Affinage

FGF22

Fibroblast growth factor 22 · UniProt Q9HCT0

Length
170 aa
Mass
19.7 kDa
Annotated
2026-06-09
18 papers in source corpus 13 papers cited in narrative 13 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

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).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2004 High

    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

    PMID:15260994

    Open questions at the time
    • Did not resolve how FGF22 is selectively delivered to synaptic sites
    • Receptor inactivation affected multiple FGF ligands, leaving FGF22-specific contribution partly inferential
  2. 2005 Medium

    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

    PMID:15806171

    Open questions at the time
    • Tested at wound sites rather than synapses
    • Single lab; in vivo relevance to neural FGF22 not established
  3. 2013 Medium

    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

    PMID:23789101

    Open questions at the time
    • Morpholino-based, no genetic mutant confirmation
    • Mechanism downstream of Fgfr2b in proliferation not defined
  4. 2014 High

    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

    PMID:25431136

    Open questions at the time
    • How cargo is loaded onto specific motors not resolved
    • Secretion step from filopodia not characterized
  5. 2016 High

    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

    PMID:27083047

    Open questions at the time
    • Signaling between FGFR2 activation and IGF2 transcription not mapped
    • Activity-dependence mechanism partly inferred
  6. 2016 Medium

    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

    PMID:27627962

    Open questions at the time
    • Single lab; reciprocal validation of SDC2-FGF22 binding limited
    • Quantitative contribution of CaMKII vs SDC2 to targeting not separated
  7. 2017 Medium

    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

    PMID:29311892

    Open questions at the time
    • Molecular link from synapse loss to behavior not established
    • Single lab
  8. 2021 Medium

    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

    PMID:34117747

    Open questions at the time
    • Downstream signaling in cancer cells not detailed
    • Single lab; in vivo tumor relevance not tested
  9. 2022 Medium

    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

    PMID:35966010

    Open questions at the time
    • Causal link from FGF22 to SNAP-25/Gipc3/MEF2D regulation not mechanistically resolved
    • Receptor mediating cochlear effect not confirmed
  10. 2023 Medium

    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

    PMID:36601738

    Open questions at the time
    • Molecular pathway underlying rewiring in injured cord not dissected
    • Single lab
  11. 2023 Medium

    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

    PMID:37783119

    Open questions at the time
    • Morpholino-based; genetic mutant confirmation absent
    • Transcriptional effectors of the gliogenic switch unknown
  12. 2025 Low

    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

    PMID:41482107

    Open questions at the time
    • Pathway analysis only; no mutagenesis or reconstitution
    • Single lab, not independently confirmed
  13. 2025 Low

    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

    PMID:41301478

    Open questions at the time
    • Abstract-level pathway readouts; direct receptor binding not shown
    • Single lab, no structural data

Open questions

Synthesis pass · forward-looking unresolved questions
  • 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.
  • 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

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0048018 receptor ligand activity 3 GO:0060089 molecular transducer activity 2
Localization
GO:0005576 extracellular region 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-112316 Neuronal System 2 R-HSA-1266738 Developmental Biology 2 R-HSA-162582 Signal Transduction 2
Partners
DLG3FGFBP1FGFR2KIF17KIF3ASDC2

