{"gene":"SPARCL1","run_date":"2026-06-10T07:46:39","timeline":{"discoveries":[{"year":1998,"finding":"MAST9/SPARCL1 protein forms homodimers, as demonstrated using bacterially expressed and endogenous protein.","method":"Western blot analysis of bacterially expressed and endogenous protein","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, single method (Western blot), no mutagenesis or reconstitution","pmids":["9485012"],"is_preprint":false},{"year":2008,"finding":"SPARCL1 (SC1) is expressed in radial glia and astrocyte derivatives in the CNS, influencing astroglial cell fate and function, as established by BAC transgenic mice with elevated Sc1 transcript and protein in an astroglial-selective pattern.","method":"BAC transgenic mouse model with BLBP regulatory elements; immunohistochemistry and transcript analysis","journal":"Glia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo transgenic model with selective overexpression and characterization, single lab","pmids":["18381651"],"is_preprint":false},{"year":2015,"finding":"SPARCL1 suppresses metastatic progression of prostate cancer by tethering to collagen in the ECM and binding to the cell cytoskeleton, directly inhibiting focal adhesion assembly and thereby constraining cell traction forces; androgen receptor (AR) activation directly suppresses SPARCL1 expression via epigenetic mechanism at the SPARCL1 locus, reversible by AR antagonists or HDAC inhibitors.","method":"In vitro focal adhesion assays; orthotopic allograft mouse model (Myc-CaP); Hi-Myc/Sparcl1-/- genetic model; ChIP for AR binding; pharmacological AR and HDAC inhibition","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods: genetic KO model, in vivo orthotopic allograft, ChIP, pharmacological intervention, focal adhesion functional assay","pmids":["26294211"],"is_preprint":false},{"year":2016,"finding":"SPARCL1 promotes endothelial cell quiescence by inhibiting proliferation, migration, and sprouting; siRNA-mediated knockdown increases sprouting. Secreted SPARCL1 from quiescent ECs inhibits mural cell migration, leading to stabilized mural cell coverage of mature vessels.","method":"In vitro EC quiescence assays; siRNA knockdown; mouse models of CRC; human CRC tissue analysis","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods: siRNA KD functional assays, mouse models, human tissue validation, secretion/paracrine experiments","pmids":["27721236"],"is_preprint":false},{"year":2017,"finding":"SPARCL1 activates WNT/β-catenin signaling by physically interacting with multiple frizzled receptors and LRP5/6, stabilizing the WNT-receptor complex; this mechanism underlies SPARCL1-mediated inhibition of osteosarcoma metastasis. Additionally, SPARCL1-activated WNT/β-catenin signaling drives paracrine secretion of CCL5, recruiting macrophages.","method":"Co-immunoprecipitation; in vitro and in vivo metastasis assays; WNT/β-catenin reporter assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP for physical interaction, functional in vitro and in vivo assays, single lab","pmids":["29084211"],"is_preprint":false},{"year":2019,"finding":"SPARCL1 binds to BMP7 (confirmed by immunoprecipitation) and regulates BMP/TGF-β signaling, promoting C2C12 muscle cell differentiation; CRISPR/Cas9 knockout of SPARCL1 confirmed its requirement for BMP/TGF-β pathway activation.","method":"Immunoprecipitation; Western blotting; immunofluorescence; CRISPR/Cas9 knockout","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for physical interaction with BMP7, CRISPR KO functional validation, single lab","pmids":["31699966"],"is_preprint":false},{"year":2019,"finding":"SPARCL1 overexpression inhibits trophoblast cell migration and invasion by suppressing ERK phosphorylation, decreasing AP-1 (Fos/Jun) expression, and altering EMT-related molecule expression (MMP2, MMP3, N-cadherin, E-cadherin, vimentin).","method":"Overexpression transfection in HTR8/SVneo and JAR cells; scratch-wound assay; Western blot for ERK phosphorylation and EMT markers; qPCR","journal":"Placenta","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — overexpression with multiple functional readouts but no KO or reconstitution; single lab with multiple assay types","pmids":["31675488"],"is_preprint":false},{"year":2020,"finding":"SPARCL1 selectively promotes excitatory (not inhibitory) synaptogenesis and enhances excitatory synaptic transmission, augmenting NMDAR-mediated responses more than AMPAR-mediated responses; these effects are independent of neurexins and neuroligins, demonstrated using triple neurexin-1/2/3 and quadruple neuroligin-1/2/3/4 conditional KO neurons.","method":"Mixed neuronal/glial cultures; electrophysiology (patch clamp); conditional KO of all neurexins or all neuroligins; synapse counting assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — rigorous genetic manipulations (conditional KO of all neurexins or neuroligins), electrophysiology, multiple orthogonal methods in one study","pmids":["32973045"],"is_preprint":false},{"year":2020,"finding":"SPARCL1 interacts physically with integrin β1 (ITGB1), and this interaction mediates SPARCL1's promotion of bovine satellite cell migration and early differentiation; SPARCL1 regulates downstream signaling molecules p-FAK, p-paxillin, vinculin, Cdc42, and Arp2/3 through ITGB1.","method":"Immunoprecipitation and mass spectrometry; co-immunoprecipitation; cell scratch assay; desmin staining; Western blotting","journal":"Animals","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus mass spectrometry identification, multiple functional readouts, single lab","pmids":["32781616"],"is_preprint":false},{"year":2021,"finding":"SPARCL1 promotes NASH progression by binding to TLR4 on hepatocytes, activating the NF-κB/p65 signaling pathway to upregulate CCL2 expression; blocking the CCL2/CCR2 pathway attenuated the hepatic inflammatory response evoked by SPARCL1. Genetic ablation, WAT-specific knockdown, and neutralizing antibody all alleviated diet-induced NASH.","method":"Recombinant protein injection; Sparcl1 KO mice; siRNA knockdown in WAT; neutralizing antibody treatment; binding assay for TLR4; NF-κB reporter; CCL2/CCR2 pharmacological blocking","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods: KO mice, WAT-specific KD, neutralizing antibody, recombinant protein gain-of-function, receptor binding assay, pathway reporter, replicated across approaches","pmids":["34651580"],"is_preprint":false},{"year":2021,"finding":"SPARCL1 inhibits angiogenesis and supports vessel morphogenesis and integrity; the acidic domain of SPARCL1 is necessary for its anti-angiogenic activity. SPARCL1-mediated vessel stabilization counteracts vascular permeability and inflammation in DSS colitis models.","method":"Metatarsal ex vivo angiogenesis assay; SPARCL1 knockout mice in acute and chronic DSS colitis models; structure-function analysis of purified SPARCL1 protein domains","journal":"Inflammatory bowel diseases","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO model with disease readout, ex vivo functional assay, domain-level structure-function with purified protein; multiple orthogonal methods","pmids":["33393634"],"is_preprint":false},{"year":2021,"finding":"SPARCL1 inhibits preadipocyte differentiation by activating the Wnt/β-catenin pathway (increasing Wnt10b, Fzd8, β-catenin, IL6) and inhibiting PPARγ, C/EBPα, LPL, IGF1; conversely, SPARCL1 deficiency promotes differentiation by inhibiting β-catenin and increasing GSK3β.","method":"siRNA knockdown and overexpression in sheep preadipocytes; Western blot; qPCR; oil red O staining for lipid droplets; triglyceride content measurement","journal":"Adipocyte","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — gain- and loss-of-function with multiple molecular readouts, single lab, no reconstitution","pmids":["34872433"],"is_preprint":false},{"year":2022,"finding":"An ASD-associated single amino acid substitution (Trp647Arg) in the EF-hand motif of SPARCL1 causes protein misfolding, ER retention, and activation of unfolded protein response; molecular dynamics simulation showed that this substitution exposes a hydrophobic residue, increasing binding to the chaperone BiP. Loss of EF-hand integrity impairs SPARCL1 secretion.","method":"Mutagenesis; immunofluorescence for ER localization; unfolded protein response assays; molecular dynamics simulation; co-immunoprecipitation with BiP","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — mutagenesis combined with MD simulation and UPR assay, Co-IP for chaperone binding; single lab","pmids":["35831437"],"is_preprint":false},{"year":2022,"finding":"Astrocyte-secreted SPARCL1 (hevin) is crucial for maintaining chronic pain through spinal cord NMDA receptor signaling; intrathecal SPARCL1 induces persistent mechanical allodynia, and re-expression of SPARCL1 in GFAP+ spinal cord astrocytes via AAV reinstates neuropathic pain. SPARCL1 potentiates NMDA currents via GluN2B-containing NMDARs. A neutralizing antibody against SPARCL1 alleviates acute and persistent pain.","method":"Intrathecal injection of recombinant protein; SPARCL1 KO mice; AAV-mediated re-expression in astrocytes; electrophysiology (NMDA currents); neutralizing antibody treatment; CSF measurement","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods: KO mice, AAV rescue, intrathecal recombinant protein, electrophysiology, neutralizing antibody; replicated across pain models","pmids":["36256481"],"is_preprint":false},{"year":2022,"finding":"KDM6A (a histone demethylase) promotes SPARCL1 transcription by demethylating histone H3K27me3 at the SPARCL1 locus; SPARCL1 in turn inhibits p65 nuclear translocation/phosphorylation, suppressing GIST metastasis in a MET- and MMP-dependent manner.","method":"ChIP for H3K27me3; Western blot; xenograft and hepatic metastasis models; SPARCL1 knockdown/overexpression","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP establishes epigenetic writer-target relationship, functional in vivo models, single lab","pmids":["35136209"],"is_preprint":false},{"year":2024,"finding":"SPARCL1 secreted from pulmonary capillary endothelial cells drives pro-inflammatory 'M1-like' macrophage polarization during viral pneumonia by signaling through TLR4 on macrophages; TLR4 inhibition in vivo ameliorates excessive inflammation caused by endothelial SPARCL1 overexpression.","method":"Endothelial-specific SPARCL1 overexpression and deletion mouse models; in vitro macrophage polarization assays; TLR4 inhibition in vivo; COVID-19 patient lung EC RNA-seq and plasma protein measurement","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific KO and overexpression, in vitro mechanistic assay with TLR4, in vivo TLR4 inhibition rescue, human patient validation","pmids":["38762489"],"is_preprint":false},{"year":2024,"finding":"SPARCL1 functions as a functional ligand for the adhesion GPCR ADGRL1 (Latrophilin-1): hevin/SPARCL1 interacts with membrane-expressed ADGRL1, induces its internalization, stabilizes its uncleaved fraction, alters ADGRL1/Neurexin-1-mediated intercellular adhesion contacts, and biases ADGRL1 coupling toward Gi3, Gs, and G13 signaling pathways.","method":"Co-immunoprecipitation; cell internalization assays; G protein coupling assays; intercellular adhesion contact assays; mouse NAc Adgrl1 KD behavioral experiments","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple binding and functional assays in a preprint; single lab, not yet peer-reviewed","pmids":["bio_10.1101_2024.07.03.601736"],"is_preprint":true},{"year":2024,"finding":"SPARCL1 promotes chondrocyte extracellular matrix degradation and inflammation in osteoarthritis by activating the TNF/NF-κB pathway; recombinant SPARCL1 protein intra-articular injection promotes OA pathogenesis in ACLT mice, and NF-κB inhibitor BAY 11-7082 reverses SPARCL1-induced inflammatory and catabolic gene expression.","method":"Recombinant SPARCL1 protein in vitro treatment; intra-articular injection in ACLT mouse model; RNA-seq; Western blot; NF-κB inhibitor rescue experiment","journal":"Journal of orthopaedic translation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro gain-of-function with recombinant protein, pathway inhibitor rescue, single lab","pmids":["38867741"],"is_preprint":false},{"year":2024,"finding":"An autosomal dominant corneal stromal dystrophy is associated with a SPARCL1 missense variant (p.Glu112Lys); immunohistochemistry showed decorin is significantly decreased in affected corneal stroma and SPARCL1 is retained in the epithelium, suggesting SPARCL1 regulates decorin in the corneal ECM.","method":"Whole genome sequencing; immunohistochemistry for SPARCL1 and decorin in patient vs. control corneal tissue","journal":"European journal of human genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — immunohistochemistry in patient tissue, no in vitro or in vivo functional reconstitution of the mechanism","pmids":["39169229"],"is_preprint":false},{"year":2025,"finding":"SPARCL1 secreted by lung microvasculature promotes alveolar type 2 (AT2) cell differentiation by activating NF-κB signaling; SPARCL1-treated organoids show lysozyme upregulation, doubling of AT2 cells, and upregulation of NF-κB target genes. Suppression of NF-κB blocked SPARCL1 effects on AT2 differentiation.","method":"Recombinant SPARCL1 protein treatment of alveolar organoids; NF-κB inhibition rescue; RNA-seq; immunofluorescence","journal":"Stem cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — recombinant protein gain-of-function in organoid model, NF-κB inhibitor epistasis, RNA-seq; single lab","pmids":["40118055"],"is_preprint":false},{"year":2025,"finding":"SPARCL1 binding to BST2 activates the NF-κB/P65 pathway, driving meniscal inflammation and catabolic metabolism; co-localization, molecular docking, and Co-IP confirmed the SPARCL1-BST2 physical interaction; SPARCL1 knockdown in vivo reduced inflammation and delayed meniscus degeneration.","method":"Co-immunoprecipitation; molecular docking; fluorescence co-localization; transcriptome sequencing; in vivo lentiviral knockdown in ACLT mouse model; Western blot; immunofluorescence","journal":"Rheumatology (Oxford, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, molecular docking, in vivo KD with functional readout; single lab","pmids":["40638212"],"is_preprint":false},{"year":2025,"finding":"Vascular resident macrophage (VRM)-derived SPARCL1 inhibits FGF2-mediated dysfunctional lymphangiogenesis in abdominal aortic aneurysm (AAA) by trapping FGF2 via its calcium-binding domain, thereby preventing TLS formation and AAA progression; a therapeutic peptide (Spa17) derived from SPARCL1 mitigated AAA in multiple models.","method":"VRM-specific Sc1 deletion mouse model; FGF2 binding assay (calcium-binding domain); lymphangiogenesis assays; TLS formation analysis; therapeutic peptide treatment in AAA models","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific KO, domain-level binding assay identifying FGF2 as cargo, multiple AAA models, therapeutic rescue; multiple orthogonal methods","pmids":["41760906"],"is_preprint":false},{"year":2025,"finding":"AAV-mediated overexpression of SPARCL1 promotes supporting cell reprogramming and hair cell regeneration in vivo; mechanistically, SPARCL1 stimulates supporting cell proliferation via follistatin (Fst) activation and ECM remodeling, as revealed by RNA-seq.","method":"AAV-mediated overexpression (AAV-ie-Sparcl1); inner ear organoid expansion; RNA-seq; recombinant protein administration; in vitro and in vivo hair cell differentiation assays","journal":"Molecular therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo AAV overexpression and recombinant protein, RNA-seq pathway analysis, single lab","pmids":["40181541"],"is_preprint":false},{"year":2025,"finding":"SPARCL1 derived from epicardial differentiated preadipocytes attenuates angiotensin II-induced oxidative stress in cardiomyocytes, functioning as a paracrine adipokine; coculture with non-POAF preadipocytes suppressed myocardial oxidative stress, and low SPARCL1 expression was associated with higher POAF risk.","method":"Preadipocyte/cardiomyocyte coculture; SPARCL1 protein treatment of neonatal rat myocytes; genome-wide expression profiling; qPCR validation","journal":"JACC. Clinical electrophysiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — coculture and recombinant protein functional assay, genome-wide expression as discovery approach, single lab","pmids":["40608034"],"is_preprint":false},{"year":2021,"finding":"SPARCL1 protein in human brain exists in two glycoforms (bands at ~130 kDa and ~100 kDa) with different glycosylation patterns; it is enriched in membrane fractions over cytosol. ADAMTS4 and MMP-3 proteases cleave SPARCL1 to generate a SPARC-like fragment (SLF).","method":"Western blot of postmortem human brain; subcellular fractionation; biochemical glycosylation assays; ADAMTS4 and MMP-3 protease digestion assays","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical characterization with multiple orthogonal methods (fractionation, glycosylation assay, protease digestion), single lab","pmids":["34033869"],"is_preprint":false},{"year":2026,"finding":"SPARCL1 suppresses papillary thyroid carcinoma progression via SLC3A2-mediated ferroptosis; overexpression of SPARCL1 gene, secretory SPARCL1, and recombinant SPARCL1 protein all inhibited PTC cell malignant behaviors and subcutaneous tumor growth and lung/liver/kidney metastasis in vivo.","method":"Viral transduction overexpression; recombinant protein treatment; xenograft and metastasis mouse models; mechanistic pathway analysis","journal":"Endocrine-related cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple gain-of-function approaches (gene OE, secreted protein, recombinant protein) with in vivo validation; single lab, pathway assignment based on gene expression rather than direct biochemical reconstitution","pmids":["42160309"],"is_preprint":false}],"current_model":"SPARCL1 is a secreted matricellular glycoprotein that functions as a context-dependent regulator of cell adhesion, migration, synaptogenesis, angiogenesis, and inflammation: it promotes endothelial quiescence and vessel stability by inhibiting proliferation and mural cell migration; selectively boosts excitatory synaptogenesis and NMDAR-mediated synaptic transmission (independent of neurexins/neuroligins) while potentiating pain signaling via GluN2B-NMDARs in the spinal cord; activates inflammatory responses through TLR4/NF-κB signaling on macrophages and hepatocytes; suppresses tumor invasion and metastasis by inhibiting focal adhesion assembly and constraining cell traction forces; physically interacts with BMP7, ITGB1, frizzled receptors/LRP5/6, BST2, and ADGRL1 to modulate downstream signaling (BMP/TGF-β, WNT/β-catenin, NF-κB/p65, FAK, ERK); traps FGF2 via its calcium-binding domain to inhibit dysfunctional lymphangiogenesis; and ASD-associated mutations in its EF-hand motif impair secretion by causing ER retention and BiP chaperone binding."},"narrative":{"mechanistic_narrative":"SPARCL1 is a secreted, glycosylated matricellular protein that acts as a context-dependent regulator of cell adhesion, vascular and synaptic remodeling, and inflammation by engaging distinct cell-surface receptors and ECM components [PMID:27721236, PMID:34651580, PMID:34033869]. In the vasculature it enforces endothelial quiescence by inhibiting proliferation, migration, and sprouting, and paracrine SPARCL1 from quiescent endothelium restrains mural cell migration to stabilize mature vessels, an anti-angiogenic activity that maps to its acidic domain [PMID:27721236, PMID:33393634]. It constrains tumor cell motility and invasion by tethering to collagen, inhibiting focal adhesion assembly, and limiting traction forces, thereby suppressing metastasis across prostate, osteosarcoma, gastrointestinal stromal, and thyroid tumor models [PMID:26294211, PMID:29084211, PMID:35136209, PMID:42160309]; this anti-metastatic program intersects with WNT/β-catenin activation through binding of frizzled receptors and LRP5/6 [PMID:29084211], integrin β1 (ITGB1)–dependent FAK/paxillin/Cdc42/Arp2/3 signaling [PMID:32781616], and ERK/AP-1 suppression [PMID:31675488]. SPARCL1 also acts as a proinflammatory signal: binding TLR4 on hepatocytes and macrophages drives NF-κB/p65 activation and chemokine induction in NASH and viral pneumonia [PMID:34651580, PMID:38762489], and engagement of BST2 or the TNF/NF-κB axis promotes catabolic inflammation in joint tissues [PMID:38867741, PMID:40638212]. In the nervous system it selectively promotes excitatory synaptogenesis and potentiates NMDAR-mediated transmission independently of neurexins and neuroligins [PMID:32973045], and astrocyte-secreted SPARCL1 sustains chronic pain via GluN2B-containing NMDARs in the spinal cord [PMID:36256481]. It additionally functions as a ligand for the adhesion GPCR ADGRL1 [PMID:bio_10.1101_2024.07.03.601736] and traps FGF2 through its calcium-binding domain to limit dysfunctional lymphangiogenesis [PMID:41760906]. ASD-associated mutation of its EF-hand motif causes misfolding, BiP-dependent ER retention, and impaired secretion, and an EF-hand-adjacent variant is linked to autosomal dominant corneal stromal dystrophy with dysregulated decorin [PMID:35831437, PMID:39169229].","teleology":[{"year":1998,"claim":"Established the basic biochemical behavior of the protein, showing it self-associates into homodimers.","evidence":"Western blot of bacterially expressed and endogenous protein","pmids":["9485012"],"confidence":"Medium","gaps":["No functional consequence of dimerization defined","No structural or domain mapping of the dimer interface"]},{"year":2008,"claim":"Defined the CNS expression domain, placing SPARCL1 in radial glia and astrocyte derivatives where it influences astroglial fate.","evidence":"BAC transgenic mouse with astroglial-selective overexpression; immunohistochemistry and transcript analysis","pmids":["18381651"],"confidence":"Medium","gaps":["Molecular mechanism of cell-fate effect not resolved","No receptor or signaling pathway identified"]},{"year":2015,"claim":"Showed how SPARCL1 mechanically suppresses metastasis and how it is silenced in cancer, linking ECM tethering to focal adhesion inhibition and AR-driven epigenetic repression.","evidence":"Focal adhesion assays, orthotopic and Hi-Myc/Sparcl1-/- genetic models, ChIP for AR, pharmacological AR/HDAC inhibition","pmids":["26294211"],"confidence":"High","gaps":["Receptor mediating cytoskeletal coupling not identified in this study","Generality across tumor types not established here"]},{"year":2016,"claim":"Demonstrated a vascular role: SPARCL1 enforces endothelial quiescence and stabilizes vessels via paracrine inhibition of mural cell migration.","evidence":"EC quiescence assays, siRNA knockdown, CRC mouse models, human tissue, secretion experiments","pmids":["27721236"],"confidence":"High","gaps":["Endothelial receptor mediating quiescence not defined","Domain responsible not mapped in this study"]},{"year":2017,"claim":"Identified WNT pathway receptors as direct partners, explaining how SPARCL1 activates WNT/β-catenin to inhibit osteosarcoma metastasis and recruit macrophages.","evidence":"Co-immunoprecipitation with frizzled/LRP5/6, metastasis and reporter assays","pmids":["29084211"],"confidence":"Medium","gaps":["Stoichiometry and binding site on receptors unresolved","Single lab; reconciliation with anti-WNT contexts in adipocytes pending"]},{"year":2019,"claim":"Connected SPARCL1 to BMP/TGF-β signaling and ERK suppression in differentiation and migration contexts via a direct BMP7 interaction.","evidence":"Co-IP with BMP7, CRISPR/Cas9 KO in C2C12; overexpression with ERK/EMT readouts in trophoblasts","pmids":["31699966","31675488"],"confidence":"Medium","gaps":["Direct biochemical reconstitution of BMP7 modulation lacking","ERK suppression mechanism in trophoblasts inferred from overexpression only"]},{"year":2020,"claim":"Resolved a long-standing question about its synaptic mechanism, showing excitatory-selective synaptogenesis and NMDAR potentiation that bypass the neurexin/neuroligin axis, and identified ITGB1 as a physical partner driving FAK-dependent migration.","evidence":"Electrophysiology with triple neurexin and quadruple neuroligin conditional KO neurons; reciprocal Co-IP plus mass spectrometry for ITGB1","pmids":["32973045","32781616"],"confidence":"High","gaps":["Receptor mediating excitatory synaptogenesis not identified","Link between ITGB1 binding and synaptic function not connected"]},{"year":2021,"claim":"Established SPARCL1 as a TLR4 ligand activating NF-κB inflammation in metabolic disease, and refined its vascular and adipogenic actions including domain-level anti-angiogenic mapping.","evidence":"Sparcl1 KO mice, WAT-specific KD, neutralizing antibody, TLR4 binding and NF-κB reporter (NASH); KO + ex vivo metatarsal assay + domain structure-function (colitis); gain/loss-of-function in preadipocytes","pmids":["34651580","33393634","34872433"],"confidence":"High","gaps":["Structural basis of TLR4 engagement not solved","How anti-inflammatory vascular roles and pro-inflammatory TLR4 signaling are balanced unclear"]},{"year":2021,"claim":"Characterized the protein's post-translational state in human brain, revealing two glycoforms, membrane enrichment, and proteolytic processing by ADAMTS4 and MMP-3 to a SPARC-like fragment.","evidence":"Western blot, subcellular fractionation, glycosylation and protease digestion assays of human brain","pmids":["34033869"],"confidence":"Medium","gaps":["Functional difference between glycoforms unknown","Activity of the SPARC-like cleavage fragment not defined"]},{"year":2022,"claim":"Linked an EF-hand mutation to disease by showing it causes misfolding, BiP binding, ER retention, and secretion failure, and extended the NMDAR mechanism to chronic pain via GluN2B-containing receptors.","evidence":"Mutagenesis, MD simulation, UPR assays, BiP Co-IP (ASD variant); KO mice, AAV astrocyte re-expression, intrathecal protein, electrophysiology, neutralizing antibody (pain)","pmids":["35831437","36256481"],"confidence":"High","gaps":["GluN2B-NMDAR potentiation mechanism (direct vs indirect) unresolved","Genotype-phenotype link of EF-hand variant to ASD relies on a single substitution"]},{"year":2022,"claim":"Defined upstream epigenetic control by KDM6A and a downstream p65-suppressing, MET/MMP-dependent anti-metastatic program in GIST.","evidence":"ChIP for H3K27me3, xenograft and hepatic metastasis models, knockdown/overexpression","pmids":["35136209"],"confidence":"Medium","gaps":["Receptor coupling SPARCL1 to p65 suppression not identified","Single lab"]},{"year":2024,"claim":"Expanded the receptor repertoire by identifying ADGRL1 as a functional receptor and demonstrating endothelial SPARCL1-TLR4 signaling drives M1 macrophage polarization in pneumonia, with human validation.","evidence":"Co-IP, internalization and G-protein coupling assays, NAc Adgrl1 KD behavior (ADGRL1, preprint); endothelial-specific OE/KO mice, macrophage assays, in vivo TLR4 inhibition, COVID-19 patient samples (pneumonia)","pmids":["bio_10.1101_2024.07.03.601736","38762489"],"confidence":"High","gaps":["ADGRL1 findings remain a non-peer-reviewed preprint","Whether ADGRL1, TLR4, and integrin signaling operate in the same cells unknown"]},{"year":2024,"claim":"Extended the proinflammatory NF-κB axis to joint tissue via a new BST2 partner and corneal disease via a missense variant affecting decorin.","evidence":"Recombinant protein + NF-κB inhibitor rescue in ACLT mice (chondrocytes); WGS plus IHC of patient cornea (dystrophy)","pmids":["38867741","39169229"],"confidence":"Medium","gaps":["Corneal mechanism is correlative IHC without functional reconstitution","Decorin regulation mechanism undefined"]},{"year":2025,"claim":"Identified FGF2 trapping via the calcium-binding domain as a discrete anti-lymphangiogenic mechanism and broadened tissue roles to AT2 differentiation, meniscal inflammation via BST2, hair cell regeneration, ferroptosis-linked thyroid tumor suppression, and cardioprotective paracrine signaling.","evidence":"VRM-specific KO, FGF2 binding assay, therapeutic peptide in AAA models; recombinant protein organoid/coculture assays, NF-κB epistasis, RNA-seq, in vivo KD/OE across multiple tissues","pmids":["41760906","40118055","40638212","40181541","42160309","40608034"],"confidence":"High","gaps":["Several tissue effects rest on recombinant-protein gain-of-function without endogenous loss-of-function","Pathway assignments (e.g., ferroptosis via SLC3A2) inferred from expression, not biochemical reconstitution"]},{"year":null,"claim":"It remains unresolved how a single secreted protein selects among its many receptors (TLR4, ITGB1, frizzled/LRP5/6, BST2, ADGRL1) and ligands (BMP7, FGF2) to produce opposite outcomes—anti-inflammatory vessel stabilization versus proinflammatory NF-κB activation, and tumor suppression versus context-specific signaling.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural framework integrating the distinct binding interfaces","Cell-type and concentration determinants of receptor choice unknown","Functional role of glycoforms and proteolytic fragments in receptor selection undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[16]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,9,21]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[21]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2,8]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[3,9,13]},{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[2,18]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[12]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,9,15]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[9,15,17]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[2,18]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[7,13]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[12,18]}],"complexes":[],"partners":["BMP7","ITGB1","TLR4","LRP5","LRP6","BST2","ADGRL1","FGF2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q14515","full_name":"SPARC-like protein 1","aliases":["High endothelial venule protein","Hevin","MAST 9"],"length_aa":664,"mass_kda":75.2,"function":"","subcellular_location":"Secreted, extracellular space, extracellular matrix","url":"https://www.uniprot.org/uniprotkb/Q14515/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SPARCL1","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SPARCL1","total_profiled":1310},"omim":[{"mim_id":"606041","title":"SPARC-LIKE PROTEIN 1; SPARCL1","url":"https://www.omim.org/entry/606041"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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immunohistochemistry and transcript analysis\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo transgenic model with selective overexpression and characterization, single lab\",\n      \"pmids\": [\"18381651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SPARCL1 suppresses metastatic progression of prostate cancer by tethering to collagen in the ECM and binding to the cell cytoskeleton, directly inhibiting focal adhesion assembly and thereby constraining cell traction forces; androgen receptor (AR) activation directly suppresses SPARCL1 expression via epigenetic mechanism at the SPARCL1 locus, reversible by AR antagonists or HDAC inhibitors.\",\n      \"method\": \"In vitro focal adhesion assays; orthotopic allograft mouse model (Myc-CaP); Hi-Myc/Sparcl1-/- genetic model; ChIP for AR binding; pharmacological AR and HDAC inhibition\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods: genetic KO model, in vivo orthotopic allograft, ChIP, pharmacological intervention, focal adhesion functional assay\",\n      \"pmids\": [\"26294211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SPARCL1 promotes endothelial cell quiescence by inhibiting proliferation, migration, and sprouting; siRNA-mediated knockdown increases sprouting. Secreted SPARCL1 from quiescent ECs inhibits mural cell migration, leading to stabilized mural cell coverage of mature vessels.\",\n      \"method\": \"In vitro EC quiescence assays; siRNA knockdown; mouse models of CRC; human CRC tissue analysis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods: siRNA KD functional assays, mouse models, human tissue validation, secretion/paracrine experiments\",\n      \"pmids\": [\"27721236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SPARCL1 activates WNT/β-catenin signaling by physically interacting with multiple frizzled receptors and LRP5/6, stabilizing the WNT-receptor complex; this mechanism underlies SPARCL1-mediated inhibition of osteosarcoma metastasis. Additionally, SPARCL1-activated WNT/β-catenin signaling drives paracrine secretion of CCL5, recruiting macrophages.\",\n      \"method\": \"Co-immunoprecipitation; in vitro and in vivo metastasis assays; WNT/β-catenin reporter assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP for physical interaction, functional in vitro and in vivo assays, single lab\",\n      \"pmids\": [\"29084211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SPARCL1 binds to BMP7 (confirmed by immunoprecipitation) and regulates BMP/TGF-β signaling, promoting C2C12 muscle cell differentiation; CRISPR/Cas9 knockout of SPARCL1 confirmed its requirement for BMP/TGF-β pathway activation.\",\n      \"method\": \"Immunoprecipitation; Western blotting; immunofluorescence; CRISPR/Cas9 knockout\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for physical interaction with BMP7, CRISPR KO functional validation, single lab\",\n      \"pmids\": [\"31699966\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SPARCL1 overexpression inhibits trophoblast cell migration and invasion by suppressing ERK phosphorylation, decreasing AP-1 (Fos/Jun) expression, and altering EMT-related molecule expression (MMP2, MMP3, N-cadherin, E-cadherin, vimentin).\",\n      \"method\": \"Overexpression transfection in HTR8/SVneo and JAR cells; scratch-wound assay; Western blot for ERK phosphorylation and EMT markers; qPCR\",\n      \"journal\": \"Placenta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — overexpression with multiple functional readouts but no KO or reconstitution; single lab with multiple assay types\",\n      \"pmids\": [\"31675488\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SPARCL1 selectively promotes excitatory (not inhibitory) synaptogenesis and enhances excitatory synaptic transmission, augmenting NMDAR-mediated responses more than AMPAR-mediated responses; these effects are independent of neurexins and neuroligins, demonstrated using triple neurexin-1/2/3 and quadruple neuroligin-1/2/3/4 conditional KO neurons.\",\n      \"method\": \"Mixed neuronal/glial cultures; electrophysiology (patch clamp); conditional KO of all neurexins or all neuroligins; synapse counting assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — rigorous genetic manipulations (conditional KO of all neurexins or neuroligins), electrophysiology, multiple orthogonal methods in one study\",\n      \"pmids\": [\"32973045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SPARCL1 interacts physically with integrin β1 (ITGB1), and this interaction mediates SPARCL1's promotion of bovine satellite cell migration and early differentiation; SPARCL1 regulates downstream signaling molecules p-FAK, p-paxillin, vinculin, Cdc42, and Arp2/3 through ITGB1.\",\n      \"method\": \"Immunoprecipitation and mass spectrometry; co-immunoprecipitation; cell scratch assay; desmin staining; Western blotting\",\n      \"journal\": \"Animals\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus mass spectrometry identification, multiple functional readouts, single lab\",\n      \"pmids\": [\"32781616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SPARCL1 promotes NASH progression by binding to TLR4 on hepatocytes, activating the NF-κB/p65 signaling pathway to upregulate CCL2 expression; blocking the CCL2/CCR2 pathway attenuated the hepatic inflammatory response evoked by SPARCL1. Genetic ablation, WAT-specific knockdown, and neutralizing antibody all alleviated diet-induced NASH.\",\n      \"method\": \"Recombinant protein injection; Sparcl1 KO mice; siRNA knockdown in WAT; neutralizing antibody treatment; binding assay for TLR4; NF-κB reporter; CCL2/CCR2 pharmacological blocking\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods: KO mice, WAT-specific KD, neutralizing antibody, recombinant protein gain-of-function, receptor binding assay, pathway reporter, replicated across approaches\",\n      \"pmids\": [\"34651580\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SPARCL1 inhibits angiogenesis and supports vessel morphogenesis and integrity; the acidic domain of SPARCL1 is necessary for its anti-angiogenic activity. SPARCL1-mediated vessel stabilization counteracts vascular permeability and inflammation in DSS colitis models.\",\n      \"method\": \"Metatarsal ex vivo angiogenesis assay; SPARCL1 knockout mice in acute and chronic DSS colitis models; structure-function analysis of purified SPARCL1 protein domains\",\n      \"journal\": \"Inflammatory bowel diseases\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO model with disease readout, ex vivo functional assay, domain-level structure-function with purified protein; multiple orthogonal methods\",\n      \"pmids\": [\"33393634\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SPARCL1 inhibits preadipocyte differentiation by activating the Wnt/β-catenin pathway (increasing Wnt10b, Fzd8, β-catenin, IL6) and inhibiting PPARγ, C/EBPα, LPL, IGF1; conversely, SPARCL1 deficiency promotes differentiation by inhibiting β-catenin and increasing GSK3β.\",\n      \"method\": \"siRNA knockdown and overexpression in sheep preadipocytes; Western blot; qPCR; oil red O staining for lipid droplets; triglyceride content measurement\",\n      \"journal\": \"Adipocyte\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — gain- and loss-of-function with multiple molecular readouts, single lab, no reconstitution\",\n      \"pmids\": [\"34872433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"An ASD-associated single amino acid substitution (Trp647Arg) in the EF-hand motif of SPARCL1 causes protein misfolding, ER retention, and activation of unfolded protein response; molecular dynamics simulation showed that this substitution exposes a hydrophobic residue, increasing binding to the chaperone BiP. Loss of EF-hand integrity impairs SPARCL1 secretion.\",\n      \"method\": \"Mutagenesis; immunofluorescence for ER localization; unfolded protein response assays; molecular dynamics simulation; co-immunoprecipitation with BiP\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis combined with MD simulation and UPR assay, Co-IP for chaperone binding; single lab\",\n      \"pmids\": [\"35831437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Astrocyte-secreted SPARCL1 (hevin) is crucial for maintaining chronic pain through spinal cord NMDA receptor signaling; intrathecal SPARCL1 induces persistent mechanical allodynia, and re-expression of SPARCL1 in GFAP+ spinal cord astrocytes via AAV reinstates neuropathic pain. SPARCL1 potentiates NMDA currents via GluN2B-containing NMDARs. A neutralizing antibody against SPARCL1 alleviates acute and persistent pain.\",\n      \"method\": \"Intrathecal injection of recombinant protein; SPARCL1 KO mice; AAV-mediated re-expression in astrocytes; electrophysiology (NMDA currents); neutralizing antibody treatment; CSF measurement\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods: KO mice, AAV rescue, intrathecal recombinant protein, electrophysiology, neutralizing antibody; replicated across pain models\",\n      \"pmids\": [\"36256481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KDM6A (a histone demethylase) promotes SPARCL1 transcription by demethylating histone H3K27me3 at the SPARCL1 locus; SPARCL1 in turn inhibits p65 nuclear translocation/phosphorylation, suppressing GIST metastasis in a MET- and MMP-dependent manner.\",\n      \"method\": \"ChIP for H3K27me3; Western blot; xenograft and hepatic metastasis models; SPARCL1 knockdown/overexpression\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP establishes epigenetic writer-target relationship, functional in vivo models, single lab\",\n      \"pmids\": [\"35136209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SPARCL1 secreted from pulmonary capillary endothelial cells drives pro-inflammatory 'M1-like' macrophage polarization during viral pneumonia by signaling through TLR4 on macrophages; TLR4 inhibition in vivo ameliorates excessive inflammation caused by endothelial SPARCL1 overexpression.\",\n      \"method\": \"Endothelial-specific SPARCL1 overexpression and deletion mouse models; in vitro macrophage polarization assays; TLR4 inhibition in vivo; COVID-19 patient lung EC RNA-seq and plasma protein measurement\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific KO and overexpression, in vitro mechanistic assay with TLR4, in vivo TLR4 inhibition rescue, human patient validation\",\n      \"pmids\": [\"38762489\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SPARCL1 functions as a functional ligand for the adhesion GPCR ADGRL1 (Latrophilin-1): hevin/SPARCL1 interacts with membrane-expressed ADGRL1, induces its internalization, stabilizes its uncleaved fraction, alters ADGRL1/Neurexin-1-mediated intercellular adhesion contacts, and biases ADGRL1 coupling toward Gi3, Gs, and G13 signaling pathways.\",\n      \"method\": \"Co-immunoprecipitation; cell internalization assays; G protein coupling assays; intercellular adhesion contact assays; mouse NAc Adgrl1 KD behavioral experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple binding and functional assays in a preprint; single lab, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2024.07.03.601736\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SPARCL1 promotes chondrocyte extracellular matrix degradation and inflammation in osteoarthritis by activating the TNF/NF-κB pathway; recombinant SPARCL1 protein intra-articular injection promotes OA pathogenesis in ACLT mice, and NF-κB inhibitor BAY 11-7082 reverses SPARCL1-induced inflammatory and catabolic gene expression.\",\n      \"method\": \"Recombinant SPARCL1 protein in vitro treatment; intra-articular injection in ACLT mouse model; RNA-seq; Western blot; NF-κB inhibitor rescue experiment\",\n      \"journal\": \"Journal of orthopaedic translation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro gain-of-function with recombinant protein, pathway inhibitor rescue, single lab\",\n      \"pmids\": [\"38867741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"An autosomal dominant corneal stromal dystrophy is associated with a SPARCL1 missense variant (p.Glu112Lys); immunohistochemistry showed decorin is significantly decreased in affected corneal stroma and SPARCL1 is retained in the epithelium, suggesting SPARCL1 regulates decorin in the corneal ECM.\",\n      \"method\": \"Whole genome sequencing; immunohistochemistry for SPARCL1 and decorin in patient vs. control corneal tissue\",\n      \"journal\": \"European journal of human genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — immunohistochemistry in patient tissue, no in vitro or in vivo functional reconstitution of the mechanism\",\n      \"pmids\": [\"39169229\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SPARCL1 secreted by lung microvasculature promotes alveolar type 2 (AT2) cell differentiation by activating NF-κB signaling; SPARCL1-treated organoids show lysozyme upregulation, doubling of AT2 cells, and upregulation of NF-κB target genes. Suppression of NF-κB blocked SPARCL1 effects on AT2 differentiation.\",\n      \"method\": \"Recombinant SPARCL1 protein treatment of alveolar organoids; NF-κB inhibition rescue; RNA-seq; immunofluorescence\",\n      \"journal\": \"Stem cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — recombinant protein gain-of-function in organoid model, NF-κB inhibitor epistasis, RNA-seq; single lab\",\n      \"pmids\": [\"40118055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SPARCL1 binding to BST2 activates the NF-κB/P65 pathway, driving meniscal inflammation and catabolic metabolism; co-localization, molecular docking, and Co-IP confirmed the SPARCL1-BST2 physical interaction; SPARCL1 knockdown in vivo reduced inflammation and delayed meniscus degeneration.\",\n      \"method\": \"Co-immunoprecipitation; molecular docking; fluorescence co-localization; transcriptome sequencing; in vivo lentiviral knockdown in ACLT mouse model; Western blot; immunofluorescence\",\n      \"journal\": \"Rheumatology (Oxford, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, molecular docking, in vivo KD with functional readout; single lab\",\n      \"pmids\": [\"40638212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Vascular resident macrophage (VRM)-derived SPARCL1 inhibits FGF2-mediated dysfunctional lymphangiogenesis in abdominal aortic aneurysm (AAA) by trapping FGF2 via its calcium-binding domain, thereby preventing TLS formation and AAA progression; a therapeutic peptide (Spa17) derived from SPARCL1 mitigated AAA in multiple models.\",\n      \"method\": \"VRM-specific Sc1 deletion mouse model; FGF2 binding assay (calcium-binding domain); lymphangiogenesis assays; TLS formation analysis; therapeutic peptide treatment in AAA models\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific KO, domain-level binding assay identifying FGF2 as cargo, multiple AAA models, therapeutic rescue; multiple orthogonal methods\",\n      \"pmids\": [\"41760906\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AAV-mediated overexpression of SPARCL1 promotes supporting cell reprogramming and hair cell regeneration in vivo; mechanistically, SPARCL1 stimulates supporting cell proliferation via follistatin (Fst) activation and ECM remodeling, as revealed by RNA-seq.\",\n      \"method\": \"AAV-mediated overexpression (AAV-ie-Sparcl1); inner ear organoid expansion; RNA-seq; recombinant protein administration; in vitro and in vivo hair cell differentiation assays\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo AAV overexpression and recombinant protein, RNA-seq pathway analysis, single lab\",\n      \"pmids\": [\"40181541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SPARCL1 derived from epicardial differentiated preadipocytes attenuates angiotensin II-induced oxidative stress in cardiomyocytes, functioning as a paracrine adipokine; coculture with non-POAF preadipocytes suppressed myocardial oxidative stress, and low SPARCL1 expression was associated with higher POAF risk.\",\n      \"method\": \"Preadipocyte/cardiomyocyte coculture; SPARCL1 protein treatment of neonatal rat myocytes; genome-wide expression profiling; qPCR validation\",\n      \"journal\": \"JACC. Clinical electrophysiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — coculture and recombinant protein functional assay, genome-wide expression as discovery approach, single lab\",\n      \"pmids\": [\"40608034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SPARCL1 protein in human brain exists in two glycoforms (bands at ~130 kDa and ~100 kDa) with different glycosylation patterns; it is enriched in membrane fractions over cytosol. ADAMTS4 and MMP-3 proteases cleave SPARCL1 to generate a SPARC-like fragment (SLF).\",\n      \"method\": \"Western blot of postmortem human brain; subcellular fractionation; biochemical glycosylation assays; ADAMTS4 and MMP-3 protease digestion assays\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical characterization with multiple orthogonal methods (fractionation, glycosylation assay, protease digestion), single lab\",\n      \"pmids\": [\"34033869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"SPARCL1 suppresses papillary thyroid carcinoma progression via SLC3A2-mediated ferroptosis; overexpression of SPARCL1 gene, secretory SPARCL1, and recombinant SPARCL1 protein all inhibited PTC cell malignant behaviors and subcutaneous tumor growth and lung/liver/kidney metastasis in vivo.\",\n      \"method\": \"Viral transduction overexpression; recombinant protein treatment; xenograft and metastasis mouse models; mechanistic pathway analysis\",\n      \"journal\": \"Endocrine-related cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple gain-of-function approaches (gene OE, secreted protein, recombinant protein) with in vivo validation; single lab, pathway assignment based on gene expression rather than direct biochemical reconstitution\",\n      \"pmids\": [\"42160309\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SPARCL1 is a secreted matricellular glycoprotein that functions as a context-dependent regulator of cell adhesion, migration, synaptogenesis, angiogenesis, and inflammation: it promotes endothelial quiescence and vessel stability by inhibiting proliferation and mural cell migration; selectively boosts excitatory synaptogenesis and NMDAR-mediated synaptic transmission (independent of neurexins/neuroligins) while potentiating pain signaling via GluN2B-NMDARs in the spinal cord; activates inflammatory responses through TLR4/NF-κB signaling on macrophages and hepatocytes; suppresses tumor invasion and metastasis by inhibiting focal adhesion assembly and constraining cell traction forces; physically interacts with BMP7, ITGB1, frizzled receptors/LRP5/6, BST2, and ADGRL1 to modulate downstream signaling (BMP/TGF-β, WNT/β-catenin, NF-κB/p65, FAK, ERK); traps FGF2 via its calcium-binding domain to inhibit dysfunctional lymphangiogenesis; and ASD-associated mutations in its EF-hand motif impair secretion by causing ER retention and BiP chaperone binding.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SPARCL1 is a secreted, glycosylated matricellular protein that acts as a context-dependent regulator of cell adhesion, vascular and synaptic remodeling, and inflammation by engaging distinct cell-surface receptors and ECM components [#3, #9, #24]. In the vasculature it enforces endothelial quiescence by inhibiting proliferation, migration, and sprouting, and paracrine SPARCL1 from quiescent endothelium restrains mural cell migration to stabilize mature vessels, an anti-angiogenic activity that maps to its acidic domain [#3, #10]. It constrains tumor cell motility and invasion by tethering to collagen, inhibiting focal adhesion assembly, and limiting traction forces, thereby suppressing metastasis across prostate, osteosarcoma, gastrointestinal stromal, and thyroid tumor models [#2, #4, #14, #25]; this anti-metastatic program intersects with WNT/β-catenin activation through binding of frizzled receptors and LRP5/6 [#4], integrin β1 (ITGB1)–dependent FAK/paxillin/Cdc42/Arp2/3 signaling [#8], and ERK/AP-1 suppression [#6]. SPARCL1 also acts as a proinflammatory signal: binding TLR4 on hepatocytes and macrophages drives NF-κB/p65 activation and chemokine induction in NASH and viral pneumonia [#9, #15], and engagement of BST2 or the TNF/NF-κB axis promotes catabolic inflammation in joint tissues [#17, #20]. In the nervous system it selectively promotes excitatory synaptogenesis and potentiates NMDAR-mediated transmission independently of neurexins and neuroligins [#7], and astrocyte-secreted SPARCL1 sustains chronic pain via GluN2B-containing NMDARs in the spinal cord [#13]. It additionally functions as a ligand for the adhesion GPCR ADGRL1 [#16] and traps FGF2 through its calcium-binding domain to limit dysfunctional lymphangiogenesis [#21]. ASD-associated mutation of its EF-hand motif causes misfolding, BiP-dependent ER retention, and impaired secretion, and an EF-hand-adjacent variant is linked to autosomal dominant corneal stromal dystrophy with dysregulated decorin [#12, #18].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established the basic biochemical behavior of the protein, showing it self-associates into homodimers.\",\n      \"evidence\": \"Western blot of bacterially expressed and endogenous protein\",\n      \"pmids\": [\"9485012\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional consequence of dimerization defined\", \"No structural or domain mapping of the dimer interface\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined the CNS expression domain, placing SPARCL1 in radial glia and astrocyte derivatives where it influences astroglial fate.\",\n      \"evidence\": \"BAC transgenic mouse with astroglial-selective overexpression; immunohistochemistry and transcript analysis\",\n      \"pmids\": [\"18381651\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism of cell-fate effect not resolved\", \"No receptor or signaling pathway identified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed how SPARCL1 mechanically suppresses metastasis and how it is silenced in cancer, linking ECM tethering to focal adhesion inhibition and AR-driven epigenetic repression.\",\n      \"evidence\": \"Focal adhesion assays, orthotopic and Hi-Myc/Sparcl1-/- genetic models, ChIP for AR, pharmacological AR/HDAC inhibition\",\n      \"pmids\": [\"26294211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating cytoskeletal coupling not identified in this study\", \"Generality across tumor types not established here\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated a vascular role: SPARCL1 enforces endothelial quiescence and stabilizes vessels via paracrine inhibition of mural cell migration.\",\n      \"evidence\": \"EC quiescence assays, siRNA knockdown, CRC mouse models, human tissue, secretion experiments\",\n      \"pmids\": [\"27721236\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endothelial receptor mediating quiescence not defined\", \"Domain responsible not mapped in this study\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified WNT pathway receptors as direct partners, explaining how SPARCL1 activates WNT/β-catenin to inhibit osteosarcoma metastasis and recruit macrophages.\",\n      \"evidence\": \"Co-immunoprecipitation with frizzled/LRP5/6, metastasis and reporter assays\",\n      \"pmids\": [\"29084211\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and binding site on receptors unresolved\", \"Single lab; reconciliation with anti-WNT contexts in adipocytes pending\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Connected SPARCL1 to BMP/TGF-β signaling and ERK suppression in differentiation and migration contexts via a direct BMP7 interaction.\",\n      \"evidence\": \"Co-IP with BMP7, CRISPR/Cas9 KO in C2C12; overexpression with ERK/EMT readouts in trophoblasts\",\n      \"pmids\": [\"31699966\", \"31675488\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical reconstitution of BMP7 modulation lacking\", \"ERK suppression mechanism in trophoblasts inferred from overexpression only\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Resolved a long-standing question about its synaptic mechanism, showing excitatory-selective synaptogenesis and NMDAR potentiation that bypass the neurexin/neuroligin axis, and identified ITGB1 as a physical partner driving FAK-dependent migration.\",\n      \"evidence\": \"Electrophysiology with triple neurexin and quadruple neuroligin conditional KO neurons; reciprocal Co-IP plus mass spectrometry for ITGB1\",\n      \"pmids\": [\"32973045\", \"32781616\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating excitatory synaptogenesis not identified\", \"Link between ITGB1 binding and synaptic function not connected\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established SPARCL1 as a TLR4 ligand activating NF-κB inflammation in metabolic disease, and refined its vascular and adipogenic actions including domain-level anti-angiogenic mapping.\",\n      \"evidence\": \"Sparcl1 KO mice, WAT-specific KD, neutralizing antibody, TLR4 binding and NF-κB reporter (NASH); KO + ex vivo metatarsal assay + domain structure-function (colitis); gain/loss-of-function in preadipocytes\",\n      \"pmids\": [\"34651580\", \"33393634\", \"34872433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of TLR4 engagement not solved\", \"How anti-inflammatory vascular roles and pro-inflammatory TLR4 signaling are balanced unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Characterized the protein's post-translational state in human brain, revealing two glycoforms, membrane enrichment, and proteolytic processing by ADAMTS4 and MMP-3 to a SPARC-like fragment.\",\n      \"evidence\": \"Western blot, subcellular fractionation, glycosylation and protease digestion assays of human brain\",\n      \"pmids\": [\"34033869\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional difference between glycoforms unknown\", \"Activity of the SPARC-like cleavage fragment not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked an EF-hand mutation to disease by showing it causes misfolding, BiP binding, ER retention, and secretion failure, and extended the NMDAR mechanism to chronic pain via GluN2B-containing receptors.\",\n      \"evidence\": \"Mutagenesis, MD simulation, UPR assays, BiP Co-IP (ASD variant); KO mice, AAV astrocyte re-expression, intrathecal protein, electrophysiology, neutralizing antibody (pain)\",\n      \"pmids\": [\"35831437\", \"36256481\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GluN2B-NMDAR potentiation mechanism (direct vs indirect) unresolved\", \"Genotype-phenotype link of EF-hand variant to ASD relies on a single substitution\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined upstream epigenetic control by KDM6A and a downstream p65-suppressing, MET/MMP-dependent anti-metastatic program in GIST.\",\n      \"evidence\": \"ChIP for H3K27me3, xenograft and hepatic metastasis models, knockdown/overexpression\",\n      \"pmids\": [\"35136209\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor coupling SPARCL1 to p65 suppression not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Expanded the receptor repertoire by identifying ADGRL1 as a functional receptor and demonstrating endothelial SPARCL1-TLR4 signaling drives M1 macrophage polarization in pneumonia, with human validation.\",\n      \"evidence\": \"Co-IP, internalization and G-protein coupling assays, NAc Adgrl1 KD behavior (ADGRL1, preprint); endothelial-specific OE/KO mice, macrophage assays, in vivo TLR4 inhibition, COVID-19 patient samples (pneumonia)\",\n      \"pmids\": [\"bio_10.1101_2024.07.03.601736\", \"38762489\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"ADGRL1 findings remain a non-peer-reviewed preprint\", \"Whether ADGRL1, TLR4, and integrin signaling operate in the same cells unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the proinflammatory NF-κB axis to joint tissue via a new BST2 partner and corneal disease via a missense variant affecting decorin.\",\n      \"evidence\": \"Recombinant protein + NF-κB inhibitor rescue in ACLT mice (chondrocytes); WGS plus IHC of patient cornea (dystrophy)\",\n      \"pmids\": [\"38867741\", \"39169229\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Corneal mechanism is correlative IHC without functional reconstitution\", \"Decorin regulation mechanism undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified FGF2 trapping via the calcium-binding domain as a discrete anti-lymphangiogenic mechanism and broadened tissue roles to AT2 differentiation, meniscal inflammation via BST2, hair cell regeneration, ferroptosis-linked thyroid tumor suppression, and cardioprotective paracrine signaling.\",\n      \"evidence\": \"VRM-specific KO, FGF2 binding assay, therapeutic peptide in AAA models; recombinant protein organoid/coculture assays, NF-κB epistasis, RNA-seq, in vivo KD/OE across multiple tissues\",\n      \"pmids\": [\"41760906\", \"40118055\", \"40638212\", \"40181541\", \"42160309\", \"40608034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Several tissue effects rest on recombinant-protein gain-of-function without endogenous loss-of-function\", \"Pathway assignments (e.g., ferroptosis via SLC3A2) inferred from expression, not biochemical reconstitution\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how a single secreted protein selects among its many receptors (TLR4, ITGB1, frizzled/LRP5/6, BST2, ADGRL1) and ligands (BMP7, FGF2) to produce opposite outcomes—anti-inflammatory vessel stabilization versus proinflammatory NF-κB activation, and tumor suppression versus context-specific signaling.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural framework integrating the distinct binding interfaces\", \"Cell-type and concentration determinants of receptor choice unknown\", \"Functional role of glycoforms and proteolytic fragments in receptor selection undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 9, 21]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [21]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [3, 9, 13]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [2, 18]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 9, 15]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [9, 15, 17]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [2, 18]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [7, 13]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12, 18]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"BMP7\", \"ITGB1\", \"TLR4\", \"LRP5\", \"LRP6\", \"BST2\", \"ADGRL1\", \"FGF2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}