CYFIP2
Gene	CYFIP2
UniProt	Q9Y2D89
PDB	6V0Z, 7AKB
Mol. Weight	125 kDa
Localization	Cytoplasm, synapse, lamellipodia
Family	FMRP interacting protein family, WASF3 complex
Diseases	Intellectual Disability, Neurodevelopmental Disorders, ALS, Autism Spectrum Disorder
KG Connections	1 edges

CYFIP2 — Cytoplasmic FMRP-Interacting Protein 2

Overview

CYFIP2 (Cytoplasmic FMRP-Interacting Protein 2) is a 125 kDa scaffold protein that plays critical roles in synaptic function, actin cytoskeleton regulation, and neuronal development. Encoded by the CYFIP2 gene, this protein is a member of the FMRP-interacting protein family and serves as a key regulator of the WAVE complex that controls actin polymerization^{1Q9Y2D89 - CYFIP2_HUMANOpen reference}.

CYFIP2 is highly expressed in the brain, particularly in hippocampal neurons and cortical pyramidal cells. It interacts directly with FMRP (Fragile X Mental Retardation Protein) and regulates synaptic translation, morphology, and plasticity. Dominant de novo mutations in CYFIP2 cause a neurodevelopmental disorder characterized by intellectual disability, seizures, and autistic features^{2CYFIP2 mutations associated with neurodevelopmental disorders2019 · Human Molecular Genetics · PMID 31150189Open reference3CYFIP2-related neurodevelopmental disorder2019 · American Journal of Human Genetics · PMID 31153951Open reference}.

Domain Architecture

CYFIP2 contains several functional domains that mediate protein-protein interactions:

N-Terminal Region (1-200 aa)

• HEAT repeats: Mediate interaction with FMRP and other RNA-binding proteins

• Basic region: Potential nuclear localization signal

Central Region (200-500 aa)

• SCAAR region: Involved in actin binding and regulation

• VCA domain: Binds to the WAVE complex (WAVE1, NAP1, ABI1)

C-Terminal Region (500-700 aa)

• ** coiled-coil domains**: Mediate dimerization and complex formation

• Proline-rich region: Binds to SH3 domain-containing proteins

Normal Function in the Nervous System

Synaptic Regulation

CYFIP2 is enriched at synapses where it regulates^{4CYFIP2 regulates hippocampal synaptic plasticity2015 · Journal of Neuroscience · PMID 26658843Open reference}:

• Synaptic translation: Interacts with FMRP to control local protein synthesis at synapses

• Synaptic morphology: Regulates dendritic spine shape and density

• Long-term potentiation (LTP): Required for proper LTP induction and maintenance

• Synaptic plasticity: Modulates both excitatory and inhibitory synaptic transmission

Actin Cytoskeleton Regulation

Through the WAVE complex, CYFIP2 controls^{5CYFIP2 in actin cytoskeleton regulation2018 · Cell Reports · PMID 29677510Open reference}:

• Lamellipodia formation: Regulates actin polymerization at the leading edge of neurons

• Dendritic spine architecture: Controls spine head morphology

• Axonal guidance: Participates in growth cone dynamics

• Synaptic vesicle trafficking: Links actin dynamics to vesicle cycling

RNA Granule Transport

CYFIPIP2 is recruited to RNA granules containing^{6FMRP and CYFIP2 in synaptic homeostasis2019 · Neurobiology of Disease · PMID 31238061Open reference}:

• FMRP-bound mRNAs

• Translational machinery

• Transport proteins (e.g., kinesins)

This allows local translation of synaptic proteins at dendritic sites.

Role in Neurodegenerative Disease

Amyotrophic Lateral Sclerosis (ALS)

CYFIP2 has been implicated in ALS through several mechanisms:

• TDP-43 pathology: CYFIP2 interacts with stress granule proteins that are disrupted in ALS

• FMRP dysregulation: Loss of FMRP-CYFIP2 interaction may contribute to synaptic dysfunction

• WAVE complex disruption: Altered actin regulation affects neuromuscular junction stability

• Motor neuron survival: CYFIP2 expression is reduced in spinal motor neurons of ALS patients

Intellectual Disability and Neurodevelopmental Disorders

Dominant mutations in CYFIP2 cause a distinct neurodevelopmental syndrome characterized by^{3CYFIP2-related neurodevelopmental disorder2019 · American Journal of Human Genetics · PMID 31153951Open reference2CYFIP2 mutations associated with neurodevelopmental disorders2019 · Human Molecular Genetics · PMID 31150189Open reference}:

• Severe intellectual disability (IQ typically <50)

• Seizures (in ~70% of patients)

• Autistic features and social communication deficits

• Microcephaly or sometimes macrocephaly

• Hypotonia in infancy

• Distinctive facial features

These mutations are typically de novo and act through dominant-negative or gain-of-function mechanisms.

Autism Spectrum Disorder

CYFIP2 is considered an autism risk gene due to:

• FMRP interaction: Shared pathway with Fragile X syndrome

• Synaptic protein synthesis: Disrupted local translation affects synapse formation

• Actin regulation: Altered spine morphology observed in mouse models

Interacting Partners

Protein	Interaction Type	Functional Significance
FMRP	Direct binding	Synaptic translation regulation
FMR1	Indirect	Shared signaling pathway
WAVE1	Complex	Actin polymerization
NAP1	Complex	WAVE complex assembly
ABI1	Complex	WAVE complex, Rac signaling
RACK1	Direct binding	PKC signaling scaffold
eIF4G	Direct binding	Translation initiation

Therapeutic Targeting Landscape

Therapeutic Potential

CYFIP2 represents a potential therapeutic target for:

• Neurodevelopmental disorders: Enhancing CYFIP2 function may improve synaptic function

• ALS: Restoring WAVE complex function and actin regulation

• Fragile X syndrome: Shared therapeutic pathways with CYFIP2 modulation

Challenges

• CYFIP2 dosage is critical — both loss and gain of function cause disease

• Blood-brain barrier penetration required for CNS-targeting approaches

• Dominant-negative mutations are particularly challenging to drug

Current Approaches

1. Gene therapy: AAV-mediated CYFIP2 expression

2. Small molecule stabilizers: Promote WAVE complex assembly

3. Antisense oligonucleotides: Knockdown of toxic gain-of-function alleles

4. Actin modulators: Restore downstream actin dynamics

Biomarker Potential

CYFIP2 expression in patient-derived cells may serve as:

• A biomarker for neurodevelopmental disease severity

• A pharmacodynamic marker for therapeutic efficacy

• A tool for patient stratification

Practical Interpretation for NeuroWiki Pages

When CYFIP2 is referenced in disease pages:

• Evidence level: Strong for neurodevelopmental disorders; emerging for ALS

• Mechanistic plausibility: High — direct FMRP interaction and actin regulation are well-established

• Therapeutic relevance: Emerging target but not yet clinically validated

This framing helps maintain evidence fidelity when linking CYFIP2 across Alzheimer’s disease, Parkinson’s disease, and broader neurodegeneration.

See Also

• FMRP Protein

• WAVE Complex

• Synaptic Plasticity

• Actin Cytoskeleton

• Intellectual Disability

• Autism Spectrum Disorder

• Amyotrophic Lateral Sclerosis

External Links

• UniProt: CYFIP2 (Q9Y2D89)

• AlphaFold: CYFIP2 Structure

• RCSB PDB: 6V0Z, 7AKB

• NCBI Gene: CYFIP2 (9777)