{"gene":"FGF22","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2004,"finding":"FGF22 is a target-derived presynaptic organizing molecule in the mammalian brain. It is expressed by cerebellar granule cells and acts via its receptor FGFR2 (expressed on mossy fiber axons) to promote clustering of synaptic vesicles and presynaptic differentiation. Neutralization of FGF22 (along with FGF7 and FGF10) or inactivation of FGFR2 inhibits presynaptic differentiation of mossy fibers at synaptic contact sites in vivo.","method":"Biochemical purification from mouse brain, synaptic vesicle clustering assay in cultured neurons, in vivo neutralization of FGF7/10/22, FGFR2 genetic inactivation","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — purification-based identification, functional in vitro assay, in vivo neutralization, and genetic receptor inactivation; foundational study independently replicated by subsequent work","pmids":["15260994"],"is_preprint":false},{"year":2005,"finding":"FGF-binding protein (FGF-BP) physically interacts with FGF-22 (as well as FGF-7 and FGF-10) and enhances the activity of low concentrations of these ligands, suggesting FGF-BP modulates FGF-22 bioavailability at wound sites.","method":"Co-immunoprecipitation / binding assays; functional activity enhancement assays with recombinant proteins","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct binding demonstrated and functional enhancement shown, single lab, two orthogonal methods (binding + activity assay)","pmids":["15806171"],"is_preprint":false},{"year":2013,"finding":"In zebrafish, Fgf22 acts downstream of Fgf3/Fgf8 signaling in the midbrain-hindbrain boundary (MHB) and is required for cell proliferation, roof plate formation, and tectum specification in the midbrain. Fgfr2b mediates Fgf22 signaling in this context. Partial rescue of the fgf3/fgf8 double morphant phenotype by fgf22 places Fgf22 genetically downstream of Fgf3/Fgf8.","method":"Morpholino knockdown (fgf22, fgfr2b, fgf3, fgf8), rescue experiments, marker gene expression analysis by in situ hybridization","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established by double morphant and rescue; single lab, multiple orthogonal readouts (proliferation, marker genes)","pmids":["23789101"],"is_preprint":false},{"year":2014,"finding":"FGF22 is selectively targeted to excitatory postsynaptic sites via intracellular microtubule transport requiring motor proteins KIF3A and KIF17 and the adaptor protein SAP102 (DLG3). Live time-lapse imaging shows FGF22 co-moves with SAP102. This targeting is distinct from FGF7 (inhibitory synapse organizer), which uses KIF5 and gephyrin. Knockdown of SAP102 or PSD95 impairs FGF22 localization.","method":"Time-lapse live imaging, knockdown of motor/adaptor proteins, co-localization and co-movement analysis, immunocytochemistry","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct live imaging of co-movement, multiple motor/adaptor knockdowns with specific localization readouts, mechanistic dissection of excitatory vs. inhibitory targeting","pmids":["25431136"],"is_preprint":false},{"year":2016,"finding":"FGF22 released from CA3 pyramidal neurons acts retrogradely on dentate granule cell (DGC) axons via FGFR2 to induce IGF2 expression in DGCs. IGF2 is then transported to DGC presynaptic terminals where it stabilizes them in an activity-dependent manner. This retrograde FGF22-to-IGF2 feedback loop is required for presynaptic stabilization (but not initial differentiation). IGF2 application rescues presynaptic defects in Fgf22−/− cultures.","method":"Local axonal FGF22 application, Fgf22 knockout mice, IGF2 rescue experiments, in vitro and in vivo synaptic analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — local ligand application, genetic knockout, rescue with downstream effector, in vitro and in vivo validation; multiple orthogonal methods in one study","pmids":["27083047"],"is_preprint":false},{"year":2016,"finding":"Postsynaptic SDC2 (syndecan-2) uses its ectodomain to interact with FGF22 and facilitate dendritic filopodial targeting of FGF22, which then triggers presynaptic maturation via presynaptic FGF receptor. CaMKII (activated downstream of NMDAR, itself enhanced by FGF22-driven neurotransmitter release) further facilitates FGF22 targeting to dendritic filopodia via regulation of KIF17.","method":"Co-immunoprecipitation, ectodomain interaction assays, knockdown of SDC2, live imaging, functional synaptic readouts","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct SDC2–FGF22 binding shown, knockdown phenotypes, functional pathway dissection; single lab","pmids":["27627962"],"is_preprint":false},{"year":2017,"finding":"CA3 pyramidal neuron-specific deletion of FGF22 reduces excitatory synapses onto CA3 neurons without affecting dentate neurogenesis, demonstrating that CA3-derived FGF22 functions as a target-derived excitatory synaptic organizer in a cell-autonomous manner in CA3, and that CA3-derived FGF22 (not FGF22 from other cells) underlies the depression-like behavioral phenotype.","method":"Conditional (CA3-specific) FGF22 knockout mice, synaptic quantification, neurogenesis assay, behavioral tests (forced swim, sucrose preference)","journal":"Frontiers in synaptic neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific conditional KO with multiple phenotypic readouts; single lab","pmids":["29311892"],"is_preprint":false},{"year":2021,"finding":"FGFBP1 secreted by cancer-associated fibroblasts (CAFs) facilitates release of FGF22 from extracellular matrix; FGF22 then acts via FGFR2 on pancreatic cancer cells to promote their migration and invasion. Silencing FGFR2 in pancreatic cancer cells blocks FGF22-driven invasion, establishing a CAF→FGF22→FGFR2 paracrine axis.","method":"Co-culture system with FGFBP1 knockdown CAFs, ELISA for FGF22 in conditioned medium, FGF22 and FGFR2 siRNA knockdown, invasion/migration assays","journal":"Acta biochimica et biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — co-culture system, ELISA quantification, receptor knockdown with functional readout; single lab","pmids":["34117747"],"is_preprint":false},{"year":2022,"finding":"FGF22 deletion in mice reduces ribbon synapse vesicle number and efficiency of exocytosis (decreased capacitance change) in inner hair cells, causing hidden hearing loss. Mechanistically, FGF22 knockout downregulates SNAP-25 and Gipc3 and upregulates MEF2D, disrupting ribbon synapse function.","method":"FGF22 knockout mice, ABR testing, immunofluorescence, patch-clamp capacitance recording, qRT-PCR","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with electrophysiological (patch-clamp) and molecular readouts; single lab","pmids":["35966010"],"is_preprint":false},{"year":2023,"finding":"Viral gene transfer of FGF22 targeted to long propriospinal neurons or excitatory interneurons enhances neuronal rewiring and restores functional recovery following incomplete spinal cord injury, establishing FGF22 as a synaptogenic organizer that can promote circuit-specific and comprehensive rewiring in the injured spinal cord.","method":"Viral vector-mediated FGF22 overexpression in specific neuron populations, spinal cord injury model, functional behavioral recovery assessment","journal":"EMBO molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific viral overexpression, in vivo injury model, functional recovery readout; single lab","pmids":["36601738"],"is_preprint":false},{"year":2023,"finding":"In zebrafish forebrain, Fgf22 signaling through Fgfr2b is required for ventral telencephalon/diencephalon patterning, generation of glutamatergic neurons, GABAergic interneurons, and astrocytes, but suppresses oligodendrocyte differentiation. Overexpression of fgf22 inhibits oligodendrocyte generation, while knockdown promotes it, establishing a bidirectional Fgf22-Fgfr2b axis in gliogenesis.","method":"Morpholino knockdown, mRNA overexpression, cell-type marker analysis, fgfr2b knockdown phenocopy","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with receptor knockdown phenocopy; single lab, multiple cell-type readouts","pmids":["37783119"],"is_preprint":false},{"year":2025,"finding":"FGF22 ameliorates cognitive deficits in an Alzheimer's disease model by signaling through FGFR2 to activate YAP, which reduces ferroptosis (iron-dependent lipid peroxidation cell death) and neuronal apoptosis, thereby attenuating synaptic impairment.","method":"Aβ1-42 AD mouse model and HT22 cell model, FGF22 treatment, biochemical analysis of FGFR2/YAP pathway activation, ferroptosis and apoptosis markers, synaptic assays","journal":"Experimental neurology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, pharmacological treatment with pathway analysis only in abstract; no mutagenesis or reconstitution described","pmids":["41482107"],"is_preprint":false},{"year":2025,"finding":"FGF22 secreted by dermal papilla cells (DPCs) promotes hair follicle stem cell (HFSC) proliferation and differentiation by upregulating FGFR1/FGFR2 on HFSCs and activating Wnt/β-catenin, Sonic Hedgehog, and Notch signaling while inhibiting BMP signaling. FGF22 knockout reduces HFSC proliferation and increases apoptosis.","method":"DPC-HFSC co-culture system, FGF22 overexpression and knockout, EdU proliferation assay, CCK-8 viability, apoptosis assay, pathway inhibitor/activation analysis","journal":"Biomolecules","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-culture gain/loss-of-function with multiple pathway readouts but abstract-level description; single lab, no structural or reconstitution data","pmids":["41301478"],"is_preprint":false}],"current_model":"FGF22 is a secreted, target-derived presynaptic organizer that signals through FGFR2 to drive clustering of synaptic vesicles and differentiation of excitatory presynaptic terminals; it is selectively trafficked to excitatory postsynaptic sites via KIF3A/KIF17/SAP102, presented to presynaptic FGFR2 in part through interaction with syndecan-2, and retrogradely induces IGF2 in presynaptic neurons to stabilize synapses in an activity-dependent manner, while also functioning in zebrafish midbrain/forebrain neurogenesis downstream of Fgf3/Fgf8 via Fgfr2b, in cochlear ribbon synapse maintenance, and in spinal cord rewiring after injury."},"narrative":{"mechanistic_narrative":"FGF22 is a secreted, target-derived presynaptic organizing molecule that signals through the receptor FGFR2 to drive clustering of synaptic vesicles and differentiation of excitatory presynaptic terminals [PMID:15260994]. Within postsynaptic neurons it is selectively trafficked to excitatory postsynaptic sites by intracellular microtubule transport requiring the motor proteins KIF3A and KIF17 together with the adaptor SAP102 (DLG3), a route distinct from the inhibitory-synapse organizer FGF7 [PMID:25431136]; its presentation to presynaptic FGFR2 is facilitated by the postsynaptic syndecan-2 (SDC2) ectodomain, which targets FGF22 to dendritic filopodia, with CaMKII downstream of NMDAR activity further regulating KIF17-dependent targeting [PMID:27627962]. Beyond initiating presynaptic differentiation, FGF22 released from CA3 pyramidal neurons acts retrogradely on dentate granule cell axons via FGFR2 to induce IGF2, which is transported to presynaptic terminals and stabilizes them in an activity-dependent manner [PMID:27083047], and CA3-specific deletion of FGF22 selectively reduces excitatory synapses and produces a depression-like phenotype [PMID:29311892]. FGF22 also maintains inner hair cell ribbon synapses, where its loss reduces vesicle number and exocytosis efficiency and dysregulates SNAP-25, Gipc3 and MEF2D, causing hidden hearing loss [PMID:35966010], and viral delivery of FGF22 to spinal neurons promotes synaptogenic rewiring and functional recovery after spinal cord injury [PMID:36601738]. In zebrafish, Fgf22 acts downstream of Fgf3/Fgf8 through Fgfr2b to control midbrain proliferation, tectum specification and roof plate formation [PMID:23789101] and forebrain patterning and gliogenesis [PMID:37783119]. FGF22 bioavailability is modulated by FGF-binding protein (FGFBP1), which interacts with the ligand and enhances its activity and extracellular-matrix release [PMID:15806171, PMID:34117747].","teleology":[{"year":2004,"claim":"Established that a target-derived secreted factor instructs presynaptic assembly, identifying FGF22 as a presynaptic organizer acting through FGFR2 — answering how postsynaptic cells direct presynaptic differentiation.","evidence":"Biochemical purification from mouse brain, synaptic vesicle clustering assays in cultured neurons, in vivo neutralization of FGF7/10/22 and FGFR2 genetic inactivation","pmids":["15260994"],"confidence":"High","gaps":["Did not resolve how FGF22 is selectively delivered to synaptic sites","Receptor inactivation affected multiple FGF ligands, leaving FGF22-specific contribution partly inferential"]},{"year":2005,"claim":"Identified an extracellular modulator of FGF22, showing FGF-binding protein binds the ligand and potentiates its activity — addressing how FGF22 bioavailability is controlled.","evidence":"Co-immunoprecipitation/binding assays and functional activity-enhancement assays with recombinant proteins","pmids":["15806171"],"confidence":"Medium","gaps":["Tested at wound sites rather than synapses","Single lab; in vivo relevance to neural FGF22 not established"]},{"year":2013,"claim":"Placed Fgf22 in a developmental signaling hierarchy, showing it acts downstream of Fgf3/Fgf8 via Fgfr2b in zebrafish midbrain patterning — extending FGF22 function beyond synaptogenesis to neurogenesis.","evidence":"Morpholino knockdown of fgf22/fgfr2b/fgf3/fgf8, rescue experiments, and in situ marker analysis","pmids":["23789101"],"confidence":"Medium","gaps":["Morpholino-based, no genetic mutant confirmation","Mechanism downstream of Fgfr2b in proliferation not defined"]},{"year":2014,"claim":"Defined the trafficking machinery that delivers FGF22 to excitatory synapses, distinguishing it from inhibitory-synapse organizers — answering how synapse-type specificity of FGF organizers is achieved.","evidence":"Time-lapse live imaging of co-movement, motor/adaptor knockdowns (KIF3A, KIF17, SAP102, PSD95), and co-localization analysis","pmids":["25431136"],"confidence":"High","gaps":["How cargo is loaded onto specific motors not resolved","Secretion step from filopodia not characterized"]},{"year":2016,"claim":"Revealed a retrograde feedback loop in which FGF22 induces IGF2 in presynaptic neurons to stabilize synapses, separating synapse initiation from maintenance.","evidence":"Local axonal FGF22 application, Fgf22 knockout mice, and IGF2 rescue of presynaptic defects in vitro and in vivo","pmids":["27083047"],"confidence":"High","gaps":["Signaling between FGFR2 activation and IGF2 transcription not mapped","Activity-dependence mechanism partly inferred"]},{"year":2016,"claim":"Identified syndecan-2 as a postsynaptic partner that captures and targets FGF22 to filopodia, linking FGF22 delivery to NMDAR/CaMKII activity — connecting ligand presentation to synaptic activity.","evidence":"Co-immunoprecipitation, ectodomain interaction assays, SDC2 knockdown, live imaging and functional synaptic readouts","pmids":["27627962"],"confidence":"Medium","gaps":["Single lab; reciprocal validation of SDC2-FGF22 binding limited","Quantitative contribution of CaMKII vs SDC2 to targeting not separated"]},{"year":2017,"claim":"Demonstrated cell-autonomous, source-specific action of FGF22, showing CA3-derived FGF22 underlies excitatory synapse number and a depression-like behavioral phenotype.","evidence":"CA3-specific conditional FGF22 knockout mice with synaptic quantification, neurogenesis assays and behavioral tests","pmids":["29311892"],"confidence":"Medium","gaps":["Molecular link from synapse loss to behavior not established","Single lab"]},{"year":2021,"claim":"Extended FGF22-FGFR2 signaling to a pathological paracrine context, showing a CAF→FGFBP1→FGF22→FGFR2 axis drives pancreatic cancer invasion.","evidence":"CAF co-culture with FGFBP1 knockdown, ELISA quantification of FGF22, FGF22/FGFR2 siRNA and invasion/migration assays","pmids":["34117747"],"confidence":"Medium","gaps":["Downstream signaling in cancer cells not detailed","Single lab; in vivo tumor relevance not tested"]},{"year":2022,"claim":"Established a role in sensory synapse maintenance, showing FGF22 loss disrupts inner hair cell ribbon synapse function and gene expression, causing hidden hearing loss.","evidence":"FGF22 knockout mice with ABR testing, patch-clamp capacitance recording, immunofluorescence and qRT-PCR","pmids":["35966010"],"confidence":"Medium","gaps":["Causal link from FGF22 to SNAP-25/Gipc3/MEF2D regulation not mechanistically