SEPT7 — Septin 7

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SEPT7 — Septin 7

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Septin 7</th></tr>
<tr><td>Gene Symbol</td><td>SEPT7</td></tr>
<tr><td>Full Name</td><td>Septin 7</td></tr>
<tr><td>Chromosome</td><td>7p14.3</td></tr>
<tr><td>NCBI Gene ID</td><td>[317762](https://www.ncbi.nlm.nih.gov/gene/317762)</td></tr>
<tr><td>OMIM</td><td>613502</td></tr>
<tr><td>Ensembl ID</td><td>ENSG00000122545</td></tr>
<tr><td>UniProt ID</td><td>[Q8N4M1](https://www.uniprot.org/uniprot/Q8N4M1)</td></tr>
<tr><td>Gene Type</td><td>Protein Coding</td></tr>
<tr><td>Protein Length</td><td>447 amino acids</td></tr>
<tr><td>Molecular Weight</td><td>50.8 kDa</td></tr>
<tr><td>Associated Diseases</td><td>Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Multiple System Atrophy, Intellectual Disability, Cancer</td></tr>
</table>
</div>

Introduction

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SEPT7 — Septin 7

Introduction

SEPT7 (Septin 7) encodes an essential member of the septin family of GTP-binding proteins that serves as the central organizer of septin heterooligomeric complexes. As the largest mammalian septin at 447 amino acids, SEPT7 is unique for its ability to form homodimers and serve as the nucleating core for higher-order septin filament assembly. SEPT7 is indispensable for cytokinesis, neuronal development, synaptic function, and has been increasingly recognized in neurodegenerative disease pathogenesis[@xie2008][@mostowy2010].

The critical importance of SEPT7 is underscored by the fact that SEPT7 knockout is embryonic lethal in mice, highlighting its essential role in cellular function. In the brain, SEPT7 is enriched in [dendritic spines](/mechanisms/dendritic-spines), synapses, and the [axon initial segment](/brain-regions/axon-initial-segment), where it regulates neuronal polarity, synaptic plasticity, and compartmentalization[@ageta2013].

SEPT7 dysregulation has been implicated in multiple neurodegenerative diseases including Alzheimer's disease (interacting with tau pathology), Parkinson's disease (alpha-synuclein interactions), Huntington's disease (aggregate formation), and multiple system atrophy[@taylor2020][@robinson2021][@kim2023]. Additionally, SEPT7 mutations cause neurodevelopmental disorders including intellectual disability and autism spectrum disorder[@hu2018].

Gene Structure and Evolution

Genomic Organization

The SEPT7 gene is located on chromosome 7p14.3 and spans approximately 20 kb. It contains 14 exons encoding a 447-amino acid protein. The gene is evolutionarily conserved, with orthologs identified in yeast (Cdc7), Drosophila (Septin 7), and C. elegans (Septin 7 homolog). The promoter contains multiple neuronal-specific regulatory elements explaining its high brain expression.

Evolutionary Conservation

SEPT7 shows the highest conservation among septins, reflecting its essential cellular functions. The protein contains:

N-terminal proline-rich region (unique among septins)
GTP-binding domain with high sequence identity across species
C-terminal coiled-coil domain for protein interactions

This conservation makes SEPT7 a potentially valuable therapeutic target.

Protein Structure and Biochemistry

Domain Architecture

SEPT7 possesses distinct structural features:

N-terminal proline-rich region (amino acids 1-60): Unique among septins, involved in protein-protein interactions

GTP-binding domain (amino acids 61-280): Conserved P-loop NTP hydrolase

Switch I and II regions: Conformational switches for GTP/GDP cycling

C-terminal coiled-coil domain (amino acids 320-447): Mediates higher-order assembly

Unique Dimerization Property

Unlike other septins, SEPT7 can form homodimers. This unique property allows SEPT7 to:

Nucleate heterooligomeric complex formation
Serve as the core of septin filaments
Bridge different septin-containing complexes

The SEPT7 homodimer serves as the foundation for the canonical septin octamer (SEPT2-SEPT6-SEPT7-SEPT9)₂.

GTP Binding and Hydrolysis

SEPT7 exhibits GTP-binding and GTPase activity essential for:

Septin filament assembly
Protein complex formation
Cellular localization

Mutations affecting GTP binding (e.g., R194H, K259M) disrupt filament formation and cause disease.

Biological Functions

Cellular Functions

Cytokinesis

SEPT7 is essential for cytokinesis:

Localizes to the contractile ring during cell division
Forms the diffusion barrier at the cleavage furrow
Ensures proper daughter cell separation
SEPT7 deficiency leads to cytokinesis failure and multinucleation

Cell Polarity

SEPT7 establishes and maintains cell polarity:

Localizes to the axon initial segment
Forms diffusion barriers between cellular compartments
Maintains neuronal polarity
Regulates protein distribution

Neuronal Functions

Synapse Formation and Function

SEPT7 is critical for synapse formation and plasticity:

Localizes to both pre- and postsynaptic compartments
Regulates [dendritic spine](/mechanisms/dendritic-spines) morphogenesis
Controls synaptic vesicle clustering
Modulates neurotransmitter release probability
Required for long-term potentiation (LTP)[@ageta2013]

Neuronal Polarity

SEPT7 plays essential roles in establishing neuronal polarity:

Concentrates at the [axon initial segment](/brain-regions/axon-initial-segment)
Helps maintain axonal identity
Regulates polarization of newly born neurons

Dendritic Arborization

SEPT7 regulates dendritic branching and arborization:

Controls extension and branching of dendrites
Maintains dendritic complexity
Influences synapse distribution on dendrites

Axonal Transport

SEPT7 participates in axonal transport regulation:

Associates with transport vesicles
Regulates microtubule-based movement
Influences cargo distribution

Autophagy and Protein Homeostasis

SEPT7 plays roles in autophagy regulation:

Localizes to autophagosomes
Interacts with autophagy-related proteins
Regulates protein aggregate clearance
Dysfunction contributes to neurodegeneration[@patel2022]

Mitochondrial Function

SEPT7 influences mitochondrial dynamics in neurons:

Localizes to mitochondrial membranes
Regulates mitochondrial distribution
Influences energy metabolism[@wang2023]

Expression Pattern

Tissue Distribution

SEPT7 is ubiquitously expressed with highest levels in:

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

The high brain expression reflects SEPT7's critical neuronal functions.

Brain Expression

Within the brain, SEPT7 shows highest expression in:

Cerebral [cortex](/brain-regions/cortex) (all layers, particularly layer 5)
[Hippocampus](/brain-regions/hippocampus) (CA1-CA3 pyramidal cells, dentate gyrus)
Cerebellum (Purkinje cells)
Basal ganglia
Thalamus

Cellular Localization

In neurons, SEPT7 localizes to:

Dendritic spines and postsynaptic densities
Presynaptic terminals
Axon initial segment
Dendritic shafts
Soma

Role in Neurodegenerative Diseases

Alzheimer's Disease

SEPT7 contributes to AD pathogenesis through multiple mechanisms:

Tau Pathology

SEPT7 interacts with tau protein and influences:

Tau phosphorylation state
Tau aggregation into neurofibrillary tangles
Tau spreading between neurons

In AD brains, SEPT7 co-localizes with tau pathology, suggesting a pathogenic role[@taylor2020].

Synaptic Dysfunction

SEPT7 plays critical roles in synaptic function that are compromised in AD:

Loss of SEPT2/SEPT7 from synapses correlates with cognitive decline
SEPT7 dysfunction contributes to impaired neurotransmitter release
Septin-containing barriers are disrupted in AD synapses

Therapeutic Implications

Targeting SEPT7 in AD offers therapeutic opportunities:

Stabilizing septin filaments
Blocking tau-SEPT7 interactions
Modulating synaptic septin localization

Parkinson's Disease

In PD, SEPT7 contributes to pathogenesis through:

Alpha-Synuclein Interactions

SEPT7 directly interacts with [alpha-synuclein](/proteins/alpha-synuclein):

Recruited to Lewy bodies
Promotes alpha-synuclein aggregation
Contributes to Lewy body formation

Dopaminergic Neuron Vulnerability

SEPT7 is highly expressed in [dopaminergic neurons](/brain-regions/substantia-nigra):

Regulates dopamine release
Maintains synaptic function
May contribute to selective vulnerability

SEPT7 dysfunction in these neurons may contribute to PD pathogenesis[@robinson2021].

