biostudies-arrayexpress