SEPTIN14 — Septin 14
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<div class="infobox-header">Septin 14</div>
Overview
SEPTIN14 encodes Septin 14, a member of the highly conserved septin family of GTP-binding proteins that play essential roles in cellular organization, cytokinesis, membrane dynamics, and cytoskeletal coordination. Located on chromosome 22q12.3, the SEPTIN14 gene encodes a 427-amino acid protein that belongs to the SEPT2/SEPT4 subfamily of septins. While historically considered primarily testis-specific with roles in male fertility, emerging research has revealed broader expression patterns and potential physiological roles in neuronal cells, including functions relevant to neurodegenerative diseases[@hall2015][@kinoshita2008].
The septin family has been increasingly implicated in neurodegenerative diseases, with several members—particularly SEPT4 and SEPT5—linked directly to Parkinson's disease pathogenesis through genetic associations and pathological findings in Lewy bodies. SEPTIN14, as a member of the same phylogenetic subfamily, shares structural and functional relationships that may confer similar disease-relevant functions or compensatory capacities[@ishida2016][@fujishima2015].
<div class="infobox-row">
<span class="infobox-label">Gene Symbol</span>
<span class="infobox-value">SEPTIN14</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Full Name</span>
<span class="infobox-value">Septin 14</span>
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<span class="infobox-label">Chromosomal Location</span>
<span class="infobox-value">22q12.3</span>
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<span class="infobox-label">NCBI Gene ID</span>
<span class="infobox-value">[340533](https://www.ncbi.nlm.nih.gov/gene/340533)</span>
</div>
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<span class="infobox-label">OMIM</span>
<span class="infobox-value">[615898](https://www.omim.org/entry/615898)</span>
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<span class="infobox-label">Ensembl ID</span>
<span class="infobox-value">[ENSG00000167036](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000167036)</span>
</div>
<div class="infobox-row">
<span class="infobox-label">UniProt ID</span>
<span class="infobox-value">[Q6ZNA4](https://www.uniprot.org/uniprot/Q6ZNA4)</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Protein Length</span>
<span class="infobox-value">427 amino acids</span>
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<div class="infobox-row">
<span class="infobox-label">Protein Class</span>
<span class="infobox-value">GTP-binding protein (Septin family)</span>
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<div class="infobox-row">
<span class="infobox-label">Associated Diseases</span>
<span class="infobox-value">Male Infertility, Parkinson's Disease, Alzheimer's Disease, Neurodegeneration</span>
</div>
</div>
Gene Structure and Evolution
Genomic Organization
The SEPTIN14 gene spans approximately 11 kb on chromosome 22q12.3 and consists of multiple exons that encode the 427-amino acid protein product. The gene structure follows the conserved septin architecture with:
N-terminal GTP-binding domain (G domain): Highly conserved region spanning approximately 300 amino acids
Switch regions: Variable regions controlling GTP hydrolysis and nucleotide exchange
C-terminal helical domain: Mediates filament formation and higher-order assembly
Polybasic membrane-binding region: Directs association with phospholipid membranesEvolutionary Conservation
Septins emerged early in eukaryotic evolution with remarkable conservation across species. SEPTIN14 underwent specific expansion in primates, representing a relatively recent addition to the septin family:
| Species | Ortholog Status | Sequence Identity | Functional Conservation |
|---------|-----------------|-------------------|-------------------------|
| Human | SEPTIN14 | Reference | Complete function |
| Chimpanzee | SEPTIN14 | 99% | Full conservation |
| Rhesus monkey | SEPTIN14 ortholog | 95% | High conservation |
| Mouse | No ortholog | N/A | Absent |
| Zebrafish | Ancestral septin | 65% | Partial function |
| Drosophila | Septin ortholog | 58% | Basic function |
| C. elegans | Septin | 45% | Primitive function |
The absence of a direct ortholog in rodents suggests that SEPTIN14 may have specialized functions in primates that are not essential for basic cellular viability, making it potentially more amenable to therapeutic modulation[@petersen2018].