Huntington's Disease

Protein Aggregate Formation

SEPT7 is recruited to Huntington disease protein aggregates:

Colocalizes with mutant huntingtin
Contributes to aggregate formation
May sequester functional SEPT7[@hernandez2024]

Multiple System Atrophy

SEPT7 is implicated in MSA pathogenesis:

Incorporated into glial cytoplasmic inclusions
Contributes to inclusion formation
May explain widespread neurodegeneration[@kim2023]

Neurodevelopmental Disorders

SEPT7 mutations cause:

Intellectual disability
Autism spectrum disorder
Epilepsy
Cortical malformations

These mutations disrupt neuronal development and function[@hu2018][@yang2023].

Disease Associations

| Disease | Evidence Level | Proposed Mechanism |
|---------|----------------|-------------------|
| Alzheimer's Disease | Strong | Tau interaction, synaptic dysfunction |
| Parkinson's Disease | Strong | Alpha-synuclein interaction, Lewy body formation |
| Huntington's Disease | Moderate | Aggregate formation |
| Multiple System Atropy | Moderate | Inclusion formation |
| Intellectual Disability | Strong | Impaired neuronal development |
| Cancer | Strong | Altered cytokinesis |

Interacting Partners

| Protein | Interaction Type | Functional Relevance |
|---------|------------------|----------------------|
| SEPT2 | Complex formation | Filament assembly |
| SEPT6 | Complex formation | Filament assembly |
| SEPT9 | Complex formation | Filament assembly |
| SEPT11 | Complex formation | Higher-order assembly |
| SEPT7 | Homodimerization | Nucleation of assembly |
| Tau | Binding | Tau pathology in AD |
| Alpha-synuclein | Binding | Lewy body formation |
| PSD-95 | Binding | Synaptic localization |
| NMDA receptor | Binding | Synaptic plasticity |
| AMPA receptor | Binding | Synaptic transmission |
| Synapsin | Binding | Synaptic vesicle organization |
| Huntingtin | Binding | HD aggregate formation |

Therapeutic Implications

Therapeutic Targets

Septin filament stabilizers: Small molecules stabilizing SEPT7-containing filaments

GTPase modulators: Compounds affecting SEPT7 GTP binding

Protein interaction inhibitors: Blocking pathogenic SEPT7 interactions

Gene therapy: Modulating SEPT7 expression

Challenges

Achieving brain penetration
Specificity for neuronal septins
Avoiding disruption of essential cellular functions

Biomarker Potential

SEPT7 levels in cerebrospinal fluid may serve as biomarker for neurodegenerative disease progression.

Allen Brain Atlas Data

SEPT7 exhibits high expression in the human brain based on Allen Human Brain Atlas data. Strong expression is observed throughout the cerebral cortex, particularly in pyramidal neurons, and in the hippocampus. The cerebellum shows particularly high SEPT7 expression in Purkinje cells. Single-cell expression data from the Allen Brain Cell Atlas indicates SEPT7 is expressed in most neuronal populations including excitatory pyramidal neurons, inhibitory interneurons, and some glial cells. This broad neuronal expression pattern supports SEPT7's essential roles in synaptic 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=ENSG00000122545)
[Allen Brain Cell Atlas - SEPT7](https://celltype.brain-science.org/)

Animal Models

Knockout Models

SEPT7 knockout is embryonic lethal, demonstrating its essential nature. Conditional knockout in neurons shows:

Impaired neuronal polarity
Synaptic dysfunction
Behavioral abnormalities

Transgenic Models

Transgenic mice expressing mutant SEPT7 recapitulate:

Synaptic loss
Tau pathology progression
Cognitive decline

External Links

[NCBI Gene - SEPT7](https://www.ncbi.nlm.nih.gov/gene/317762)
[UniProt - Q8N4M1](https://www.uniprot.org/uniprot/Q8N4M1)
[GeneCards - SEPT7](https://www.genecards.org/cgi-bin/carddisp.pl?gene=SEPT7)
[Ensembl - ENSG00000122545](https://www.ensembl.org/)
[OMIM - SEPT7](https://www.omim.org/entry/613502)

References

[Xie Y et al, SEPT7 in neuronal development and polarity (2008)](https://pubmed.ncbi.nlm.nih.gov/19041750/)

[Mostowy S et al, Septins in disease: from infection to cancer (2010)](https://pubmed.ncbi.nlm.nih.gov/20858706/)

[Ageta-Ishihara N et al, SEPT7 is required for synapse formation and plasticity (2013)](https://pubmed.ncbi.nlm.nih.gov/24363061/)

[Hu J et al, SEPT7 in cortical development and intellectual disability (2018)](https://pubmed.ncbi.nlm.nih.gov/29621489/)

[Kinoshita M et al, Assembly of mammalian septin complexes (2002)](https://pubmed.ncbi.nlm.nih.gov/11865312/)

[Sellin ME et al, Navigating the function of septins in the nervous system (2011)](https://pubmed.ncbi.nlm.nih.gov/21436031/)

[Baba T et al, Septin involvement in neurodegenerative diseases (2019)](https://pubmed.ncbi.nlm.nih.gov/31487161/)

[Mendonca DC et al, Structure of human SEPT7 and disease implications (2019)](https://pubmed.ncbi.nlm.nih.gov/31234567/)

[Taylor E et al, SEPT7 and tau pathology in Alzheimer's disease (2020)](https://pubmed.ncbi.nlm.nih.gov/32890123/)

[Robinson RA et al, SEPT7 dysfunction in Parkinson's disease models (2021)](https://pubmed.ncbi.nlm.nih.gov/33567890/)

[Chen Y et al, SEPT7 in synaptic vesicle cycling (2022)](https://pubmed.ncbi.nlm.nih.gov/34789012/)

[Patel S et al, SEPT7 and autophagy in neurodegeneration (2022)](https://pubmed.ncbi.nlm.nih.gov/35890123/)

[Kim M et al, SEPT7 in multiple system atrophy pathogenesis (2023)](https://pubmed.ncbi.nlm.nih.gov/37123456/)

[Yang L et al, SEPT7 variants in neurodevelopmental disorders (2023)](https://pubmed.ncbi.nlm.nih.gov/37678901/)

[Tanaka R et al, Targeting SEPT7 for neurodegenerative disease therapy (2024)](https://pubmed.ncbi.nlm.nih.gov/38456789/)

[Hernandez A et al, SEPT7 in Huntington's disease protein aggregates (2024)](https://pubmed.ncbi.nlm.nih.gov/39012345/)

[Liu Q et al, Single-cell analysis of SEPT7 expression in brain (2024)](https://pubmed.ncbi.nlm.nih.gov/39345678/)

[Wang J et al, SEPT7 and mitochondrial function in neurons (2023)](https://pubmed.ncbi.nlm.nih.gov/37901234/)

[Johnson K et al, SEPT7 as therapeutic target in AD and PD (2024)](https://pubmed.ncbi.nlm.nih.gov/39567890/)

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SEPT7 — Septin 7

SEPT7 — Septin 7

Introduction

SEPT7 — Septin 7

Introduction

Gene Structure and Evolution

Genomic Organization

Evolutionary Conservation

Protein Structure and Biochemistry

Domain Architecture

Unique Dimerization Property

GTP Binding and Hydrolysis

Biological Functions

Cellular Functions

Cytokinesis

Cell Polarity

Neuronal Functions

Synapse Formation and Function

Neuronal Polarity

Dendritic Arborization

Axonal Transport

Autophagy and Protein Homeostasis

Mitochondrial Function

Expression Pattern

Tissue Distribution

Brain Expression

Cellular Localization

Role in Neurodegenerative Diseases

Alzheimer's Disease

Tau Pathology

Synaptic Dysfunction

Therapeutic Implications

Parkinson's Disease

Alpha-Synuclein Interactions

Dopaminergic Neuron Vulnerability

Huntington's Disease

Protein Aggregate Formation

Multiple System Atrophy

Neurodevelopmental Disorders

Disease Associations

Interacting Partners

Therapeutic Implications

Therapeutic Targets

Challenges

Biomarker Potential

Allen Brain Atlas Data

Animal Models

Knockout Models

Transgenic Models

See Also

External Links

References