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2004 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. Biochemical purification from mouse brain, synaptic vesicle clustering assay in cultured neurons, in vivo neutralization of FGF7/10/22, FGFR2 genetic inactivation Cell High 15260994
2005 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. Co-immunoprecipitation / binding assays; functional activity enhancement assays with recombinant proteins Oncogene Medium 15806171
2013 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. Morpholino knockdown (fgf22, fgfr2b, fgf3, fgf8), rescue experiments, marker gene expression analysis by in situ hybridization Biology open Medium 23789101
2014 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. Time-lapse live imaging, knockdown of motor/adaptor proteins, co-localization and co-movement analysis, immunocytochemistry Journal of cell science High 25431136
2016 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. Local axonal FGF22 application, Fgf22 knockout mice, IGF2 rescue experiments, in vitro and in vivo synaptic analysis eLife High 27083047
2016 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. Co-immunoprecipitation, ectodomain interaction assays, knockdown of SDC2, live imaging, functional synaptic readouts Scientific reports Medium 27627962
2017 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. Conditional (CA3-specific) FGF22 knockout mice, synaptic quantification, neurogenesis assay, behavioral tests (forced swim, sucrose preference) Frontiers in synaptic neuroscience Medium 29311892
2021 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. Co-culture system with FGFBP1 knockdown CAFs, ELISA for FGF22 in conditioned medium, FGF22 and FGFR2 siRNA knockdown, invasion/migration assays Acta biochimica et biophysica Sinica Medium 34117747
2022 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. FGF22 knockout mice, ABR testing, immunofluorescence, patch-clamp capacitance recording, qRT-PCR Frontiers in molecular neuroscience Medium 35966010
2023 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. Viral vector-mediated FGF22 overexpression in specific neuron populations, spinal cord injury model, functional behavioral recovery assessment EMBO molecular medicine Medium 36601738
2023 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. Morpholino knockdown, mRNA overexpression, cell-type marker analysis, fgfr2b knockdown phenocopy Biochemical and biophysical research communications Medium 37783119
2025 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. Aβ1-42 AD mouse model and HT22 cell model, FGF22 treatment, biochemical analysis of FGFR2/YAP pathway activation, ferroptosis and apoptosis markers, synaptic assays Experimental neurology Low 41482107
2025 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. DPC-HFSC co-culture system, FGF22 overexpression and knockout, EdU proliferation assay, CCK-8 viability, apoptosis assay, pathway inhibitor/activation analysis Biomolecules Low 41301478

Source papers

Stage 0 corpus · 18 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2004 FGF22 and its close relatives are presynaptic organizing molecules in the mammalian brain. Cell 232 15260994
2005 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. Oncogene 81 15806171
2001 Identification of a novel fibroblast growth factor, FGF-22, preferentially expressed in the inner root sheath of the hair follicle. Biochimica et biophysica acta 63 11342227
2016 Retrograde fibroblast growth factor 22 (FGF22) signaling regulates insulin-like growth factor 2 (IGF2) expression for activity-dependent synapse stabilization in the mammalian brain. eLife 39 27083047
2014 Selective synaptic targeting of the excitatory and inhibitory presynaptic organizers FGF22 and FGF7. Journal of cell science 25 25431136
2015 FGF22 protects hearing function from gentamycin ototoxicity by maintaining ribbon synapse number. Hearing research 23 26639016
2013 Suppression of epileptogenesis-associated changes in response to seizures in FGF22-deficient mice. Frontiers in cellular neuroscience 23 23616746
2016 Postsynaptic SDC2 induces transsynaptic signaling via FGF22 for bidirectional synaptic formation. Scientific reports 22 27627962
2005 Comparative genomics on FGF7, FGF10, FGF22 orthologs, and identification of fgf25. International journal of molecular medicine 19 16142419
2023 Synaptogenic gene therapy with FGF22 improves circuit plasticity and functional recovery following spinal cord injury. EMBO molecular medicine 17 36601738
2021 FGFBP1-mediated crosstalk between fibroblasts and pancreatic cancer cells via FGF22/FGFR2 promotes invasion and metastasis of pancreatic cancer. Acta biochimica et biophysica Sinica 17 34117747
2013 Fgf22 regulated by Fgf3/Fgf8 signaling is required for zebrafish midbrain development. Biology open 16 23789101
2017 Selective Inactivation of Fibroblast Growth Factor 22 (FGF22) in CA3 Pyramidal Neurons Impairs Local Synaptogenesis and Affective Behavior Without Affecting Dentate Neurogenesis. Frontiers in synaptic neuroscience 12 29311892
2022 FGF22 deletion causes hidden hearing loss by affecting the function of inner hair cell ribbon synapses. Frontiers in molecular neuroscience 7 35966010
2018 Expression of fibroblast growth factor 22 (FGF22) and its receptor, FGFR1B, during development and regression of bovine corpus luteum. Theriogenology 6 30366151
2023 Fgf22 and Fgfr2b are required for neurogenesis and gliogenesis in the zebrafish forebrain. Biochemical and biophysical research communications 4 37783119
2025 FGF22 Secreted by Hair Papilla Cells Regulates Hair Follicle Stem Cell Proliferation and Differentiation. Biomolecules 1 41301478
2025 FGF22/FGFR2/YAP modulates ferroptosis to suppress neurodegeneration and cognitive impairment in Alzheimer's disease. Experimental neurology 1 41482107

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