[^1]
| Property | Value | [^2]
|---------|-------| [^3]
| **Protein Name** | FGF17 (Fibroblast Growth Factor 17) | [^4]
| **Gene** | [FGF17](/genes/fgf17) |
| **UniProt ID** | [Q9G079](https://www.uniprot.org/uniprot/Q9G079) |
| **Molecular Weight** | ~20 kDa |
| **Subcellular Localization** | Secreted |
| **Protein Family** | FGF family (FGF8 subfamily) |
| **Receptors** | FGFR1, FGFR2, FGFR4 |
| **Expression** | Brain, heart, skeletal tissue |
FGF17 (Fibroblast Growth Factor 17) is a member of the FGF family of proteins that play essential roles in development, tissue patterning, and homeostasis. As part of the FGF8 subfamily, FGF17 is particularly important for brain development, where it regulates forebrain patterning, cortical area specification, and the formation of neural circuits. Recent research has revealed that FGF17 continues to have important functions in the adult brain, including roles in synaptic plasticity, learning and memory, and potentially in neurodegenerative diseases.
FGF17 signals through fibroblast growth factor receptors (FGFRs), primarily FGFR1 and FGFR2, with some capability to signal through FGFR4. Like other FGFs, FGF17 exerts its effects through multiple downstream signaling pathways including the MAPK/ERK pathway, PI3K/Akt pathway, and PLCγ pathway.
¶ Gene and Protein Structure
The human FGF17 gene is located on chromosome 8p21.3 and consists of 5 exons encoding a secreted protein. The gene is approximately 4.5 kb in length and is transcribed as a single mRNA isoform.
FGF17 is a ~20 kDa secreted protein that shares the characteristic fold of the FGF family:
- N-terminal signal peptide (1-20 aa): Directs secretion via the secretory pathway
- Core domain (21-203 aa): The conserved FGF homology domain
- Heparin-binding region: Basic residues for binding to heparin sulfate proteoglycans
The tertiary structure consists of a β-trefoil fold with 12 antiparallel β-strands organized into three β-sheet motifs. This structure is highly conserved across the FGF family and is essential for receptor binding.
FGF17 interacts with FGFRs through:
- Receptor-binding interface: Central region of the FGF core domain
- Heparin/heparan sulfate binding: Stabilizes FGF-FGFR complexes
- Heparin-binding domain: Enables presentation of FGF to receptors
FGF17 binds to FGFRs with distinct binding characteristics:
- FGFR1c: High-affinity binding
- FGFR2c: Moderate-affinity binding
- FGFR4: Lower-affinity binding
Binding requires heparan sulfate proteoglycans (HSPGs) as co-receptors, which dimerize FGFRs and stabilize the ligand-receptor complex.
The primary signaling pathway for FGF17:
- FGF17 binding: Binds FGFR extracellular domain
- Dimerization: FGFR dimerization
- Autophosphorylation: Intrinsic tyrosine kinase activation
- FRS2 recruitment: Docking protein recruitment
- GRB2/SOS recruitment: Adaptor protein complex formation
- Ras activation: SOS catalyzes Ras-GTP formation
- MAPK cascade: Raf → MEK → ERK activation
- Cellular outcomes:
- Cell proliferation and survival
- Neuronal differentiation
- Synaptic plasticity
- Gene expression changes
FGF17 also activates PI3K signaling:
- FRS2 phosphorylation: Recruitment of PI3K adaptor proteins
- PI3K activation: Conversion of PIP2 to PIP3
- Akt activation: PKB phosphorylation and activation
- Cellular outcomes:
- Cell survival (anti-apoptotic signaling)
- Protein synthesis (mTOR activation)
- Metabolic regulation
Alternative signaling:
- PLCγ recruitment: Phosphorylated FGFR recruits PLCγ
- DAG and IP3 generation: PIP2 hydrolysis
- Cellular outcomes:
- Calcium signaling
- PKC activation
- Gene transcription
During embryogenesis, FGF17 shows dynamic expression patterns:
Early development (E9.5-E12.5):
- Forebrain patterning
- Midbrain-hindbrain boundary establishment
- Limb bud development
Mid-late development (E12.5-E18.5):
- Cortical development
- Cerebellar development
- Skeletal development
Specific brain regions:
- Ventral forebrain
- Cortical ventricular zone
- Hippocampal primordium
- Cerebellar Purkinje cell layer
In the adult brain, FGF17 expression is maintained in specific regions:
High expression:
- Hippocampus (CA1, CA3, dentate gyrus)
- Cerebral cortex (layers 2-3, 5)
- Cerebellum (Purkinje cells)
- Subventricular zone (neural stem cell niche)
Moderate expression:
Low or absent:
- Most white matter regions
- Brainstem (except specific nuclei)
- Neurons: High expression in pyramidal neurons, granule cells
- Astrocytes: Low expression, upregulated in reactive astrocytes
- Neural stem cells: Expressed in SVZ and subgranular zone
- Oligodendrocytes: Very low expression
FGF17 plays critical roles in brain development:
Forebrain patterning:
- Establishes ventral-dorsal gradient
- Regulates morphogen signaling centers
- Controls area specification in cortex
Cortical development:
- Regulates neuronal progenitor proliferation
- Controls cortical layer formation
- Influences neuronal differentiation
Midbrain-hindbrain boundary:
- Maintains isthmus organizer
- Controls midbrain and cerebellum development
Synaptic plasticity:
Learning and memory:
- Required for spatial memory formation
- Involved in contextual learning
- Supports memory consolidation
Neural stem cell maintenance:
- Promotes neural progenitor cell proliferation
- Supports neurogenesis in adult brain
- Influences neural differentiation
Angiogenesis:
- Promotes blood vessel formation in CNS
- Maintains vascular health
- May influence blood-brain barrier function
FGF17 has emerging roles in AD pathophysiology :
Expression changes:
- Altered FGF17 expression in AD brains
- Changes in FGF17 in hippocampus
- Association with disease severity
Potential mechanisms:
- Modulation of tau pathology
- Influence on amyloid response
- Effects on synaptic function
- Regulation of neuroinflammation
Therapeutic potential:
- FGF17 as therapeutic target
- FGFR agonists under investigation
- Neuroprotective effects of FGF signaling
FGF17 in PD:
- Expression in dopaminergic regions
- Potential neuroprotective effects
- May influence dopaminergic neuron survival
- Effects on neuroinflammation
Therapeutic implications:
- FGFR activation as neuroprotective strategy
- Potential for dopaminergic neuron support
- Combination with other growth factors
¶ Stroke and Brain Injury
FGF17 in CNS injury:
- Upregulation following stroke
- Promotes neural repair
- Supports angiogenesis
- May enhance functional recovery
Therapeutic potential:
- FGF17 delivery after stroke
- Gene therapy approaches
- Combination with rehabilitation
FGF17 and related FGFs are implicated in:
- Autism spectrum disorders: Altered FGF signaling
- Schizophrenia: FGF dysregulation
- Intellectual disability: FGF pathway mutations
Several approaches are being developed:
Recombinant FGF17:
- Protein therapeutics
- Direct delivery to CNS
- Challenges: short half-life, delivery
Small molecule FGFR agonists:
- Oral bioavailability potential
- Broader receptor activation
- Under development
- AAV-mediated FGF17 delivery
- Targeted expression in CNS
- Potential for long-term effects
- FGF17 + other growth factors
- FGF17 + rehabilitation
- FGF17 + immunomodulation
- Delivery across blood-brain barrier
- Optimal dosing and timing
- Receptor specificity
- Off-target effects
- Long-term safety
¶ Genetics and Variants
FGF17 genetic variants associated with:
- Neurodevelopmental disorders
- Psychiatric conditions
- Response to growth factor therapy
Rare FGF17 variants cause:
- Developmental disorders
- Skeletal anomalies
- Rare neurodevelopmental phenotypes
- Immunohistochemistry: Protein localization
- In situ hybridization: mRNA distribution
- ELISA: Protein levels in tissues/fluids
- RNA-seq: Transcriptome analysis
- In vitro: Neuronal cultures, organoids
- In vivo: Mouse models, zebrafish
- Human: Post-mortem brain tissue
- Knockout/knockin mice
- CRISPR editing
- Viral vectors
- Pharmacological inhibitors