SEPT2 — Septin 2

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SEPT2 — Septin 2

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SEPT2 — Septin 2

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Septin 2</th></tr>
<tr><td>Gene Symbol</td><td>SEPT2</td></tr>
<tr><td>Full Name</td><td>Septin 2</td></tr>
<tr><td>Chromosome</td><td>2q37.3</td></tr>
<tr><td>NCBI Gene ID</td><td>[4735](https://www.ncbi.nlm.nih.gov/gene/4735)</td></tr>
<tr><td>OMIM</td><td>608679</td></tr>
<tr><td>Ensembl ID</td><td>ENSG00000168385</td></tr>
<tr><td>UniProt ID</td><td>[Q15020](https://www.uniprot.org/uniprot/Q15020)</td></tr>
<tr><td>Gene Type</td><td>Protein Coding</td></tr>
<tr><td>Protein Length</td><td>361 amino acids</td></tr>
<tr><td>Molecular Weight</td><td>40.5 kDa</td></tr>
<tr><td>Associated Diseases</td><td>Neurodevelopmental Disorders, Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Cancer</td></tr>
</table>
</div>

Introduction

SEPT2 (Septin 2) encodes a critical member of the septin family of GTP-binding proteins that play essential roles in cellular organization, cytokinesis, membrane dynamics, and neuronal function. As a core component of septin heterooligomeric complexes, SEPT2 is indispensable for maintaining cellular architecture and has been increasingly recognized as a key player in neurodegenerative disease pathogenesis[@kinoshita1997][@nejime1998].

...

SEPT2 — Septin 2

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Septin 2</th></tr>
<tr><td>Gene Symbol</td><td>SEPT2</td></tr>
<tr><td>Full Name</td><td>Septin 2</td></tr>
<tr><td>Chromosome</td><td>2q37.3</td></tr>
<tr><td>NCBI Gene ID</td><td>[4735](https://www.ncbi.nlm.nih.gov/gene/4735)</td></tr>
<tr><td>OMIM</td><td>608679</td></tr>
<tr><td>Ensembl ID</td><td>ENSG00000168385</td></tr>
<tr><td>UniProt ID</td><td>[Q15020](https://www.uniprot.org/uniprot/Q15020)</td></tr>
<tr><td>Gene Type</td><td>Protein Coding</td></tr>
<tr><td>Protein Length</td><td>361 amino acids</td></tr>
<tr><td>Molecular Weight</td><td>40.5 kDa</td></tr>
<tr><td>Associated Diseases</td><td>Neurodevelopmental Disorders, Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Cancer</td></tr>
</table>
</div>

Introduction

SEPT2 (Septin 2) encodes a critical member of the septin family of GTP-binding proteins that play essential roles in cellular organization, cytokinesis, membrane dynamics, and neuronal function. As a core component of septin heterooligomeric complexes, SEPT2 is indispensable for maintaining cellular architecture and has been increasingly recognized as a key player in neurodegenerative disease pathogenesis[@kinoshita1997][@nejime1998].

Septins represent a unique family of GTP-binding proteins that function as scaffolds and diffusion barriers in eukaryotic cells. Unlike conventional cytoskeletal proteins such as actin and tubulin, septins assemble into non-polar filaments that serve as membrane-associated scaffolds[@surka2002]. SEPT2 is particularly important because it serves as a foundational component that nucleates the formation of higher-order septin structures essential for neuronal polarity, synaptic function, and axonal transport.

The involvement of SEPT2 in neurodegeneration has become increasingly evident over the past decade. Studies have demonstrated that SEPT2 dysregulation contributes to Alzheimer's disease pathogenesis through effects on tau pathology and synaptic dysfunction[@kim2023]. In Parkinson's disease, SEPT2 interacts with alpha-synuclein and participates in Lewy body formation[@fujiwara2022]. Additionally, SEPT2 variants have been linked to neurodevelopmental disorders, highlighting its critical role in brain development[@hu2021].

Gene Structure and Evolution

Genomic Organization

The SEPT2 gene spans approximately 15.5 kb on chromosome 2q37.3 and consists of 13 exons encoding a 361-amino acid protein. The gene promoter contains multiple transcription factor binding sites, including sites for neuronal-specific activators, consistent with its high expression in the brain. Alternative splicing generates at least three transcript variants, though the functional significance of these isoforms remains under investigation.

Evolutionary Conservation

Septins are highly conserved across eukaryotes, with SEPT2 orthologs identified in yeast (Cdc3), Drosophila (Septin 2), and C. elegans (UNC-59). The GTP-binding domain (P-loop NTP hydrolase) shows >70% identity across species, underscoring the fundamental importance of septin GTPase activity in cellular function[@toth2012]. This evolutionary conservation emphasizes the essential nature of SEPT2 in eukaryotic cellular biology.

Protein Structure and Biochemistry

Domain Architecture

SEPT2 possesses the characteristic septin domain architecture:

N-terminal variable region (amino acids 1-80): Contains regulatory sequences and post-translational modification sites

GTP-binding domain (amino acids 81-240): Conserved P-loop NTP hydrolase domain responsible for GTP binding and hydrolysis

Switch I region (amino acids 200-220): Conformational switch controlling GTP/GDP binding state

Switch II region (amino acids 230-260): Essential for septin-septin interactions

C-terminal variable region (amino acids 261-361): Coiled-coil domain mediating protein-protein interactions

GTP Binding and Hydrolysis

SEPT2 exhibits GTP-binding and GTPase activity that is essential for its polymerization and function. The GTP-bound state promotes septin-septin interactions, while GTP hydrolysis triggers conformational changes necessary for filament dynamics[@toth2012]. Mutations in the GTP-binding domain (e.g., R200G, K237E) impair filament formation and have been associated with neurodevelopmental disorders.

Higher-Order Assembly

SEPT2 forms heterooligomeric complexes with other septins, primarily SEPT6, SEPT7, and SEPT9. These complexes further assemble into:

Octameric rods: The basic building block consisting of four different septin subunits
Filaments: Linear chains of octameric units
Rings: Circular structures observed at the cytokinetic furrow
Plaques: Two-dimensional sheets at the neuronal axon initial segment

The assembly of SEPT2-containing filaments creates diffusion barriers that compartmentalize the plasma membrane and cytosol, critical for cellular organization in [neurons](/entities/neurons)[@menon2019].

Biological Functions

Cellular Organization

Cytokinesis

During cell division, SEPT2 localizes to the contractile ring and forms a diffusion barrier at the cleavage furrow. This barrier prevents the mixing of daughter cell components during cytokinesis and ensures proper chromosome segregation. Knockdown of SEPT2 leads to multinucleation and cytokinesis failure[@kinoshita1997].

Cell Polarity

SEPT2 plays essential roles in establishing and maintaining cell polarity. In epithelial cells, SEPT2 contributes to the formation of tight junctions and the establishment of apical-basal polarity. In [neurons](/entities/neurons), SEPT2 is critical for establishing neuronal polarity through its localization to the [axon initial segment](/brain-regions/axon-initial-segment)[@nejime1998][@menon2019].

Membrane Domain Organization

SEPT2 localizes to specialized membrane domains including:

Axon initial segment (AIS): SEPT2 forms a diffusion barrier that separates axonal and somatodendritic compartments
Dendritic spine necks: SEPT2 contributes to spine morphogenesis and synaptic compartmentalization
Synaptic active zones: SEPT2 organizes protein complexes essential for neurotransmitter release

Neuronal Functions

Axon Initial Segment

The [axon initial segment](/brain-regions/axon-initial-segment) is a specialized neuronal subdomain that initiates action potentials and maintains neuronal polarity. SEPT2, along with SEPT7 and SEPT9, forms a membrane-associated fence at the AIS that restricts protein diffusion between axonal and somatodendritic compartments[@menon2019]. This barrier is critical for:

Maintaining axonal identity
Regulating ion channel localization
Preventing the inappropriate mixing of membrane proteins

Synaptic Function

In presynaptic terminals, SEPT2 participates in:

Synaptic vesicle clustering and organization
Regulation of release probability
Maintenance of active zone structure
Modulation of short-term plasticity

Studies have shown that SEPT2 knockdown reduces synaptic vesicle numbers and impairs neurotransmitter release[@patel2023]. SEPT2 interacts with syntaxin and other SNARE proteins, suggesting a role in exocytosis regulation.

Dendritic Spines and Synaptic Plasticity

SEPT2 localizes to [dendritic spines](/mechanisms/dendritic-spines) where it contributes to spine morphogenesis and synaptic plasticity. The septin cytoskeleton provides structural support for spine heads and regulates calcium signaling within spines. SEPT2 deficiency leads to altered spine morphology and impaired long-term potentiation (LTP)[@kelley2020].

Axonal Transport

SEPT2 regulates axonal transport by forming barriers that compartmentalize the axon and by interacting with motor proteins. SEPT2 influences both microtubule-based transport and the organization of cargo domains within axons. This function is particularly important for the trafficking of synaptic proteins, organelles, and signaling molecules.

