{"gene":"GRN","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":2001,"finding":"PCDGF/progranulin (GRN) mediates estrogen (E2) mitogenic signaling in MCF-7 breast cancer cells by stimulating MAPK activity and cyclin D1 expression; neutralizing antibody or antisense inhibition of PGRN blocked E2-induced DNA synthesis, and PGRN overexpression conferred estrogen-independent proliferation and tamoxifen resistance.","method":"Neutralizing antibody, antisense transfection, PGRN overexpression, MAPK activity assay, cyclin D1 Western blot in MCF-7 cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (antibody neutralization, antisense KD, OE) with defined signaling readouts in single rigorous study","pmids":["11134521"],"is_preprint":false},{"year":1998,"finding":"Autocrine production of PCDGF/progranulin (GRN) is required for tumorigenicity of PC teratoma cells; inhibition of PGRN expression by antisense cDNA transfection dramatically reduced in vivo tumor formation in syngeneic mice, and PGRN expression level positively correlated with tumorigenic potential.","method":"Antisense cDNA transfection, in vivo tumor growth assay in syngeneic C3H mice, Northern/Western blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function with defined in vivo phenotype plus expression correlation, single lab but orthogonal methods","pmids":["9826678"],"is_preprint":false},{"year":2008,"finding":"A missense mutation in the GRN signal peptide (p.A9D) prevents progranulin secretion, trapping the protein in an intracellular compartment, resulting in functional haploinsufficiency despite normal total GRN mRNA levels; a splice-site mutation (IVS6-2A>G) causes exon 7 skipping and reduces GRN mRNA and protein by ~50%.","method":"Subcellular fractionation, confocal microscopy, RT-PCR, Western blot in patient mutation carriers","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 2 — orthogonal methods (fractionation + confocal + quantitative PCR/protein) establishing mechanistic consequence of specific mutations","pmids":["18183624"],"is_preprint":false},{"year":2019,"finding":"Progranulin (PGRN) directly interacts with TNF receptors (TNFR2), and this interaction mediates PGRN's anti-inflammatory and protective functions; PGRN-deficient mice are highly susceptible to experimental colitis, whereas recombinant PGRN protects via IL-10 and TNFR2-dependent pathways.","method":"Co-immunoprecipitation (PGRN-TNFR2), genetic knockout mice (PGRN-/-, TNFR2-/-, IL-10-/-), DSS/TNBS colitis models, bone marrow chimeras, T cell transfer colitis","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic models with specific pathway placement (TNFR2, IL-10 dependence) plus biochemical interaction","pmids":["25387791"],"is_preprint":false},{"year":2018,"finding":"PGRN deficiency in a knock-in mouse (PGRN-KI, R504X) leads to activation of Gas6-Tyro3-PLCγ-PKCα signaling, causing tau phosphorylation at Ser203, tau mislocalization to dendritic spines, and spine loss preceding TDP43 aggregation; targeting Gas6/Tyro3 or PKC/MAPK signaling rescues spine loss and cognitive impairment.","method":"Phosphoproteomics, PKC inhibitor/B-Raf inhibitor treatment, knockdown of Gas6/Tyro3 axis in PGRN-KI mice, behavioral testing, spine analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 — phosphoproteomics + pharmacological intervention + genetic KD with behavioral phenotype rescue, moderate replication within single study","pmids":["29382817"],"is_preprint":false},{"year":2021,"finding":"PGRN is a lysosomal protein that interacts with bis(monoacylglycero)phosphate (BMP) in a pH-dependent manner; PGRN loss in mice causes global BMP deficiency and secondary glucosylsphingosine storage, implicating PGRN in lysosomal phospholipid homeostasis and proteolysis/lipolysis.","method":"BMP mass spectrometry, pH-dependent binding assay, Grn-/- mouse biochemistry, primary macrophage and iPSC-derived microglia functional assays, PTV:PGRN replacement rescue","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 — biochemical interaction identified, multiple model systems (mouse, primary cells, iPSC), rescue experiment with defined mechanistic readouts","pmids":["34450028"],"is_preprint":false},{"year":2022,"finding":"PGRN-deficient human cells and Grn-/- mouse brains accumulate gangliosides (including GM1, GM2, GM3); granulins are required to maintain bis(monoacylglycero)phosphate (BMP) levels needed for lysosomal ganglioside catabolism, indicating that PGRN loss causes gangliosidosis without reducing ganglioside-catabolizing enzyme levels.","method":"Lipidomics of PGRN-deficient cells and mouse brains, lysosomal enzyme activity assays, BMP quantification, human FTD-GRN frontal lobe analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 — enzyme activity assays plus quantitative lipidomics in multiple models (cell, mouse, human tissue), strong mechanistic conclusion","pmids":["36207292"],"is_preprint":false},{"year":2021,"finding":"Grn knockout mice accumulate myelin debris in microglial lysosomes in white matter; PGRN insufficiency in microglia impairs lysosomal-mediated clearance of myelin debris, and double-KO of Grn and cathepsin D (Ctsd) augments myelin debris accumulation and neuronal TDP-43 pathology, placing PGRN upstream of cathepsin D in microglial lysosomal clearance.","method":"Grn KO mice, Ctsd/Grn double-KO epistasis, immunofluorescence for myelin debris and TDP-43, microgliosis quantification","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis (double KO) with defined cellular and molecular phenotypes, pathway placement established","pmids":["34433069"],"is_preprint":false},{"year":2023,"finding":"Progranulin-deficient astrocytes (from Grn-/- mice and FTLD-GRN patients) upregulate GJA1, AQP4, and APOE and downregulate glutamate transporter SLC1A2; these progranulin-deficient astrocytes promote synaptic degeneration, neuronal stress, and TDP-43 proteinopathy in neuron co-cultures and cortical organoids with iPSC-derived astrocytes.","method":"Single-cell RNA-seq, astrocyte-neuron co-cultures, iPSC-derived astrocyte transplantation into cortical organoids, comparative mouse/human transcriptomics","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — single-cell transcriptomics plus functional reconstitution in co-culture and organoid systems with mechanistic pathway identification","pmids":["36602862"],"is_preprint":false},{"year":2019,"finding":"Progranulin (PGRN) directly interacts with NF-κB essential modulator (NEMO) via its Grn CDE domains during influenza virus infection, recruiting A20 to deubiquitinate K63-linked polyubiquitin chains on NEMO at K264, thereby suppressing NF-κB and IRF3 signaling and inhibiting type I interferon production.","method":"Co-immunoprecipitation (PGRN-NEMO interaction), domain mapping (Grn CDE domains), deubiquitination assay (A20 recruitment, K63-Ub chains on NEMO K264), PGRN KD and Grn-/- mice, in vivo challenge with influenza","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1–2 — biochemical interaction, domain mapping, deubiquitination site identified, confirmed in KD and KO mouse models","pmids":["31585000"],"is_preprint":false},{"year":2013,"finding":"PGRN haploinsufficiency in lymphoblasts from FTLD-TDP (c.709-1G>A) mutation carriers activates noncanonical Wnt5a signaling; PGRN-deficient cells show increased cellular and secreted Wnt5a, enhanced phospho-CaMKII, and ERK1/2 activation via Ca2+/PKC-dependent, pertussis toxin-sensitive mechanism; exogenous PGRN or control conditioned medium normalized these responses.","method":"ERK1/2 and CaMKII phosphorylation assays, Wnt5a ELISA, pertussis toxin treatment, exogenous PGRN rescue, PGRN knockdown in SH-SY5Y cells","journal":"Neurobiology of aging","confidence":"Medium","confidence_rationale":"Tier 2 — multiple signaling assays in patient-derived cells with rescue, single lab","pmids":["24139281"],"is_preprint":false},{"year":2011,"finding":"PGRN deficit in lymphoblasts from PGRN mutation (c.709-1G>A) carriers increases CDK6 levels and retinoblastoma protein phosphorylation, causing G1/S regulatory failure; this is associated with altered subcellular TDP-43 distribution and loss of TDP-43-mediated repression of CDK6 expression.","method":"CDK6 and phospho-Rb Western blot, cell cycle analysis (flow cytometry), TDP-43 localization (immunofluorescence), patient-derived lymphoblasts","journal":"Neurobiology of aging","confidence":"Medium","confidence_rationale":"Tier 2–3 — mechanistic signaling pathway identified in patient-derived cells, single lab","pmids":["21232819"],"is_preprint":false},{"year":2014,"finding":"PGRN promotes macrophage M2 polarization through direct binding to TNFR2; co-immunoprecipitation confirmed PGRN-TNFR2 physical interaction, and TNFR2-blocking neutralizing antibody abrogated PGRN-mediated increases in M2 markers (CD206, IL-10, Arg-1) in RAW264.7 macrophages and bone marrow-derived macrophages.","method":"Co-immunoprecipitation (PGRN-TNFR2), TNFR2 neutralizing antibody, flow cytometry for M1/M2 markers, ELISA for cytokines, multiplex IHC","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2–3 — biochemical interaction confirmed plus functional rescue with neutralizing antibody, single lab","pmids":["38689292"],"is_preprint":false},{"year":2015,"finding":"PGRN induces hepatic insulin resistance via TNFR1, activating NF-κB-dependent pathways; TNFR1 blocking peptide-Fc fusion protein or TNFR1 siRNA reversed PGRN-induced defective autophagy and impaired insulin signaling in hepatocytes in vivo and in vitro.","method":"In vivo mouse PGRN treatment, TNFR1 blocking peptide-Fc, TNFR1 siRNA, glucose/insulin tolerance tests, insulin signaling Western blots","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 — genetic and pharmacological blockade of TNFR1 with rescue of defined phenotypes, single lab","pmids":["25664864"],"is_preprint":false},{"year":2020,"finding":"Loss of both TMEM106B and PGRN in mice results in severe neuronal loss, glial activation, and enlarged lysosomes in microglia and astrocytes, with greatly enhanced accumulation of lysosomal vacuoles in the axon initial segment of motor neurons; TMEM106B deficiency alone causes lysosomal vacuole accumulation at the axon initial segment, identifying TMEM106B as a lysosomal membrane protein that genetically interacts with PGRN in neurodegeneration.","method":"Grn-/-/Tmem106b-/- double-KO mice, histopathology, electron microscopy, immunofluorescence for lysosomal markers and neuronal markers","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with double-KO model, multiple orthogonal histopathological readouts","pmids":["32852886"],"is_preprint":false},{"year":2019,"finding":"Loss of Grn in mice shifts microglia from a homeostatic state to the microglial neurodegenerative phenotype (MGnD), with suppression of homeostatic genes, reciprocally opposite to the effect of Trem2 loss; both Grn-/- and Trem2-/- result in reduced brain glucose metabolism despite opposite microglial activation states.","method":"Isolated microglia transcriptomics from Grn-/- and Trem2-/- mice, FDG-µPET brain imaging","journal":"EMBO molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 — comparative transcriptomics with functional imaging, establishes pathway position; single study","pmids":["31122931"],"is_preprint":false},{"year":2012,"finding":"GRN promoter methylation is increased in sporadic FTLD patients relative to controls, with a negative correlation between GRN promoter methylation and GRN mRNA levels in peripheral blood mononuclear cells, identifying promoter methylation as a mechanism that can reduce GRN expression.","method":"Bisulfite pyrosequencing of GRN promoter, RT-PCR for GRN mRNA, correlation analysis in patient cohort","journal":"Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology","confidence":"Medium","confidence_rationale":"Tier 3 — methylation quantification with mRNA correlation, single cohort study","pmids":["22797721"],"is_preprint":false},{"year":2020,"finding":"Transcription factor REST (repressor element 1 silencing transcription factor) directly binds the PGRN promoter and represses PGRN expression; REST knockdown increases PGRN levels and promotes BV2 microglia-like cell migration, while REST overexpression suppresses migration, placing REST as an inhibitory transcriptional regulator of PGRN.","method":"Dual luciferase reporter assay (REST binding to PGRN promoter), siRNA KD and REST overexpression in BV2 cells, transwell migration assay, PGRN siRNA","journal":"Neural plasticity","confidence":"Medium","confidence_rationale":"Tier 2–3 — luciferase reporter confirms direct promoter binding plus functional KD/OE with migration phenotype, single lab","pmids":["33299399"],"is_preprint":false},{"year":2023,"finding":"Antisense oligonucleotides (ASOs) targeting the miR-29b binding site in the 3' UTR of GRN mRNA increase progranulin protein translation in a dose-dependent manner in neuroglioma cells, iPSC-derived neurons, and a humanized GRN mouse model; mechanism was confirmed by FRET competition assays showing ASO displacement of miR-29b from GRN 3'UTR and polysome profiling demonstrating increased translation.","method":"FRET-based miRNA binding competition assay, polysome profiling, Western blot for progranulin protein, iPSC-derived neurons, humanized GRN mouse model","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — mechanistic assays (FRET, polysome profiling) plus multiple cell models and in vivo validation in single study","pmids":["37981208"],"is_preprint":false},{"year":2024,"finding":"Progranulin (PGRN) mediates liver pathology caused by ADAR1 deficiency by promoting interferon signaling and recruiting EGFR+ macrophages into the liver; the PGRN-EGFR axis drives hepatic inflammation in ADAR1-deficient hepatocytes, and this signaling is repressed in ADAR1-high tumors to facilitate immune evasion.","method":"Liver-specific Adar KO and Ifih1;Adar double-KO mouse models, PGRN expression analysis in hepatocytes, macrophage recruitment assays, EGFR co-localization","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2–3 — genetic mouse models with defined mechanistic interaction (PGRN-EGFR), single lab","pmids":["38935501"],"is_preprint":false},{"year":2021,"finding":"PGRN deficiency reduces parkin protein levels in fibroblasts from FTLD patients with four different PGRN mutations, and parkin knockdown is also observed upon PGRN silencing in control fibroblasts; this is accompanied by decreases in parkin targets MFN2 and VDAC1. TDP-43 overexpression rescues PRKN levels during transient PGRN silencing but not in stable PGRN-mutant fibroblasts, and TDP-43 silencing reduces PRKN, suggesting TDP-43 loss-of-function contributes to parkin downregulation downstream of PGRN deficiency.","method":"Western blot for parkin/MFN2/VDAC1 in patient fibroblasts, PGRN siRNA in control fibroblasts, TDP-43 overexpression/knockdown rescue experiments","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2–3 — multiple orthogonal genetic manipulations (patient cells, siRNA, rescue) establishing pathway order, single lab","pmids":["34054428"],"is_preprint":false},{"year":2022,"finding":"PGRN deficiency exacerbates GBA1 mutation-associated disease in Grn-/-/Gba9v/9v mice, including neurobehavioral deficits, neuroinflammation (microgliosis, astrogliosis), and impaired autophagy; a BBB-penetrant PGRN-derived peptide (ND7) ameliorated neuronopathic Gaucher disease and PD-like pathology in vivo, identifying PGRN as a modifier of GCase/GBA1 pathway.","method":"Double-mutant mouse model (Grn-/-/Gba9v/9v), ND7 peptide BBB penetration and treatment, neuropathology, behavioral assays, patient fibroblast ex vivo rescue","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis (double KO) plus pharmacological rescue with BBB-penetrant biologic, multiple model systems","pmids":["36574647"],"is_preprint":false}],"current_model":"Progranulin (GRN/PGRN) is a secreted and lysosomal glycoprotein that functions as a growth factor stimulating MAPK and cyclin D1 signaling downstream of TNFR2, maintains lysosomal homeostasis by supporting bis(monoacylglycero)phosphate (BMP) levels required for sphingolipid/ganglioside catabolism, regulates microglial activation state, and suppresses innate immune signaling by binding NEMO via its granulin CDE domains to recruit A20 and deubiquitinate NEMO; haploinsufficiency causes lysosomal dysfunction, impaired myelin clearance by microglia, astroglial toxicity with synaptic degeneration, and TDP-43 proteinopathy characteristic of frontotemporal dementia."},"narrative":{"teleology":[{"year":1998,"claim":"The initial functional identity of progranulin as an autocrine growth factor was established when antisense suppression of PGRN expression abolished tumorigenicity of teratoma cells in vivo, demonstrating that secreted PGRN is required for tumor growth.","evidence":"Antisense cDNA transfection with in vivo tumor growth assay in syngeneic C3H mice","pmids":["9826678"],"confidence":"High","gaps":["Receptor mediating autocrine signaling not identified","No defined downstream signaling pathway"]},{"year":2001,"claim":"The mitogenic signaling mechanism was defined when PGRN was shown to activate MAPK and cyclin D1 downstream of estrogen stimulation, establishing PGRN as a mediator of proliferative signaling in breast cancer cells.","evidence":"Neutralizing antibody, antisense KD, PGRN overexpression, MAPK/cyclin D1 assays in MCF-7 cells","pmids":["11134521"],"confidence":"High","gaps":["Direct receptor for PGRN in this context not identified","Relevance to non-cancer proliferative settings untested"]},{"year":2008,"claim":"The molecular basis of GRN haploinsufficiency in FTLD was clarified when a signal-peptide missense mutation (A9D) was shown to trap progranulin intracellularly, preventing secretion and producing functional haploinsufficiency despite normal mRNA levels—establishing that both null and secretion-defective alleles cause disease.","evidence":"Subcellular fractionation, confocal microscopy, RT-PCR, and Western blot in cells from mutation carriers","pmids":["18183624"],"confidence":"High","gaps":["Whether intracellularly retained PGRN retains any lysosomal function not addressed","Scope of secretion-defective mutations in broader FTLD cohorts not surveyed"]},{"year":2011,"claim":"A link between PGRN deficiency and cell-cycle dysregulation was revealed when patient-derived lymphoblasts showed increased CDK6 and Rb phosphorylation tied to altered TDP-43 localization, suggesting that PGRN loss disrupts TDP-43-mediated transcriptional repression of CDK6.","evidence":"Western blot, flow cytometry cell-cycle analysis, TDP-43 immunofluorescence in patient lymphoblasts","pmids":["21232819"],"confidence":"Medium","gaps":["Direct regulation of CDK6 by TDP-43 not confirmed by ChIP or reporter assay","Relevance to neuronal pathology unclear"]},{"year":2014,"claim":"The receptor mediating PGRN's anti-inflammatory signaling was identified as TNFR2, with co-IP confirming physical interaction and TNFR2 neutralizing antibody blocking PGRN-driven M2 macrophage polarization, and genetic models showing TNFR2/IL-10 dependence for colitis protection.","evidence":"Co-IP of PGRN-TNFR2, TNFR2 neutralizing antibody in macrophages, Grn-/- and TNFR2-/- colitis models","pmids":["25387791","38689292"],"confidence":"High","gaps":["Structural basis of PGRN-TNFR2 interaction not resolved","Whether PGRN competes with TNFα for TNFR2 binding in vivo not quantified"]},{"year":2015,"claim":"PGRN was shown to also signal through TNFR1 in a metabolic context, inducing hepatic insulin resistance via NF-κB-dependent pathways and impaired autophagy, expanding the receptor repertoire beyond TNFR2.","evidence":"TNFR1 blocking peptide-Fc and siRNA in mouse hepatocytes, glucose/insulin tolerance tests","pmids":["25664864"],"confidence":"Medium","gaps":["Whether TNFR1 vs TNFR2 engagement is context- or dose-dependent not resolved","Relevance to neurodegeneration unclear"]},{"year":2018,"claim":"The mechanism linking PGRN loss to synaptic degeneration was elucidated: PGRN deficiency activates Gas6-Tyro3-PLCγ-PKCα signaling, causing tau hyperphosphorylation at Ser203, tau mislocalization to dendritic spines, and spine loss prior to TDP-43 aggregation—and pharmacological blockade of this axis rescued cognitive deficits.","evidence":"Phosphoproteomics, PKC/B-Raf inhibitors, Gas6/Tyro3 knockdown in PGRN-KI (R504X) mice, behavioral testing","pmids":["29382817"],"confidence":"High","gaps":["Whether tau phosphorylation is a primary driver or bystander in human FTLD-GRN not established","Relationship between Gas6-Tyro3 axis and lysosomal dysfunction not explored"]},{"year":2019,"claim":"A direct mechanism for PGRN's suppression of innate immune signaling was mapped: the granulin CDE domains bind NEMO and recruit deubiquitinase A20 to remove K63-linked polyubiquitin at NEMO K264, suppressing NF-κB and IRF3 activation and type I interferon production during influenza infection.","evidence":"Co-IP, domain mapping, deubiquitination assay, Grn-/- mice challenged with influenza virus","pmids":["31585000"],"confidence":"High","gaps":["Whether NEMO deubiquitination occurs in CNS microglia or only in peripheral immunity not tested","Stoichiometry and regulation of PGRN-A20-NEMO complex not determined"]},{"year":2019,"claim":"Microglial transcriptomic profiling placed PGRN loss as a driver of the neurodegenerative microglial (MGnD) activation state—reciprocal to TREM2 loss—linking PGRN to microglial phenotype switching and brain glucose hypometabolism.","evidence":"Isolated microglia transcriptomics from Grn-/- and Trem2-/- mice, FDG-µPET imaging","pmids":["31122931"],"confidence":"Medium","gaps":["Causal relationship between microglial activation state and neurodegeneration not directly tested","Molecular link between PGRN and TREM2 signaling not established"]},{"year":2020,"claim":"Genetic epistasis between PGRN and the lysosomal membrane protein TMEM106B was demonstrated in vivo: double knockout of Grn and Tmem106b caused severe neuronal loss and lysosomal vacuole accumulation exceeding either single KO, establishing TMEM106B as a genetic modifier in PGRN-dependent neurodegeneration.","evidence":"Grn-/-/Tmem106b-/- double-KO mice, histopathology, electron microscopy","pmids":["32852886"],"confidence":"High","gaps":["Biochemical mechanism of PGRN-TMEM106B functional interaction not identified","Whether TMEM106B variants modify human GRN disease progression not addressed"]},{"year":2021,"claim":"The core lysosomal function of progranulin was defined biochemically: PGRN binds bis(monoacylglycero)phosphate (BMP) in a pH-dependent manner, and its loss causes global BMP deficiency with secondary glucosylsphingosine storage, directly linking progranulin to lysosomal lipid homeostasis.","evidence":"BMP mass spectrometry, pH-dependent binding assay, Grn-/- mice, iPSC-derived microglia, PGRN replacement rescue","pmids":["34450028"],"confidence":"High","gaps":["Whether PGRN stabilizes BMP production or prevents its degradation not resolved","Structural basis of PGRN-BMP interaction unknown"]},{"year":2021,"claim":"PGRN was positioned upstream of cathepsin D in microglial lysosomal clearance when Grn-/- mice showed myelin debris accumulation in microglial lysosomes, exacerbated by Ctsd co-deletion and accompanied by TDP-43 pathology.","evidence":"Grn-/-, Ctsd/Grn double-KO epistasis, immunofluorescence for myelin debris and TDP-43","pmids":["34433069"],"confidence":"High","gaps":["Whether PGRN directly activates cathepsin D or acts indirectly via BMP not distinguished","Applicability to human white-matter pathology not confirmed"]},{"year":2022,"claim":"Lysosomal ganglioside accumulation was identified as a hallmark of PGRN deficiency: lipidomics revealed GM1/GM2/GM3 ganglioside storage without reduction in catabolic enzyme levels, establishing that PGRN-dependent BMP maintenance is the rate-limiting factor for ganglioside catabolism.","evidence":"Lipidomics in PGRN-deficient cells, Grn-/- mouse brains, and human FTD-GRN frontal lobe tissue","pmids":["36207292"],"confidence":"High","gaps":["Whether ganglioside accumulation is directly neurotoxic or a marker of broader lysosomal failure not tested","Therapeutic reversal of gangliosidosis by PGRN replacement not demonstrated"]},{"year":2022,"claim":"PGRN was established as a genetic modifier of GBA1/glucocerebrosidase pathway disease: Grn-/-/Gba9v/9v double-mutant mice showed exacerbated neuronopathic Gaucher pathology, and a BBB-penetrant PGRN-derived peptide rescued neurobehavioral and neuropathological deficits.","evidence":"Double-mutant mouse model, ND7 peptide treatment, behavioral/neuropathological assays, patient fibroblast rescue","pmids":["36574647"],"confidence":"High","gaps":["Mechanism by which PGRN/granulins modulate GCase activity not defined","Whether PGRN replacement benefits human Gaucher or PD patients unknown"]},{"year":2023,"claim":"Progranulin-deficient astrocytes were shown to be active drivers of neurodegeneration: they upregulate APOE and GJA1 while losing the glutamate transporter SLC1A2, promoting synaptic degeneration and TDP-43 proteinopathy in neuron co-cultures and cortical organoids.","evidence":"Single-cell RNA-seq, iPSC-derived astrocyte transplantation into cortical organoids, mouse/human comparative transcriptomics","pmids":["36602862"],"confidence":"High","gaps":["Whether astrocyte toxicity is cell-autonomous or secondary to impaired lysosomal lipid handling not resolved","Relative contribution of astrocyte vs microglial dysfunction to human FTLD-GRN pathology not quantified"]},{"year":2023,"claim":"A post-transcriptional mechanism for boosting PGRN levels was validated: ASOs displacing miR-29b from the GRN 3′ UTR increased progranulin translation dose-dependently in iPSC neurons and humanized mice, confirmed by FRET competition and polysome profiling.","evidence":"FRET-based miRNA binding competition assay, polysome profiling, iPSC-derived neurons, humanized GRN mouse model","pmids":["37981208"],"confidence":"High","gaps":["Long-term safety and efficacy of miR-29b-blocking ASOs in vivo not established","Whether this approach achieves therapeutically relevant PGRN increases in human brain not tested"]},{"year":null,"claim":"Key unresolved questions include the structural basis of progranulin-BMP interaction, whether PGRN directly activates cathepsin D or acts via BMP, how lysosomal and signaling functions are coordinately regulated, and whether PGRN replacement can reverse established neurodegeneration in humans.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of progranulin bound to BMP or TNFR2","Relative pathogenic contributions of lysosomal, microglial, and astrocytic dysfunction to FTLD-GRN not dissected in humans","Whether processed granulins versus full-length PGRN have distinct lysosomal vs signaling roles not resolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,1,3,12]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[9,13]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[5,6]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[5,6,7,14]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1,2,3]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,9,12,15]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,4,13]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,6,21]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,4,8,14]}],"complexes":[],"partners":["TNFRSF1B","NEMO","TNFAIP3","CTSD","TMEM106B","TARDBP","GAS6","TYRO3"],"other_free_text":[]},"mechanistic_narrative":"Progranulin (GRN) is a secreted glycoprotein that functions as a growth factor, lysosomal regulator, and immunomodulator, with central roles in lysosomal lipid homeostasis, microglial activation, and inflammatory signaling. In the lysosome, progranulin maintains bis(monoacylglycero)phosphate (BMP) levels required for ganglioside and sphingolipid catabolism, and its loss causes ganglioside accumulation and impaired myelin debris clearance by microglia upstream of cathepsin D [PMID:34450028, PMID:36207292, PMID:34433069]. Progranulin binds TNFR2 to promote anti-inflammatory macrophage polarization and IL-10-dependent tissue protection, and suppresses NF-κB/IRF3 innate immune signaling by recruiting A20 to deubiquitinate K63-linked polyubiquitin on NEMO via its granulin CDE domains [PMID:25387791, PMID:31585000, PMID:38689292]. Heterozygous loss-of-function mutations in GRN cause frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP), driven by lysosomal dysfunction, aberrant astrocyte-mediated synaptic degeneration, and dysregulated tau phosphorylation through Gas6-Tyro3-PKCα signaling [PMID:18183624, PMID:36602862, PMID:29382817]."},"prefetch_data":{"uniprot":{"accession":"P28799","full_name":"Progranulin","aliases":["Acrogranin","Epithelin precursor","Glycoprotein of 88 Kda","GP88","Glycoprotein 88","Granulin precursor","PC cell-derived growth factor","PCDGF","Proepithelin","PEPI"],"length_aa":593,"mass_kda":63.5,"function":"Secreted protein that acts as a key regulator of lysosomal function and as a growth factor involved in inflammation, wound healing and cell proliferation (PubMed:12526812, PubMed:18378771, PubMed:28073925, PubMed:28453791, PubMed:28541286). Regulates protein trafficking to lysosomes, and also the activity of lysosomal enzymes (PubMed:28453791, PubMed:28541286). Also facilitates the acidification of lysosomes, causing degradation of mature CTSD by CTSB (PubMed:28073925). In addition, functions as a wound-related growth factor that acts directly on dermal fibroblasts and endothelial cells to promote division, migration and the formation of capillary-like tubule structures (By similarity). Also promotes epithelial cell proliferation by blocking TNF-mediated neutrophil activation preventing release of oxidants and proteases (PubMed:12526812). Moreover, modulates inflammation in neurons by preserving neurons survival, axonal outgrowth and neuronal integrity (PubMed:18378771) Promotes proliferation of the epithelial cell line A431 in culture Inhibits epithelial cell proliferation and induces epithelial cells to secrete IL-8 Stabilizes CTSD through interaction with CTSD leading to maintain its aspartic-type peptidase activity","subcellular_location":"Secreted; Lysosome","url":"https://www.uniprot.org/uniprotkb/P28799/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GRN","classification":"Not Classified","n_dependent_lines":13,"n_total_lines":1208,"dependency_fraction":0.01076158940397351},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GRN","total_profiled":1310},"omim":[{"mim_id":"621213","title":"FAMILY WITH SEQUENCE SIMILARITY 171, MEMBER A2; FAM171A2","url":"https://www.omim.org/entry/621213"},{"mim_id":"615596","title":"CONGENITAL DISORDER OF GLYCOSYLATION, TYPE Iw, AUTOSOMAL RECESSIVE; CDG1WAR","url":"https://www.omim.org/entry/615596"},{"mim_id":"614706","title":"CEROID LIPOFUSCINOSIS, NEURONAL, 11; CLN11","url":"https://www.omim.org/entry/614706"},{"mim_id":"613556","title":"MICRO RNA 659; MIR659","url":"https://www.omim.org/entry/613556"},{"mim_id":"613413","title":"TRANSMEMBRANE PROTEIN 106B; TMEM106B","url":"https://www.omim.org/entry/613413"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Lysosomes","reliability":"Enhanced"},{"location":"Endosomes","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GRN"},"hgnc":{"alias_symbol":["PCDGF","PGRN","CLN11"],"prev_symbol":[]},"alphafold":{"accession":"P28799","domains":[{"cath_id":"-","chopping":"23-115","consensus_level":"medium","plddt":75.9111,"start":23,"end":115},{"cath_id":"2.10.25","chopping":"125-196","consensus_level":"medium","plddt":86.1476,"start":125,"end":196},{"cath_id":"-","chopping":"207-279","consensus_level":"medium","plddt":87.1229,"start":207,"end":279},{"cath_id":"2.10.25","chopping":"282-353","consensus_level":"medium","plddt":85.3726,"start":282,"end":353},{"cath_id":"2.10.25","chopping":"365-434","consensus_level":"medium","plddt":88.2061,"start":365,"end":434},{"cath_id":"-","chopping":"452-497","consensus_level":"high","plddt":81.9237,"start":452,"end":497},{"cath_id":"2.10.25","chopping":"525-575","consensus_level":"high","plddt":85.4796,"start":525,"end":575}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P28799","model_url":"https://alphafold.ebi.ac.uk/files/AF-P28799-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P28799-F1-predicted_aligned_error_v6.png","plddt_mean":77.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GRN","jax_strain_url":"https://www.jax.org/strain/search?query=GRN"},"sequence":{"accession":"P28799","fasta_url":"https://rest.uniprot.org/uniprotkb/P28799.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P28799/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P28799"}},"corpus_meta":[{"pmid":"21178100","id":"PMC_21178100","title":"TMEM106B regulates progranulin levels and the penetrance of FTLD in GRN mutation carriers.","date":"2010","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/21178100","citation_count":214,"is_preprint":false},{"pmid":"18771956","id":"PMC_18771956","title":"Mutations in progranulin (GRN) within the spectrum of clinical and pathological phenotypes of frontotemporal dementia.","date":"2008","source":"The Lancet. 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communications","url":"https://pubmed.ncbi.nlm.nih.gov/38744843","citation_count":18,"is_preprint":false},{"pmid":"34918030","id":"PMC_34918030","title":"Shared brain transcriptomic signature in TDP-43 type A FTLD patients with or without GRN mutations.","date":"2022","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/34918030","citation_count":17,"is_preprint":false},{"pmid":"29031143","id":"PMC_29031143","title":"C5a/C5aR pathway accelerates renal ischemia-reperfusion injury by downregulating PGRN expression.","date":"2017","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29031143","citation_count":16,"is_preprint":false},{"pmid":"31114443","id":"PMC_31114443","title":"The role of progranulin (PGRN) in the modulation of anti-inflammatory response in asthma.","date":"2019","source":"Central-European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/31114443","citation_count":16,"is_preprint":false},{"pmid":"33029756","id":"PMC_33029756","title":"GRN, NOTCH3, FN1, and PINK1 expression in eutopic endometrium - potential biomarkers in the detection of endometriosis - a pilot study.","date":"2020","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33029756","citation_count":16,"is_preprint":false},{"pmid":"27307215","id":"PMC_27307215","title":"Identification of biological pathways regulated by PGRN and GRN peptide treatments using transcriptome analysis.","date":"2016","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/27307215","citation_count":15,"is_preprint":false},{"pmid":"33299399","id":"PMC_33299399","title":"Repressor Element 1 Silencing Transcription Factor (REST) Governs Microglia-Like BV2 Cell Migration via Progranulin (PGRN).","date":"2020","source":"Neural plasticity","url":"https://pubmed.ncbi.nlm.nih.gov/33299399","citation_count":15,"is_preprint":false},{"pmid":"33969679","id":"PMC_33969679","title":"Elevated serum and urine levels of progranulin (PGRN) as a predictor of microglia activation in the early phase of traumatic brain injury: a further link with the development of neurodegenerative diseases.","date":"2021","source":"Folia neuropathologica","url":"https://pubmed.ncbi.nlm.nih.gov/33969679","citation_count":15,"is_preprint":false},{"pmid":"32961397","id":"PMC_32961397","title":"Isolated parkinsonism is an atypical presentation of GRN and C9orf72 gene mutations.","date":"2020","source":"Parkinsonism & related disorders","url":"https://pubmed.ncbi.nlm.nih.gov/32961397","citation_count":15,"is_preprint":false},{"pmid":"25580532","id":"PMC_25580532","title":"Profiling of ubiquitination pathway genes in peripheral cells from patients with frontotemporal dementia due to C9ORF72 and GRN mutations.","date":"2015","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/25580532","citation_count":15,"is_preprint":false},{"pmid":"31818769","id":"PMC_31818769","title":"Interaction between PGRN gene and the early trauma on clinical characteristics in patients with obsessive-compulsive disorder.","date":"2019","source":"Journal of affective disorders","url":"https://pubmed.ncbi.nlm.nih.gov/31818769","citation_count":14,"is_preprint":false},{"pmid":"38539243","id":"PMC_38539243","title":"A systematic review of progranulin concentrations in biofluids in over 7,000 people-assessing the pathogenicity of GRN mutations and other influencing factors.","date":"2024","source":"Alzheimer's research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/38539243","citation_count":14,"is_preprint":false},{"pmid":"31918955","id":"PMC_31918955","title":"Trajectory of lobar atrophy in asymptomatic and symptomatic GRN mutation carriers: a longitudinal MRI study.","date":"2019","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/31918955","citation_count":14,"is_preprint":false},{"pmid":"34054428","id":"PMC_34054428","title":"Parkin Levels Decrease in Fibroblasts With Progranulin (PGRN) Pathogenic Variants and in a Cellular Model of PGRN Deficiency.","date":"2021","source":"Frontiers in molecular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/34054428","citation_count":14,"is_preprint":false},{"pmid":"36574647","id":"PMC_36574647","title":"PGRN deficiency exacerbates, whereas a brain penetrant PGRN derivative protects, GBA1 mutation-associated pathologies and diseases.","date":"2022","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/36574647","citation_count":14,"is_preprint":false},{"pmid":"38935501","id":"PMC_38935501","title":"Hepatocyte-macrophage crosstalk via the PGRN-EGFR axis modulates ADAR1-mediated immunity in the liver.","date":"2024","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/38935501","citation_count":13,"is_preprint":false},{"pmid":"37561339","id":"PMC_37561339","title":"The Role of Progranulin (PGRN) in the Pathogenesis of Ischemic Stroke.","date":"2023","source":"Cellular and molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/37561339","citation_count":13,"is_preprint":false},{"pmid":"30026730","id":"PMC_30026730","title":"Thyrotropin Regulates eNOS Expression in the Endothelium by PGRN Through Akt Pathway.","date":"2018","source":"Frontiers in endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/30026730","citation_count":13,"is_preprint":false},{"pmid":"33896652","id":"PMC_33896652","title":"CSF sTREM2 is elevated in a subset in GRN-related frontotemporal dementia.","date":"2021","source":"Neurobiology of 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communications","url":"https://pubmed.ncbi.nlm.nih.gov/37118844","citation_count":13,"is_preprint":false},{"pmid":"33834216","id":"PMC_33834216","title":"Inference of dynamic spatial GRN models with multi-GPU evolutionary computation.","date":"2021","source":"Briefings in bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/33834216","citation_count":12,"is_preprint":false},{"pmid":"37003407","id":"PMC_37003407","title":"Plasma lysosphingolipids in GRN-related diseases: Monitoring lysosomal dysfunction to track disease progression.","date":"2023","source":"Neurobiology of disease","url":"https://pubmed.ncbi.nlm.nih.gov/37003407","citation_count":12,"is_preprint":false},{"pmid":"35790423","id":"PMC_35790423","title":"Differences in Motor Features of C9orf72, MAPT, or GRN Variant Carriers With Familial Frontotemporal Lobar Degeneration.","date":"2022","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/35790423","citation_count":12,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":55307,"output_tokens":5863,"usd":0.126933},"stage2":{"model":"claude-opus-4-6","input_tokens":9426,"output_tokens":4260,"usd":0.230445},"total_usd":0.357378,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"PCDGF/progranulin (GRN) mediates estrogen (E2) mitogenic signaling in MCF-7 breast cancer cells by stimulating MAPK activity and cyclin D1 expression; neutralizing antibody or antisense inhibition of PGRN blocked E2-induced DNA synthesis, and PGRN overexpression conferred estrogen-independent proliferation and tamoxifen resistance.\",\n      \"method\": \"Neutralizing antibody, antisense transfection, PGRN overexpression, MAPK activity assay, cyclin D1 Western blot in MCF-7 cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (antibody neutralization, antisense KD, OE) with defined signaling readouts in single rigorous study\",\n      \"pmids\": [\"11134521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Autocrine production of PCDGF/progranulin (GRN) is required for tumorigenicity of PC teratoma cells; inhibition of PGRN expression by antisense cDNA transfection dramatically reduced in vivo tumor formation in syngeneic mice, and PGRN expression level positively correlated with tumorigenic potential.\",\n      \"method\": \"Antisense cDNA transfection, in vivo tumor growth assay in syngeneic C3H mice, Northern/Western blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with defined in vivo phenotype plus expression correlation, single lab but orthogonal methods\",\n      \"pmids\": [\"9826678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"A missense mutation in the GRN signal peptide (p.A9D) prevents progranulin secretion, trapping the protein in an intracellular compartment, resulting in functional haploinsufficiency despite normal total GRN mRNA levels; a splice-site mutation (IVS6-2A>G) causes exon 7 skipping and reduces GRN mRNA and protein by ~50%.\",\n      \"method\": \"Subcellular fractionation, confocal microscopy, RT-PCR, Western blot in patient mutation carriers\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — orthogonal methods (fractionation + confocal + quantitative PCR/protein) establishing mechanistic consequence of specific mutations\",\n      \"pmids\": [\"18183624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Progranulin (PGRN) directly interacts with TNF receptors (TNFR2), and this interaction mediates PGRN's anti-inflammatory and protective functions; PGRN-deficient mice are highly susceptible to experimental colitis, whereas recombinant PGRN protects via IL-10 and TNFR2-dependent pathways.\",\n      \"method\": \"Co-immunoprecipitation (PGRN-TNFR2), genetic knockout mice (PGRN-/-, TNFR2-/-, IL-10-/-), DSS/TNBS colitis models, bone marrow chimeras, T cell transfer colitis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic models with specific pathway placement (TNFR2, IL-10 dependence) plus biochemical interaction\",\n      \"pmids\": [\"25387791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PGRN deficiency in a knock-in mouse (PGRN-KI, R504X) leads to activation of Gas6-Tyro3-PLCγ-PKCα signaling, causing tau phosphorylation at Ser203, tau mislocalization to dendritic spines, and spine loss preceding TDP43 aggregation; targeting Gas6/Tyro3 or PKC/MAPK signaling rescues spine loss and cognitive impairment.\",\n      \"method\": \"Phosphoproteomics, PKC inhibitor/B-Raf inhibitor treatment, knockdown of Gas6/Tyro3 axis in PGRN-KI mice, behavioral testing, spine analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — phosphoproteomics + pharmacological intervention + genetic KD with behavioral phenotype rescue, moderate replication within single study\",\n      \"pmids\": [\"29382817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PGRN is a lysosomal protein that interacts with bis(monoacylglycero)phosphate (BMP) in a pH-dependent manner; PGRN loss in mice causes global BMP deficiency and secondary glucosylsphingosine storage, implicating PGRN in lysosomal phospholipid homeostasis and proteolysis/lipolysis.\",\n      \"method\": \"BMP mass spectrometry, pH-dependent binding assay, Grn-/- mouse biochemistry, primary macrophage and iPSC-derived microglia functional assays, PTV:PGRN replacement rescue\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — biochemical interaction identified, multiple model systems (mouse, primary cells, iPSC), rescue experiment with defined mechanistic readouts\",\n      \"pmids\": [\"34450028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PGRN-deficient human cells and Grn-/- mouse brains accumulate gangliosides (including GM1, GM2, GM3); granulins are required to maintain bis(monoacylglycero)phosphate (BMP) levels needed for lysosomal ganglioside catabolism, indicating that PGRN loss causes gangliosidosis without reducing ganglioside-catabolizing enzyme levels.\",\n      \"method\": \"Lipidomics of PGRN-deficient cells and mouse brains, lysosomal enzyme activity assays, BMP quantification, human FTD-GRN frontal lobe analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — enzyme activity assays plus quantitative lipidomics in multiple models (cell, mouse, human tissue), strong mechanistic conclusion\",\n      \"pmids\": [\"36207292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Grn knockout mice accumulate myelin debris in microglial lysosomes in white matter; PGRN insufficiency in microglia impairs lysosomal-mediated clearance of myelin debris, and double-KO of Grn and cathepsin D (Ctsd) augments myelin debris accumulation and neuronal TDP-43 pathology, placing PGRN upstream of cathepsin D in microglial lysosomal clearance.\",\n      \"method\": \"Grn KO mice, Ctsd/Grn double-KO epistasis, immunofluorescence for myelin debris and TDP-43, microgliosis quantification\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (double KO) with defined cellular and molecular phenotypes, pathway placement established\",\n      \"pmids\": [\"34433069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Progranulin-deficient astrocytes (from Grn-/- mice and FTLD-GRN patients) upregulate GJA1, AQP4, and APOE and downregulate glutamate transporter SLC1A2; these progranulin-deficient astrocytes promote synaptic degeneration, neuronal stress, and TDP-43 proteinopathy in neuron co-cultures and cortical organoids with iPSC-derived astrocytes.\",\n      \"method\": \"Single-cell RNA-seq, astrocyte-neuron co-cultures, iPSC-derived astrocyte transplantation into cortical organoids, comparative mouse/human transcriptomics\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — single-cell transcriptomics plus functional reconstitution in co-culture and organoid systems with mechanistic pathway identification\",\n      \"pmids\": [\"36602862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Progranulin (PGRN) directly interacts with NF-κB essential modulator (NEMO) via its Grn CDE domains during influenza virus infection, recruiting A20 to deubiquitinate K63-linked polyubiquitin chains on NEMO at K264, thereby suppressing NF-κB and IRF3 signaling and inhibiting type I interferon production.\",\n      \"method\": \"Co-immunoprecipitation (PGRN-NEMO interaction), domain mapping (Grn CDE domains), deubiquitination assay (A20 recruitment, K63-Ub chains on NEMO K264), PGRN KD and Grn-/- mice, in vivo challenge with influenza\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — biochemical interaction, domain mapping, deubiquitination site identified, confirmed in KD and KO mouse models\",\n      \"pmids\": [\"31585000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PGRN haploinsufficiency in lymphoblasts from FTLD-TDP (c.709-1G>A) mutation carriers activates noncanonical Wnt5a signaling; PGRN-deficient cells show increased cellular and secreted Wnt5a, enhanced phospho-CaMKII, and ERK1/2 activation via Ca2+/PKC-dependent, pertussis toxin-sensitive mechanism; exogenous PGRN or control conditioned medium normalized these responses.\",\n      \"method\": \"ERK1/2 and CaMKII phosphorylation assays, Wnt5a ELISA, pertussis toxin treatment, exogenous PGRN rescue, PGRN knockdown in SH-SY5Y cells\",\n      \"journal\": \"Neurobiology of aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple signaling assays in patient-derived cells with rescue, single lab\",\n      \"pmids\": [\"24139281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PGRN deficit in lymphoblasts from PGRN mutation (c.709-1G>A) carriers increases CDK6 levels and retinoblastoma protein phosphorylation, causing G1/S regulatory failure; this is associated with altered subcellular TDP-43 distribution and loss of TDP-43-mediated repression of CDK6 expression.\",\n      \"method\": \"CDK6 and phospho-Rb Western blot, cell cycle analysis (flow cytometry), TDP-43 localization (immunofluorescence), patient-derived lymphoblasts\",\n      \"journal\": \"Neurobiology of aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — mechanistic signaling pathway identified in patient-derived cells, single lab\",\n      \"pmids\": [\"21232819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PGRN promotes macrophage M2 polarization through direct binding to TNFR2; co-immunoprecipitation confirmed PGRN-TNFR2 physical interaction, and TNFR2-blocking neutralizing antibody abrogated PGRN-mediated increases in M2 markers (CD206, IL-10, Arg-1) in RAW264.7 macrophages and bone marrow-derived macrophages.\",\n      \"method\": \"Co-immunoprecipitation (PGRN-TNFR2), TNFR2 neutralizing antibody, flow cytometry for M1/M2 markers, ELISA for cytokines, multiplex IHC\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — biochemical interaction confirmed plus functional rescue with neutralizing antibody, single lab\",\n      \"pmids\": [\"38689292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PGRN induces hepatic insulin resistance via TNFR1, activating NF-κB-dependent pathways; TNFR1 blocking peptide-Fc fusion protein or TNFR1 siRNA reversed PGRN-induced defective autophagy and impaired insulin signaling in hepatocytes in vivo and in vitro.\",\n      \"method\": \"In vivo mouse PGRN treatment, TNFR1 blocking peptide-Fc, TNFR1 siRNA, glucose/insulin tolerance tests, insulin signaling Western blots\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological blockade of TNFR1 with rescue of defined phenotypes, single lab\",\n      \"pmids\": [\"25664864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss of both TMEM106B and PGRN in mice results in severe neuronal loss, glial activation, and enlarged lysosomes in microglia and astrocytes, with greatly enhanced accumulation of lysosomal vacuoles in the axon initial segment of motor neurons; TMEM106B deficiency alone causes lysosomal vacuole accumulation at the axon initial segment, identifying TMEM106B as a lysosomal membrane protein that genetically interacts with PGRN in neurodegeneration.\",\n      \"method\": \"Grn-/-/Tmem106b-/- double-KO mice, histopathology, electron microscopy, immunofluorescence for lysosomal markers and neuronal markers\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with double-KO model, multiple orthogonal histopathological readouts\",\n      \"pmids\": [\"32852886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Loss of Grn in mice shifts microglia from a homeostatic state to the microglial neurodegenerative phenotype (MGnD), with suppression of homeostatic genes, reciprocally opposite to the effect of Trem2 loss; both Grn-/- and Trem2-/- result in reduced brain glucose metabolism despite opposite microglial activation states.\",\n      \"method\": \"Isolated microglia transcriptomics from Grn-/- and Trem2-/- mice, FDG-µPET brain imaging\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — comparative transcriptomics with functional imaging, establishes pathway position; single study\",\n      \"pmids\": [\"31122931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GRN promoter methylation is increased in sporadic FTLD patients relative to controls, with a negative correlation between GRN promoter methylation and GRN mRNA levels in peripheral blood mononuclear cells, identifying promoter methylation as a mechanism that can reduce GRN expression.\",\n      \"method\": \"Bisulfite pyrosequencing of GRN promoter, RT-PCR for GRN mRNA, correlation analysis in patient cohort\",\n      \"journal\": \"Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — methylation quantification with mRNA correlation, single cohort study\",\n      \"pmids\": [\"22797721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Transcription factor REST (repressor element 1 silencing transcription factor) directly binds the PGRN promoter and represses PGRN expression; REST knockdown increases PGRN levels and promotes BV2 microglia-like cell migration, while REST overexpression suppresses migration, placing REST as an inhibitory transcriptional regulator of PGRN.\",\n      \"method\": \"Dual luciferase reporter assay (REST binding to PGRN promoter), siRNA KD and REST overexpression in BV2 cells, transwell migration assay, PGRN siRNA\",\n      \"journal\": \"Neural plasticity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — luciferase reporter confirms direct promoter binding plus functional KD/OE with migration phenotype, single lab\",\n      \"pmids\": [\"33299399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Antisense oligonucleotides (ASOs) targeting the miR-29b binding site in the 3' UTR of GRN mRNA increase progranulin protein translation in a dose-dependent manner in neuroglioma cells, iPSC-derived neurons, and a humanized GRN mouse model; mechanism was confirmed by FRET competition assays showing ASO displacement of miR-29b from GRN 3'UTR and polysome profiling demonstrating increased translation.\",\n      \"method\": \"FRET-based miRNA binding competition assay, polysome profiling, Western blot for progranulin protein, iPSC-derived neurons, humanized GRN mouse model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mechanistic assays (FRET, polysome profiling) plus multiple cell models and in vivo validation in single study\",\n      \"pmids\": [\"37981208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Progranulin (PGRN) mediates liver pathology caused by ADAR1 deficiency by promoting interferon signaling and recruiting EGFR+ macrophages into the liver; the PGRN-EGFR axis drives hepatic inflammation in ADAR1-deficient hepatocytes, and this signaling is repressed in ADAR1-high tumors to facilitate immune evasion.\",\n      \"method\": \"Liver-specific Adar KO and Ifih1;Adar double-KO mouse models, PGRN expression analysis in hepatocytes, macrophage recruitment assays, EGFR co-localization\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — genetic mouse models with defined mechanistic interaction (PGRN-EGFR), single lab\",\n      \"pmids\": [\"38935501\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PGRN deficiency reduces parkin protein levels in fibroblasts from FTLD patients with four different PGRN mutations, and parkin knockdown is also observed upon PGRN silencing in control fibroblasts; this is accompanied by decreases in parkin targets MFN2 and VDAC1. TDP-43 overexpression rescues PRKN levels during transient PGRN silencing but not in stable PGRN-mutant fibroblasts, and TDP-43 silencing reduces PRKN, suggesting TDP-43 loss-of-function contributes to parkin downregulation downstream of PGRN deficiency.\",\n      \"method\": \"Western blot for parkin/MFN2/VDAC1 in patient fibroblasts, PGRN siRNA in control fibroblasts, TDP-43 overexpression/knockdown rescue experiments\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — multiple orthogonal genetic manipulations (patient cells, siRNA, rescue) establishing pathway order, single lab\",\n      \"pmids\": [\"34054428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PGRN deficiency exacerbates GBA1 mutation-associated disease in Grn-/-/Gba9v/9v mice, including neurobehavioral deficits, neuroinflammation (microgliosis, astrogliosis), and impaired autophagy; a BBB-penetrant PGRN-derived peptide (ND7) ameliorated neuronopathic Gaucher disease and PD-like pathology in vivo, identifying PGRN as a modifier of GCase/GBA1 pathway.\",\n      \"method\": \"Double-mutant mouse model (Grn-/-/Gba9v/9v), ND7 peptide BBB penetration and treatment, neuropathology, behavioral assays, patient fibroblast ex vivo rescue\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (double KO) plus pharmacological rescue with BBB-penetrant biologic, multiple model systems\",\n      \"pmids\": [\"36574647\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Progranulin (GRN/PGRN) is a secreted and lysosomal glycoprotein that functions as a growth factor stimulating MAPK and cyclin D1 signaling downstream of TNFR2, maintains lysosomal homeostasis by supporting bis(monoacylglycero)phosphate (BMP) levels required for sphingolipid/ganglioside catabolism, regulates microglial activation state, and suppresses innate immune signaling by binding NEMO via its granulin CDE domains to recruit A20 and deubiquitinate NEMO; haploinsufficiency causes lysosomal dysfunction, impaired myelin clearance by microglia, astroglial toxicity with synaptic degeneration, and TDP-43 proteinopathy characteristic of frontotemporal dementia.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"Progranulin (GRN) is a secreted glycoprotein that functions as a growth factor, lysosomal regulator, and immunomodulator, with central roles in lysosomal lipid homeostasis, microglial activation, and inflammatory signaling. In the lysosome, progranulin maintains bis(monoacylglycero)phosphate (BMP) levels required for ganglioside and sphingolipid catabolism, and its loss causes ganglioside accumulation and impaired myelin debris clearance by microglia upstream of cathepsin D [PMID:34450028, PMID:36207292, PMID:34433069]. Progranulin binds TNFR2 to promote anti-inflammatory macrophage polarization and IL-10-dependent tissue protection, and suppresses NF-κB/IRF3 innate immune signaling by recruiting A20 to deubiquitinate K63-linked polyubiquitin on NEMO via its granulin CDE domains [PMID:25387791, PMID:31585000, PMID:38689292]. Heterozygous loss-of-function mutations in GRN cause frontotemporal lobar degeneration with TDP-43 proteinopathy (FTLD-TDP), driven by lysosomal dysfunction, aberrant astrocyte-mediated synaptic degeneration, and dysregulated tau phosphorylation through Gas6-Tyro3-PKCα signaling [PMID:18183624, PMID:36602862, PMID:29382817].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"The initial functional identity of progranulin as an autocrine growth factor was established when antisense suppression of PGRN expression abolished tumorigenicity of teratoma cells in vivo, demonstrating that secreted PGRN is required for tumor growth.\",\n      \"evidence\": \"Antisense cDNA transfection with in vivo tumor growth assay in syngeneic C3H mice\",\n      \"pmids\": [\"9826678\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating autocrine signaling not identified\", \"No defined downstream signaling pathway\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"The mitogenic signaling mechanism was defined when PGRN was shown to activate MAPK and cyclin D1 downstream of estrogen stimulation, establishing PGRN as a mediator of proliferative signaling in breast cancer cells.\",\n      \"evidence\": \"Neutralizing antibody, antisense KD, PGRN overexpression, MAPK/cyclin D1 assays in MCF-7 cells\",\n      \"pmids\": [\"11134521\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct receptor for PGRN in this context not identified\", \"Relevance to non-cancer proliferative settings untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The molecular basis of GRN haploinsufficiency in FTLD was clarified when a signal-peptide missense mutation (A9D) was shown to trap progranulin intracellularly, preventing secretion and producing functional haploinsufficiency despite normal mRNA levels—establishing that both null and secretion-defective alleles cause disease.\",\n      \"evidence\": \"Subcellular fractionation, confocal microscopy, RT-PCR, and Western blot in cells from mutation carriers\",\n      \"pmids\": [\"18183624\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether intracellularly retained PGRN retains any lysosomal function not addressed\", \"Scope of secretion-defective mutations in broader FTLD cohorts not surveyed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"A link between PGRN deficiency and cell-cycle dysregulation was revealed when patient-derived lymphoblasts showed increased CDK6 and Rb phosphorylation tied to altered TDP-43 localization, suggesting that PGRN loss disrupts TDP-43-mediated transcriptional repression of CDK6.\",\n      \"evidence\": \"Western blot, flow cytometry cell-cycle analysis, TDP-43 immunofluorescence in patient lymphoblasts\",\n      \"pmids\": [\"21232819\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct regulation of CDK6 by TDP-43 not confirmed by ChIP or reporter assay\", \"Relevance to neuronal pathology unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"The receptor mediating PGRN's anti-inflammatory signaling was identified as TNFR2, with co-IP confirming physical interaction and TNFR2 neutralizing antibody blocking PGRN-driven M2 macrophage polarization, and genetic models showing TNFR2/IL-10 dependence for colitis protection.\",\n      \"evidence\": \"Co-IP of PGRN-TNFR2, TNFR2 neutralizing antibody in macrophages, Grn-/- and TNFR2-/- colitis models\",\n      \"pmids\": [\"25387791\", \"38689292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PGRN-TNFR2 interaction not resolved\", \"Whether PGRN competes with TNFα for TNFR2 binding in vivo not quantified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"PGRN was shown to also signal through TNFR1 in a metabolic context, inducing hepatic insulin resistance via NF-κB-dependent pathways and impaired autophagy, expanding the receptor repertoire beyond TNFR2.\",\n      \"evidence\": \"TNFR1 blocking peptide-Fc and siRNA in mouse hepatocytes, glucose/insulin tolerance tests\",\n      \"pmids\": [\"25664864\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TNFR1 vs TNFR2 engagement is context- or dose-dependent not resolved\", \"Relevance to neurodegeneration unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The mechanism linking PGRN loss to synaptic degeneration was elucidated: PGRN deficiency activates Gas6-Tyro3-PLCγ-PKCα signaling, causing tau hyperphosphorylation at Ser203, tau mislocalization to dendritic spines, and spine loss prior to TDP-43 aggregation—and pharmacological blockade of this axis rescued cognitive deficits.\",\n      \"evidence\": \"Phosphoproteomics, PKC/B-Raf inhibitors, Gas6/Tyro3 knockdown in PGRN-KI (R504X) mice, behavioral testing\",\n      \"pmids\": [\"29382817\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether tau phosphorylation is a primary driver or bystander in human FTLD-GRN not established\", \"Relationship between Gas6-Tyro3 axis and lysosomal dysfunction not explored\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"A direct mechanism for PGRN's suppression of innate immune signaling was mapped: the granulin CDE domains bind NEMO and recruit deubiquitinase A20 to remove K63-linked polyubiquitin at NEMO K264, suppressing NF-κB and IRF3 activation and type I interferon production during influenza infection.\",\n      \"evidence\": \"Co-IP, domain mapping, deubiquitination assay, Grn-/- mice challenged with influenza virus\",\n      \"pmids\": [\"31585000\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NEMO deubiquitination occurs in CNS microglia or only in peripheral immunity not tested\", \"Stoichiometry and regulation of PGRN-A20-NEMO complex not determined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Microglial transcriptomic profiling placed PGRN loss as a driver of the neurodegenerative microglial (MGnD) activation state—reciprocal to TREM2 loss—linking PGRN to microglial phenotype switching and brain glucose hypometabolism.\",\n      \"evidence\": \"Isolated microglia transcriptomics from Grn-/- and Trem2-/- mice, FDG-µPET imaging\",\n      \"pmids\": [\"31122931\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal relationship between microglial activation state and neurodegeneration not directly tested\", \"Molecular link between PGRN and TREM2 signaling not established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Genetic epistasis between PGRN and the lysosomal membrane protein TMEM106B was demonstrated in vivo: double knockout of Grn and Tmem106b caused severe neuronal loss and lysosomal vacuole accumulation exceeding either single KO, establishing TMEM106B as a genetic modifier in PGRN-dependent neurodegeneration.\",\n      \"evidence\": \"Grn-/-/Tmem106b-/- double-KO mice, histopathology, electron microscopy\",\n      \"pmids\": [\"32852886\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical mechanism of PGRN-TMEM106B functional interaction not identified\", \"Whether TMEM106B variants modify human GRN disease progression not addressed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"The core lysosomal function of progranulin was defined biochemically: PGRN binds bis(monoacylglycero)phosphate (BMP) in a pH-dependent manner, and its loss causes global BMP deficiency with secondary glucosylsphingosine storage, directly linking progranulin to lysosomal lipid homeostasis.\",\n      \"evidence\": \"BMP mass spectrometry, pH-dependent binding assay, Grn-/- mice, iPSC-derived microglia, PGRN replacement rescue\",\n      \"pmids\": [\"34450028\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PGRN stabilizes BMP production or prevents its degradation not resolved\", \"Structural basis of PGRN-BMP interaction unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"PGRN was positioned upstream of cathepsin D in microglial lysosomal clearance when Grn-/- mice showed myelin debris accumulation in microglial lysosomes, exacerbated by Ctsd co-deletion and accompanied by TDP-43 pathology.\",\n      \"evidence\": \"Grn-/-, Ctsd/Grn double-KO epistasis, immunofluorescence for myelin debris and TDP-43\",\n      \"pmids\": [\"34433069\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PGRN directly activates cathepsin D or acts indirectly via BMP not distinguished\", \"Applicability to human white-matter pathology not confirmed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Lysosomal ganglioside accumulation was identified as a hallmark of PGRN deficiency: lipidomics revealed GM1/GM2/GM3 ganglioside storage without reduction in catabolic enzyme levels, establishing that PGRN-dependent BMP maintenance is the rate-limiting factor for ganglioside catabolism.\",\n      \"evidence\": \"Lipidomics in PGRN-deficient cells, Grn-/- mouse brains, and human FTD-GRN frontal lobe tissue\",\n      \"pmids\": [\"36207292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ganglioside accumulation is directly neurotoxic or a marker of broader lysosomal failure not tested\", \"Therapeutic reversal of gangliosidosis by PGRN replacement not demonstrated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"PGRN was established as a genetic modifier of GBA1/glucocerebrosidase pathway disease: Grn-/-/Gba9v/9v double-mutant mice showed exacerbated neuronopathic Gaucher pathology, and a BBB-penetrant PGRN-derived peptide rescued neurobehavioral and neuropathological deficits.\",\n      \"evidence\": \"Double-mutant mouse model, ND7 peptide treatment, behavioral/neuropathological assays, patient fibroblast rescue\",\n      \"pmids\": [\"36574647\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PGRN/granulins modulate GCase activity not defined\", \"Whether PGRN replacement benefits human Gaucher or PD patients unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Progranulin-deficient astrocytes were shown to be active drivers of neurodegeneration: they upregulate APOE and GJA1 while losing the glutamate transporter SLC1A2, promoting synaptic degeneration and TDP-43 proteinopathy in neuron co-cultures and cortical organoids.\",\n      \"evidence\": \"Single-cell RNA-seq, iPSC-derived astrocyte transplantation into cortical organoids, mouse/human comparative transcriptomics\",\n      \"pmids\": [\"36602862\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether astrocyte toxicity is cell-autonomous or secondary to impaired lysosomal lipid handling not resolved\", \"Relative contribution of astrocyte vs microglial dysfunction to human FTLD-GRN pathology not quantified\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A post-transcriptional mechanism for boosting PGRN levels was validated: ASOs displacing miR-29b from the GRN 3′ UTR increased progranulin translation dose-dependently in iPSC neurons and humanized mice, confirmed by FRET competition and polysome profiling.\",\n      \"evidence\": \"FRET-based miRNA binding competition assay, polysome profiling, iPSC-derived neurons, humanized GRN mouse model\",\n      \"pmids\": [\"37981208\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Long-term safety and efficacy of miR-29b-blocking ASOs in vivo not established\", \"Whether this approach achieves therapeutically relevant PGRN increases in human brain not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of progranulin-BMP interaction, whether PGRN directly activates cathepsin D or acts via BMP, how lysosomal and signaling functions are coordinately regulated, and whether PGRN replacement can reverse established neurodegeneration in humans.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure of progranulin bound to BMP or TNFR2\", \"Relative pathogenic contributions of lysosomal, microglial, and astrocytic dysfunction to FTLD-GRN not dissected in humans\", \"Whether processed granulins versus full-length PGRN have distinct lysosomal vs signaling roles not resolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 1, 3, 12]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [9, 13]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [5, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [5, 6, 7, 14]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1, 2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 9, 12, 15]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 4, 13]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 6, 21]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 4, 8, 14]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TNFRSF1B\",\n      \"NEMO\",\n      \"TNFAIP3\",\n      \"CTSD\",\n      \"TMEM106B\",\n      \"TARDBP\",\n      \"GAS6\",\n      \"TYRO3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}