SLC6A1

SLC6A1

Overview

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classDef protein fill:#0a1929,stroke:#2196f3
classDef disease fill:#2d0f0f,stroke:#e91e63
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SLC6A1["SLC6A1"] -->|"implicated_in"| neurodegeneration["neurodegeneration"]
SLC6A1["SLC6A1"] -->|"interacts_with"| GJA1["GJA1"]
SLC6A1["SLC6A1"] -->|"interacts_with"| LRRK2["LRRK2"]
SLC6A1["SLC6A1"] -->|"interacts_with"| TXN["TXN"]
SLC6A1["SLC6A1"] -->|"expressed_in"| Alzheimer["Alzheimer"]
SLC6A1["SLC6A1"] -->|"expressed_in"| Diabetes["Diabetes"]
SLC6A1["SLC6A1"] -->|"expressed_in"| DIABETES_MELLITUS["DIABETES MELLITUS"]
SLC6A1["SLC6A1"] -->|"expressed_in"| Synaptic_Vesicle["Synaptic Vesicle"]
SLC6A1["SLC6A1"] -->|"interacts_with"| CALM1["CALM1"]
SLC6A1["SLC6A1"] -->|"interacts_with"| Genes["Genes"]
SLC6A1["SLC6A1"] -->|"interacts_with"| LPL["LPL"]
SLC6A1["SLC6A1"] -->|"interacts_with"| Rb["Rb"]
SLC6A1["SLC6A1"] -->|"expressed_in"| neurons["neurons"]
SLC6A1["SLC6A1"] -->|"co_expressed_with"| TXN["TXN"]
SLC6A1["SLC6A1"] -->|"co_expressed_with"| VWF["VWF"]
SLC6A1["SLC6A1"] -->|"associated_with"| Alzheimer["Alzheimer"]
ALZHEIMER["ALZHEIMER"] -->|"expressed_in"| SLC6A1["SLC6A1"]
LPL["LPL"] -->|"interacts_with"| SLC6A1["SLC6A1"]
CALM1["CALM1"] -->|"interacts_with"| SLC6A1["SLC6A1"]
GJA1["GJA1"] -->|"interacts_with"| SLC6A1["SLC6A1"]
GENES["GENES"] -->|"inter

SLC6A1

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">SLC6A1</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>SLC6A1</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>3p25.3</td>
</tr>
<tr>
<td class="label">Genomic Coordinates</td>
<td>chr3:11,000,000-11,200,000 (GRCh38)</td>
</tr>
<tr>
<td class="label">Gene Length</td>
<td>~65 kb</td>
</tr>
<tr>
<td class="label">Number of Exons</td>
<td>16 coding exons</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>599 amino acids</td>
</tr>
<tr>
<td class="label">Protein Class</td>
<td>Sodium/chloride-dependent GABA transporter (SLC6 family)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Brain (neurons and astrocytes), peripheral tissues at low levels</td>
</tr>
<tr>
<td class="label">Inheritance</td>
<td>Autosomal dominant (de novo in most cases)</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>137165</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>P30531</td>
</tr>
<tr>
<td class="label">Disorder</td>
<td>Variant Type</td>
</tr>
<tr>
<td class="label">Myoclonic-atonic epilepsy (MAE / Doose syndrome)</td>
<td>Missense, truncating</td>
</tr>
<tr>
<td class="label">Childhood absence epilepsy</td>
<td>Missense</td>
</tr>
<tr>
<td class="label">Generalized epilepsy with febrile seizures plus</td>
<td>Missense</td>
</tr>
<tr>
<td class="label">Autism spectrum disorder</td>
<td>Missense, truncating</td>
</tr>
<tr>
<td class="label">Non-syndromic intellectual disability</td>
<td>Missense</td>
</tr>
</table>

[SLC6A1](/entities/slc6a1) encodes GAT-1 (GABA transporter 1), the principal sodium- and chloride-dependent GABA transporter in the central nervous system. GAT-1 is responsible for reuptake of GABA from the synaptic cleft and extrasynaptic space, terminating GABAergic signaling and maintaining GABA homeostasis. Pathogenic variants in [SLC6A1](/entities/slc6a1) cause a spectrum of epilepsy phenotypes, most commonly myoclonic-atonic epilepsy (MAE) and related generalized epilepsy syndromes. PMID: 39475571

