<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><strong>Gene Symbol</strong></td><td>SEPT2</td></tr>
<tr><td><strong>Full Name</strong></td><td>Septin 2</td></tr>
<tr><td><strong>Chromosome</strong></td><td>2q37.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[4735](https://www.ncbi.nlm.nih.gov/gene/4735)</td></tr>
<tr><td><strong>OMIM</strong></td><td>608679</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000168385</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q15020](https://www.uniprot.org/uniprot/Q15020)</td></tr>
<tr><td><strong>Gene Type</strong></td><td>Protein Coding</td></tr>
<tr><td><strong>Protein Length</strong></td><td>361 amino acids</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>40.5 kDa</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Neurodevelopmental Disorders, Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Cancer</td></tr>
</table>
</div>
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].
<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><strong>Gene Symbol</strong></td><td>SEPT2</td></tr>
<tr><td><strong>Full Name</strong></td><td>Septin 2</td></tr>
<tr><td><strong>Chromosome</strong></td><td>2q37.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[4735](https://www.ncbi.nlm.nih.gov/gene/4735)</td></tr>
<tr><td><strong>OMIM</strong></td><td>608679</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000168385</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q15020](https://www.uniprot.org/uniprot/Q15020)</td></tr>
<tr><td><strong>Gene Type</strong></td><td>Protein Coding</td></tr>
<tr><td><strong>Protein Length</strong></td><td>361 amino acids</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>40.5 kDa</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>Neurodevelopmental Disorders, Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Cancer</td></tr>
</table>
</div>
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].
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.
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.
SEPT2 possesses the characteristic septin domain architecture:
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.
SEPT2 forms heterooligomeric complexes with other septins, primarily SEPT6, SEPT7, and SEPT9. These complexes further assemble into:
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].
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].
SEPT2 localizes to specialized membrane domains including:
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:
In presynaptic terminals, SEPT2 participates in:
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].
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.
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].
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].
SEPT2 is ubiquitously expressed in most human tissues, with highest expression in:
In neurons, SEPT2 localizes to:
SEPT2 dysregulation contributes to Alzheimer's disease pathogenesis through multiple mechanisms:
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.
SEPT2 plays critical roles in synaptic structure and function that are compromised in AD:
[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.
Targeting SEPT2 in AD offers several therapeutic approaches:
SEPT2 directly interacts with [alpha-synuclein](/proteins/alpha-synuclein) and is recruited to Lewy bodies in PD[@fujiwara2022]. This interaction:
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:
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].
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.
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.
SEPT2 mutations have been linked to neurodevelopmental disorders including:
| 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 | 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 |
SEPT2 levels in cerebrospinal fluid may serve as a biomarker for:
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:
SEPT2 knockout mice exhibit embryonic lethality, highlighting the essential nature of this protein for cellular function. Conditional knockout models in neurons show:
Transgenic mouse models expressing mutant SEPT2 recapitulate aspects of neurodegenerative disease: