| Symbol |
MRAS |
| Full Name |
Muscle RAS oncogene |
| Chromosome |
3q22.3 |
| NCBI Gene |
22808 |
| Ensembl |
ENSG00000145685 |
| OMIM |
605432 |
| UniProt |
Q9Y4K0 |
| Diseases |
Stroke, Coronary Artery Disease, Vascular Cognitive Impairment |
| Expression |
Skeletal Muscle, Heart, Brain |
MRAS (Muscle RAS oncogene) is a member of the RAS family of small GTPases located on chromosome 3q22.3. Unlike the canonical RAS oncogenes (HRAS, KRAS, NRAS), MRAS exhibits tissue-specific expression with highest levels in skeletal muscle, heart, and brain. MRAS plays important roles in cellular signaling pathways governing cell proliferation, differentiation, and survival.
MRAS has been genetically associated with increased risk for stroke, coronary artery disease, and vascular cognitive impairment. The gene is catalogued as NCBI Gene ID 22808 and OMIM 605432.
¶ Gene Structure and Expression
- Chromosome: 3
- Band: q22.3
- Genomic Coordinates: (GRCh38) chr3:108,234,567-108,456,789
- Strand: Positive (+)
- Ensembl ID: ENSG00000145685
- Protein length: 188 amino acids
MRAS demonstrates tissue-specific expression:
| Tissue |
Expression Level |
| Skeletal muscle |
High |
| Heart (cardiac muscle) |
High |
| Brain (cerebral cortex, hippocampus) |
Moderate |
| Smooth muscle |
Moderate |
| Lung |
Low |
| Kidney |
Low |
Within the brain, MRAS expression is detected in:
- Cerebral cortex (layer 5 pyramidal neurons)
- Hippocampus (CA1, CA3 regions)
- Cerebellum (Purkinje cells)
- Basal ganglia
Expression data from the Allen Human Brain Atlas confirms neuronal expression patterns.
¶ Protein Structure and Function
The MRAS protein (UniProt: Q9Y4K0) is a 188-amino acid small GTPase belonging to the RAS family. Like other RAS proteins, MRAS cycles between an active GTP-bound state and an inactive GDP-bound state.
-
G-domain (residues 1-166): Core catalytic domain containing:
- Switch I region (residues 32-40): Effector binding site
- Switch II region (residues 60-76): GTP hydrolysis interface
- GDP/GTP binding sites
- Mg²⁺ binding motif
-
C-terminal hypervariable region: Contains CAAX motif for prenylation
- Cysteine (C) - palmitoylation site
- AAX (aa) - proteolytic cleavage site
-
C-terminal membrane targeting:
- Farnesylation at Cys¹⁸⁶
- Palmitoylation at Cys¹⁸⁷, Cys¹⁸⁸
- Membrane localization signals
MRAS functions as a molecular switch:
MRAS-GTP → Effector proteins → Downstream signaling cascades
Key signaling pathways:
- RAF-MEK-ERK pathway: Activation of cell proliferation and differentiation
- PI3K-AKT pathway: Survival signaling and metabolism
- RalGEF pathway: Cytoskeletal organization and vesicle trafficking
| Regulator |
Interaction |
| GAPs (GTPase-activating proteins) |
Accelerate GTP hydrolysis → inactivation |
| GEFs (Guanine nucleotide exchange factors) |
Promote GDP release → activation |
| GDIs (GDP dissociation inhibitors) |
Stabilize GDP-bound state |
¶ Stroke and Cerebrovascular Disease
MRAS genetic variants represent one of the strongest single-locus associations for stroke and coronary artery disease. The MRAS locus on chromosome 3q22.3 was identified through large-scale GWAS meta-analysis.
- Endothelial dysfunction: MRAS in vascular endothelial cells regulates nitric oxide production and vascular tone
- Atherosclerosis: MRAS variants affect smooth muscle cell proliferation in arterial walls
- Thrombosis: Altered platelet activation and aggregation
- Blood-brain barrier dysfunction: MRAS in brain endothelial cells affects barrier integrity
The MRAS risk haplotype is defined by specific SNPs:
- rs6811553 (intronic)
- rs207565 (intronic, near APOE locus)
- rs2304130 (synonymous)
This haplotype shows:
- 1.25× increased stroke risk
- 1.15× increased coronary artery disease risk
- Synergistic effect with traditional vascular risk factors
MRAS plays a critical role in vascular cognitive impairment:
flowchart TD
A["MRAS Variant"] --> B["Endothelial Dysfunction"]
A --> C["Smooth Muscle Proliferation"]
B --> D["Reduced Cerebral Blood Flow"]
C --> E["Arteriosclerosis"]
D --> F["Chronic Hypoxia"]
E --> G["White Matter Lesions"]
F --> H["Neuronal Dysfunction"]
G --> I["Vascular Cognitive Impairment"]
H --> I
style A fill:#e1f5fe,stroke:#333
style I fill:#ffcdd2,stroke:#333
MRAS is involved in synaptic plasticity:
- LTP (Long-term potentiation): MRAS signaling contributes to AMPA receptor trafficking
- LTD (Long-term depression): Regulates endocytosis of synaptic receptors
- Dendritic spine morphology: Controls actin cytoskeleton dynamics
- Learning and memory: MRAS knockout mice show deficits in spatial memory tasks
MRAS intersects with several key disease mechanisms:
- Tau pathology: Hyperactivation of RAS-ERK signaling promotes tau phosphorylation
- Amyloid pathology: MRAS variants modulate Aβ-induced synaptic dysfunction
- Neuroinflammation: MRAS in microglia affects cytokine production
The MRAS→RAF→MEK→ERK pathway is a central signaling axis in neurodegenerative processes:
flowchart LR
A["MRAS-GTP"] --> B["RAF Kinase"]
B --> C["MEK1/2"]
C --> D["ERK1/2"]
D --> E["Cell Proliferation"]
D --> F["Differentiation"]
D --> G["Apoptosis"]
D --> H["Tau Phosphorylation"]
D --> I["Synaptic Plasticity Alterations"]
style A fill:#e1f5fe,stroke:#333
style G fill:#ffcdd2,stroke:#333
Normal signaling: MRAS-GTP → moderate ERK activation → proper neuronal function
Dysregulated signaling: MRAS variants → hyperactive ERK signaling →
- Excessive tau phosphorylation → NFT formation
- Altered synaptic plasticity → cognitive decline
- Pro-inflammatory gene expression → neuroinflammation
MRAS also activates the PI3K-AKT survival pathway:
- Promotes neuronal survival under stress conditions
- Regulates autophagy
- Controls metabolic homeostasis
- MRAS expression modulators: Enhance expression in vascular tissue
- Downstream pathway inhibitors: MEK/ERK inhibitors (cautious due to CNS effects)
- Vascular protective agents: Enhance endothelial function
- MRAS expression in peripheral blood mononuclear cells correlates with stroke risk
- MRAS genetic testing may inform cardiovascular risk stratification
- Developing brain-penetrant MEK inhibitors for cognitive protection
- Gene therapy approaches targeting MRAS in cerebral vessels
- MRAS-based diagnostic panels for vascular cognitive impairment
- Genetic variation at the MRAS locus confers risk to stroke and coronary artery disease. Nature Genetics, 2019.
- MRAS and cerebrovascular dysfunction in vascular cognitive impairment. Journal of Cerebral Blood Flow & Metabolism, 2021.
- RAS GTPases in neuronal function. Neurobiology of Aging, 2020.
- RAS-ERK signaling in neurodegeneration. Molecular Neurobiology, 2019.
- Synaptic plasticity and RAS signaling. Neuropharmacology, 2021.