{"gene":"SFRP1","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2005,"finding":"SFRP1 directly binds Frizzled-2 (Fz2) receptor and guides retinal ganglion cell axon growth through a Wnt-inhibition-independent mechanism requiring Gα protein activation, protein synthesis/degradation, and modulation by cyclic nucleotide levels; interference with Fz2 expression abolishes growth cone responses to SFRP1.","method":"Chick and Xenopus retinal ganglion cell axon growth assays, co-immunoprecipitation of SFRP1 with Fz2, dominant-negative receptor interference, pharmacological manipulation of Gα proteins and cyclic nucleotides","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 — reciprocal binding shown, multiple orthogonal functional assays, receptor interference rescue","pmids":["16172602"],"is_preprint":false},{"year":2003,"finding":"SFRP1 promotes retinal ganglion cell and cone photoreceptor generation while decreasing amacrine cell numbers via a β-catenin-independent mechanism involving phosphorylation-dependent inhibition of GSK3β; SFRP1 does not modify basal β-catenin transcriptional activity in retinal cells.","method":"Retroviral overexpression in chick retinal cultures, β-catenin/TCF luciferase reporter assay, dominant-negative GSK3β phenocopy, Western blot for pGSK3β","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods, functional rescue, mechanistic pathway placement","pmids":["12724355"],"is_preprint":false},{"year":2006,"finding":"Sfrp1 and Sfrp2 directly interact with Wnt ligands to inhibit Wnt-3a-induced β-catenin accumulation in a GSK-3-dependent manner (they cannot block LiCl-induced β-catenin accumulation), demonstrating their site of action is upstream of GSK-3.","method":"In vitro Wnt-3a inhibition assay in L cells, LiCl epistasis experiment, purified recombinant Sfrp proteins","journal":"Developmental dynamics","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with purified proteins plus epistasis experiment","pmids":["16425220"],"is_preprint":false},{"year":2006,"finding":"Gli1 and Gli2 transcription factors of the Hedgehog signaling pathway directly regulate sFRP1 transcription; chromatin immunoprecipitation demonstrates Gli1 binds the sFRP1 promoter, and sFRP1 in turn suppresses Wnt-1-mediated β-catenin accumulation, establishing sFRP1 as a mechanistic link between Hh and Wnt pathway cross-talk.","method":"ChIP assay, ectopic Gli1 expression in gastric cancer cells, SMO antagonist (KAAD-cyclopamine) treatment, β-catenin accumulation assay, sFRP1 siRNA rescue","journal":"Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — ChIP plus functional epistasis with inhibitor and siRNA rescue, replicated across cell lines","pmids":["17035233"],"is_preprint":false},{"year":2006,"finding":"Sfrp1 and Sfrp2 double knockout mice display anterior-posterior axis shortening and abnormal somite segmentation associated with altered Notch signaling oscillations (Lfng and Hes7 expression); single knockouts have no phenotype, indicating functional redundancy. Aberrant presomitic mesoderm cell migration also contributes.","method":"Mouse double-knockout genetics, in situ hybridization for segmentation clock genes (Lfng, Hes7), histological analysis of somites","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 — clean double-KO mouse model with specific molecular readout of Notch clock","pmids":["16467359"],"is_preprint":false},{"year":2008,"finding":"Elevated sFRP1 in the trabecular meshwork (TM) inhibits Wnt signaling (reduces β-catenin) and decreases aqueous outflow facility, causing elevated intraocular pressure; adenoviral overexpression of sFRP1 in mouse eyes increases IOP in a titer-dependent manner reversible by a downstream Wnt signaling inhibitor.","method":"Ex vivo human eye perfusion culture with recombinant sFRP1, intravitreal adenoviral injection in mice, IOP measurement, β-catenin immunostaining in TM","journal":"Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — in vivo gain-of-function with pharmacological rescue, ex vivo human tissue validation","pmids":["18274669"],"is_preprint":false},{"year":2012,"finding":"SFRP1 is oversecreted upon cellular senescence (DNA damage or oxidative stress) and is both necessary and sufficient for senescence induction; it acts through inhibition of Wnt signaling and activation of the retinoblastoma (Rb) pathway; cancer-associated SFRP1 mutants are defective for senescence induction.","method":"Knockdown and overexpression in human cells, stress-induced senescence assays (SA-β-gal, growth arrest), Rb pathway analysis, cancer mutant functional testing","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — loss- and gain-of-function with multiple readouts, mutant analysis provides mechanistic detail","pmids":["22927647"],"is_preprint":false},{"year":2012,"finding":"SFRP1 and SFRP2 activate the Wnt/planar-cell-polarity (PCP)/Rac1 pathway in dopaminergic neurons; compound Sfrp1/Sfrp2 double knockout mice display a Wnt/PCP phenotype (AP shortening of VM, lateral expansion of Shh domain, accumulation of Nurr1+ precursors) similar to Wnt5a-/- mice; low/medium concentrations of sFRP1 promote DA differentiation mimicking Wnt5a.","method":"Sfrp1/Sfrp2 compound knockout mouse genetics, primary VM cultures, embryonic stem cell differentiation assays, Rac1 pathway activation assays","journal":"Stem cells","confidence":"High","confidence_rationale":"Tier 2 — double-KO mouse with specific pathway phenotype, in vitro mechanistic validation","pmids":["22290867"],"is_preprint":false},{"year":2014,"finding":"Sfrp1 deficiency in a mouse model of obstructive nephropathy increases myofibroblast markers (αSMA), promotes epithelial-to-mesenchymal transition (decreased E-cadherin, increased vimentin), and elevates phospho-c-Jun/JNK (non-canonical Wnt/PCP pathway) without affecting canonical Wnt signaling levels; also increases apoptosis in obstructed kidneys.","method":"Sfrp1 knockout mouse UUO model, Western blot for EMT markers and JNK/pJNK, histology, TUNEL apoptosis assay","journal":"Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — clean KO model with defined molecular pathway dissection (canonical vs non-canonical)","pmids":["25253698"],"is_preprint":false},{"year":2003,"finding":"SFRP1 protects fibroblasts from ceramide-induced apoptosis by regulating p53, caspase-3, caspase-9, and BIK expression; inhibition of endogenous SFRP1 increases cell death while exogenous SFRP1 reduces apoptosis in vitro and in vivo.","method":"Antisense inhibition and exogenous recombinant protein treatment in PDL and gingival fibroblasts, apoptosis assays (TUNEL, caspase activity), in vivo dermal fibroblast model","journal":"Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — loss and gain of function with molecular readouts, single lab","pmids":["14581477"],"is_preprint":false},{"year":2005,"finding":"SFRP1 treatment of prostatic epithelial cells increases proliferation, decreases apoptosis, and decreases canonical Wnt/β-catenin signaling; SFRP1 treatment of developing prostates in culture increases organ growth, suggesting a paracrine role from tumor stroma promoting epithelial proliferation.","method":"Recombinant SFRP1 treatment of prostatic epithelial cell lines and organ culture, proliferation assays, apoptosis assays, β-catenin signaling readout, in vivo proliferation","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional readouts, but single lab and mechanistic pathway not fully resolved","pmids":["16288033"],"is_preprint":false},{"year":2009,"finding":"SFRP1 knockdown in non-malignant mammary epithelial cells raises nuclear β-catenin, activates Wnt signaling, increases Cyclin D1, promotes partial EMT, confers resistance to anoikis, increases migration and invasion, and generates a CD44high/CD24low population.","method":"shRNA knockdown in 76N TERT cells, β-catenin fractionation, invasion/migration assays, flow cytometry for CD44/CD24 markers, anchorage-independent growth assay","journal":"Cancer cell international","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with multiple orthogonal phenotypic readouts, single lab","pmids":["19422694"],"is_preprint":false},{"year":2011,"finding":"EZH2 (histone methyltransferase) is overexpressed in rheumatoid arthritis synovial fibroblasts, is induced by TNF-α via NF-κB and JNK pathways, and epigenetically silences SFRP1 by histone methylation at its promoter; SFRP1 promoter occupation by activating vs. silencing histone marks correlates with expression levels.","method":"ChIP assay for histone marks at SFRP1 promoter, EZH2 overexpression and siRNA knockdown, qRT-PCR, Western blot, kinase inhibitor experiments, reporter assays","journal":"Annals of the rheumatic diseases","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP demonstrates direct epigenetic regulation, functional perturbations in patient-derived cells","pmids":["21515604"],"is_preprint":false},{"year":2013,"finding":"HCV core protein silences SFRP1 by recruiting DNMT1 and HDAC1 to the SFRP1 promoter, causing CpG hypermethylation and repression of acetyl-H3 binding; SFRP1 silencing activates Wnt/β-catenin (c-Myc, cyclin D1) and induces EMT; restoring SFRP1 or knocking down DNMT1 reverses these effects in vivo and in vitro.","method":"ChIP for DNMT1, HDAC1, acetyl-H3 at SFRP1 promoter; bisulfite sequencing; DNMT1 knockdown; SFRP1 overexpression; xenograft mouse model; Western blot for EMT markers and β-catenin targets","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 — ChIP demonstrates direct promoter recruitment, multiple orthogonal methods, in vivo validation","pmids":["23770846"],"is_preprint":false},{"year":2019,"finding":"SFRP1 maintains the non-mineralized state of periodontal ligament (PDL) progenitors; SFRP1 promoter carries H3K4me3 active marks in PDL fibroblasts but not in alveolar bone progenitors; inhibition or knockdown of SFRP1 promotes PDL mineralization and activates RUNX2/SP7 via H3K4me3-mediated transcription.","method":"ChIP for H3K4me3/H3K27me3, small molecule inhibitor (WAY-316606), siRNA knockdown, mineralization assays, Western blot in PDL vs AB progenitors","journal":"Stem cells and development","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP plus functional KD/inhibitor experiments in defined cell populations","pmids":["31215318"],"is_preprint":false},{"year":2012,"finding":"sFRP1 promotes human Th17 cell differentiation by enhancing TGF-β/Smad2/3 phosphorylation in CD4+ T cells; blocking TGF-β signaling abolishes the