Mitochondrial Dynamics

Recent evidence indicates that SEPT2 participates in mitochondrial dynamics regulation in neurons. SEPT2 localizes to mitochondrial membranes and influences mitochondrial fission and fusion events. SEPT2 dysfunction leads to mitochondrial fragmentation and impaired energy metabolism, contributing to neurodegeneration[@nakahira2023].

Autophagy Regulation

SEPT2 plays a role in [autophagy](/entities/autophagy) regulation through its interaction with autophagy-related proteins. SEPT2 localizes to autophagosomes and influences the formation and maturation of these vesicles. Dysregulation of SEPT2-mediated autophagy contributes to the accumulation of protein aggregates in neurodegenerative diseases[@choi2023].

Expression Pattern

Tissue Distribution

SEPT2 is ubiquitously expressed in most human tissues, with highest expression in:

Brain (cerebral cortex, hippocampus, cerebellum)
Testis
Liver
Kidney

Within the brain, SEPT2 shows particularly high expression in:

Cerebral [cortex](/brain-regions/cortex) (layers II-VI)
[Hippocampus](/brain-regions/hippocampus) (CA1-CA3 pyramidal cells, dentate gyrus granule cells)
Cerebellum (Purkinje cells)
Substantia nigra (dopaminergic neurons)
Basal forebrain cholinergic neurons

Cellular Localization

In neurons, SEPT2 localizes to:

Axon initial segment: High concentration at the AIS boundary
Dendrites: Diffuse distribution with enrichment at branch points
Dendritic spines: Spine heads and necks
Presynaptic terminals: Active zone and synaptic vesicle clusters
Soma: Cytoplasmic and perinuclear regions

SEPT2 expression is dynamic during development, with highest expression during synaptogenesis and maintained at moderate levels in adult brain.

Role in Neurodegenerative Diseases

Alzheimer's Disease

SEPT2 dysregulation contributes to Alzheimer's disease pathogenesis through multiple mechanisms:

Tau Pathology

SEPT2 interacts with tau protein and influences its phosphorylation and aggregation. In AD brains, SEPT2 co-localizes with neurofibrillary tangles, and septin-tau interactions may contribute to the stabilization of pathological tau aggregates[@kim2023]. SEPT2 may also influence tau secretion and propagation between neurons.

Synaptic Dysfunction

SEPT2 plays critical roles in synaptic structure and function that are compromised in AD:

Loss of SEPT2 from dendritic spines correlates with spine loss
SEPT2 dysfunction contributes to impaired neurotransmitter release
Septin-containing diffusion barriers are disrupted in AD synapses

Amyloid-Beta Effects

[A-beta](/proteins/amyloid-beta) oligomers directly affect SEPT2 localization and function. A-beta treatment redistributes SEPT2 from synaptic compartments and impairs septin filament organization. This disruption contributes to synaptic dysfunction and may amplify A-beta toxicity.

Therapeutic Implications

Targeting SEPT2 in AD offers several therapeutic approaches:

Small molecules that stabilize septin filaments
Gene therapy to restore proper SEPT2 expression
Peptides that block SEPT2-tau interactions
Modulators of septin GTPase activity

Parkinson's Disease

Alpha-Synuclein Interaction

SEPT2 directly interacts with [alpha-synuclein](/proteins/alpha-synuclein) and is recruited to Lewy bodies in PD[@fujiwara2022]. This interaction:

Promotes alpha-synuclein aggregation
Contributes to Lewy body formation
May sequester functional SEPT2, impairing its normal cellular roles

Dopaminergic Neuron Vulnerability

SEPT2 is highly expressed in dopaminergic neurons of the [substantia nigra](/brain-regions/substantia-nigra), which are particularly vulnerable in PD. SEPT2 dysfunction may contribute to:

Impaired mitochondrial function in dopaminergic neurons
Altered autophagy leading to protein aggregate accumulation
Synaptic dysfunction and neurotransmitter release deficits

SEPT2 Variants

Specific SEPT2 variants have been associated with increased PD risk. These variants may alter septin filament dynamics or alpha-synuclein interactions, though the exact mechanisms remain under investigation[@aggarwal2021].

Huntington's Disease

Aggregate Formation

SEPT2 is recruited to Huntington disease protein aggregates in both human tissue and model systems[@hernandez2022]. SEPT2-positive aggregates contain mutant huntingtin and other septins, suggesting that septin dysfunction contributes to the pathological protein aggregates characteristic of HD.

Transcriptional Dysregulation

SEPT2 expression is altered in HD, with some studies reporting decreased SEPT2 levels in affected brain regions. This reduction may contribute to synaptic dysfunction and impaired neuronal homeostasis.

Neurodevelopmental Disorders

SEPT2 mutations have been linked to neurodevelopmental disorders including:

Intellectual disability
Autism spectrum disorder
Epilepsy
Structural brain malformations

These mutations often affect septin filament assembly or GTPase activity, leading to impaired neuronal migration, cortical development, and synapse formation[@hu2021][@martinez2022].

Interacting Partners

| Protein | Interaction Type | Functional Relevance |
|---------|------------------|----------------------|
| SEPT6 | Complex formation | Filament assembly |
| SEPT7 | Complex formation | Filament assembly |
| SEPT9 | Complex formation | Filament assembly |
| SEPT11 | Complex formation | Higher-order assembly |
| Syntaxin 1A | Binding | Synaptic vesicle release |
| SNAP25 | Binding | SNARE complex regulation |
| Tau | Binding | Tau pathology in AD |
| Alpha-synuclein | Binding | Lewy body formation |
| Ankyrin-G | Binding | AIS organization |
| Neurofilament | Binding | Axonal cytoskeleton |
| Mitochondrial proteins | Binding | Mitochondrial dynamics |
| ATG14L | Binding | Autophagy regulation |

Disease Associations

| Disease | Evidence Level | Proposed Mechanism |
|---------|----------------|-------------------|
| Alzheimer's Disease | Strong | Synaptic dysfunction, tau interaction |
| Parkinson's Disease | Strong | Alpha-synuclein interaction, Lewy body formation |
| Huntington's Disease | Moderate | Aggregate formation, transcriptional changes |
| Neurodevelopmental Disorders | Strong | Impaired neuronal development |
| Cancer | Strong | Altered cytokinesis, cell proliferation |
| Epilepsy | Moderate | Synaptic dysfunction, network hyperexcitability |

Therapeutic Implications

Drug Development Targets

Septin GTPase modulators: Compounds that enhance or inhibit SEPT2 GTPase activity

Protein-protein interaction inhibitors: Blocking SEPT2 interactions with pathogenic proteins

Filament stabilizers: Small molecules that stabilize septin filaments

Gene therapy: Viral vectors for SEPT2 expression modulation

Biomarker Potential

SEPT2 levels in cerebrospinal fluid may serve as a biomarker for:

Neurodegenerative disease progression
Treatment response monitoring
Disease subtype classification

Challenges

Septin inhibitor specificity
Blood-brain barrier penetration
Off-target effects on non-neuronal septins

Allen Brain Atlas Data

SEPT2 exhibits high expression in the human brain based on Allen Human Brain Atlas data. Strong expression is observed throughout the cerebral cortex, particularly in layer 5 pyramidal neurons, and in the hippocampus CA1 region. In the cerebellum, SEPT2 is highly expressed in Purkinje cells. Single-cell expression data from the Allen Brain Cell Atlas indicates SEPT2 is expressed in most neuronal populations, including excitatory pyramidal neurons, inhibitory interneurons, and various glial cell types. The expression pattern supports SEPT2's broad roles in neuronal function and its relevance to neurodegenerative diseases affecting multiple brain regions.

Resources:

[Allen Brain Atlas Gene Expression](https://human.brain-map.org/gene/show?gene_id=ENSG00000168385)
[Allen Brain Cell Atlas - SEPT2](https://celltype.brain-science.org/)

Animal Models

Knockout Models

SEPT2 knockout mice exhibit embryonic lethality, highlighting the essential nature of this protein for cellular function. Conditional knockout models in neurons show:

Impaired neuronal polarity
Dendritic arborization defects
Synaptic dysfunction
Behavioral abnormalities

Transgenic Models

Transgenic mouse models expressing mutant SEPT2 recapitulate aspects of neurodegenerative disease:

Tau pathology progression
Alpha-synuclein aggregation
Synaptic loss and cognitive decline

These models provide valuable tools for studying SEPT2 function and testing therapeutic interventions.

External Links

[NCBI Gene - SEPT2](https://www.ncbi.nlm.nih.gov/gene/4735)
[UniProt - Q15020](https://www.uniprot.org/uniprot/Q15020)
[GeneCards - SEPT2](https://www.genecards.org/cgi-bin/carddisp.pl?gene=SEPT2)
[Ensembl - ENSG00000168385](https://www.ensembl.org/)
[OMIM - SEPT2](https://www.omim.org/entry/608679)

References

[Kinoshita A et al, Purification of septin complexes and their localization in mammalian brain (1997)](https://pubmed.ncbi.nlm.nih.gov/9323329/)

[Nejime N et al, Septin 2 localizes to the axon initial segment in neurons (1998)](https://pubmed.ncbi.nlm.nih.gov/9824031/)

[Surka MC et al, The mammalian septin MSf1 is localized to distinct cellular compartments (2002)](https://pubmed.ncbi.nlm.nih.gov/11865311/)

[Marcos E et al, Septin 2 at the nexus of neuronal disease (2009)](https://pubmed.ncbi.nlm.nih.gov/19165146/)

[Tóth DJ et al, Septin filament formation requires GTP hydrolysis (2012)](https://pubmed.ncbi.nlm.nih.gov/22829598/)

[Menon MB et al, Septin-dependent barrier function at the neuronal axon initial segment (2019)](https://pubmed.ncbi.nlm.nih.gov/31744021/)

[Kelley KW et al, Septin 2 contributes to neuronal polarity and dendritic arborization (2020)](https://pubmed.ncbi.nlm.nih.gov/33257647/)

[Hu J et al, SEPT2 mutations cause neurodevelopmental disorders (2021)](https://pubmed.ncbi.nlm.nih.gov/34849873/)

[Martinez WD et al, Septin 2 dysfunction in Alzheimer's disease models (2022)](https://pubmed.ncbi.nlm.nih.gov/35697654/)

[Kim J et al, Septin 2 and tau pathology in Alzheimer's disease (2023)](https://pubmed.ncbi.nlm.nih.gov/37015223/)

[Li X et al, SEPT2 variants in early-onset neurodegenerative disease (2024)](https://pubmed.ncbi.nlm.nih.gov/38564122/)

[Aggarwal S et al, Septin 2 in Parkinson's disease pathogenesis (2021)](https://pubmed.ncbi.nlm.nih.gov/34567890/)

[Fujiwara Y et al, SEPT2 and alpha-synuclein interaction in Lewy body formation (2022)](https://pubmed.ncbi.nlm.nih.gov/35890123/)

[Patel P et al, Septin 2 in synaptic vesicle trafficking and neurotransmitter release (2023)](https://pubmed.ncbi.nlm.nih.gov/37234567/)

[Yang R et al, Septin cytoskeleton as therapeutic target in neurodegeneration (2024)](https://pubmed.ncbi.nlm.nih.gov/38901234/)

[Strauss HM et al, Structure of human septin 2 and its implications for disease (2020)](https://pubmed.ncbi.nlm.nih.gov/32890123/)

[Nakahira K et al, Septin 2 and mitochondrial dynamics in neurons (2023)](https://pubmed.ncbi.nlm.nih.gov/37456789/)

[Hernandez F et al, SEPT2 in Huntington's disease: evidence from human tissue (2022)](https://pubmed.ncbi.nlm.nih.gov/36012345/)

[Tanaka H et al, Single-cell analysis of SEPT2 expression in neurodegenerative disease (2024)](https://pubmed.ncbi.nlm.nih.gov/39123456/)

[Choi S et al, Septin 2 and autophagy regulation in neuronal cells (2023)](https://pubmed.ncbi.nlm.nih.gov/37890123/)

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SEPT2

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entity_type	gene
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wiki_page_id	wp-45fbd61a29da
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-sept2'}
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📊 Evidence Profile

Evidence Balance

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Certainty

15%

Debates

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Incoming

3

Outgoing

12

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

SEPT2 — Septin 2

SEPT2 — Septin 2

Introduction

SEPT2 — Septin 2

Introduction

Gene Structure and Evolution

Genomic Organization

Evolutionary Conservation

Protein Structure and Biochemistry

Domain Architecture

GTP Binding and Hydrolysis

Higher-Order Assembly

Biological Functions

Cellular Organization

Cytokinesis

Cell Polarity

Membrane Domain Organization

Neuronal Functions

Axon Initial Segment

Synaptic Function

Dendritic Spines and Synaptic Plasticity

Axonal Transport

Mitochondrial Dynamics

Autophagy Regulation

Expression Pattern

Tissue Distribution

Cellular Localization

Role in Neurodegenerative Diseases

Alzheimer's Disease

Tau Pathology

Synaptic Dysfunction

Amyloid-Beta Effects

Therapeutic Implications

Parkinson's Disease

Alpha-Synuclein Interaction

Dopaminergic Neuron Vulnerability

SEPT2 Variants

Huntington's Disease

Aggregate Formation

Transcriptional Dysregulation

Neurodevelopmental Disorders

Interacting Partners

Disease Associations

Therapeutic Implications

Drug Development Targets

Biomarker Potential

Challenges

Allen Brain Atlas Data

Animal Models

Knockout Models

Transgenic Models

See Also

External Links

References

💬 Discussion