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AARS2
alanyl-tRNA synthetase 2, mitochondrial
AARS2 provides instructions for making an enzyme that attaches the amino acid alanine to transfer RNA molecules inside mitochondria, the cell's energy-producing compartments. The AARS2 gene encodes alanyl-tRNA synthetase 2, a mitochondrial enzyme critical for protein synthesis within mitochondria.
AARS2 is located on the short (p) arm of chromosome 6, at band 6p21.1. Arm ratio per GRCh38 - banding schematic.
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Overview
AARS2 produces a specialised enzyme that operates exclusively within mitochondria, the cellular structures responsible for generating energy. This enzyme belongs to the aminoacyl-tRNA synthetase family, which ensures that genetic instructions are accurately translated into functional proteins. The mitochondrial location of this enzyme means it supports the synthesis of proteins encoded by mitochondrial DNA, which are essential for energy production through oxidative phosphorylation.
Pathogenic changes in AARS2 impair mitochondrial protein synthesis, reducing the efficiency of cellular energy production. The resulting mitochondrial dysfunction can manifest in various ways depending on which tissues are most affected, with particular vulnerability observed in organs with high energy demands such as the brain, heart, and skeletal muscle.
What the gene does
The AARS2 protein functions as a mitochondrial aminoacyl-tRNA synthetase, catalysing the attachment of alanine to its cognate transfer RNA molecules. This aminoacylation reaction represents a crucial early step in mitochondrial protein synthesis, ensuring that alanine residues are correctly incorporated into proteins at positions specified by the genetic code.
The enzyme recognises specific structural features of mitochondrial tRNA molecules, distinguishing them from the cytoplasmic tRNAs used in protein synthesis outside mitochondria. This specificity allows the mitochondrial translation machinery to operate independently of cytoplasmic protein synthesis. By charging tRNAs with the correct amino acid, AARS2 maintains the fidelity of mitochondrial translation, preventing errors that could compromise the function of respiratory chain complexes.
Because mitochondria produce most of the cell's energy through oxidative phosphorylation, tissues with high metabolic demands rely heavily on functional AARS2. The enzyme's activity directly influences the production of proteins that form the electron transport chain, linking amino acid metabolism to cellular energy homeostasis.
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Chromosome location
AARS2 is located on the short arm of chromosome 6 at position 21.1 (6p21.1). This chromosomal region contains numerous genes involved in diverse cellular processes. The gene spans a genomic interval that includes multiple exons encoding the 985-amino-acid mitochondrial alanyl-tRNA synthetase protein.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Pathogenic variants in AARS2 typically reduce or abolish the enzyme's ability to charge mitochondrial tRNA molecules with alanine. The specific functional consequence depends on the variant's location and the nature of the amino acid change. Variants that disrupt the catalytic core tend to have severe effects on enzyme activity, whilst those affecting regulatory regions may permit residual function.
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.1329T>A | p.Cys443Ter | Pathogenic | ★★☆☆ | not provided |
c.1561C>T | p.Arg521Ter | Pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 8 |
c.1701dup | p.Gln568fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1774C>T | p.Arg592Trp | Pathogenic/Likely pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 8 |
c.1940del | p.Gly647fs | Pathogenic/Likely pathogenic | ★★☆☆ | Leukoencephalopathy, progressive, with ovarian failure |
c.2146-2A>G | - | Pathogenic/Likely pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 8 |
c.2255+1G>A | - | Pathogenic | ★★☆☆ | Combined oxidative phosphorylation defect type 8 |
c.2598+1G>T | - | Pathogenic/Likely pathogenic | ★★☆☆ | AARS2-related disorder |
c.2611dup | p.Thr871fs | Pathogenic/Likely pathogenic | ★★☆☆ | AARS2-related disorder |
c.2872C>T | p.Arg958Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Inborn genetic diseases |
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
AARS2-related disorders represent a spectrum of mitochondrial disease phenotypes with variable age of onset and organ involvement. Individuals with pathogenic variants may present with neurological symptoms including developmental delay, ataxia, or leukodystrophy. Cardiac manifestations such as cardiomyopathy have been observed in some affected individuals. The severity and combination of features can differ substantially between families, reflecting the complex relationship between residual enzyme activity and clinical phenotype. Some presentations involve white matter abnormalities visible on brain imaging, whilst others primarily affect peripheral nerves or muscle tissue.
No disease links recorded for this gene in our reference set.
UK clinical status
AARS2 appears on multiple NHS Genomic Medicine Service gene panels as a green-rated gene, indicating strong evidence for its clinical validity. The gene is included in panels for mitochondrial disorders, inherited white matter disorders, and likely inborn errors of metabolism. Additional panel memberships include adult-onset leukodystrophy, foetal anomalies, paediatric or syndromic cardiomyopathy, and primary ovarian insufficiency. This broad representation across clinical panels reflects the diverse presentations associated with AARS2 variants. The green classification on these panels supports the use of AARS2 testing in UK clinical practice for individuals with phenotypes consistent with mitochondrial dysfunction.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the AARS2 gene do?
AARS2 provides instructions for an enzyme that attaches alanine to transfer RNA molecules inside mitochondria, enabling the production of proteins essential for cellular energy generation. This process supports the function of the respiratory chain complexes that produce ATP.
How are AARS2 variants inherited?
AARS2-related conditions typically follow an autosomal recessive pattern, meaning an affected individual inherits one pathogenic variant from each parent. Parents who each carry one variant are usually unaffected but have a 25% chance with each pregnancy of having a child with two pathogenic variants.
Why is AARS2 on multiple NHS gene panels?
AARS2 appears on numerous NHS panels because pathogenic variants can cause diverse clinical features affecting the nervous system, heart, muscles, and other organs. The varied presentations mean the gene is relevant to several diagnostic pathways within the NHS Genomic Medicine Service.