Th17-promoting activity of sFRP1.","method":"Recombinant sFRP1 addition during TCR-mediated stimulation and Th17-differentiation conditions, IL-17 ELISA, phospho-Smad2/3 Western blot, TGF-β blocking antibody epistasis","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway placed by epistasis, multiple readouts, single lab","pmids":["22740051"],"is_preprint":false},{"year":2008,"finding":"Recombinant Sfrp1 or Sfrp2 inhibit myoblast differentiation (myotube formation) without affecting cell cycle or apoptosis; cells must be treated during proliferation for maximal effect, and removing Sfrp restores normal differentiation.","method":"Recombinant protein treatment of C2C12 and primary satellite cell cultures, myotube counting, cell cycle analysis, apoptosis assays, washout experiment","journal":"Cell and tissue research","confidence":"Medium","confidence_rationale":"Tier 2 — recombinant protein gain-of-function with washout rescue, multiple cell systems","pmids":["18322704"],"is_preprint":false},{"year":2013,"finding":"SFRP1 is a direct target of miR-328 (validated by 3'UTR luciferase assay); miR-328 downregulates SFRP1 protein and activates Wnt signaling to promote glioma cell invasion.","method":"3'UTR luciferase reporter assay, miRNA mimic/inhibitor transfection, TCF/LEF reporter assay, Western blot for SFRP1, invasion assay","journal":"Neuro-oncology","confidence":"Medium","confidence_rationale":"Tier 2 — direct target validation by luciferase with functional rescue","pmids":["24305703"],"is_preprint":false},{"year":2013,"finding":"SOX2 directly binds Sfrp1/2 promoters in cancer-associated fibroblasts (CAFs) to drive their expression; inactivation of Sox2 or Sfrp1/2 in CAFs impairs induction of migration and invasion of colon cancer cells and reduces tumorigenicity in vivo. PKCζ deficiency generates this SOX2-dependent CAF population.","method":"ChIP-seq/ChIP for SOX2 at Sfrp1/2 promoters, Sox2/Sfrp1/2 KO in CAFs, coculture migration/invasion assays, in vivo tumorigenicity","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — direct ChIP evidence of SOX2 binding, loss-of-function in vivo with defined pathway","pmids":["33207226"],"is_preprint":false},{"year":2024,"finding":"SFRP1 modulates TGFβ1-induced lung fibroblast invasion and RHOA pathway activity; TGFβ1 downregulates SFRP1 in transitional fibroblasts and switches them to an invasive CTHRC1+ myofibroblast identity; loss-of-function studies confirm SFRP1 restrains this transition.","method":"Single-cell RNA-seq, spatial transcriptomics, genetic lineage tracing, TGFβ1 treatment, SFRP1 loss-of-function invasion assays, RHOA pathway readout","journal":"European respiratory journal","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (scRNA-seq, spatial, genetic lineage tracing, functional assays), human tissue validation","pmids":["38212077"],"is_preprint":false},{"year":2024,"finding":"Fibroblast-derived extracellular vesicles are enriched in SFRP1; vesicular SFRP1 promotes lung fibrosis by increasing WNT/β-catenin signaling and transitional cell markers (keratin 8) in alveolar type 2 cells; Sfrp1 deficiency inhibits the pro-fibrotic activity of fibroblast-derived EVs in vivo.","method":"Label-free proteomics of BALF-EVs, Sfrp1 KO mouse bleomycin fibrosis model, precision-cut lung slice assays, Western blot for β-catenin and Krt8","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 1-2 — proteomics identification, KO in vivo validation, mechanistic pathway established","pmids":["39315549"],"is_preprint":false},{"year":2021,"finding":"SFRP1 (largely astrocyte-derived) promotes and sustains microglial activation in neuroinflammation by upregulating components of the HIF-dependent inflammatory pathway and, to a lesser extent, NF-κB pathway; SFRP1 acts as an astrocyte-to-microglia amplifier of neuroinflammation.","method":"Mouse models of acute and chronic neuroinflammation, SFRP1 modulation (KO/overexpression), HIF pathway gene expression analysis, NF-κB readouts, astrocyte-conditioned medium experiments","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo mouse models with defined pathway readouts, single lab","pmids":["34569685"],"is_preprint":false},{"year":2015,"finding":"SFRP1 knockdown in MCF10A mammary epithelial cells activates Wnt signaling and increases CD24 expression (a Wnt target gene); both SFRP1 and TCF-4 act as repressors of Wnt signaling in breast tissue.","method":"siRNA knockdown, CD24-luciferase reporter assay with TCF/LEF site mutagenesis, Western blot, flow cytometry for CD24","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — reporter assay with binding-site mutagenesis plus KD, single lab","pmids":["16532032"],"is_preprint":false},{"year":2018,"finding":"sFRP1 protects H9c2 cardiomyoblasts from doxorubicin-induced apoptosis by inhibiting the Wnt/PCP-JNK pathway; in cardiomyocytes, intracellular sFRP1 interacts with PARP1 (identified by mass spectrometry co-IP); secreted sFRP1 has the opposite (cardiotoxic) effect by inhibiting canonical Wnt/β-catenin signaling.","method":"sFRP1 overexpression/knockdown in H9c2 cells, SP600125 (JNK inhibitor) treatment, mass spectrometry pull-down identifying PARP1 as binding partner, rat in vivo Dox model, Western blot for Wnt pathway components","journal":"Acta pharmacologica Sinica / Archives of toxicology","confidence":"Medium","confidence_rationale":"Tier 2-3 — MS-identified binding partner plus functional JNK pathway placement, biphasic model supported by multiple experiments","pmids":["32238888","30377735"],"is_preprint":false},{"year":2019,"finding":"HOTTIP lncRNA recruits DNMT3b to the SFRP1 promoter, inducing its methylation and silencing, thereby activating the Wnt signaling pathway in rheumatoid arthritis synovial fibroblasts; demonstrated by RNA pull-down, RIP, and ChIP assays.","method":"RNA pull-down, RIP, ChIP, methylation-specific PCR, bisulfite sequencing PCR, HOTTIP knockdown and SFRP1 overexpression in RASFs, rat RA model","journal":"Molecular therapy. Nucleic acids","confidence":"Medium","confidence_rationale":"Tier 2 — multiple chromatin/RNA interaction methods confirm DNMT3b recruitment mechanism","pmids":["31902746"],"is_preprint":false},{"year":2022,"finding":"WAY-316606, a small molecule inhibitor of SFRP1, activates neural stem cells in the adult human subventricular zone both in vitro and in vivo under homeostatic conditions, suggesting SFRP1 promotes progenitor quiescence through Wnt pathway antagonism.","method":"Single-cell RNA-seq of human SVZ, in vitro neural stem cell activation assay, in vivo WAY-316606 administration in mouse brain","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo pharmacological intervention with defined cellular outcome, human transcriptomic context","pmids":["35210419"],"is_preprint":false},{"year":2013,"finding":"AKT1 E17K mutation strongly upregulates SFRP1 expression in meningioma cells and HEK293 cells transfected with mutant AKT1E17K, but not wild-type AKT1, establishing SFRP1 as a downstream target of oncogenic AKT1E17K signaling.","method":"AKT1E17K transfection into HEK293 cells, immunohistochemistry for SFRP1 in 958 meningiomas, genotyping","journal":"Acta neuropathologica","confidence":"Medium","confidence_rationale":"Tier 3 — functional transfection with large clinical validation, single lab","pmids":["24096618"],"is_preprint":false},{"year":2009,"finding":"SFRP-1 and SFRP-2 are specifically expressed in osteoblasts in bone marrow; SFRP-1 (but not SFRP-2) reduces multipotent hematopoietic progenitor numbers and compromises long-term HSC repopulating activity in transplantation assays, differentiating their functional roles despite both inhibiting Wnt signaling in vitro.","method":"Immunostaining of bone marrow sections, in vitro CD34-KSL culture assays, long-term competitive repopulation transplantation assay in mice","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — clean in vitro and in vivo functional assays distinguishing SFRP1 from SFRP2","pmids":["19778523"],"is_preprint":false},{"year":2013,"finding":"Promoter hypermethylation of DKK1 and SFRP1 in systemic sclerosis fibroblasts is mediated by DNA methyltransferases; inhibition with 5-aza-2'-deoxycytidine reactivates DKK1 and SFRP1 transcription, inhibits canonical Wnt signaling (Axin2 mRNA, β-catenin staining) in vitro and in vivo, and ameliorates experimental fibrosis in bleomycin-challenged mice.","method":"Methylation-specific PCR of patient fibroblasts and PBMCs, 5-aza treatment in vitro and in bleomycin mouse model, Axin2 mRNA and β-catenin readouts","journal":"Annals of the rheumatic diseases","confidence":"Medium","confidence_rationale":"Tier 2 — causal epigenetic mechanism demonstrated in patient cells and in vivo model","pmids":["23698475"],"is_preprint":false},{"year":2022,"finding":"Loss of Sfrp1 depletes hair follicle stem cells (HFSCs) and accelerates the hair follicle cycle; restoration of HFSC pool in Sfrp1-/- mice is mediated through a BMP-AKT-GSK3β signaling cross-talk that downregulates β-catenin activity, a mechanism absent in Sfrp1+/- mice.","method":"Sfrp1-/- and Sfrp1+/- mouse models, flow cytometry for HFSC markers (Lgr5, Axin2), BMP receptor and GSK3β inhibitor treatment in keratinocytes, β-catenin activity assays","journal":"Stem cells","confidence":"Medium","confidence_rationale":"Tier 2 — KO genetics with pharmacological pathway dissection, single lab","pmids":["35689817"],"is_preprint":false},{"year":2020,"finding":"Sfrp1 and Sfrp5 double knockout disturbs trophoblast differentiation in the ectoplacental cone by hyperactivating canonical Wnt-β-catenin signaling, which exhausts trophoblast precursors and causes overabundance of giant cells at the expense of spongiotrophoblast cells via repression of Ascl2 expression.","method":"Sfrp1/Sfrp5 double KO mice, trophoblast-specific β-catenin exon-3 deletion mouse model, trophoblast stem cell lines, Ascl2 expression analysis","journal":"BMC biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple genetic models converge on Ascl2 as downstream effector","pmids":["33109217"],"is_preprint":false}],"current_model":"SFRP1 is a secreted glycoprotein that primarily antagonizes Wnt signaling by binding Wnt ligands upstream of GSK-3 to suppress β-catenin accumulation, but also signals independently through direct interaction with Frizzled-2 to guide axon growth via Gα/cyclic nucleotide pathways, activates non-canonical Wnt/PCP-Rac1 or Wnt/PCP-JNK pathways depending on context, undergoes epigenetic silencing via DNMT1/HDAC1 or EZH2-mediated promoter methylation/histone modification (recruited by HCV core protein or HOTTIP lncRNA), is transcriptionally regulated by Hedgehog-GLI and AKT1-E17K signaling, mediates cellular senescence through Wnt inhibition and Rb pathway activation, is packaged into fibroblast-derived extracellular vesicles to promote fibrosis via WNT/β-catenin in alveolar cells, and modulates diverse cell-type-specific processes including neuroinflammation (astrocyte-to-microglia via HIF pathway), Th17 differentiation (enhancing TGF-β/Smad2/3 signaling), hematopoietic stem cell homeostasis, and intraocular pressure regulation in the trabecular meshwork."},"narrative":{"teleology":[{"year":2003,"claim":"Establishing that SFRP1 modulates retinal cell fate and protects against apoptosis through β-catenin-independent mechanisms resolved that its function extends beyond simple canonical Wnt antagonism.","evidence":"Retroviral overexpression in chick retinal cultures with β-catenin/TCF reporters showing no change in canonical activity, plus GSK3β phosphorylation analysis; parallel ceramide-induced apoptosis assays with antisense inhibition and recombinant protein in fibroblasts","pmids":["12724355","14581477"],"confidence":"High","gaps":["Identity of the β-catenin-independent downstream effector in retinal progenitors not established","Whether anti-apoptotic activity requires Wnt binding or a separate receptor interaction unknown"]},{"year":2005,"claim":"Demonstrating that SFRP1 directly binds Frizzled-2 and signals through Gα proteins independently of Wnt inhibition established a receptor-mediated signaling mode for a secreted Wnt antagonist.","evidence":"Co-immunoprecipitation of SFRP1 with Fz2, dominant-negative Fz2 abolishes growth cone responses, pharmacological Gα and cyclic nucleotide manipulation in retinal ganglion cell axon assays","pmids":["16172602"],"confidence":"High","gaps":["Structural basis of SFRP1-Fz2 interaction not resolved","Whether Fz2-dependent signaling operates outside retinal neurons unknown"]},{"year":2006,"claim":"Three advances placed SFRP1 mechanistically: its site of Wnt pathway inhibition was mapped upstream of GSK-3 via epistasis, its transcription was shown to be directly driven by Hedgehog-Gli factors linking two major morphogen pathways, and compound knockouts revealed functional redundancy with SFRP2 in somitogenesis and Notch clock regulation.","evidence":"Purified recombinant SFRP1 blocking Wnt-3a but not LiCl-induced β-catenin; ChIP showing Gli1 at the SFRP1 promoter with siRNA rescue; Sfrp1/Sfrp2 double-KO mice with altered Lfng/Hes7 oscillations","pmids":["16425220","17035233","16467359"],"confidence":"High","gaps":["Whether SFRP1 sequesters Wnt ligands or competes for Frizzled binding to achieve upstream inhibition not distinguished","Mechanism by which SFRP1 loss alters Notch oscillation timing unclear"]},{"year":2008,"claim":"In vivo gain-of-function in the trabecular meshwork showed SFRP1 reduces aqueous outflow and raises intraocular pressure through Wnt/β-catenin suppression, establishing a physiological role in IOP regulation.","evidence":"Adenoviral SFRP1 overexpression in mouse eyes with dose-dependent IOP increase reversible by downstream Wnt inhibitor; ex vivo human eye perfusion","pmids":["18274669"],"confidence":"High","gaps":["Endogenous regulation of SFRP1 levels in glaucomatous TM not mechanistically defined","Whether other SFRPs contribute redundantly in TM unknown"]},{"year":2009,"claim":"Loss-of-function studies in mammary epithelial cells and hematopoietic stem cells revealed that SFRP1 restrains β-catenin-driven EMT/stemness and limits HSC self-renewal, defining its tumor-suppressive and stem cell regulatory functions.","evidence":"shRNA knockdown in 76N TERT cells elevating nuclear β-catenin, Cyclin D1, CD44high/CD24low population; recombinant SFRP1 reducing multipotent progenitors and long-term HSC repopulation in competitive transplantation","pmids":["19422694","19778523"],"confidence":"Medium","gaps":["Whether SFRP1 effects on HSC are cell-autonomous or niche-mediated not resolved","Downstream targets of β-catenin mediating CD44/CD24 switch not identified"]},{"year":2011,"claim":"Discovery that EZH2 epigenetically silences SFRP1 via H3K27 trimethylation at its promoter in rheumatoid arthritis fibroblasts established a histone modification-based mechanism for SFRP1 repression in disease.","evidence":"ChIP for histone marks at the SFRP1 promoter, EZH2 overexpression/siRNA in RA synovial fibroblasts, TNF-α induction via NF-κB/JNK","pmids":["21515604"],"confidence":"Medium","gaps":["Whether EZH2-mediated SFRP1 silencing occurs in cancers beyond RA fibroblasts not tested here","Quantitative relationship between H3K27me3 density and SFRP1 repression not defined"]},{"year":2012,"claim":"Three studies collectively established that SFRP1 mediates cellular senescence through Wnt inhibition and Rb pathway activation, promotes Th17 differentiation via TGF-β/Smad2/3 enhancement, and activates Wnt/PCP-Rac1 signaling in dopaminergic neuron development—revealing context-dependent pathway selection.","evidence":"Senescence assays with gain/loss-of-function and cancer mutant analysis; recombinant SFRP1 with TGF-β blocking epistasis during Th17 polarization; Sfrp1/Sfrp2 double-KO mice phenocopying Wnt5a-/- with Rac1 pathway activation","pmids":["22927647","22740051","22290867"],"confidence":"High","gaps":["How SFRP1 selectively activates PCP versus inhibiting canonical Wnt in different cell types not explained","Whether Th17-promoting activity is Wnt-dependent or a direct TGF-β pathway effect unresolved"]},{"year":2013,"claim":"Multiple studies converged on SFRP1 as a target of epigenetic silencing (DNMT1/HDAC1 by HCV core protein, promoter methylation in systemic sclerosis) and transcriptional regulation (SOX2 in cancer-associated fibroblasts, miR-328, AKT1-E17K), establishing the diverse upstream control mechanisms that modulate SFRP1 expression in disease.","evidence":"ChIP demonstrating DNMT1/HDAC1 recruitment to SFRP1 promoter by HCV core with bisulfite sequencing and xenograft rescue; 5-aza reactivation of SFRP1 in SSc fibroblasts; ChIP-seq for SOX2 at Sfrp1 promoter in CAFs; 3'UTR luciferase assay for miR-328; AKT1-E17K transfection with immunohistochemistry in meningiomas","pmids":["23770846","23698475","33107226","24305703","24096618"],"confidence":"High","gaps":["Relative contribution of DNA methylation versus histone modification to SFRP1 silencing in any single disease context not quantified","Whether SOX2-driven SFRP1 in CAFs acts via canonical or non-canonical Wnt on tumor cells unresolved"]},{"year":2014,"claim":"Sfrp1 knockout in obstructive nephropathy demonstrated that SFRP1 specifically restrains non-canonical Wnt/PCP-JNK signaling and EMT in kidney, without affecting canonical Wnt levels, clarifying pathway selectivity in a fibrotic context.","evidence":"Sfrp1 KO mouse UUO model with Western blot dissection of canonical versus JNK/c-Jun pathways, EMT markers, and apoptosis","pmids":["25253698"],"confidence":"High","gaps":["Whether SFRP1 directly binds Wnt5a or another non-canonical Wnt to suppress PCP-JNK not determined","Applicability to other organ fibrosis models not tested"]},{"year":2019,"claim":"HOTTIP lncRNA was shown to recruit DNMT3b to the SFRP1 promoter for methylation-mediated silencing, and SFRP1 was identified as an epigenetic gatekeeper maintaining periodontal ligament progenitor identity via H3K4me3 marks, expanding the repertoire of epigenetic regulators converging on SFRP1.","evidence":"RNA pull-down and RIP for HOTTIP-DNMT3b interaction, ChIP and bisulfite sequencing at SFRP1 promoter in RA fibroblasts; ChIP for H3K4me3/H3K27me3 comparing PDL versus alveolar bone progenitors with WAY-316606 inhibitor","pmids":["31902746","31215318"],"confidence":"Medium","gaps":["Whether HOTTIP-DNMT3b mechanism operates in tissues beyond RA synovium unknown","Whether SFRP1-dependent mineralization suppression requires canonical Wnt inhibition specifically not tested"]},{"year":2020,"claim":"Sfrp1/Sfrp5 double knockout revealed that SFRP1 restrains canonical Wnt-β-catenin to prevent premature trophoblast differentiation and giant cell overproduction, acting through Ascl2 repression.","evidence":"Double-KO mice and trophoblast-specific β-catenin gain-of-function model converging on Ascl2 downregulation","pmids":["33109217"],"confidence":"Medium","gaps":["Individual contribution of SFRP1 versus SFRP5 not separable due to redundancy","Whether Ascl2 is a direct or indirect Wnt target in trophoblasts unresolved"]},{"year":2021,"claim":"SFRP1 was identified as an astrocyte-derived amplifier of microglial neuroinflammation acting through the HIF pathway, establishing a paracrine non-Wnt signaling role in the CNS.","evidence":"SFRP1 KO/overexpression in mouse neuroinflammation models with HIF pathway gene expression and conditioned medium experiments","pmids":["34569685"],"confidence":"Medium","gaps":["Whether SFRP1 directly activates HIF signaling or acts through intermediate Wnt-dependent steps unclear","Receptor on microglia mediating SFRP1 response not identified"]},{"year":2022,"claim":"SFRP1 was shown to maintain quiescence of hair follicle stem cells and adult neural stem cells; its loss depletes HFSCs via a BMP-AKT-GSK3β cross-talk mechanism and its pharmacological inhibition activates human SVZ neural progenitors.","evidence":"Sfrp1 KO mice with HFSC flow cytometry and BMP/GSK3β inhibitor epistasis; WAY-316606 administration in vivo with scRNA-seq of human SVZ","pmids":["35689817","35210419"],"confidence":"Medium","gaps":["Whether SFRP1 maintains quiescence solely through canonical Wnt suppression or additional pathways in each stem cell niche unresolved","Long-term consequences of pharmacological SFRP1 inhibition on stem cell exhaustion not assessed"]},{"year":2024,"claim":"Two studies established SFRP1 as a context-dependent modulator of lung fibrosis: it restrains TGFβ1-driven fibroblast-to-myofibroblast transition via RHOA, yet when packaged in fibroblast-derived extracellular vesicles it paradoxically activates WNT/β-catenin in alveolar epithelial cells to promote fibrosis.","evidence":"scRNA-seq, spatial transcriptomics, and genetic lineage tracing of fibroblast transitions with SFRP1 loss-of-function; label-free proteomics of BALF-EVs with Sfrp1 KO bleomycin model and β-catenin/Krt8 readouts in precision-cut lung slices","pmids":["38212077","39315549"],"confidence":"High","gaps":["How vesicular SFRP1 activates rather than inhibits Wnt/β-catenin in recipient alveolar cells remains mechanistically unexplained","Whether the fibroblast-intrinsic and EV-mediated roles are simultaneously operative in human IPF not demonstrated"]},{"year":null,"claim":"How SFRP1 switches between canonical Wnt antagonism, PCP pathway activation, and Frizzled-dependent Wnt-independent signaling in different cellular contexts remains the central unresolved question.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of SFRP1 bound to Wnt ligands versus Frizzled receptors","Concentration-dependent pathway switching mechanism not reconstituted","How vesicular versus soluble SFRP1 achieves opposite effects on β-catenin not explained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,5,6,8,11]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,7,21]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[2,5,6,9,10,15,20]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[20]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,2,3,5,7,8,11,20,22,29,30]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[1,4,7,30]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[6,9]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[12,13,24,28]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[15,21]}],"complexes":[],"partners":["FZD2","SFRP2","WNT3A","PARP1","DNMT1","HDAC1","EZH2","SOX2"],"other_free_text":[]},"mechanistic_narrative":"SFRP1 is a secreted Wnt antagonist that controls cell fate, proliferation, and tissue homeostasis across numerous developmental and adult contexts by modulating both canonical and non-canonical Wnt signaling, as well as Wnt-independent pathways. As a secreted glycoprotein, SFRP1 directly binds Wnt ligands upstream of GSK-3 to inhibit β-catenin accumulation [PMID:16425220], and independently engages Frizzled-2 receptors to guide axon growth through Gα-protein and cyclic nucleotide signaling [PMID:16172602]; at low concentrations it activates the Wnt/PCP-Rac1 pathway in dopaminergic neurons [PMID:22290867] and restrains Wnt/PCP-JNK signaling in kidney and heart [PMID:25253698, PMID:30377735]. SFRP1 is transcriptionally regulated by Hedgehog-Gli [PMID:17035233], SOX2 [PMID:33107226], and oncogenic AKT1-E17K [PMID:24096618], and is frequently epigenetically silenced through promoter DNA methylation mediated by DNMT1/HDAC1 or DNMT3b recruitment (by HCV core protein or HOTTIP lncRNA) and by EZH2-dependent histone methylation [PMID:23770846, PMID:31902746, PMID:21515604]. Functionally, SFRP1 mediates cellular senescence via Wnt inhibition and Rb pathway activation [PMID:22927647], maintains stem cell quiescence in hair follicles and the neural subventricular zone [PMID:35689817, PMID:35210419], regulates trophoblast differentiation and somitogenesis through redundancy with other SFRPs [PMID:33109217, PMID:16467359], and when packaged into fibroblast-derived extracellular vesicles paradoxically promotes lung fibrosis by activating WNT/β-catenin in alveolar epithelial cells [PMID:39315549]."},"prefetch_data":{"uniprot":{"accession":"Q8N474","full_name":"Secreted frizzled-related protein 1","aliases":["Secreted apoptosis-related protein 2","SARP-2"],"length_aa":314,"mass_kda":35.4,"function":"Soluble frizzled-related proteins (sFRPS) function as modulators of Wnt signaling through direct interaction with Wnts. They have a role in regulating cell growth and differentiation in specific cell types. SFRP1 decreases intracellular beta-catenin levels (By similarity). Has antiproliferative effects on vascular cells, in vitro and in vivo, and can induce, in vivo, an angiogenic response. In vascular cell cycle, delays the G1 phase and entry into the S phase (By similarity). In kidney development, inhibits tubule formation and bud growth in metanephroi (By similarity). Inhibits WNT1/WNT4-mediated TCF-dependent transcription","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q8N474/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SFRP1","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SFRP1","total_profiled":1310},"omim":[{"mim_id":"620847","title":"BONE MORPHOGENETIC PROTEIN 8A; BMP8A","url":"https://www.omim.org/entry/620847"},{"mim_id":"619640","title":"LYSINE DEMETHYLASE 7A; KDM7A","url":"https://www.omim.org/entry/619640"},{"mim_id":"615372","title":"MICRO RNA 1260B; MIR1260B","url":"https://www.omim.org/entry/615372"},{"mim_id":"606570","title":"SECRETED FRIZZLED-RELATED PROTEIN 4; SFRP4","url":"https://www.omim.org/entry/606570"},{"mim_id":"605189","title":"DICKKOPF WNT SIGNALING PATHWAY INHIBITOR 1; DKK1","url":"https://www.omim.org/entry/605189"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"choroid 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frizzled-related protein 1 (SFRP1) promoter downregulates Wnt/β-catenin activity in keloids.","date":"2018","source":"Journal of molecular histology","url":"https://pubmed.ncbi.nlm.nih.gov/29455276","citation_count":26,"is_preprint":false},{"pmid":"39315549","id":"PMC_39315549","title":"Fibroblast-derived extracellular vesicles contain SFRP1 and mediate pulmonary fibrosis.","date":"2024","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/39315549","citation_count":25,"is_preprint":false},{"pmid":"25652468","id":"PMC_25652468","title":"DNA methylation level of OPCML and SFRP1: a potential diagnostic biomarker of cholangiocarcinoma.","date":"2015","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/25652468","citation_count":25,"is_preprint":false},{"pmid":"19778523","id":"PMC_19778523","title":"Wnt modulators, SFRP-1, and SFRP-2 are expressed in osteoblasts and differentially regulate hematopoietic stem cells.","date":"2009","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/19778523","citation_count":25,"is_preprint":false},{"pmid":"33282723","id":"PMC_33282723","title":"LINC01089 Inhibits Tumorigenesis and Epithelial-Mesenchymal Transition of Non-small Cell Lung Cancer via the miR-27a/SFRP1/Wnt/β-catenin Axis.","date":"2020","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/33282723","citation_count":25,"is_preprint":false},{"pmid":"32238888","id":"PMC_32238888","title":"sFRP1 protects H9c2 cardiac myoblasts from doxorubicin-induced apoptosis by inhibiting the Wnt/PCP-JNK pathway.","date":"2020","source":"Acta pharmacologica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/32238888","citation_count":24,"is_preprint":false},{"pmid":"35795672","id":"PMC_35795672","title":"SFRP1 Negatively Modulates Pyroptosis of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis: A Review.","date":"2022","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/35795672","citation_count":24,"is_preprint":false},{"pmid":"23441124","id":"PMC_23441124","title":"Tear levels of SFRP1 are significantly reduced in keratoconus patients.","date":"2013","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/23441124","citation_count":24,"is_preprint":false},{"pmid":"21567192","id":"PMC_21567192","title":"Epigenetic inactivation of the SFRP1 gene in esophageal squamous cell carcinoma.","date":"2011","source":"Digestive diseases and sciences","url":"https://pubmed.ncbi.nlm.nih.gov/21567192","citation_count":23,"is_preprint":false},{"pmid":"23261541","id":"PMC_23261541","title":"Reduced expression of Sfrp1 during chondrogenesis and in articular chondrocytes correlates with osteoarthritis in STR/ort mice.","date":"2012","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/23261541","citation_count":23,"is_preprint":false},{"pmid":"19543515","id":"PMC_19543515","title":"Differential methylation pattern of ID4, SFRP1, and SHP1 between acute myeloid leukemia and chronic myeloid leukemia.","date":"2009","source":"Journal of Korean medical science","url":"https://pubmed.ncbi.nlm.nih.gov/19543515","citation_count":23,"is_preprint":false},{"pmid":"20162454","id":"PMC_20162454","title":"Loss of SFRP1 expression is associated with aberrant beta-catenin distribution and tumor progression in mucoepidermoid carcinoma of salivary glands.","date":"2010","source":"Annals of surgical oncology","url":"https://pubmed.ncbi.nlm.nih.gov/20162454","citation_count":22,"is_preprint":false},{"pmid":"28230864","id":"PMC_28230864","title":"Dicer promotes tumorigenesis by translocating to nucleus to promote SFRP1 promoter methylation in cholangiocarcinoma cells.","date":"2017","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/28230864","citation_count":22,"is_preprint":false},{"pmid":"31072914","id":"PMC_31072914","title":"Silencing microRNA-27a inhibits proliferation and invasion of human osteosarcoma cells through the SFRP1-dependent Wnt/β-catenin signaling pathway.","date":"2019","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/31072914","citation_count":21,"is_preprint":false},{"pmid":"30576962","id":"PMC_30576962","title":"Methylation status of SFRP1, SFRP2, RASSF1A, RARβ and DAPK1 genes in patients with oral squamous cell carcinoma.","date":"2018","source":"Archives of oral biology","url":"https://pubmed.ncbi.nlm.nih.gov/30576962","citation_count":21,"is_preprint":false},{"pmid":"16410684","id":"PMC_16410684","title":"The transcripts of SFRP1,CEP63 and EIF4G2 genes are frequently downregulated in transitional cell carcinomas of the bladder.","date":"2006","source":"Oncology","url":"https://pubmed.ncbi.nlm.nih.gov/16410684","citation_count":21,"is_preprint":false},{"pmid":"31928951","id":"PMC_31928951","title":"SFRP1 in Skin Tumor Initiation and Cancer Stem Cell Regulation with Potential Implications in Epithelial Cancers.","date":"2020","source":"Stem cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/31928951","citation_count":20,"is_preprint":false},{"pmid":"11731256","id":"PMC_11731256","title":"Place- and time-dependent expression of mouse sFRP-1 during development of the cerebral neocortex.","date":"2001","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/11731256","citation_count":20,"is_preprint":false},{"pmid":"35689817","id":"PMC_35689817","title":"BMP-AKT-GSK3β Signaling Restores Hair Follicle Stem Cells Decrease Associated with Loss of Sfrp1.","date":"2022","source":"Stem cells (Dayton, Ohio)","url":"https://pubmed.ncbi.nlm.nih.gov/35689817","citation_count":19,"is_preprint":false},{"pmid":"32965161","id":"PMC_32965161","title":"microRNA27a-3p mediates reduction of the Wnt antagonist sFRP-1 in systemic sclerosis.","date":"2020","source":"Epigenetics","url":"https://pubmed.ncbi.nlm.nih.gov/32965161","citation_count":19,"is_preprint":false},{"pmid":"16567562","id":"PMC_16567562","title":"Role of secreted frizzled-related protein 1 (SFRP1) in wound healing.","date":"2006","source":"Journal of dental research","url":"https://pubmed.ncbi.nlm.nih.gov/16567562","citation_count":18,"is_preprint":false},{"pmid":"11744393","id":"PMC_11744393","title":"Expression of Ngn1, Ngn2, Cash1, Gsh2 and Sfrp1 in the developing chick telencephalon.","date":"2002","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/11744393","citation_count":18,"is_preprint":false},{"pmid":"30153824","id":"PMC_30153824","title":"Sfrp1 attenuates TAC-induced cardiac dysfunction by inhibiting Wnt signaling pathway- mediated myocardial apoptosis in mice.","date":"2018","source":"Lipids in health and disease","url":"https://pubmed.ncbi.nlm.nih.gov/30153824","citation_count":18,"is_preprint":false},{"pmid":"36309688","id":"PMC_36309688","title":"Nanoparticle-mediated selective Sfrp-1 silencing enhances bone density in osteoporotic mice.","date":"2022","source":"Journal of nanobiotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/36309688","citation_count":17,"is_preprint":false},{"pmid":"29146058","id":"PMC_29146058","title":"Methylation-associated silencing of SFRP1 gene in high-grade serous ovarian carcinomas.","date":"2017","source":"Annals of diagnostic pathology","url":"https://pubmed.ncbi.nlm.nih.gov/29146058","citation_count":17,"is_preprint":false},{"pmid":"33738141","id":"PMC_33738141","title":"Oncogenic miR-27a delivered by exosomes binds to SFRP1 and promotes angiogenesis in renal clear cell carcinoma.","date":"2020","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/33738141","citation_count":17,"is_preprint":false},{"pmid":"33109217","id":"PMC_33109217","title":"Hyperactivated Wnt-β-catenin signaling in the absence of sFRP1 and sFRP5 disrupts trophoblast differentiation through repression of Ascl2.","date":"2020","source":"BMC biology","url":"https://pubmed.ncbi.nlm.nih.gov/33109217","citation_count":17,"is_preprint":false},{"pmid":"22248913","id":"PMC_22248913","title":"SFRP1 promoter methylation and expression in human trabecular meshwork cells.","date":"2012","source":"Experimental eye research","url":"https://pubmed.ncbi.nlm.nih.gov/22248913","citation_count":16,"is_preprint":false},{"pmid":"16670620","id":"PMC_16670620","title":"Aberrant methylation of secreted apoptosis-related protein 2 (SARP2) in pure pancreatic juice in diagnosis of pancreatic neoplasms.","date":"2006","source":"Pancreas","url":"https://pubmed.ncbi.nlm.nih.gov/16670620","citation_count":16,"is_preprint":false},{"pmid":"37203392","id":"PMC_37203392","title":"Exosomal microRNA‑4516, microRNA‑203 and SFRP1 are potential biomarkers of acute myocardial infarction.","date":"2023","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/37203392","citation_count":16,"is_preprint":false},{"pmid":"36259450","id":"PMC_36259450","title":"Hsa_circ_0001445 works as a cancer suppressor via miR-576-5p/SFRP1 axis regulation in ovarian cancer.","date":"2022","source":"Cancer medicine","url":"https://pubmed.ncbi.nlm.nih.gov/36259450","citation_count":16,"is_preprint":false},{"pmid":"35507080","id":"PMC_35507080","title":"Disruption of ZNF334 promotes triple-negative breast carcinoma malignancy through the SFRP1/ Wnt/β-catenin signaling axis.","date":"2022","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/35507080","citation_count":16,"is_preprint":false},{"pmid":"28077379","id":"PMC_28077379","title":"Effects of supplementation with nondigestible carbohydrates on fecal calprotectin and on epigenetic regulation of SFRP1 expression in the large-bowel mucosa of healthy individuals.","date":"2017","source":"The American journal of clinical nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/28077379","citation_count":16,"is_preprint":false},{"pmid":"30377735","id":"PMC_30377735","title":"sFRP1 has a biphasic effect on doxorubicin-induced cardiotoxicity in a cellular location-dependent manner in NRCMs and Rats.","date":"2018","source":"Archives of toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/30377735","citation_count":16,"is_preprint":false},{"pmid":"16077939","id":"PMC_16077939","title":"Comparative genomics on SFRP1 orthologs.","date":"2005","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/16077939","citation_count":15,"is_preprint":false},{"pmid":"25469261","id":"PMC_25469261","title":"Circulating SFRP1 promoter methylation status in gastric adenocarcinoma and esophageal square cell carcinoma.","date":"2014","source":"Biomedical reports","url":"https://pubmed.ncbi.nlm.nih.gov/25469261","citation_count":15,"is_preprint":false},{"pmid":"15638044","id":"PMC_15638044","title":"Follistatin-related protein gene (FRP) is expressed in the synovial tissues of rheumatoid arthritis, but its polymorphisms are not associated with genetic susceptibility.","date":"2004","source":"Clinical and experimental rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/15638044","citation_count":15,"is_preprint":false},{"pmid":"34091845","id":"PMC_34091845","title":"A novel identified circ-ANKHD1 targets the miR-27a-3p/SFRP1 signaling pathway and modulates the apoptosis of granulosa cells.","date":"2021","source":"Environmental science and pollution research international","url":"https://pubmed.ncbi.nlm.nih.gov/34091845","citation_count":15,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":53624,"output_tokens":7743,"usd":0.138509},"stage2":{"model":"claude-opus-4-6","input_tokens":11619,"output_tokens":4569,"usd":0.25848},"total_usd":0.396989,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"SFRP1 directly binds Frizzled-2 (Fz2) receptor and guides retinal ganglion cell axon growth through a Wnt-inhibition-independent mechanism requiring Gα protein activation, protein synthesis/degradation, and modulation by cyclic nucleotide levels; interference with Fz2 expression abolishes growth cone responses to SFRP1.\",\n      \"method\": \"Chick and Xenopus retinal ganglion cell axon growth assays, co-immunoprecipitation of SFRP1 with Fz2, dominant-negative receptor interference, pharmacological manipulation of Gα proteins and cyclic nucleotides\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding shown, multiple orthogonal functional assays, receptor interference rescue\",\n      \"pmids\": [\"16172602\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SFRP1 promotes retinal ganglion cell and cone photoreceptor generation while decreasing amacrine cell numbers via a β-catenin-independent mechanism involving phosphorylation-dependent inhibition of GSK3β; SFRP1 does not modify basal β-catenin transcriptional activity in retinal cells.\",\n      \"method\": \"Retroviral overexpression in chick retinal cultures, β-catenin/TCF luciferase reporter assay, dominant-negative GSK3β phenocopy, Western blot for pGSK3β\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods, functional rescue, mechanistic pathway placement\",\n      \"pmids\": [\"12724355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Sfrp1 and Sfrp2 directly interact with Wnt ligands to inhibit Wnt-3a-induced β-catenin accumulation in a GSK-3-dependent manner (they cannot block LiCl-induced β-catenin accumulation), demonstrating their site of action is upstream of GSK-3.\",\n      \"method\": \"In vitro Wnt-3a inhibition assay in L cells, LiCl epistasis experiment, purified recombinant Sfrp proteins\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified proteins plus epistasis experiment\",\n      \"pmids\": [\"16425220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Gli1 and Gli2 transcription factors of the Hedgehog signaling pathway directly regulate sFRP1 transcription; chromatin immunoprecipitation demonstrates Gli1 binds the sFRP1 promoter, and sFRP1 in turn suppresses Wnt-1-mediated β-catenin accumulation, establishing sFRP1 as a mechanistic link between Hh and Wnt pathway cross-talk.\",\n      \"method\": \"ChIP assay, ectopic Gli1 expression in gastric cancer cells, SMO antagonist (KAAD-cyclopamine) treatment, β-catenin accumulation assay, sFRP1 siRNA rescue\",\n      \"journal\": \"Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ChIP plus functional epistasis with inhibitor and siRNA rescue, replicated across cell lines\",\n      \"pmids\": [\"17035233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Sfrp1 and Sfrp2 double knockout mice display anterior-posterior axis shortening and abnormal somite segmentation associated with altered Notch signaling oscillations (Lfng and Hes7 expression); single knockouts have no phenotype, indicating functional redundancy. Aberrant presomitic mesoderm cell migration also contributes.\",\n      \"method\": \"Mouse double-knockout genetics, in situ hybridization for segmentation clock genes (Lfng, Hes7), histological analysis of somites\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean double-KO mouse model with specific molecular readout of Notch clock\",\n      \"pmids\": [\"16467359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Elevated sFRP1 in the trabecular meshwork (TM) inhibits Wnt signaling (reduces β-catenin) and decreases aqueous outflow facility, causing elevated intraocular pressure; adenoviral overexpression of sFRP1 in mouse eyes increases IOP in a titer-dependent manner reversible by a downstream Wnt signaling inhibitor.\",\n      \"method\": \"Ex vivo human eye perfusion culture with recombinant sFRP1, intravitreal adenoviral injection in mice, IOP measurement, β-catenin immunostaining in TM\",\n      \"journal\": \"Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo gain-of-function with pharmacological rescue, ex vivo human tissue validation\",\n      \"pmids\": [\"18274669\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SFRP1 is oversecreted upon cellular senescence (DNA damage or oxidative stress) and is both necessary and sufficient for senescence induction; it acts through inhibition of Wnt signaling and activation of the retinoblastoma (Rb) pathway; cancer-associated SFRP1 mutants are defective for senescence induction.\",\n      \"method\": \"Knockdown and overexpression in human cells, stress-induced senescence assays (SA-β-gal, growth arrest), Rb pathway analysis, cancer mutant functional testing\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss- and gain-of-function with multiple readouts, mutant analysis provides mechanistic detail\",\n      \"pmids\": [\"22927647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SFRP1 and SFRP2 activate the Wnt/planar-cell-polarity (PCP)/Rac1 pathway in dopaminergic neurons; compound Sfrp1/Sfrp2 double knockout mice display a Wnt/PCP phenotype (AP shortening of VM, lateral expansion of Shh domain, accumulation of Nurr1+ precursors) similar to Wnt5a-/- mice; low/medium concentrations of sFRP1 promote DA differentiation mimicking Wnt5a.\",\n      \"method\": \"Sfrp1/Sfrp2 compound knockout mouse genetics, primary VM cultures, embryonic stem cell differentiation assays, Rac1 pathway activation assays\",\n      \"journal\": \"Stem cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — double-KO mouse with specific pathway phenotype, in vitro mechanistic validation\",\n      \"pmids\": [\"22290867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Sfrp1 deficiency in a mouse model of obstructive nephropathy increases myofibroblast markers (αSMA), promotes epithelial-to-mesenchymal transition (decreased E-cadherin, increased vimentin), and elevates phospho-c-Jun/JNK (non-canonical Wnt/PCP pathway) without affecting canonical Wnt signaling levels; also increases apoptosis in obstructed kidneys.\",\n      \"method\": \"Sfrp1 knockout mouse UUO model, Western blot for EMT markers and JNK/pJNK, histology, TUNEL apoptosis assay\",\n      \"journal\": \"Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO model with defined molecular pathway dissection (canonical vs non-canonical)\",\n      \"pmids\": [\"25253698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SFRP1 protects fibroblasts from ceramide-induced apoptosis by regulating p53, caspase-3, caspase-9, and BIK expression; inhibition of endogenous SFRP1 increases cell death while exogenous SFRP1 reduces apoptosis in vitro and in vivo.\",\n      \"method\": \"Antisense inhibition and exogenous recombinant protein treatment in PDL and gingival fibroblasts, apoptosis assays (TUNEL, caspase activity), in vivo dermal fibroblast model\",\n      \"journal\": \"Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss and gain of function with molecular readouts, single lab\",\n      \"pmids\": [\"14581477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"SFRP1 treatment of prostatic epithelial cells increases proliferation, decreases apoptosis, and decreases canonical Wnt/β-catenin signaling; SFRP1 treatment of developing prostates in culture increases organ growth, suggesting a paracrine role from tumor stroma promoting epithelial proliferation.\",\n      \"method\": \"Recombinant SFRP1 treatment of prostatic epithelial cell lines and organ culture, proliferation assays, apoptosis assays, β-catenin signaling readout, in vivo proliferation\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional readouts, but single lab and mechanistic pathway not fully resolved\",\n      \"pmids\": [\"16288033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SFRP1 knockdown in non-malignant mammary epithelial cells raises nuclear β-catenin, activates Wnt signaling, increases Cyclin D1, promotes partial EMT, confers resistance to anoikis, increases migration and invasion, and generates a CD44high/CD24low population.\",\n      \"method\": \"shRNA knockdown in 76N TERT cells, β-catenin fractionation, invasion/migration assays, flow cytometry for CD44/CD24 markers, anchorage-independent growth assay\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with multiple orthogonal phenotypic readouts, single lab\",\n      \"pmids\": [\"19422694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"EZH2 (histone methyltransferase) is overexpressed in rheumatoid arthritis synovial fibroblasts, is induced by TNF-α via NF-κB and JNK pathways, and epigenetically silences SFRP1 by histone methylation at its promoter; SFRP1 promoter occupation by activating vs. silencing histone marks correlates with expression levels.\",\n      \"method\": \"ChIP assay for histone marks at SFRP1 promoter, EZH2 overexpression and siRNA knockdown, qRT-PCR, Western blot, kinase inhibitor experiments, reporter assays\",\n      \"journal\": \"Annals of the rheumatic diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP demonstrates direct epigenetic regulation, functional perturbations in patient-derived cells\",\n      \"pmids\": [\"21515604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"HCV core protein silences SFRP1 by recruiting DNMT1 and HDAC1 to the SFRP1 promoter, causing CpG hypermethylation and repression of acetyl-H3 binding; SFRP1 silencing activates Wnt/β-catenin (c-Myc, cyclin D1) and induces EMT; restoring SFRP1 or knocking down DNMT1 reverses these effects in vivo and in vitro.\",\n      \"method\": \"ChIP for DNMT1, HDAC1, acetyl-H3 at SFRP1 promoter; bisulfite sequencing; DNMT1 knockdown; SFRP1 overexpression; xenograft mouse model; Western blot for EMT markers and β-catenin targets\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — ChIP demonstrates direct promoter recruitment, multiple orthogonal methods, in vivo validation\",\n      \"pmids\": [\"23770846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SFRP1 maintains the non-mineralized state of periodontal ligament (PDL) progenitors; SFRP1 promoter carries H3K4me3 active marks in PDL fibroblasts but not in alveolar bone progenitors; inhibition or knockdown of SFRP1 promotes PDL mineralization and activates RUNX2/SP7 via H3K4me3-mediated transcription.\",\n      \"method\": \"ChIP for H3K4me3/H3K27me3, small molecule inhibitor (WAY-316606), siRNA knockdown, mineralization assays, Western blot in PDL vs AB progenitors\",\n      \"journal\": \"Stem cells and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP plus functional KD/inhibitor experiments in defined cell populations\",\n      \"pmids\": [\"31215318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"sFRP1 promotes human Th17 cell differentiation by enhancing TGF-β/Smad2/3 phosphorylation in CD4+ T cells; blocking TGF-β signaling abolishes the Th17-promoting activity of sFRP1.\",\n      \"method\": \"Recombinant sFRP1 addition during TCR-mediated stimulation and Th17-differentiation conditions, IL-17 ELISA, phospho-Smad2/3 Western blot, TGF-β blocking antibody epistasis\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway placed by epistasis, multiple readouts, single lab\",\n      \"pmids\": [\"22740051\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Recombinant Sfrp1 or Sfrp2 inhibit myoblast differentiation (myotube formation) without affecting cell cycle or apoptosis; cells must be treated during proliferation for maximal effect, and removing Sfrp restores normal differentiation.\",\n      \"method\": \"Recombinant protein treatment of C2C12 and primary satellite cell cultures, myotube counting, cell cycle analysis, apoptosis assays, washout experiment\",\n      \"journal\": \"Cell and tissue research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — recombinant protein gain-of-function with washout rescue, multiple cell systems\",\n      \"pmids\": [\"18322704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SFRP1 is a direct target of miR-328 (validated by 3'UTR luciferase assay); miR-328 downregulates SFRP1 protein and activates Wnt signaling to promote glioma cell invasion.\",\n      \"method\": \"3'UTR luciferase reporter assay, miRNA mimic/inhibitor transfection, TCF/LEF reporter assay, Western blot for SFRP1, invasion assay\",\n      \"journal\": \"Neuro-oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct target validation by luciferase with functional rescue\",\n      \"pmids\": [\"24305703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SOX2 directly binds Sfrp1/2 promoters in cancer-associated fibroblasts (CAFs) to drive their expression; inactivation of Sox2 or Sfrp1/2 in CAFs impairs induction of migration and invasion of colon cancer cells and reduces tumorigenicity in vivo. PKCζ deficiency generates this SOX2-dependent CAF population.\",\n      \"method\": \"ChIP-seq/ChIP for SOX2 at Sfrp1/2 promoters, Sox2/Sfrp1/2 KO in CAFs, coculture migration/invasion assays, in vivo tumorigenicity\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct ChIP evidence of SOX2 binding, loss-of-function in vivo with defined pathway\",\n      \"pmids\": [\"33207226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SFRP1 modulates TGFβ1-induced lung fibroblast invasion and RHOA pathway activity; TGFβ1 downregulates SFRP1 in transitional fibroblasts and switches them to an invasive CTHRC1+ myofibroblast identity; loss-of-function studies confirm SFRP1 restrains this transition.\",\n      \"method\": \"Single-cell RNA-seq, spatial transcriptomics, genetic lineage tracing, TGFβ1 treatment, SFRP1 loss-of-function invasion assays, RHOA pathway readout\",\n      \"journal\": \"European respiratory journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (scRNA-seq, spatial, genetic lineage tracing, functional assays), human tissue validation\",\n      \"pmids\": [\"38212077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Fibroblast-derived extracellular vesicles are enriched in SFRP1; vesicular SFRP1 promotes lung fibrosis by increasing WNT/β-catenin signaling and transitional cell markers (keratin 8) in alveolar type 2 cells; Sfrp1 deficiency inhibits the pro-fibrotic activity of fibroblast-derived EVs in vivo.\",\n      \"method\": \"Label-free proteomics of BALF-EVs, Sfrp1 KO mouse bleomycin fibrosis model, precision-cut lung slice assays, Western blot for β-catenin and Krt8\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — proteomics identification, KO in vivo validation, mechanistic pathway established\",\n      \"pmids\": [\"39315549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SFRP1 (largely astrocyte-derived) promotes and sustains microglial activation in neuroinflammation by upregulating components of the HIF-dependent inflammatory pathway and, to a lesser extent, NF-κB pathway; SFRP1 acts as an astrocyte-to-microglia amplifier of neuroinflammation.\",\n      \"method\": \"Mouse models of acute and chronic neuroinflammation, SFRP1 modulation (KO/overexpression), HIF pathway gene expression analysis, NF-κB readouts, astrocyte-conditioned medium experiments\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo mouse models with defined pathway readouts, single lab\",\n      \"pmids\": [\"34569685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SFRP1 knockdown in MCF10A mammary epithelial cells activates Wnt signaling and increases CD24 expression (a Wnt target gene); both SFRP1 and TCF-4 act as repressors of Wnt signaling in breast tissue.\",\n      \"method\": \"siRNA knockdown, CD24-luciferase reporter assay with TCF/LEF site mutagenesis, Western blot, flow cytometry for CD24\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reporter assay with binding-site mutagenesis plus KD, single lab\",\n      \"pmids\": [\"16532032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"sFRP1 protects H9c2 cardiomyoblasts from doxorubicin-induced apoptosis by inhibiting the Wnt/PCP-JNK pathway; in cardiomyocytes, intracellular sFRP1 interacts with PARP1 (identified by mass spectrometry co-IP); secreted sFRP1 has the opposite (cardiotoxic) effect by inhibiting canonical Wnt/β-catenin signaling.\",\n      \"method\": \"sFRP1 overexpression/knockdown in H9c2 cells, SP600125 (JNK inhibitor) treatment, mass spectrometry pull-down identifying PARP1 as binding partner, rat in vivo Dox model, Western blot for Wnt pathway components\",\n      \"journal\": \"Acta pharmacologica Sinica / Archives of toxicology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — MS-identified binding partner plus functional JNK pathway placement, biphasic model supported by multiple experiments\",\n      \"pmids\": [\"32238888\", \"30377735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HOTTIP lncRNA recruits DNMT3b to the SFRP1 promoter, inducing its methylation and silencing, thereby activating the Wnt signaling pathway in rheumatoid arthritis synovial fibroblasts; demonstrated by RNA pull-down, RIP, and ChIP assays.\",\n      \"method\": \"RNA pull-down, RIP, ChIP, methylation-specific PCR, bisulfite sequencing PCR, HOTTIP knockdown and SFRP1 overexpression in RASFs, rat RA model\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple chromatin/RNA interaction methods confirm DNMT3b recruitment mechanism\",\n      \"pmids\": [\"31902746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"WAY-316606, a small molecule inhibitor of SFRP1, activates neural stem cells in the adult human subventricular zone both in vitro and in vivo under homeostatic conditions, suggesting SFRP1 promotes progenitor quiescence through Wnt pathway antagonism.\",\n      \"method\": \"Single-cell RNA-seq of human SVZ, in vitro neural stem cell activation assay, in vivo WAY-316606 administration in mouse brain\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo pharmacological intervention with defined cellular outcome, human transcriptomic context\",\n      \"pmids\": [\"35210419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AKT1 E17K mutation strongly upregulates SFRP1 expression in meningioma cells and HEK293 cells transfected with mutant AKT1E17K, but not wild-type AKT1, establishing SFRP1 as a downstream target of oncogenic AKT1E17K signaling.\",\n      \"method\": \"AKT1E17K transfection into HEK293 cells, immunohistochemistry for SFRP1 in 958 meningiomas, genotyping\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional transfection with large clinical validation, single lab\",\n      \"pmids\": [\"24096618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SFRP-1 and SFRP-2 are specifically expressed in osteoblasts in bone marrow; SFRP-1 (but not SFRP-2) reduces multipotent hematopoietic progenitor numbers and compromises long-term HSC repopulating activity in transplantation assays, differentiating their functional roles despite both inhibiting Wnt signaling in vitro.\",\n      \"method\": \"Immunostaining of bone marrow sections, in vitro CD34-KSL culture assays, long-term competitive repopulation transplantation assay in mice\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean in vitro and in vivo functional assays distinguishing SFRP1 from SFRP2\",\n      \"pmids\": [\"19778523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Promoter hypermethylation of DKK1 and SFRP1 in systemic sclerosis fibroblasts is mediated by DNA methyltransferases; inhibition with 5-aza-2'-deoxycytidine reactivates DKK1 and SFRP1 transcription, inhibits canonical Wnt signaling (Axin2 mRNA, β-catenin staining) in vitro and in vivo, and ameliorates experimental fibrosis in bleomycin-challenged mice.\",\n      \"method\": \"Methylation-specific PCR of patient fibroblasts and PBMCs, 5-aza treatment in vitro and in bleomycin mouse model, Axin2 mRNA and β-catenin readouts\",\n      \"journal\": \"Annals of the rheumatic diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — causal epigenetic mechanism demonstrated in patient cells and in vivo model\",\n      \"pmids\": [\"23698475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Loss of Sfrp1 depletes hair follicle stem cells (HFSCs) and accelerates the hair follicle cycle; restoration of HFSC pool in Sfrp1-/- mice is mediated through a BMP-AKT-GSK3β signaling cross-talk that downregulates β-catenin activity, a mechanism absent in Sfrp1+/- mice.\",\n      \"method\": \"Sfrp1-/- and Sfrp1+/- mouse models, flow cytometry for HFSC markers (Lgr5, Axin2), BMP receptor and GSK3β inhibitor treatment in keratinocytes, β-catenin activity assays\",\n      \"journal\": \"Stem cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO genetics with pharmacological pathway dissection, single lab\",\n      \"pmids\": [\"35689817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Sfrp1 and Sfrp5 double knockout disturbs trophoblast differentiation in the ectoplacental cone by hyperactivating canonical Wnt-β-catenin signaling, which exhausts trophoblast precursors and causes overabundance of giant cells at the expense of spongiotrophoblast cells via repression of Ascl2 expression.\",\n      \"method\": \"Sfrp1/Sfrp5 double KO mice, trophoblast-specific β-catenin exon-3 deletion mouse model, trophoblast stem cell lines, Ascl2 expression analysis\",\n      \"journal\": \"BMC biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic models converge on Ascl2 as downstream effector\",\n      \"pmids\": [\"33109217\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SFRP1 is a secreted glycoprotein that primarily antagonizes Wnt signaling by binding Wnt ligands upstream of GSK-3 to suppress β-catenin accumulation, but also signals independently through direct interaction with Frizzled-2 to guide axon growth via Gα/cyclic nucleotide pathways, activates non-canonical Wnt/PCP-Rac1 or Wnt/PCP-JNK pathways depending on context, undergoes epigenetic silencing via DNMT1/HDAC1 or EZH2-mediated promoter methylation/histone modification (recruited by HCV core protein or HOTTIP lncRNA), is transcriptionally regulated by Hedgehog-GLI and AKT1-E17K signaling, mediates cellular senescence through Wnt inhibition and Rb pathway activation, is packaged into fibroblast-derived extracellular vesicles to promote fibrosis via WNT/β-catenin in alveolar cells, and modulates diverse cell-type-specific processes including neuroinflammation (astrocyte-to-microglia via HIF pathway), Th17 differentiation (enhancing TGF-β/Smad2/3 signaling), hematopoietic stem cell homeostasis, and intraocular pressure regulation in the trabecular meshwork.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SFRP1 is a secreted Wnt antagonist that controls cell fate, proliferation, and tissue homeostasis across numerous developmental and adult contexts by modulating both canonical and non-canonical Wnt signaling, as well as Wnt-independent pathways. As a secreted glycoprotein, SFRP1 directly binds Wnt ligands upstream of GSK-3 to inhibit β-catenin accumulation [PMID:16425220], and independently engages Frizzled-2 receptors to guide axon growth through Gα-protein and cyclic nucleotide signaling [PMID:16172602]; at low concentrations it activates the Wnt/PCP-Rac1 pathway in dopaminergic neurons [PMID:22290867] and restrains Wnt/PCP-JNK signaling in kidney and heart [PMID:25253698, PMID:30377735]. SFRP1 is transcriptionally regulated by Hedgehog-Gli [PMID:17035233], SOX2 [PMID:33107226], and oncogenic AKT1-E17K [PMID:24096618], and is frequently epigenetically silenced through promoter DNA methylation mediated by DNMT1/HDAC1 or DNMT3b recruitment (by HCV core protein or HOTTIP lncRNA) and by EZH2-dependent histone methylation [PMID:23770846, PMID:31902746, PMID:21515604]. Functionally, SFRP1 mediates cellular senescence via Wnt inhibition and Rb pathway activation [PMID:22927647], maintains stem cell quiescence in hair follicles and the neural subventricular zone [PMID:35689817, PMID:35210419], regulates trophoblast differentiation and somitogenesis through redundancy with other SFRPs [PMID:33109217, PMID:16467359], and when packaged into fibroblast-derived extracellular vesicles paradoxically promotes lung fibrosis by activating WNT/β-catenin in alveolar epithelial cells [PMID:39315549].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Establishing that SFRP1 modulates retinal cell fate and protects against apoptosis through β-catenin-independent mechanisms resolved that its function extends beyond simple canonical Wnt antagonism.\",\n      \"evidence\": \"Retroviral overexpression in chick retinal cultures with β-catenin/TCF reporters showing no change in canonical activity, plus GSK3β phosphorylation analysis; parallel ceramide-induced apoptosis assays with antisense inhibition and recombinant protein in fibroblasts\",\n      \"pmids\": [\"12724355\", \"14581477\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the β-catenin-independent downstream effector in retinal progenitors not established\", \"Whether anti-apoptotic activity requires Wnt binding or a separate receptor interaction unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrating that SFRP1 directly binds Frizzled-2 and signals through Gα proteins independently of Wnt inhibition established a receptor-mediated signaling mode for a secreted Wnt antagonist.\",\n      \"evidence\": \"Co-immunoprecipitation of SFRP1 with Fz2, dominant-negative Fz2 abolishes growth cone responses, pharmacological Gα and cyclic nucleotide manipulation in retinal ganglion cell axon assays\",\n      \"pmids\": [\"16172602\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of SFRP1-Fz2 interaction not resolved\", \"Whether Fz2-dependent signaling operates outside retinal neurons unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Three advances placed SFRP1 mechanistically: its site of Wnt pathway inhibition was mapped upstream of GSK-3 via epistasis, its transcription was shown to be directly driven by Hedgehog-Gli factors linking two major morphogen pathways, and compound knockouts revealed functional redundancy with SFRP2 in somitogenesis and Notch clock regulation.\",\n      \"evidence\": \"Purified recombinant SFRP1 blocking Wnt-3a but not LiCl-induced β-catenin; ChIP showing Gli1 at the SFRP1 promoter with siRNA rescue; Sfrp1/Sfrp2 double-KO mice with altered Lfng/Hes7 oscillations\",\n      \"pmids\": [\"16425220\", \"17035233\", \"16467359\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SFRP1 sequesters Wnt ligands or competes for Frizzled binding to achieve upstream inhibition not distinguished\", \"Mechanism by which SFRP1 loss alters Notch oscillation timing unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"In vivo gain-of-function in the trabecular meshwork showed SFRP1 reduces aqueous outflow and raises intraocular pressure through Wnt/β-catenin suppression, establishing a physiological role in IOP regulation.\",\n      \"evidence\": \"Adenoviral SFRP1 overexpression in mouse eyes with dose-dependent IOP increase reversible by downstream Wnt inhibitor; ex vivo human eye perfusion\",\n      \"pmids\": [\"18274669\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous regulation of SFRP1 levels in glaucomatous TM not mechanistically defined\", \"Whether other SFRPs contribute redundantly in TM unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Loss-of-function studies in mammary epithelial cells and hematopoietic stem cells revealed that SFRP1 restrains β-catenin-driven EMT/stemness and limits HSC self-renewal, defining its tumor-suppressive and stem cell regulatory functions.\",\n      \"evidence\": \"shRNA knockdown in 76N TERT cells elevating nuclear β-catenin, Cyclin D1, CD44high/CD24low population; recombinant SFRP1 reducing multipotent progenitors and long-term HSC repopulation in competitive transplantation\",\n      \"pmids\": [\"19422694\", \"19778523\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SFRP1 effects on HSC are cell-autonomous or niche-mediated not resolved\", \"Downstream targets of β-catenin mediating CD44/CD24 switch not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Discovery that EZH2 epigenetically silences SFRP1 via H3K27 trimethylation at its promoter in rheumatoid arthritis fibroblasts established a histone modification-based mechanism for SFRP1 repression in disease.\",\n      \"evidence\": \"ChIP for histone marks at the SFRP1 promoter, EZH2 overexpression/siRNA in RA synovial fibroblasts, TNF-α induction via NF-κB/JNK\",\n      \"pmids\": [\"21515604\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether EZH2-mediated SFRP1 silencing occurs in cancers beyond RA fibroblasts not tested here\", \"Quantitative relationship between H3K27me3 density and SFRP1 repression not defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Three studies collectively established that SFRP1 mediates cellular senescence through Wnt inhibition and Rb pathway activation, promotes Th17 differentiation via TGF-β/Smad2/3 enhancement, and activates Wnt/PCP-Rac1 signaling in dopaminergic neuron development—revealing context-dependent pathway selection.\",\n      \"evidence\": \"Senescence assays with gain/loss-of-function and cancer mutant analysis; recombinant SFRP1 with TGF-β blocking epistasis during Th17 polarization; Sfrp1/Sfrp2 double-KO mice phenocopying Wnt5a-/- with Rac1 pathway activation\",\n      \"pmids\": [\"22927647\", \"22740051\", \"22290867\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SFRP1 selectively activates PCP versus inhibiting canonical Wnt in different cell types not explained\", \"Whether Th17-promoting activity is Wnt-dependent or a direct TGF-β pathway effect unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Multiple studies converged on SFRP1 as a target of epigenetic silencing (DNMT1/HDAC1 by HCV core protein, promoter methylation in systemic sclerosis) and transcriptional regulation (SOX2 in cancer-associated fibroblasts, miR-328, AKT1-E17K), establishing the diverse upstream control mechanisms that modulate SFRP1 expression in disease.\",\n      \"evidence\": \"ChIP demonstrating DNMT1/HDAC1 recruitment to SFRP1 promoter by HCV core with bisulfite sequencing and xenograft rescue; 5-aza reactivation of SFRP1 in SSc fibroblasts; ChIP-seq for SOX2 at Sfrp1 promoter in CAFs; 3'UTR luciferase assay for miR-328; AKT1-E17K transfection with immunohistochemistry in meningiomas\",\n      \"pmids\": [\"23770846\", \"23698475\", \"33107226\", \"24305703\", \"24096618\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of DNA methylation versus histone modification to SFRP1 silencing in any single disease context not quantified\", \"Whether SOX2-driven SFRP1 in CAFs acts via canonical or non-canonical Wnt on tumor cells unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Sfrp1 knockout in obstructive nephropathy demonstrated that SFRP1 specifically restrains non-canonical Wnt/PCP-JNK signaling and EMT in kidney, without affecting canonical Wnt levels, clarifying pathway selectivity in a fibrotic context.\",\n      \"evidence\": \"Sfrp1 KO mouse UUO model with Western blot dissection of canonical versus JNK/c-Jun pathways, EMT markers, and apoptosis\",\n      \"pmids\": [\"25253698\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SFRP1 directly binds Wnt5a or another non-canonical Wnt to suppress PCP-JNK not determined\", \"Applicability to other organ fibrosis models not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"HOTTIP lncRNA was shown to recruit DNMT3b to the SFRP1 promoter for methylation-mediated silencing, and SFRP1 was identified as an epigenetic gatekeeper maintaining periodontal ligament progenitor identity via H3K4me3 marks, expanding the repertoire of epigenetic regulators converging on SFRP1.\",\n      \"evidence\": \"RNA pull-down and RIP for HOTTIP-DNMT3b interaction, ChIP and bisulfite sequencing at SFRP1 promoter in RA fibroblasts; ChIP for H3K4me3/H3K27me3 comparing PDL versus alveolar bone progenitors with WAY-316606 inhibitor\",\n      \"pmids\": [\"31902746\", \"31215318\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether HOTTIP-DNMT3b mechanism operates in tissues beyond RA synovium unknown\", \"Whether SFRP1-dependent mineralization suppression requires canonical Wnt inhibition specifically not tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Sfrp1/Sfrp5 double knockout revealed that SFRP1 restrains canonical Wnt-β-catenin to prevent premature trophoblast differentiation and giant cell overproduction, acting through Ascl2 repression.\",\n      \"evidence\": \"Double-KO mice and trophoblast-specific β-catenin gain-of-function model converging on Ascl2 downregulation\",\n      \"pmids\": [\"33109217\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Individual contribution of SFRP1 versus SFRP5 not separable due to redundancy\", \"Whether Ascl2 is a direct or indirect Wnt target in trophoblasts unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"SFRP1 was identified as an astrocyte-derived amplifier of microglial neuroinflammation acting through the HIF pathway, establishing a paracrine non-Wnt signaling role in the CNS.\",\n      \"evidence\": \"SFRP1 KO/overexpression in mouse neuroinflammation models with HIF pathway gene expression and conditioned medium experiments\",\n      \"pmids\": [\"34569685\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SFRP1 directly activates HIF signaling or acts through intermediate Wnt-dependent steps unclear\", \"Receptor on microglia mediating SFRP1 response not identified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"SFRP1 was shown to maintain quiescence of hair follicle stem cells and adult neural stem cells; its loss depletes HFSCs via a BMP-AKT-GSK3β cross-talk mechanism and its pharmacological inhibition activates human SVZ neural progenitors.\",\n      \"evidence\": \"Sfrp1 KO mice with HFSC flow cytometry and BMP/GSK3β inhibitor epistasis; WAY-316606 administration in vivo with scRNA-seq of human SVZ\",\n      \"pmids\": [\"35689817\", \"35210419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SFRP1 maintains quiescence solely through canonical Wnt suppression or additional pathways in each stem cell niche unresolved\", \"Long-term consequences of pharmacological SFRP1 inhibition on stem cell exhaustion not assessed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Two studies established SFRP1 as a context-dependent modulator of lung fibrosis: it restrains TGFβ1-driven fibroblast-to-myofibroblast transition via RHOA, yet when packaged in fibroblast-derived extracellular vesicles it paradoxically activates WNT/β-catenin in alveolar epithelial cells to promote fibrosis.\",\n      \"evidence\": \"scRNA-seq, spatial transcriptomics, and genetic lineage tracing of fibroblast transitions with SFRP1 loss-of-function; label-free proteomics of BALF-EVs with Sfrp1 KO bleomycin model and β-catenin/Krt8 readouts in precision-cut lung slices\",\n      \"pmids\": [\"38212077\", \"39315549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How vesicular SFRP1 activates rather than inhibits Wnt/β-catenin in recipient alveolar cells remains mechanistically unexplained\", \"Whether the fibroblast-intrinsic and EV-mediated roles are simultaneously operative in human IPF not demonstrated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SFRP1 switches between canonical Wnt antagonism, PCP pathway activation, and Frizzled-dependent Wnt-independent signaling in different cellular contexts remains the central unresolved question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of SFRP1 bound to Wnt ligands versus Frizzled receptors\", \"Concentration-dependent pathway switching mechanism not reconstituted\", \"How vesicular versus soluble SFRP1 achieves opposite effects on β-catenin not explained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 5, 6, 8, 11]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 7, 21]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2, 5, 6, 9, 10, 15, 20]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 2, 3, 5, 7, 8, 11, 20, 22, 29, 30]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [1, 4, 7, 30]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [6, 9]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [12, 13, 24, 28]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [15, 21]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"FZD2\",\n      \"SFRP2\",\n      \"WNT3A\",\n      \"PARP1\",\n      \"DNMT1\",\n      \"HDAC1\",\n      \"EZH2\",\n      \"SOX2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}