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Discovery of small molecules that normalize the transcriptome and enhance cysteine cathepsin activity in progranulin-deficient microglia

ABSTRACT: Patients with frontotemporal dementia (FTD) resulting from granulin (GRN) haploinsufficiency have reduced levels of progranulin and exhibit dysregulation in inflammatory and lysosomal networks. Microglia produce high levels of progranulin, and reduction of progranulin in microglia alone is sufficient to recapitulate inflammation, lysosomal dysfunction, and hyperproliferation in a cell-autonomous manner. Therefore, targeting microglial dysfunction caused by progranulin insufficiency represents a potential therapeutic strategy to manage neurodegeneration in FTD. Limitations of current progranulin-enhancing strategies necessitate the discovery of new targets.To identify compounds that can reverse microglial defects in Grn-deficient mouse microglia, we performed a compound screen coupled with high throughput sequencing to assess key transcriptional changes in inflammatory and lysosomal pathways. Positive hits from this initial screen were then further narrowed down based on their ability to rescue cathepsin activity, a critical biochemical readout of lysosomal capacity. The screen identified nor-binaltorphimine dihydrochloride (nor-BNI) and dibutyryl-cAMP, sodium salt (DB-cAMP) as two phenotypic modulators of progranulin deficiency. In addition, nor-BNI and DB-cAMP also rescued cell cycle abnormalities in progranulin-deficient cells. These data highlight the potential of a transcription-based platform for drug screening, and advance two novel lead compounds for FTD.

ORGANISM(S): Mus musculus

PROVIDER: GSE143144 | GEO | 2020/08/02

REPOSITORIES: GEO

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Progranulin Deficiency Promotes Circuit-Specific Synaptic Pruning by Microglia via Complement Activation

Project description:Microglia repair injury and maintain homeostasis in the brain, but whether aberrant microglial activation can contribute to neurodegeneration remains unclear. Here, we use transcriptome profiling to demonstrate that deficiency in frontotemporal dementia (FTD) gene progranulin (Grn) leads to an age-dependent, progressive up-regulation of lysosomal and innate immunity genes, increased complement production, and synaptic pruning activity in microglia. During aging, Grn-/- mice show profound accumulation of microglia and preferential elimination of inhibitory synapses in the ventral thalamus, which contribute to hyperexcitability in the thalamocortical circuits and obsessive-compulsive disorder (OCD)-like grooming behaviors. Remarkably, blocking complement activation by deleting C1qa gene significantly reduces synaptic pruning by Grn-/- microglia, and mitigates neurodegeneration, behavioral phenotypes and premature mortality in Grn-/- mice. These results uncover a previously unrecognized role of progranulin in suppressing microglia activation during aging, and support the idea that blocking complement activation is a promising therapeutic target for neurodegeneration caused by progranulin deficiency. Gene expression study in multiple brain regions from a mouse model of progranulin deficiency Please note that 9 outlier samples were excluded from data analysis. Therefore, there are 326 raw data columns (i.e. 163 samples) in the non_normalized data matrix while 154 samples are represented here.

2016-03-31 | E-GEOD-75083 | biostudies-arrayexpress

Progranulin Deficiency Promotes Circuit-Specific Synaptic Pruning by Microglia via Complement Activation

2016-03-31 | GSE75083 | GEO

Deficiency of the frontotemporal dementia gene GRN results in gangliosidosis

Project description:Haploinsufficiency of GRN causes frontotemporal dementia (FTD). The GRN locus produces progranulin (PGRN), which is cleaved to lysosomal granulin polypeptides. The function of lysosomal granulins and why their absence causes neurodegeneration are unclear. Here we discover that PGRN-deficient human cells and murine brains, as well as human frontal lobes from GRN-mutation FTD patients have increased levels of gangliosides, glycosphingolipids that contain sialic acid. In these cells and tissues, levels of lysosomal enzymes that catabolize gangliosides were normal, but levels of bis(monoacylglycero)phosphates (BMP), lipids required for ganglioside catabolism, were reduced with PGRN deficiency. Our findings indicate that granulins are required to maintain BMP levels to support ganglioside catabolism, and that PGRN deficiency in lysosomes leads to gangliosidosis. Lysosomal ganglioside accumulation may contribute to neuroinflammation and neurodegeneration susceptibility observed in FTD due to PGRN deficiency and other neurodegenerative diseases.

2022-09-18 | PXD035889 | Pride

Neurovascular dysfunction in GRN-associated frontotemporal dementia identified by single-nucleus RNA-sequencing of human cerebral cortex

Project description:Frontotemporal dementia (FTD) is the second most prevalent form of early-onset dementia, affecting predominantly frontal and temporal cerebral lobes. Heterozygous mutations in the progranulin gene (GRN) cause autosomal-dominant FTD (FTD-GRN), associated with TDP-43 inclusions, neuronal loss, axonal degeneration and gliosis, but FTD-GRN pathogenesis is largely unresolved. Here we report single-nucleus RNA sequencing of microglia, astrocytes and the neurovasculature from frontal, temporal and occipital cortical tissue from control and FTD-GRN brains. We show that fibroblast and mesenchymal cell numbers were enriched in FTD-GRN, and we identified disease-associated subtypes of astrocytes and endothelial cells. Expression of gene modules associated with blood–brain barrier (BBB) dysfunction was significantly enriched in FTD-GRN endothelial cells. The vasculature supportive function and capillary coverage by pericytes was reduced in FTD-GRN tissue, with increased and hypertrophic vascularization and an enrichment of perivascular T cells. Our results indicate a perturbed BBB and suggest that the neurovascular unit is severely affected in FTD-GRN.

