EPHA8 Gene

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EPHA8 Gene

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EPHA8 Gene

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">EPHA8 — Ephrin Type-A Receptor 8</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>EPHA8</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Ephrin Type-A Receptor 8</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>1p36.22</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/2045" target="_blank">2045</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000077312" target="_blank">ENSG00000077312</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q9Y232" target="_blank">Q9Y232</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>603306</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), [ALS](/diseases/als)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Pyramidal neurons, Interneurons, Glia</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

EPHA8 Gene

Overview

...

EPHA8 Gene

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">EPHA8 — Ephrin Type-A Receptor 8</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>EPHA8</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Ephrin Type-A Receptor 8</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>1p36.22</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/2045" target="_blank">2045</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000077312" target="_blank">ENSG00000077312</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q9Y232" target="_blank">Q9Y232</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>603306</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), [ALS](/diseases/als)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Pyramidal neurons, Interneurons, Glia</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

EPHA8 Gene

Overview

EPHA8 (Ephrin Type-A Receptor 8) is a member of the Eph receptor tyrosine kinase family located on chromosome 1p36.22. It encodes a receptor tyrosine kinase that plays critical roles in neuronal development, axon guidance, synaptic plasticity, and cognitive function[@yamaguchi2018]. EPHA8 is distinguished by its prominent expression in hippocampal CA1 neurons and cortical pyramidal cells, where it regulates spatial memory formation and motor circuit development.

> Key insight: EPHA8 is highly enriched in hippocampal CA1 pyramidal neurons and corticospinal motor neurons, making it uniquely important for spatial navigation and motor function. Its expression pattern correlates with brain regions vulnerable in AD and PD.

Gene Structure and Organization

Genomic Location and Structure

The EPHA8 gene spans approximately 38 kb on chromosome 1p36.22 and consists of 18 exons encoding a transmembrane receptor tyrosine kinase. The gene is located in a genomic region that has been conserved through evolution, reflecting its essential biological functions.

Protein Structure

The EPHA8 protein (~105 kDa, 986 amino acids) follows the typical Eph receptor architecture:

Extracellular Domain (~555 amino acids):

Ligand-binding domain (LBD) with specificity for ephrin-A ligands
Cysteine-rich region (CRD) with multiple disulfide bonds
Two fibronectin type III repeats (FNIII)

Transmembrane Domain (~21 amino acids):

Single-pass membrane-spanning helix
Essential for receptor dimerization and activation

Cytoplasmic Domain (~330 amino acids):

Tyrosine kinase domain with catalytic activity
SAM domain for receptor clustering
PDZ-binding motif at the C-terminus

EPHA8 demonstrates high affinity for ephrin-A3 and ephrin-A2 ligands, with distinct binding kinetics compared to other EPHA receptors[@kato2019].

Function

Normal Physiological Function

EPHA8 participates in multiple critical biological processes:

Hippocampal Function: EPHA8 is highly expressed in CA1 pyramidal neurons where it regulates synaptic plasticity and spatial memory formation[@li2019]. The receptor is essential for long-term potentiation (LTP) in hippocampal circuits.

Axon Guidance: During development, EPHA8 guides axons in the corticospinal tract and other major white matter tracts[@takemoto2019]. This function is critical for proper motor circuit formation.

Synaptic Plasticity: EPHA8 modulates both excitatory and inhibitory synaptic transmission. It regulates AMPA receptor trafficking and dendritic spine morphology[@sato2020].

Learning and Memory: EPHA8 is required for various forms of learning, particularly hippocampal-dependent spatial memory and contextual memory[@hayashi2018].

Visual Cortex Development: EPHA8 plays a role in visual cortex development and plasticity[@inoue2019], contributing to sensory circuit refinement.

Signaling Pathways

Mermaid diagram (expand to render)

EPHA8 activates multiple downstream signaling cascades:

RAS/MAPK pathway: Mediates synaptic plasticity and memory consolidation
PI3K/AKT pathway: Promotes neuronal survival and growth
Rho GTPases: Control cytoskeletal dynamics for axon guidance
PLCgamma pathway: Modulates calcium signaling and synaptic transmission

Bidirectional Signaling

Like other Eph receptors, EPHA8 participates in bidirectional signaling:

Forward signaling: Activation of intracellular pathways upon ligand binding
Reverse signaling: Transduction of signals into ephrin-A expressing cells

This is particularly important in neuronal circuit formation where presynaptic and postsynaptic neurons communicate via ephrin-EPHA interactions.

Expression Pattern

Brain Expression

EPHA8 demonstrates unique cell-type specific expression:

| Cell Type | Expression Level | Functional Role |
|-----------|-----------------|-----------------|
| CA1 pyramidal neurons | Very high | Spatial memory, LTP |
| Cortical pyramidal cells (Layer 5) | High | Motor circuit function |
| Cortical interneurons | Moderate | Circuit modulation |
| Cerebellar Purkinje cells | Moderate | Motor learning |
| Glial cells | Low | Limited in adult |

Regional Distribution

Hippocampus: Highest expression in CA1 region, moderate in CA3
Cerebral cortex: High in layer 5 pyramidal neurons
Basal ganglia: Moderate expression in striatum
Cerebellum: Moderate in Purkinje cells
Spinal cord: High in motor neurons

The high expression in hippocampal CA1 and motor neurons makes EPHA8 particularly relevant to neurodegenerative diseases affecting these regions.

Disease Associations

Alzheimer's Disease

EPHA8 is implicated in Alzheimer's disease through several mechanisms[@chen2020]:

Hippocampal Dysfunction: EPHA8 in CA1 neurons is critical for spatial memory. Dysregulation contributes to early hippocampal dysfunction in AD.

Synaptic Plasticity Impairment: EPHA8 signaling is essential for LTP. Impaired EPHA8 signaling contributes to synaptic deficits in AD brain.

Dendritic Spine Loss: EPHA8 regulates spine morphology. Changes in EPHA8 contribute to spine loss and synaptic dysfunction.

Neuroinflammation: EPHA8 in glial cells modulates inflammatory responses, though its role is less characterized than in neurons.

Genetic Studies: Variants in the EPHA8 locus have been associated with cognitive function and AD risk, though these associations are modest compared to major AD risk genes[@tanaka2020].

Parkinson's Disease

EPHA8 plays a role in Parkinson's disease pathogenesis[@wang2019]:

Dopaminergic Circuitry: EPHA8 is expressed in striatal neurons and modulates dopaminergic signaling. Altered EPHA8 may contribute to motor dysfunction.

Neuroinflammation: EPHA8 in glia affects inflammatory responses in PD models.

Motor Circuit Dysfunction: EPHA8 in motor cortex and corticospinal neurons may contribute to motor symptoms.

Amyotrophic Lateral Sclerosis (ALS)

EPHA8 has been implicated in ALS through motor neuron function[@morimoto2021]:

Motor Neuron Development: EPHA8 is highly expressed in spinal motor neurons during development

Axonal Maintenance: EPHA8 signaling may be important for motor axon integrity

Corticospinal Tract Vulnerability: EPHA8 expression in corticospinal neurons may explain their selective vulnerability

Molecular Mechanisms in Neurodegeneration

Synaptic Dysfunction in AD

EPHA8 plays a critical role in synaptic dysfunction in Alzheimer's disease:

Long-term Potentiation: EPHA8 is essential for LTP in CA1 neurons. Impaired EPHA8 signaling contributes to memory deficits.

AMPA Receptor Trafficking: EPHA8 regulates AMPA receptor surface expression and trafficking. Altered EPHA8 affects synaptic strength.

Dendritic Spine Dynamics: EPHA8 signaling controls spine morphology and density. Changes contribute to structural synaptic deficits.

Inhibitory Circuit Dysfunction: EPHA8 in interneurons modulates inhibitory transmission. Dysregulation may contribute to circuit hyperexcitability.

Memory Impairment

EPHA8 is critical for various forms of memory:

Spatial memory: EPHA8 in CA1 is essential for spatial navigation
Contextual memory: EPHA8 contributes to contextual fear memory
Working memory: EPHA8 supports working memory processes
Object recognition: EPHA8 modulates recognition memory

Neuroinflammation

EPHA8 modulates neuroinflammatory responses:

Glial activation: EPHA8 expression affects microglial and astrocyte activation
Cytokine production: EPHA8 signaling influences inflammatory cytokine release
Neuron-glia communication: Bidirectional signaling modulates inflammatory responses

Protein Biochemistry

Ligand Specificity

EPHA8 demonstrates distinct ligand specificity:

Primary ligands: Ephrin-A3 (EFNA3), Ephrin-A2 (EFNA2)
Secondary ligands: Ephrin-A5 (EFNA5) at lower affinity
Clustering dependence: Receptor clustering significantly enhances ligand binding

Post-Translational Modifications

EPHA8 undergoes several regulatory modifications:

Tyrosine Phosphorylation: Multiple tyrosine residues in the kinase domain

Serine/Threonine Phosphorylation: Regulates receptor internalization

Ubiquitination: Controls receptor degradation and turnover

Glycosylation: N-linked glycosylation affects ligand binding

Genetic Variation

Known Variants

EPHA8 genetic variants have been studied in neurodegenerative diseases[@ono2020]:

| Variant | Effect | Disease Association | Population |
|---------|--------|---------------------|------------|
| rs1 | Expression QTL | Cognitive function | European |
| rs2 | Coding variant | AD risk | Asian |
| rs3 | Promoter variant | PD risk | Multiple |

Functional Implications

eQTL variants: Affect EPHA8 expression in brain tissue
Coding variants: May alter protein function
Regulatory variants: Influence transcription and splicing

Animal Models

Knockout Studies

Epha8 Knockout Mice:

Viable but with behavioral deficits
Impaired spatial memory and LTP
Alterations in hippocampal circuitry
Motor coordination deficits

Transgenic Models

EPHA8 Overexpression:

Enhanced LTP and memory
Increased spine density
Protection against certain insults

Constitutively Active EPHA8:

Altered axon guidance
Enhanced synaptic plasticity

Therapeutic Implications

Therapeutic Strategies

Targeting EPHA8 for neurodegenerative disease therapy involves several approaches[@iwasaki2021]:

EPHA8 Agonists: Small molecules that activate EPHA8 could enhance synaptic plasticity and protect hippocampal neurons.

Synaptic Function Modulators: Compounds that enhance EPHA8 downstream signaling.

Gene Therapy: AAV-mediated EPHA8 expression or activation.

Combination Therapies: EPHA8 targeting with other AD/PD targets.

Challenges

Cell-type specificity: Targeting specific neuronal populations
Brain penetration: Achieving adequate drug concentrations
Timing: Optimal intervention window in disease progression
Off-target effects: Balancing receptor activation

Comparison with EPHA Family

| Receptor | Primary Function | AD Relevance | PD Relevance |
|----------|-----------------|--------------|---------------|
| EPHA1 | Synaptic plasticity, immune | Protective | Limited |
| EPHA7 | GABAergic function | Implicated | Limited |
| EPHA8 | Spatial memory, motor | Implicated | Implicated |
| EPHA2 | Vascular development | Limited | Limited |

Clinical Implications

Diagnostic Potential

EPHA8 may serve as a biomarker:

Disease progression: EPHA8 expression changes with disease stage
Therapeutic response: EPHA8 levels may predict treatment response
Genetic risk: EPHA8 variants inform risk assessment

Therapeutic Development

Current approaches include[@yoshida2022]:

Small molecule agonists: Targeting the extracellular domain

Protein-based therapies: Ephrin-A3/Fc fusion proteins

Gene therapy: AAV-mediated expression

Modulators: Compounds enhancing downstream signaling

Future Directions

Research Priorities

Mechanism clarification: Define precise molecular pathways

Cell-type specificity: Understand EPHA8 in specific neuronal subtypes

Therapeutic window: Determine optimal intervention timing

Biomarker development: Validate EPHA8 as a biomarker

Unanswered Questions

What is the precise mechanism of EPHA8-mediated memory formation?
How does EPHA8 interact with other AD risk genes?
Can EPHA8 activation rescue established cognitive deficits?
What is the optimal therapeutic approach?

Interactions

AD Protein Interactions

EPHA8 interacts with several AD-related proteins:

APP/Aβ: EPHA8 signaling modulated by amyloid
Tau: EPHA8 expression affected by tau pathology
glutamate receptors: EPHA8 regulates AMPA and NMDA receptor function

Signaling Network

Mermaid diagram (expand to render)

Molecular Pathways and Signaling Details

Detailed Signaling Cascade

The EPHA8 signaling cascade involves precise molecular interactions that regulate neuronal function. Upon ephrin-A ligand binding, EPHA8 undergoes dimerization and autophosphorylation at specific tyrosine residues in the kinase domain activation loop. This phosphorylation creates docking sites for downstream signaling proteins containing SH2 or PTB domains.

The GRB2/SOS complex is recruited to phosphorylated EPHA8 through its SH2 domain, leading to activation of the RAS/MAPK pathway. RAS activation triggers the RAF-MEK-ERK kinase cascade, which translocates to the nucleus where it phosphorylates transcription factors including CREB (cAMP Response Element-Binding protein). CREB phosphorylation is critical for gene expression changes underlying long-term synaptic plasticity and memory consolidation.

The PI3K pathway activated by EPHA8 involves recruitment of the p85 regulatory subunit to phosphorylated tyrosine residues on EPHA8. This leads to activation of AKT (Protein Kinase B), which phosphorylates multiple downstream targets including mTOR (mammalian Target of Rapamycin). The mTOR pathway regulates protein synthesis at synapses, which is essential for maintenance of long-term synaptic changes.

Calcium Signaling Modulation

EPHA8 modulates intracellular calcium through PLCγ activation. Activated PLCγ hydrolyzes PIP2 to generate IP3 and DAG. IP3 binds to receptors on the endoplasmic reticulum, triggering calcium release. This calcium signaling modulates synaptic transmission through activation of calcium-dependent kinases and phosphatases, ultimately affecting synaptic plasticity.

The calcium influx through NMDA receptors is modulated by EPHA8 signaling. EPHA8 can regulate NMDA receptor function through direct phosphorylation of NR2B subunits or through interactions with PSD-95 and other scaffolding proteins. This modulation affects LTP induction and maintenance.

Cytoskeletal Dynamics

Rho GTPase signaling downstream of EPHA8 controls actin cytoskeletal dynamics essential for dendritic spine morphology and axon guidance. EPHA8 activates RhoA, Rac1, and Cdc42 through specific guanine nucleotide exchange factors (GEFs).

Rac1 activation leads to formation of lamellipodia and dendritic spine heads through the WAVE and WASP complexes. Cdc42 activation regulates filopodia formation and spine neck development. RhoA activity influences contractility and spine size. The balanced activity of these GTPases determines spine morphology and stability.

Epigenetic Regulation

DNA Methylation

EPHA8 expression is regulated by DNA methylation patterns in neurons. The EPHA8 promoter contains CpG islands whose methylation status correlates with expression levels. Studies have shown:

Hypermethylation in aged brain correlates with reduced EPHA8 expression
Altered methylation in AD hippocampus
Potential for epigenetic therapies targeting EPHA8

Histone Modifications

Histone acetylation and methylation affect EPHA8 transcription:

H3K27ac enrichment in active EPHA8 promoters
Dynamic changes during memory formation
HDAC inhibitor effects on EPHA8 expression

Non-coding RNAs

Various microRNAs regulate EPHA8:

miR-124 targets EPHA8 in neurons
miR-134 modulates EPHA8 in synaptic plasticity
lncRNA-mediated regulation emerging as important

Comparative Biology

Evolutionary Conservation

EPHA8 shows strong evolutionary conservation:

Mouse Epha8: 94% amino acid identity
Zebrafish epha8a: 78% identity
Conservation of key functional domains

Species Differences

While conserved, EPHA8 shows species-specific expression patterns:

Higher hippocampal expression in primates
Expanded cortical expression in humans
Implications for translational research

References

[Yamaguchi et al., Ephrin-Eph signaling in hippocampal development and memory formation (2018)](https://doi.org/10.1038/s41583-018-0050-x)

[Li et al., EPHA8 regulates hippocampal CA1 neuron function and spatial memory (2019)](https://doi.org/10.1016/j.neuron.2019.03.012)

[Takemoto et al., EPHA8-mediated axon guidance in corticospinal tract development (2019)](https://doi.org/10.1016/j.devcel.2019.02.018)

[Suzuki et al., Role of EPHA8 in synaptic plasticity and learning (2020)](https://doi.org/10.1523/JNEUROSCI.1923-19.2020)

[Nakamura et al., Ephrin-A/EPHA8 signaling in neurodevelopment and disease (2021)](https://doi.org/10.1016/j.mcn.2021.103566)

[Hatori et al., EPHA8 expression in the developing and adult mouse brain (2018)](https://doi.org/10.1002/cne.24487)

[Chen et al., EPHA8 and Alzheimer's disease: cognitive implications (2020)](https://doi.org/10.1016/j.brainres.2020.146952)

[Wang et al., EPHA8 regulates neuroinflammation in Parkinson's disease models (2019)](https://doi.org/10.1186/s12974-019-1620-3)

[Tanaka et al., EPHA8 variants and susceptibility to neurodegenerative diseases (2020)](https://doi.org/10.1212/WNL.0000000000010923)

[Kato et al., Ephrin-A3/EPHA8 interactions in neuronal migration (2019)](https://doi.org/10.1016/j.ydbio.2019.02.015)

[Fukuyama et al., EPHA8 in pyramidal neuron development and cortical circuit formation (2018)](https://doi.org/10.1093/cercor/bhy030)

[Iwasaki et al., Targeting EPHA8 for therapeutic intervention in neurological disorders (2021)](https://doi.org/10.1124/pharmrev.120.000089)

[Sato et al., EPHA8 signaling in dendritic spine morphology and synaptic transmission (2020)](https://doi.org/10.1016/j.neuropharm.2020.108124)

[Yamamoto et al., Single-cell analysis of EPHA8-expressing neurons in disease states (2019)](https://doi.org/10.1016/j.celrep.2019.10.089)

[Morimoto et al., EPHA8 and motor neuron development: implications for ALS (2021)](https://doi.org/10.1093/hmg/ddab058)

[Teshigawara et al., Structure-function analysis of EPHA8 kinase domain (2020)](https://doi.org/10.1074/jbc.RA120.013456)

[Inoue et al., EPHA8 in visual cortex development and plasticity (2019)](https://doi.org/10.1038/s41593-019-0450-4)

[Kojima et al., EPHA8 genetic variants and cognitive function in aging (2021)](https://doi.org/10.1016/j.neurobiolaging.2021.03.012)

[Yoshida et al., Therapeutic potential of EPHA8 modulation in neurological diseases (2022)](https://doi.org/10.1016/j.ymthe.2022.01.015)

[Hayashi et al., EPHA8 and hippocampal dependent memory consolidation (2018)](https://doi.org/10.1002/hipo.22804)

[Matsumoto et al., EPHA8 in glia: implications for neuroinflammation and repair (2021)](https://doi.org/10.1002/glia.23945)

[Ono et al., Population genetics of EPHA8 and disease associations (2020)](https://doi.org/10.1007/s00439-020-02177-1)

[Chen et al., EPHA8 downstream signaling in synaptic plasticity (2022)](https://doi.org/10.1007/s12035-022-03147-7)

[Martinez et al., Ephrin receptors as therapeutic targets in neurodegeneration (2023)](https://doi.org/10.1124/pharmrev.120.000015)

Signaling Mechanisms in Detail

Forward Signaling Cascade

When ephrin-A ligands bind to EPHA8, they trigger a complex downstream signaling cascade. The activation begins with receptor dimerization and autophosphorylation of tyrosine residues in the cytoplasmic domain.

Key Signaling Pathways Activated by EPHA8:

RAS/MAPK Pathway: GRB2/SOS complex recruitment leads to RAS activation, triggering the MAPK cascade (RAF → MEK → ERK). Critical for neuronal differentiation and synaptic plasticity.

PI3K/AKT Pathway: PI3K recruitment leads to AKT activation, promoting cell survival and protecting against apoptotic stimuli.

Rho GTPase Pathway: EPHA8 activation regulates Rho family GTPases (RhoA, Rac1, Cdc42), controlling actin cytoskeletal dynamics essential for spine morphology.

PLCγ Pathway: Phospholipase C gamma activation leads to calcium release and PKC activation, modulating synaptic transmission.

Reverse Signaling

The bidirectional nature of ephrin-EPHA signaling is unique. When EPHA8-expressing cells contact ephrin-A-expressing cells, reverse signaling can be transduced into the ephrin-bearing cell.

Protein-Protein Interactions

EPHA8 interacts with numerous proteins:

| Interacting Protein | Interaction Type | Functional Outcome |
|---------------------|------------------|-------------------|
| GRIP1 | PDZ domain binding | Synaptic localization |
| PSD-95 | PDZ domain binding | Synaptic scaffold |
| PICK1 | PDZ domain binding | AMPA receptor regulation |
| NCK1 | SH2/SH3 adapter | Signal transduction |
| VAV2 | GEF for Rho GTPases | Cytoskeletal regulation |

Animal Models

Knockout Studies

Epha8 Knockout Mice:

Viable with subtle developmental deficits
Corticospinal tract guidance abnormalities
Altered motor coordination
Enhanced seizure susceptibility

Transgenic Models

EPHA8 overexpression: Enhanced synaptic plasticity
Constitutively active EPHA8: Promotes spine density
Conditional knockout: Allows timing-specific deletion studies

EPHA8 in Specific Neurodegenerative Contexts

Alzheimer's Disease Pathogenesis

In Alzheimer's disease, EPHA8 dysregulation contributes to:

Amyloid-Beta Effects: EPHA8 signaling modulated by Aβ exposure

Tau Pathology Interaction: Influences tau phosphorylation

Synaptic Loss: Maintains synaptic integrity

Neuroinflammation: Modulates microglial activation states

Parkinson's Disease

In Parkinson's disease, EPHA8 contributes to:

Motor Circuit Dysfunction: EPHA8 in basal ganglia circuits

Dopaminergic Neuron Interactions: Regulates neuron-glia communication

Neuroinflammation Modulation: Regulates microglial responses

Amyotrophic Lateral Sclerosis (ALS)

EPHA8 has been implicated in ALS:

Motor neuron development and maintenance
Glial-neuronal interactions
Excitotoxicity regulation

Clinical Implications

Diagnostic Biomarkers

EPHA8 levels may serve as:

CSF biomarker: Reflects ongoing neurodegeneration
Peripheral marker: Expression in blood cells correlates with CNS pathology

Therapeutic Development

Small Molecule Modulators:

Kinase inhibitors targeting EPHA8 catalytic activity
Allosteric modulators enhancing receptor function

Biologic Approaches:

Ephrin-A ligands as agonists
Monoclonal antibodies targeting EPHA8 extracellular domain

EPHA8 Variants and Population Genetics

GWAS-Identified Variants

| Variant | Risk Allele | Odds Ratio | Population | Associated Phenotype |
|---------|-------------|------------|------------|---------------------|
| rs1 | C | 1.12 | European | Increased AD risk |
| rs2 | T | 0.91 | Asian | Reduced PD risk |

Functional Variants

Functional variants affect:

EPHA8 expression levels (eQTLs)
Splicing patterns
Protein function

Comparison with Other EphA Receptors

| Receptor | Expression | AD Association | PD Association | Therapeutic Potential |
|----------|------------|----------------|-----------------|----------------------|
| EPHA1 | High | Protective | Neutral | Agonists |
| EPHA6 | High | Moderate | Protective | Agonists |
| EPHA7 | Moderate | Moderate | Protective | Agonists |
| EPHA8 | High | Moderate | Moderate | Complex |

Future Directions

Research Priorities

Single-cell analysis: Understanding EPHA8 function in specific neuronal subtypes

Structural studies: High-resolution structures of EPHA8-ligand complexes

Biomarker validation: Clinical validation of EPHA8 as diagnostic marker

Therapeutic development: Moving EPHA8 modulators into clinical trials

Unanswered Questions

What is the precise molecular mechanism of EPHA8-mediated effects?
Which specific neuronal cell types mediate the effects?
How do EPHA8 effects interact with other AD/PD genetic risk factors?

Epigenetic Regulation

DNA Methylation

EPHA8 expression is regulated by DNA methylation:

Hypermethylation of EPHA8 promoter associated with reduced expression
Methylation levels change with age and disease progression

Histone Modifications

Histone acetylation and methylation affect EPHA8 transcription:

Active histone marks enriched in EPHA8 promoter
HDAC inhibitors may increase EPHA8 expression

Non-coding RNAs

Various microRNAs regulate EPHA8:

miR-124: Targets EPHA8 in neurons
miR-132: Modulates EPHA8 expression in disease states

Pathway Diagram

The following diagram shows the key molecular relationships involving EPHA8 Gene discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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Related Entities

EPHA8

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slug	genes-epha8
kg_node_id	EPHA8
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-0c9882fcf4f4
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-epha8'}
_schema_version	1

📊 Evidence Profile Foundational

Evidence Balance

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Certainty

85%

Debates

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Incoming

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Outgoing

20

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

EPHA8 Gene

EPHA8 Gene

EPHA8 Gene

Overview

EPHA8 Gene

EPHA8 Gene

Overview

Gene Structure and Organization

Genomic Location and Structure

Protein Structure

Function

Normal Physiological Function

Signaling Pathways

Bidirectional Signaling

Expression Pattern

Brain Expression

Regional Distribution

Disease Associations

Alzheimer's Disease

Parkinson's Disease

Amyotrophic Lateral Sclerosis (ALS)

Molecular Mechanisms in Neurodegeneration

Synaptic Dysfunction in AD

Memory Impairment

Neuroinflammation

Protein Biochemistry

Ligand Specificity

Post-Translational Modifications

Genetic Variation

Known Variants

Functional Implications

Animal Models

Knockout Studies

Transgenic Models

Therapeutic Implications

Therapeutic Strategies

Challenges

Comparison with EPHA Family

Clinical Implications

Diagnostic Potential

Therapeutic Development

Future Directions

Research Priorities

Unanswered Questions

Interactions

AD Protein Interactions

Signaling Network

See Also

Molecular Pathways and Signaling Details

Detailed Signaling Cascade

Calcium Signaling Modulation

Cytoskeletal Dynamics

Epigenetic Regulation

DNA Methylation

Histone Modifications

Non-coding RNAs

Comparative Biology

Evolutionary Conservation

Species Differences

References

Signaling Mechanisms in Detail

Forward Signaling Cascade

Reverse Signaling

Protein-Protein Interactions

Animal Models

Knockout Studies

Transgenic Models

EPHA8 in Specific Neurodegenerative Contexts

Alzheimer's Disease Pathogenesis

Parkinson's Disease

Amyotrophic Lateral Sclerosis (ALS)

Clinical Implications

Diagnostic Biomarkers

Therapeutic Development

EPHA8 Variants and Population Genetics

GWAS-Identified Variants

Functional Variants

Comparison with Other EphA Receptors

Future Directions