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GNAL
G protein subunit alpha L
GNAL encodes a G protein subunit that enables dopamine signalling in the brain, with variants linked to inherited movement disorders including dystonia. The GNAL gene provides instructions for making a protein subunit that plays a critical role in dopamine receptor signalling pathways in the central nervous system.
GNAL is located on the short (p) arm of chromosome 18, at band 18p11.21. Arm ratio per GRCh38 - banding schematic.
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GNAL encodes the alpha subunit of a G protein (originally discovered in olfactory tissue, though it functions primarily in movement-control regions of the brain), a molecular switch that transmits signals from dopamine receptors on the cell surface to downstream cellular machinery. This protein is particularly abundant in the striatum, a brain region essential for coordinating movement and motor control. Variants in GNAL were first identified as a cause of inherited dystonia in 2012, expanding our understanding of the genetic architecture underlying movement disorders. The gene exhibits autosomal dominant inheritance, meaning a single altered copy can lead to clinical features in some carriers.
What the gene does
The GNAL protein functions as a signalling intermediary that couples certain dopamine receptors to intracellular effector molecules, particularly the enzyme adenylyl cyclase. When dopamine binds to its receptor, the GNAL protein undergoes a conformational change that allows it to activate adenylyl cyclase, which in turn produces cyclic AMP, a critical second messenger molecule. This cascade modulates neuronal excitability and synaptic plasticity in striatal circuits. The protein cycles between an inactive GDP-bound state and an active GTP-bound state, with intrinsic GTPase activity returning it to the resting configuration. GNAL is expressed predominantly in the caudate nucleus and putamen, structures that integrate cortical input to regulate voluntary movement and procedural learning. Disruption of GNAL-mediated signalling appears to alter the balance of excitatory and inhibitory signals within basal ganglia networks, contributing to the motor abnormalities observed in affected individuals.
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Chromosome location
GNAL is located on the short arm of chromosome 18 at cytogenetic band 18p11.21. The gene spans multiple exons encoding a 381-amino-acid protein product.
Protein structure
The GNAL protein comprises 381 amino acids with a modular architecture characteristic of G protein alpha subunits. The N-terminal region provides regulatory flexibility, while the core G-alpha domain contains the nucleotide-binding pocket and surfaces that interact with receptors and effector proteins. Five conserved sequence motifs within this domain coordinate GDP and GTP binding and hydrolysis, forming the structural framework that enables the protein to function as a molecular switch. Conformational changes in these regions transmit receptor activation signals to downstream targets, allowing the protein to regulate adenylyl cyclase activity and control striatal neuron function.
Key variants
Pathogenic variants in GNAL typically arise as missense changes that alter amino acid residues critical for nucleotide binding, GTP hydrolysis, or interaction with receptor and effector proteins. The majority of reported variants occur within the G-alpha domain, where they disrupt the protein's ability to cycle properly between active and inactive states. Most disease-causing variants have been identified in families with adult-onset or childhood-onset dystonia, though incomplete penetrance is recognised, meaning not all carriers develop clinical symptoms. Studies have reported penetrance estimates of approximately 40-60%, though this varies considerably between families.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.964C>T | p.Arg322Ter | Pathogenic | ★★☆☆ | Dystonic disorder |
c.3G>A | p.Met1Ile | Pathogenic | ★☆☆☆ | Dystonic disorder |
c.55_64dup | p.Arg22fs | Pathogenic | ★☆☆☆ | Dystonic disorder |
c.91C>T | p.Gln31Ter | Pathogenic | ★☆☆☆ | Dystonic disorder |
c.1292T>C | p.Val431Ala | Pathogenic | ★☆☆☆ | Dystonic disorder |
c.462_463del | p.Lys155fs | Pathogenic | ★☆☆☆ | not provided |
c.514dup | p.Ser172fs | Pathogenic | ★☆☆☆ | GNAL-related disorder |
c.667G>A | p.Val223Met | Pathogenic | ★☆☆☆ | Dystonic disorder |
c.710_713del | p.Asp237fs | Pathogenic | ★☆☆☆ | Dystonic disorder |
c.61C>T | p.Arg21Ter | Pathogenic | - | Dystonia 25 |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Variants in GNAL are primarily associated with isolated dystonia, a movement disorder characterised by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements and postures. Clinical presentations range from focal dystonia affecting a single body region to segmental or generalised forms. Age of onset varies, with some individuals experiencing symptoms in childhood and others not developing features until adulthood. The severity and distribution of dystonia can differ even among family members carrying the same variant, reflecting the influence of genetic and environmental modifying factors.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic GNAL variants typically follow autosomal dominant inheritance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
UK clinical status
GNAL is included on two NHS Genomic Medicine Service gene panels for movement disorders. The gene holds green (high-evidence) classification on both the Adult onset dystonia, chorea or related movement disorder panel (R56) and the Childhood onset dystonia, chorea or related movement disorder panel (R57). This means GNAL variants are considered clinically relevant findings in patients undergoing NHS genomic testing for these indications, and results may inform clinical management and family screening.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
No specific lifestyle modifications have been shown to modify GNAL-related dystonia. Management focuses on symptomatic treatment under specialist care.
Supplement considerations
No dietary supplements have been shown to modify GNAL-related dystonia. Management focuses on symptomatic treatment under specialist care.
Frequently asked questions
What does the GNAL gene do?
GNAL encodes a G protein alpha subunit that transmits signals from dopamine receptors to intracellular machinery in brain regions controlling movement. It is particularly important for striatal neuron function and motor coordination.
How are GNAL variants inherited?
GNAL follows an autosomal dominant inheritance pattern, meaning a variant in one copy of the gene can be sufficient to cause disease features. Each child of an affected parent has a 50% chance of inheriting the variant, though not all carriers develop symptoms due to incomplete penetrance.
Can GNAL variants be detected through NHS testing?
Yes, GNAL is included on NHS Genomic Medicine Service panels for both childhood-onset and adult-onset movement disorders. Genetic testing may be offered when clinical features suggest an inherited dystonia or related condition.