resolved","Receptor mediating cochlear effect not confirmed"]},{"year":2023,"claim":"Showed FGF22 can drive therapeutic circuit reconstruction, with targeted overexpression promoting rewiring and functional recovery after spinal cord injury.","evidence":"Cell-type-specific viral FGF22 overexpression in a spinal cord injury model with functional recovery assessment","pmids":["36601738"],"confidence":"Medium","gaps":["Molecular pathway underlying rewiring in injured cord not dissected","Single lab"]},{"year":2023,"claim":"Defined a bidirectional Fgf22-Fgfr2b axis in zebrafish forebrain neurogenesis and gliogenesis, including suppression of oligodendrocyte differentiation.","evidence":"Morpholino knockdown, mRNA overexpression, cell-type marker analysis and fgfr2b knockdown phenocopy","pmids":["37783119"],"confidence":"Medium","gaps":["Morpholino-based; genetic mutant confirmation absent","Transcriptional effectors of the gliogenic switch unknown"]},{"year":2025,"claim":"Proposed an FGFR2-YAP-mediated, ferroptosis-suppressing neuroprotective role for FGF22 in an Alzheimer's disease model.","evidence":"Aβ1-42 mouse and HT22 cell models with FGF22 treatment and FGFR2/YAP, ferroptosis and apoptosis marker analysis","pmids":["41482107"],"confidence":"Low","gaps":["Pathway analysis only; no mutagenesis or reconstitution","Single lab, not independently confirmed"]},{"year":2025,"claim":"Reported a role for FGF22 in hair follicle stem cell proliferation via FGFR1/FGFR2 and multiple developmental pathways.","evidence":"DPC-HFSC co-culture with FGF22 overexpression/knockout, proliferation, viability and apoptosis assays and pathway inhibitor analysis","pmids":["41301478"],"confidence":"Low","gaps":["Abstract-level pathway readouts; direct receptor binding not shown","Single lab, no structural data"]},{"year":null,"claim":"How FGF22-FGFR2 engagement is transduced into the distinct downstream programs across contexts — presynaptic vesicle clustering, IGF2 induction, gliogenic switching, and YAP activation — remains undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of FGF22-FGFR2 complex in the corpus","Intracellular signaling cascade linking FGFR2 to vesicle clustering not mapped","Mechanism selecting between maintenance vs. initiation outputs unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,4,7]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,7]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,5]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,4]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,7]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,10]}],"complexes":[],"partners":["FGFR2","SDC2","FGFBP1","KIF17","KIF3A","DLG3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9HCT0","full_name":"Fibroblast growth factor 22","aliases":[],"length_aa":170,"mass_kda":19.7,"function":"Plays a role in the fasting response, glucose homeostasis, lipolysis and lipogenesis. Can stimulate cell proliferation (in vitro). May be involved in hair development","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9HCT0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FGF22","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FGF22","total_profiled":1310},"omim":[{"mim_id":"605831","title":"FIBROBLAST GROWTH FACTOR 22; FGF22","url":"https://www.omim.org/entry/605831"},{"mim_id":"602115","title":"FIBROBLAST GROWTH FACTOR 10; FGF10","url":"https://www.omim.org/entry/602115"},{"mim_id":"148180","title":"FIBROBLAST GROWTH FACTOR 7; FGF7","url":"https://www.omim.org/entry/148180"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":5.6},{"tissue":"skin 1","ntpm":13.0}],"url":"https://www.proteinatlas.org/search/FGF22"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9HCT0","domains":[{"cath_id":"2.80.10.50","chopping":"36-167","consensus_level":"high","plddt":97.0734,"start":36,"end":167}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HCT0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HCT0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HCT0-F1-predicted_aligned_error_v6.png","plddt_mean":88.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FGF22","jax_strain_url":"https://www.jax.org/strain/search?query=FGF22"},"sequence":{"accession":"Q9HCT0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9HCT0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9HCT0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HCT0"}},"corpus_meta":[{"pmid":"15260994","id":"PMC_15260994","title":"FGF22 and its close relatives are presynaptic organizing molecules in the mammalian brain.","date":"2004","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/15260994","citation_count":232,"is_preprint":false},{"pmid":"15806171","id":"PMC_15806171","title":"The fibroblast growth factor binding protein is a novel interaction partner of FGF-7, FGF-10 and FGF-22 and regulates FGF activity: implications for epithelial repair.","date":"2005","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/15806171","citation_count":81,"is_preprint":false},{"pmid":"11342227","id":"PMC_11342227","title":"Identification of a novel fibroblast growth factor, FGF-22, preferentially expressed in the inner root sheath of the hair follicle.","date":"2001","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/11342227","citation_count":63,"is_preprint":false},{"pmid":"27083047","id":"PMC_27083047","title":"Retrograde fibroblast growth factor 22 (FGF22) signaling regulates insulin-like growth factor 2 (IGF2) expression for activity-dependent synapse stabilization in the mammalian brain.","date":"2016","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/27083047","citation_count":39,"is_preprint":false},{"pmid":"25431136","id":"PMC_25431136","title":"Selective synaptic targeting of the excitatory and inhibitory presynaptic organizers FGF22 and FGF7.","date":"2014","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/25431136","citation_count":25,"is_preprint":false},{"pmid":"26639016","id":"PMC_26639016","title":"FGF22 protects hearing function from gentamycin ototoxicity by maintaining ribbon synapse number.","date":"2015","source":"Hearing research","url":"https://pubmed.ncbi.nlm.nih.gov/26639016","citation_count":23,"is_preprint":false},{"pmid":"23616746","id":"PMC_23616746","title":"Suppression of epileptogenesis-associated changes in response to seizures in FGF22-deficient mice.","date":"2013","source":"Frontiers in cellular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/23616746","citation_count":23,"is_preprint":false},{"pmid":"27627962","id":"PMC_27627962","title":"Postsynaptic SDC2 induces transsynaptic signaling via FGF22 for bidirectional synaptic formation.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27627962","citation_count":22,"is_preprint":false},{"pmid":"16142419","id":"PMC_16142419","title":"Comparative genomics on FGF7, FGF10, FGF22 orthologs, and identification of fgf25.","date":"2005","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/16142419","citation_count":19,"is_preprint":false},{"pmid":"36601738","id":"PMC_36601738","title":"Synaptogenic gene therapy with FGF22 improves circuit plasticity and functional recovery following spinal cord injury.","date":"2023","source":"EMBO molecular 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neurology","url":"https://pubmed.ncbi.nlm.nih.gov/41482107","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11212,"output_tokens":3604,"usd":0.043848,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11159,"output_tokens":4291,"usd":0.081535,"stage2_stop_reason":"end_turn"},"total_usd":0.125383,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"FGF22 is a target-derived presynaptic organizing molecule in the mammalian brain. It is expressed by cerebellar granule cells and acts via its receptor FGFR2 (expressed on mossy fiber axons) to promote clustering of synaptic vesicles and presynaptic differentiation. Neutralization of FGF22 (along with FGF7 and FGF10) or inactivation of FGFR2 inhibits presynaptic differentiation of mossy fibers at synaptic contact sites in vivo.\",\n      \"method\": \"Biochemical purification from mouse brain, synaptic vesicle clustering assay in cultured neurons, in vivo neutralization of FGF7/10/22, FGFR2 genetic inactivation\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — purification-based identification, functional in vitro assay, in vivo neutralization, and genetic receptor inactivation; foundational study independently replicated by subsequent work\",\n      \"pmids\": [\"15260994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FGF-binding protein (FGF-BP) physically interacts with FGF-22 (as well as FGF-7 and FGF-10) and enhances the activity of low concentrations of these ligands, suggesting FGF-BP modulates FGF-22 bioavailability at wound sites.\",\n      \"method\": \"Co-immunoprecipitation / binding assays; functional activity enhancement assays with recombinant proteins\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct binding demonstrated and functional enhancement shown, single lab, two orthogonal methods (binding + activity assay)\",\n      \"pmids\": [\"15806171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In zebrafish, Fgf22 acts downstream of Fgf3/Fgf8 signaling in the midbrain-hindbrain boundary (MHB) and is required for cell proliferation, roof plate formation, and tectum specification in the midbrain. Fgfr2b mediates Fgf22 signaling in this context. Partial rescue of the fgf3/fgf8 double morphant phenotype by fgf22 places Fgf22 genetically downstream of Fgf3/Fgf8.\",\n      \"method\": \"Morpholino knockdown (fgf22, fgfr2b, fgf3, fgf8), rescue experiments, marker gene expression analysis by in situ hybridization\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by double morphant and rescue; single lab, multiple orthogonal readouts (proliferation, marker genes)\",\n      \"pmids\": [\"23789101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FGF22 is selectively targeted to excitatory postsynaptic sites via intracellular microtubule transport requiring motor proteins KIF3A and KIF17 and the adaptor protein SAP102 (DLG3). Live time-lapse imaging shows FGF22 co-moves with SAP102. This targeting is distinct from FGF7 (inhibitory synapse organizer), which uses KIF5 and gephyrin. Knockdown of SAP102 or PSD95 impairs FGF22 localization.\",\n      \"method\": \"Time-lapse live imaging, knockdown of motor/adaptor proteins, co-localization and co-movement analysis, immunocytochemistry\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct live imaging of co-movement, multiple motor/adaptor knockdowns with specific localization readouts, mechanistic dissection of excitatory vs. inhibitory targeting\",\n      \"pmids\": [\"25431136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FGF22 released from CA3 pyramidal neurons acts retrogradely on dentate granule cell (DGC) axons via FGFR2 to induce IGF2 expression in DGCs. IGF2 is then transported to DGC presynaptic terminals where it stabilizes them in an activity-dependent manner. This retrograde FGF22-to-IGF2 feedback loop is required for presynaptic stabilization (but not initial differentiation). IGF2 application rescues presynaptic defects in Fgf22−/− cultures.\",\n      \"method\": \"Local axonal FGF22 application, Fgf22 knockout mice, IGF2 rescue experiments, in vitro and in vivo synaptic analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — local ligand application, genetic knockout, rescue with downstream effector, in vitro and in vivo validation; multiple orthogonal methods in one study\",\n      \"pmids\": [\"27083047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Postsynaptic SDC2 (syndecan-2) uses its ectodomain to interact with FGF22 and facilitate dendritic filopodial targeting of FGF22, which then triggers presynaptic maturation via presynaptic FGF receptor. CaMKII (activated downstream of NMDAR, itself enhanced by FGF22-driven neurotransmitter release) further facilitates FGF22 targeting to dendritic filopodia via regulation of KIF17.\",\n      \"method\": \"Co-immunoprecipitation, ectodomain interaction assays, knockdown of SDC2, live imaging, functional synaptic readouts\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct SDC2–FGF22 binding shown, knockdown phenotypes, functional pathway dissection; single lab\",\n      \"pmids\": [\"27627962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CA3 pyramidal neuron-specific deletion of FGF22 reduces excitatory synapses onto CA3 neurons without affecting dentate neurogenesis, demonstrating that CA3-derived FGF22 functions as a target-derived excitatory synaptic organizer in a cell-autonomous manner in CA3, and that CA3-derived FGF22 (not FGF22 from other cells) underlies the depression-like behavioral phenotype.\",\n      \"method\": \"Conditional (CA3-specific) FGF22 knockout mice, synaptic quantification, neurogenesis assay, behavioral tests (forced swim, sucrose preference)\",\n      \"journal\": \"Frontiers in synaptic neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific conditional KO with multiple phenotypic readouts; single lab\",\n      \"pmids\": [\"29311892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FGFBP1 secreted by cancer-associated fibroblasts (CAFs) facilitates release of FGF22 from extracellular matrix; FGF22 then acts via FGFR2 on pancreatic cancer cells to promote their migration and invasion. Silencing FGFR2 in pancreatic cancer cells blocks FGF22-driven invasion, establishing a CAF→FGF22→FGFR2 paracrine axis.\",\n      \"method\": \"Co-culture system with FGFBP1 knockdown CAFs, ELISA for FGF22 in conditioned medium, FGF22 and FGFR2 siRNA knockdown, invasion/migration assays\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — co-culture system, ELISA quantification, receptor knockdown with functional readout; single lab\",\n      \"pmids\": [\"34117747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FGF22 deletion in mice reduces ribbon synapse vesicle number and efficiency of exocytosis (decreased capacitance change) in inner hair cells, causing hidden hearing loss. Mechanistically, FGF22 knockout downregulates SNAP-25 and Gipc3 and upregulates MEF2D, disrupting ribbon synapse function.\",\n      \"method\": \"FGF22 knockout mice, ABR testing, immunofluorescence, patch-clamp capacitance recording, qRT-PCR\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with electrophysiological (patch-clamp) and molecular readouts; single lab\",\n      \"pmids\": [\"35966010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Viral gene transfer of FGF22 targeted to long propriospinal neurons or excitatory interneurons enhances neuronal rewiring and restores functional recovery following incomplete spinal cord injury, establishing FGF22 as a synaptogenic organizer that can promote circuit-specific and comprehensive rewiring in the injured spinal cord.\",\n      \"method\": \"Viral vector-mediated FGF22 overexpression in specific neuron populations, spinal cord injury model, functional behavioral recovery assessment\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific viral overexpression, in vivo injury model, functional recovery readout; single lab\",\n      \"pmids\": [\"36601738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In zebrafish forebrain, Fgf22 signaling through Fgfr2b is required for ventral telencephalon/diencephalon patterning, generation of glutamatergic neurons, GABAergic interneurons, and astrocytes, but suppresses oligodendrocyte differentiation. Overexpression of fgf22 inhibits oligodendrocyte generation, while knockdown promotes it, establishing a bidirectional Fgf22-Fgfr2b axis in gliogenesis.\",\n      \"method\": \"Morpholino knockdown, mRNA overexpression, cell-type marker analysis, fgfr2b knockdown phenocopy\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with receptor knockdown phenocopy; single lab, multiple cell-type readouts\",\n      \"pmids\": [\"37783119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FGF22 ameliorates cognitive deficits in an Alzheimer's disease model by signaling through FGFR2 to activate YAP, which reduces ferroptosis (iron-dependent lipid peroxidation cell death) and neuronal apoptosis, thereby attenuating synaptic impairment.\",\n      \"method\": \"Aβ1-42 AD mouse model and HT22 cell model, FGF22 treatment, biochemical analysis of FGFR2/YAP pathway activation, ferroptosis and apoptosis markers, synaptic assays\",\n      \"journal\": \"Experimental neurology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, pharmacological treatment with pathway analysis only in abstract; no mutagenesis or reconstitution described\",\n      \"pmids\": [\"41482107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FGF22 secreted by dermal papilla cells (DPCs) promotes hair follicle stem cell (HFSC) proliferation and differentiation by upregulating FGFR1/FGFR2 on HFSCs and activating Wnt/β-catenin, Sonic Hedgehog, and Notch signaling while inhibiting BMP signaling. FGF22 knockout reduces HFSC proliferation and increases apoptosis.\",\n      \"method\": \"DPC-HFSC co-culture system, FGF22 overexpression and knockout, EdU proliferation assay, CCK-8 viability, apoptosis assay, pathway inhibitor/activation analysis\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-culture gain/loss-of-function with multiple pathway readouts but abstract-level description; single lab, no structural or reconstitution data\",\n      \"pmids\": [\"41301478\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FGF22 is a secreted, target-derived presynaptic organizer that signals through FGFR2 to drive clustering of synaptic vesicles and differentiation of excitatory presynaptic terminals; it is selectively trafficked to excitatory postsynaptic sites via KIF3A/KIF17/SAP102, presented to presynaptic FGFR2 in part through interaction with syndecan-2, and retrogradely induces IGF2 in presynaptic neurons to stabilize synapses in an activity-dependent manner, while also functioning in zebrafish midbrain/forebrain neurogenesis downstream of Fgf3/Fgf8 via Fgfr2b, in cochlear ribbon synapse maintenance, and in spinal cord rewiring after injury.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FGF22 is a secreted, target-derived presynaptic organizing molecule that signals through the receptor FGFR2 to drive clustering of synaptic vesicles and differentiation of excitatory presynaptic terminals [#0]. Within postsynaptic neurons it is selectively trafficked to excitatory postsynaptic sites by intracellular microtubule transport requiring the motor proteins KIF3A and KIF17 together with the adaptor SAP102 (DLG3), a route distinct from the inhibitory-synapse organizer FGF7 [#3]; its presentation to presynaptic FGFR2 is facilitated by the postsynaptic syndecan-2 (SDC2) ectodomain, which targets FGF22 to dendritic filopodia, with CaMKII downstream of NMDAR activity further regulating KIF17-dependent targeting [#5]. Beyond initiating presynaptic differentiation, FGF22 released from CA3 pyramidal neurons acts retrogradely on dentate granule cell axons via FGFR2 to induce IGF2, which is transported to presynaptic terminals and stabilizes them in an activity-dependent manner [#4], and CA3-specific deletion of FGF22 selectively reduces excitatory synapses and produces a depression-like phenotype [#6]. FGF22 also maintains inner hair cell ribbon synapses, where its loss reduces vesicle number and exocytosis efficiency and dysregulates SNAP-25, Gipc3 and MEF2D, causing hidden hearing loss [#8], and viral delivery of FGF22 to spinal neurons promotes synaptogenic rewiring and functional recovery after spinal cord injury [#9]. In zebrafish, Fgf22 acts downstream of Fgf3/Fgf8 through Fgfr2b to control midbrain proliferation, tectum specification and roof plate formation [#2] and forebrain patterning and gliogenesis [#10]. FGF22 bioavailability is modulated by FGF-binding protein (FGFBP1), which interacts with the ligand and enhances its activity and extracellular-matrix release [#1, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established that a target-derived secreted factor instructs presynaptic assembly, identifying FGF22 as a presynaptic organizer acting through FGFR2 — answering how postsynaptic cells direct presynaptic differentiation.\",\n      \"evidence\": \"Biochemical purification from mouse brain, synaptic vesicle clustering assays in cultured neurons, in vivo neutralization of FGF7/10/22 and FGFR2 genetic inactivation\",\n      \"pmids\": [\"15260994\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how FGF22 is selectively delivered to synaptic sites\", \"Receptor inactivation affected multiple FGF ligands, leaving FGF22-specific contribution partly inferential\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified an extracellular modulator of FGF22, showing FGF-binding protein binds the ligand and potentiates its activity — addressing how FGF22 bioavailability is controlled.\",\n      \"evidence\": \"Co-immunoprecipitation/binding assays and functional activity-enhancement assays with recombinant proteins\",\n      \"pmids\": [\"15806171\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Tested at wound sites rather than synapses\", \"Single lab; in vivo relevance to neural FGF22 not established\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Placed Fgf22 in a developmental signaling hierarchy, showing it acts downstream of Fgf3/Fgf8 via Fgfr2b in zebrafish midbrain patterning — extending FGF22 function beyond synaptogenesis to neurogenesis.\",\n      \"evidence\": \"Morpholino knockdown of fgf22/fgfr2b/fgf3/fgf8, rescue experiments, and in situ marker analysis\",\n      \"pmids\": [\"23789101\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Morpholino-based, no genetic mutant confirmation\", \"Mechanism downstream of Fgfr2b in proliferation not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the trafficking machinery that delivers FGF22 to excitatory synapses, distinguishing it from inhibitory-synapse organizers — answering how synapse-type specificity of FGF organizers is achieved.\",\n      \"evidence\": \"Time-lapse live imaging of co-movement, motor/adaptor knockdowns (KIF3A, KIF17, SAP102, PSD95), and co-localization analysis\",\n      \"pmids\": [\"25431136\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How cargo is loaded onto specific motors not resolved\", \"Secretion step from filopodia not characterized\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed a retrograde feedback loop in which FGF22 induces IGF2 in presynaptic neurons to stabilize synapses, separating synapse initiation from maintenance.\",\n      \"evidence\": \"Local axonal FGF22 application, Fgf22 knockout mice, and IGF2 rescue of presynaptic defects in vitro and in vivo\",\n      \"pmids\": [\"27083047\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling between FGFR2 activation and IGF2 transcription not mapped\", \"Activity-dependence mechanism partly inferred\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified syndecan-2 as a postsynaptic partner that captures and targets FGF22 to filopodia, linking FGF22 delivery to NMDAR/CaMKII activity — connecting ligand presentation to synaptic activity.\",\n      \"evidence\": \"Co-immunoprecipitation, ectodomain interaction assays, SDC2 knockdown, live imaging and functional synaptic readouts\",\n      \"pmids\": [\"27627962\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; reciprocal validation of SDC2-FGF22 binding limited\", \"Quantitative contribution of CaMKII vs SDC2 to targeting not separated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated cell-autonomous, source-specific action of FGF22, showing CA3-derived FGF22 underlies excitatory synapse number and a depression-like behavioral phenotype.\",\n      \"evidence\": \"CA3-specific conditional FGF22 knockout mice with synaptic quantification, neurogenesis assays and behavioral tests\",\n      \"pmids\": [\"29311892\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link from synapse loss to behavior not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended FGF22-FGFR2 signaling to a pathological paracrine context, showing a CAF→FGFBP1→FGF22→FGFR2 axis drives pancreatic cancer invasion.\",\n      \"evidence\": \"CAF co-culture with FGFBP1 knockdown, ELISA quantification of FGF22, FGF22/FGFR2 siRNA and invasion/migration assays\",\n      \"pmids\": [\"34117747\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream signaling in cancer cells not detailed\", \"Single lab; in vivo tumor relevance not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established a role in sensory synapse maintenance, showing FGF22 loss disrupts inner hair cell ribbon synapse function and gene expression, causing hidden hearing loss.\",\n      \"evidence\": \"FGF22 knockout mice with ABR testing, patch-clamp capacitance recording, immunofluorescence and qRT-PCR\",\n      \"pmids\": [\"35966010\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal link from FGF22 to SNAP-25/Gipc3/MEF2D regulation not mechanistically resolved\", \"Receptor mediating cochlear effect not confirmed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed FGF22 can drive therapeutic circuit reconstruction, with targeted overexpression promoting rewiring and functional recovery after spinal cord injury.\",\n      \"evidence\": \"Cell-type-specific viral FGF22 overexpression in a spinal cord injury model with functional recovery assessment\",\n      \"pmids\": [\"36601738\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular pathway underlying rewiring in injured cord not dissected\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a bidirectional Fgf22-Fgfr2b axis in zebrafish forebrain neurogenesis and gliogenesis, including suppression of oligodendrocyte differentiation.\",\n      \"evidence\": \"Morpholino knockdown, mRNA overexpression, cell-type marker analysis and fgfr2b knockdown phenocopy\",\n      \"pmids\": [\"37783119\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Morpholino-based; genetic mutant confirmation absent\", \"Transcriptional effectors of the gliogenic switch unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Proposed an FGFR2-YAP-mediated, ferroptosis-suppressing neuroprotective role for FGF22 in an Alzheimer's disease model.\",\n      \"evidence\": \"Aβ1-42 mouse and HT22 cell models with FGF22 treatment and FGFR2/YAP, ferroptosis and apoptosis marker analysis\",\n      \"pmids\": [\"41482107\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway analysis only; no mutagenesis or reconstitution\", \"Single lab, not independently confirmed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Reported a role for FGF22 in hair follicle stem cell proliferation via FGFR1/FGFR2 and multiple developmental pathways.\",\n      \"evidence\": \"DPC-HFSC co-culture with FGF22 overexpression/knockout, proliferation, viability and apoptosis assays and pathway inhibitor analysis\",\n      \"pmids\": [\"41301478\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Abstract-level pathway readouts; direct receptor binding not shown\", \"Single lab, no structural data\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FGF22-FGFR2 engagement is transduced into the distinct downstream programs across contexts — presynaptic vesicle clustering, IGF2 induction, gliogenic switching, and YAP activation — remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of FGF22-FGFR2 complex in the corpus\", \"Intracellular signaling cascade linking FGFR2 to vesicle clustering not mapped\", \"Mechanism selecting between maintenance vs. initiation outputs unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 4, 7]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 10]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"FGFR2\", \"SDC2\", \"FGFBP1\", \"KIF17\", \"KIF3A\", \"DLG3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}