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Molecular signatures of neuroinflammation induced by α-synuclein aggregates-A multi-proteomics approach (Mouse Arm)

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2020-01-24 | PXD013691 | Pride

Loss of TREM2 reduces hyperactivation of progranulin deficient microglia but not lysosomal pathology [14 months]

Project description:GRN haploinsufficiency causes frontotemporal lobar degeneration and results in microglial hyperactivation, lysosomal dysfunction and TDP-43 deposition. To understand the contribution of microglial hyperactivation to pathology we evaluated genetic and pharmacological approaches suppressing TREM2 dependent transition of microglia from a homeostatic to a disease associated state. Trem2 deficiency in Grn KO mice led to a reduction of microglia activation. To explore antibody-mediated pharmacological modulation of TREM2-dependent microglial states, we identified antagonistic TREM2 antibodies. Treatment of macrophages from GRN-FTLD patients with these antibodies allowed a complete rescue of elevated levels of TREM2 together with increased shedding and reduction of TREM2 signaling. Furthermore, antibody-treated PGRN deficient hiMGL showed dampened microglial hyperactivation, reduced TREM2 signaling and phagocytic activity, however, lack of rescue of lysosomal dysfunction. Similarly, lysosomal dysfunction, lipid dysregulation and glucose hypometabolism of Grn KO mice were not rescued by TREM2 ablation. Furthermore, NfL, a biomarker for neurodegeneration, was elevated in the Grn/Trem2 KO. These findings suggest that microglia hyperactivation is not necessarily contributing to neurotoxicity, and instead demonstrates that TREM2 exhibits neuroprotective potential in this model.

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Loss of TREM2 reduces hyperactivation of progranulin deficient microglia but not lysosomal pathology

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Loss of TMEM106B potentiates lysosomal and FTLD-like pathology in progranulin deficient mice [neuroinflammation panel]

Project description:Polygenic risk factors influence onset and progression of neurodegenerative diseases, but are difficult to be functionally explored in isolation. Single nucleotide polymorphisms (SNPs) in TMEM106B increase the risk for frontotemporal lobar degeneration (FTLD) of GRN mutation carriers. Currently, it is not clear if progranulin (PGRN) and TMEM106B are synergistically linked and if a gain or a loss-of-function of TMEM106B is responsible for the increased disease risk of patients with PGRN haploinsufficiency. We therefore compared behavioral abnormalities, gene expression patterns, lysosomal activity and TDP-43 pathology in single and double knockout animals. Grn–/–/Tmem106b–/– mice showed a strongly reduced life span and massive motor deficits. Gene expression analysis revealed an upregulation of molecular signatures characteristic for disease associated microglia and autophagy. Dysregulation of maturation of lysosomal proteins as well as a pronounced accumulation of ubiquitinated proteins and wide spread p62 deposition suggest that proteostasis is impaired. Moreover, while single Grn–/– knockouts only occasionally showed TDP-43 pathology, the double knockout mice exhibit robust deposition of phosphorylated TDP-43. Thus, a loss-of-function of TMEM106B may enhance the risk for GRN-associated FTD by reduced protein turnover in the lysosomal/autophagic system.

2020-07-25 | GSE155066 | GEO

Loss of TMEM106B potentiates lysosomal and FTLD-like pathology in progranulin deficient mice [neuropathology panel]

2020-07-25 | GSE155065 | GEO

Opposite microglial activation stages upon loss of PGRN result in reduced cerebral glucose metabolism

Project description:Microglia adopt numerous fates with homeostatic microglia (HM) and a microglial neurodegenerative phenotype (MGnD) representing two opposite ends. A number of variants in genes selectively expressed in microglia are associated with an increased risk for neurodegenerative diseases such as Alzheimer's disease (AD) and Frontotemporal lobar degeneration (FTLD). Among these genes are progranulin (GRN) and the triggering receptor expressed on myeloid cells 2 (TREM2). Both cause neurodegeneration by mechanisms involving loss-of-function. We have now isolated microglia from Grn–/– mice and compared their transcriptomes to those of Trem2–/– mice. Surprisingly, while loss of Trem2 enhances the expression of genes associated with a homeostatic state, microglia derived from Grn–/– mice showed a reciprocal activation of the MGnD molecular signature and suppression of genes characteristic for HM. The opposite mRNA expression profiles are associated with divergent functional phenotypes. Although loss of TREM2 and progranulin resulted in opposite activation states and functional phenotypes of microglia, FDG (fluoro-2-deoxy-D-glucose)-µPET of brain revealed reduced glucose metabolism in both conditions, suggesting that opposite microglial phenotypes result in similar wide spread brain dysfunction.

2019-04-18 | GSE129709 | GEO

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