Protein Structure and Biochemistry
GTP-Binding and Hydrolysis Mechanism
Septins share features with classical GTPases but possess unique properties that distinguish them:
Nucleotide Binding:
- Binds GDP and GTP with moderate affinity (Kd ~ 0.1-1 μM)
- Exhibits slow intrinsic GTPase activity compared to Ras family GTPases
- GTP/GDP exchange rates are regulated by interactions with other proteins
GTPase Cycle:
- GTP-bound form is typically the active, polymerization-competent state
- Hydrolysis to GDP induces conformational changes that affect assembly
- Nucleotide exchange factors and GTPase-activating proteins modulate the cycle
Conformational Switch:
- The switch regions (Switch I and Switch II) undergo structural changes between GTP and GDP states
- These conformational shifts regulate protein-protein interactions
- Allow septins to function as molecular switches in cellular processes[@weirich2016]
Oligomerization and Filament Assembly
SEPTIN14 forms hetero-oligomeric complexes with other septins, a fundamental property of septin biology:
Basic Oligomeric Units:
- The fundamental building block is a hexamer or octamer of mixed septin subunits
- SEPTIN14 preferentially pairs with SEPT2/SEPT4 subfamily members
- Heterooligomer composition determines functional specificity
Filament Formation:
- Linear polymers can extend from oligomeric cores
- Filaments typically consist of alternating septin subtypes
- Higher-order structures include bundles, rings, and lattices
Membrane Association:
- The polybasic region at the C-terminus binds phospholipids
- Preferentially associates with phosphatidylinositol species
- Targets septin filaments to specific membrane domains[@silvius2015][@nakahira2021]
Protein-Protein Interaction Network
SEPTIN14 interacts with multiple cellular proteins to execute its functions:
| Partner | Interaction Type | Functional Consequence |
|---------|-----------------|------------------------|
| SEPT2 | Direct binding | Core complex formation |
| SEPT4 | Direct binding | Complex formation, potential redundancy |
| SEPT6 | Direct binding | Filament extension |
| SEPT7 | Scaffold binding | Higher-order structure formation |
| Actin cytoskeleton | Indirect | Cytoskeletal coordination |
| Microtubules | Indirect | Transport and positioning |
| Phospholipids | Direct binding | Membrane targeting |
| α-Synuclein | Potential | Aggregation modulation |
Expression Patterns and Cellular Localization
Tissue Distribution
SEPTIN14 exhibits a distinctive and tissue-specific expression pattern:
High Expression:
- Testis: Highest expression in spermatogenic cells, particularly spermatids
- Epididymis: Detected in epithelial cells of the epididymal duct
Moderate Expression:
- Brain: Low but detectable expression in various neuronal populations
- Ovary: Some expression in female reproductive tissues
Low/Trace Expression:
- Most other somatic tissues show minimal expression
Brain Expression and Neuronal Localization
In the nervous system, SEPTIN14 shows specific patterns:
Neuronal Expression:
- Detected in cortical neurons
- Present in hippocampal pyramidal neurons
- Expressed in cerebellar Purkinje cells
- Lower levels in subcortical structures
Cellular Compartmentalization:
- Cytoplasmic: Diffuse cytoplasmic distribution in neuronal soma
- Membrane-associated: Concentrated at plasma membrane, particularly in dendrites
- Organelle membranes: Associates with Golgi apparatus and endosomal compartments
- Neuronal processes: Found in both axons and dendrites
- Synaptic terminals: Present at presynaptic and postsynaptic compartments
The neuronal expression pattern suggests potential roles in synaptic function and membrane trafficking, making SEPTIN14 relevant to neurodegenerative disease mechanisms[@tornam2020][@sanchez2020].
Biological Functions
Cellular Organization and Cytoskeletal Coordination
Septins serve as critical scaffolds for cellular organization:
Cytoskeletal Coordination: SEPTIN14 interacts with actin microfilaments and microtubules to coordinate cytoskeletal dynamics
Membrane Domain Organization: Organizes lipid rafts and signaling platforms at specific membrane compartments
Organelle Positioning: Maintains subcellular organization of Golgi, endosomes, and other organelles
Cell Polarity: Contributes to establishment and maintenance of cellular polarity
Cytokinesis: In non-neuronal cells, participates in cytokinesis through contractile ring formationSpermatogenesis and Male Fertility
In testis, SEPTIN14 plays essential roles in male reproduction:
Spermatid Development:
- Essential for proper spermiogenesis (the transformation of spermatids to spermatozoa)
- Contributes to sperm head formation and elongation
- Involved in the organization of the manchette, a transient microtubule structure
Sperm Motility:
- Contributes to flagellar function and motility
- Mutations associated with asthenozoospermia (reduced sperm motility)
- Structural role in the sperm tail axoneme
Male Infertility:
- SEPTIN14 mutations cause male infertility through multiple mechanisms
- Biallelic loss-of-function mutations lead to oligospermia or azoospermia
- Associated with abnormal sperm morphology (teratozoospermia)[@ota2017]
Neuronal Functions
Emerging evidence supports neuronal roles for SEPTIN14:
Synaptic Function:
- Septins are enriched at synaptic terminals where they regulate neurotransmitter release
- SEPTIN14 may contribute to synaptic vesicle trafficking and positioning
- Potential roles in synaptic plasticity mechanisms
Axonal Transport:
- Coordinates with microtubule motors for efficient transport
- May contribute to organelle transport in neuronal processes
- Potential involvement in axonal maintenance
Membrane Trafficking:
- Participates in endocytic and exocytic pathways
- Contributes to protein sorting and trafficking
- Potential roles in receptor turnover at synapses
Dendritic Arborization:
- May influence neuronal morphology and branching
- Contributes to cytoskeletal organization in dendrites
- Potential impact on connectivity
Role in Neurodegenerative Diseases
Parkinson's Disease
SEPTIN14 shares structural and functional relationships with septins directly linked to Parkinson's disease pathogenesis:
SEPT4 and SEPT5 Connections (PARK17 Locus):
- SEPT4 mutations have been linked to familial PD
- SEPT5 deficiency causes parkinsonism in mouse models
- Both SEPT4 and SEPT5 are found in Lewy bodies, the pathological hallmark of PD
SEPTIN14 Relevance:
- Belongs to the same SEPT2/SEPT4 subfamily as disease-linked septins
- May have overlapping functions with SEPT4/SEPT5
- Potential to compensate for deficient septin function
- May serve as a genetic modifier of PD risk
Mechanisms of Contribution:
- Impaired dopamine release due to septin dysfunction
- Synaptic vesicle trafficking defects
- Mitochondrial distribution abnormalities
- Potential modulation of α-synuclein aggregation
- Involvement in protein quality control pathways[@arai2002][@kawashima2017][@kim2020]
Alzheimer's Disease
Septin alterations are documented in AD brain pathology:
Septin Family Dysregulation:
- SEPT11 shows altered expression patterns in AD brain
- SEPT2 and SEPT3 are found in neurofibrillary tangles composed of hyperphosphorylated tau
- SEPT5 expression correlates with cognitive decline severity
- Overall septin homeostasis is disrupted in AD
SEPTIN14 Potential Role:
- While direct involvement of SEPTIN14 in AD is not established, the broader septin family connections suggest potential interactions
- May modify disease progression through cytoskeletal mechanisms
- Could affect tau pathology through microtubule-related functions
- Potential biomarker utility given testis-specific expression patterns[@matsui2018][@zhang2019]
Huntington's Disease
Septin changes are observed in HD models and patient tissue:
- Altered septin expression in striatal neurons, the primary affected cell type in HD
- Contributes to synaptic dysfunction through vesicle trafficking defects
- May affect mitochondrial dynamics and distribution
- SEPT4 variants may modify disease progression in HD models
Amyotrophic Lateral Sclerosis
Septin involvement in motor neuron disease:
- SEPT4 variants modify disease progression in ALS patients
- Septin filaments found in motor neuron inclusions
- Cytoskeletal disruption is a feature of ALS pathology
- Potential roles in TDP-43 proteinopathy
Other Neurodegenerative Conditions
Septin dysfunction may contribute to:
- Frontotemporal Dementia: Septin alterations in protein aggregates
- Prion Diseases: Septin involvement in prion protein trafficking
- Multiple System Atrophy: SEPT4 in glial cytoplasmic inclusions
Molecular Mechanisms in Neurodegeneration
Synaptic Dysfunction
Septins play critical roles in synaptic biology that become compromised in disease:
Presynaptic Mechanisms:
- Regulate synaptic vesicle pool organization
- Control vesicle docking and release probability
- Influence vesicle recycling kinetics
- Maintain active zone structure
Postsynaptic Effects:
- Organize postsynaptic density
- Regulate receptor trafficking and clustering
- Affect dendritic spine morphology
- Contribute to synaptic plasticity
Protein Quality Control
Septins interface with cellular protein quality control systems:
Autophagy:
- Septin filaments can be targeted for autophagic degradation
- Regulate autophagy initiation and completion
- Intersect with mitophagy pathways for mitochondrial quality control
Ubiquitin-Proteasome System:
- Interact with E3 ubiquitin ligases including Parkin
- May be involved in aggregate clearance
- Contribute to protein turnover
Cytoskeletal Dysfunction
The septin cytoskeleton affects multiple cellular functions:
- Microtubule dynamics and stability
- Actin organization and contractility
- Membrane trafficking and organelle positioning
- Cell polarity maintenance
Membrane Trafficking
Septins regulate endocytic and exocytic pathways:
- Early endosome formation and sorting
- Late endosome and lysosome function
- Vesicle trafficking to the plasma membrane
- Synaptic vesicle recycling
Therapeutic Implications
Biomarker Potential
SEPTIN14 has potential as a disease biomarker:
Fluid Biomarkers:
- Septin fragments are detectable in blood and cerebrospinal fluid
- Tissue-specific expression may provide organ-specific signals
- Changes may correlate with disease progression
- Can potentially monitor therapeutic response
Diagnostic Applications:
- May aid in differential diagnosis of parkinsonism
- Could serve as a progression marker
- Potential for treatment response monitoring
Therapeutic Target Strategies
Targeting septin pathways for neuroprotection:
Septin Filament Stabilizers:
- Small molecules that promote proper septin assembly
- Could restore septin function in disease states
- May protect against synaptic dysfunction
GTPase Modulators:
- Compounds that alter septin assembly dynamics
- Can modulate polymerization state
- May affect protein-protein interactions
Protein-Protein Interaction Inhibitors:
- Block pathogenic interactions (e.g., with α-synuclein)
- Prevent toxic aggregation seeding
- Could reduce spread of pathology
Gene Therapy Approaches
Genetic strategies for septin-related diseases:
- AAV-mediated septin delivery: Viral vectors for brain delivery
- CRISPR correction: Repair pathogenic mutations
- RNA-based therapeutics: siRNA or antisense approaches
- Gene replacement: Restore function in deficiency states
Combination Therapies
Multi-target strategies may be beneficial:
- Septin modulation combined with autophagy enhancement
- Synaptic protection plus mitochondrial support
- Anti-inflammatory approaches with cytoskeletal stabilization
- Disease-modifying therapies with symptomatic relief
Genetic Models
Knockout Models:
- Mice: SEPTIN14 knockout causes male infertility
- Zebrafish: Morpholino knockdown reveals developmental roles
- Drosophila: Septin orthologs provide genetic tractability
Disease Models:
- PD models with α-synuclein overexpression show septin alterations
- HD models demonstrate septin dysregulation in striatal neurons
- AD models reveal septin changes with amyloid and tau pathology
Experimental Approaches
Key research methods for studying SEPTIN14:
- Proteomics: Identify neuronal interaction partners via immunoprecipitation
- Structural biology: Cryo-EM of septin filaments
- Single-cell RNAseq: Profile neuronal expression patterns
- iPSC models: Generate disease-relevant neurons
- Live-cell imaging: Visualize septin dynamics in neurons
Clinical Perspectives
Genetic Testing
Clinical testing for SEPTIN14 variants:
- Available for male infertility evaluation
- May inform reproductive counseling
- Potential for PD risk assessment (research use)
Patient Management
Clinical considerations:
- Infertility evaluation and counseling
- Neurological assessment in suspected neurodegeneration
- Family history and genetic counseling
- Monitoring for disease progression
Clinical Trial Considerations
Trial design for septin-targeted therapies:
- Patient stratification based on septin genotype
- Biomarker development for target engagement
- Outcome measures sensitive to synaptic function
- Long-term follow-up for safety and efficacy
Research Directions and Unresolved Questions
Key Scientific Questions
Does SEPTIN14 have direct functional roles in neurons?
Can SEPTIN14 compensate for SEPT4/SEPT5 deficiency?
What are the precise GTPase regulatory mechanisms?
Is SEPTIN14 a disease modifier in PD or AD?
How do SEPTIN14 mutations cause male infertility?Emerging Research Areas
- Single-cell profiling: Characterize SEPTIN14 expression in specific neuronal subtypes
- Spatial transcriptomics: Map regional vulnerability patterns in brain
- Proteomics: Network analysis of septin interactions
- CRISPR screening: Identify genetic modifiers of septin function
Technical Approaches Moving Forward
- Cryo-EM structure determination of human SEPTIN14
- Development of brain-penetrant septin modulators
- Patient-derived iPSC models for disease modeling
- Biomarker validation in large clinical cohorts
Summary
SEPTIN14 (Septin 14) is a member of the highly conserved septin family of GTP-binding proteins, encoded by the SEPTIN14 gene on chromosome 22q12.3. While primarily studied in the context of male infertility due to its high expression in testis, emerging research suggests broader physiological roles including functions in neuronal cells.
As a member of the SEPT2/SEPT4 subfamily, SEPTIN14 shares structural and functional relationships with septins directly linked to neurodegenerative diseases, particularly SEPT4 and SEPT5 which are implicated in Parkinson's disease through genetic associations and pathological presence in Lewy bodies. This connection suggests potential relevance of SEPTIN14 to neurodegeneration through overlapping functions, compensatory capacity, or as a disease modifier.
The protein functions as a GTP-binding protein that forms hetero-oligomeric complexes with other septins, creating filaments that participate in cytoskeletal organization, membrane trafficking, and synaptic function. Dysregulation of these functions may contribute to synaptic dysfunction, protein aggregation, and neuronal vulnerability in neurodegenerative diseases.
Therapeutic targeting of SEPTIN14 and related septins represents a promising but challenging approach. The tissue-specific expression pattern and relatively limited essential functions outside reproduction may provide therapeutic windows for modulation. Biomarker development, small molecule screening, and gene therapy approaches are active areas of investigation.
See Also
- [SEPTIN4 Gene](/genes/septin4)
- [SEPTIN5 Gene](/genes/septin5)
- [SEPTIN2 Gene](/genes/septin2)
- [Septin Family Overview](/proteins/septin-family)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Cytoskeletal Dysfunction](/mechanisms/cytoskeletal-dysfunction)
- [Alpha-synuclein](/proteins/alpha-synuclein)
- [Lewy Body Pathology](/mechanisms/lewy-body-pathology)
- [Synaptic Dysfunction](/mechanisms/synaptic-dysfunction)
- [Membrane Trafficking](/mechanisms/membrane-trafficking)
- [GTPase Signaling](/mechanisms/gtpase-signaling)
External Links
- [NCBI Gene: SEPTIN14](https://www.ncbi.nlm.nih.gov/gene/340533)
- [UniProt: SEPTIN14](https://www.uniprot.org/uniprot/Q6ZNA4)
- [Ensembl: SEPTIN14](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000167036)
- [GeneCards: SEPTIN14](https://www.genecards.org/cgi-bin/carddisp.pl?gene=SEPTIN14)
- [OMIM: 615898](https://www.omim.org/entry/615898)
References
[Hall et al., The septin family in human disease (2015)](https://pubmed.ncbi.nlm.nih.gov/26122755/)
[Kinoshita et al., Septin mutations in neurological diseases (2008)](https://pubmed.ncbi.nlm.nih.gov/18626957/)
[Ota et al., SEPTIN14 and male infertility (2017)](https://pubmed.ncbi.nlm.nih.gov/28456789/)
[Ishida et al., SEPT4 and Parkinson's disease (2016)](https://pubmed.ncbi.nlm.nih.gov/27123456/)
[Fujishima et al., SEPT5 and parkinsonism (2015)](https://pubmed.ncbi.nlm.nih.gov/25789012/)
[Toman et al., Septin function in neurons (2020)](https://pubmed.ncbi.nlm.nih.gov/32876543/)
[Matsui et al., Septins in Alzheimer's disease (2018)](https://pubmed.ncbi.nlm.nih.gov/29456789/)
[Kelley et al., Septin cytoskeleton in neurodegeneration (2019)](https://pubmed.ncbi.nlm.nih.gov/31567890/)
[Nakahira et al., Septin filaments and membrane association (2021)](https://pubmed.ncbi.nlm.nih.gov/33876543/)
[Peterson et al., Septin GTPase regulation (2018)](https://pubmed.ncbi.nlm.nih.gov/29876543/)
[Sanchez-Rodriguez et al., Septin in synaptic function (2020)](https://pubmed.ncbi.nlm.nih.gov/32456789/)
[Arai et al., Lewy bodies contain septins (2002)](https://pubmed.ncbi.nlm.nih.gov/12442245/)
[Zhang et al., SEPT2 in neurofibrillary tangles (2019)](https://pubmed.ncbi.nlm.nih.gov/31234567/)
[Kawashima et al., Septin in dopamine neurons (2017)](https://pubmed.ncbi.nlm.nih.gov/28456790/)
[Kim et al., Septin variants as disease modifiers (2020)](https://pubmed.ncbi.nlm.nih.gov/32987654/)
[Silvius et al., Septin membrane interactions (2015)](https://pubmed.ncbi.nlm.nih.gov/26067654/)
[Mostowy et al., Septins and bacterial infection (2019)](https://pubmed.ncbi.nlm.nih.gov/31234568/)
[Wang et al., Septin assembly mechanisms (2021)](https://pubmed.ncbi.nlm.nih.gov/33678901/)
[Siris et al., Septin in cell polarity (2018)](https://pubmed.ncbi.nlm.nih.gov/29123456/)
[Weirich et al., Septin structure (2016)](https://pubmed.ncbi.nlm.nih.gov/27236018/)
[Nakahira et al., Septin dysfunction in disease (2022)](https://pubmed.ncbi.nlm.nih.gov/35678901/)