[SLC6A1](/entities/slc6a1) is one of the few monogenic epilepsy genes where the mechanism is clearly understood (loss of GABA reuptake -> reduced inhibition -> hyperexcitability) and where a natural small-molecule therapeutic exists: tiagabine, which inhibits GAT-1, partially compensating for the reduced endogenous transporter function. PMID: 26250687

Gene Information

Structure and Function

Transporter Architecture

GAT-1 is a 12-transmembrane domain transporter belonging to the SLC6 family (sodium-coupled transporters): PMID: 29874566

• N-terminal extracellular domain: contains N-glycosylation sites
• Transmembrane domains 1-12: form the pore and substrate binding site
• Large extracellular loop between TM3 and TM4: contains glycosylation sites
• C-terminal intracellular domain: regulatory interactions PMID: 32755557

GABA Transport Mechanism

GAT-1 uses the sodium gradient to drive GABA transport:

One Cl- ion is also transported per cycle, contributing to the overall electrochemical driving force.

GABA Clearance and Inhibition

GAT-1 is the primary mechanism for terminating GABAergic transmission:

• Reuptake of synaptic GABA into presynaptic neurons (70-80% of clearance)
• Uptake into astrocytes (remaining clearance)
• Regulation of extracellular GABA concentrations
• Prevention of GABA spillover to adjacent synapses

• Prolonged GABA receptor activation
• Desensitization of GABA receptors
• Reduced GABA synthesis (less GABA recycled)
• Network hyperexcitability

Pathophysiology in SLC6A1 Epilepsy

Loss-of-Function Mechanism

All pathogenic [SLC6A1](/entities/slc6a1) variants cause loss of GABA transporter function:

The key consequence: reduced GABA reuptake → prolonged GABAergic inhibition followed by receptor desensitization → net disinhibition at the circuit level.

Seizure Mechanisms

SLC6A1-related epilepsy likely involves:

• Impaired GABA clearance leading to altered synaptic timing
• Desensitization of GABA-A receptors from excessive activation
• Compensatory downregulation of GABA-A receptor expression
• Network-level hyperexcitability from disrupted inhibition

Phenotype Spectrum

SLC6A1 variants associate with a range of epilepsy phenotypes:

• Myoclonic-atonic epilepsy (MAE): most common; onset 1-5 years
• Childhood absence epilepsy (CAE): some patients present with pure absences
• Epilepsy with generalized tonic-clonic seizures: overlap with GGE
• Autism spectrum disorder: some patients have ASD features without epilepsy
• Developmental delay/intellectual disability: variable; may be primary or secondary

Disease Associations

Therapeutic Approaches

Current Management

Standard ASMs are used, with variable efficacy:

• Valproic acid: broad-spectrum, often first-line
• Ethosuximide: effective for absence component
• Clobazam: adjunct for myoclonic seizures
• Avoid: tiagabine itself (GAT-1 inhibitor — would worsen condition)

GAT-1 Inhibition as Therapeutic Strategy

Interestingly, tiagabine (GAT-1 inhibitor used to treat focal epilepsy) would worsen SLC6A1-related epilepsy by further reducing GABA reuptake. However, the principle of compensating for reduced transporter function through other mechanisms is valid.

Gene Therapy Approach

SB-001 (formerly TX-004) (Takeda/Shinobi/Recode): AAV-based gene therapy delivering functional SLC6A1 (GAT-1) to neurons. The approach:

• Delivers wild-type SLC6A1 coding sequence (~1.8 kb — fits easily in AAV)
• Uses neuronal-specific promoter (e.g., synapsin or MECP2)
• Targets neurons to restore GABA reuptake capacity
• Delivered via ICV or intrathecal administration

• Partial restoration of GABA uptake activity
• Reduced seizure susceptibility
• Improved behavioral outcomes

Alternative Approaches

• ASOs to increase SLC6A1 expression: Upregulate the remaining wild-type allele
• Small molecule correctors: Enhance trafficking/function of missense variants
• GABA-A receptor modulators: Compensate at the receptor level (but limited by receptor desensitization)

Research and Open Questions

References

Pathway Diagram

The following diagram shows the key molecular relationships involving SLC6A1 discovered through SciDEX knowledge graph analysis: