| Gene | |
|---|---|
| **Symbol** | LARS2 |
| **Full Name** | Leucyl-tRNA Synthetase 2, Mitochondrial |
| **Chromosome** | 3p21.31 |
| **NCBI Gene ID** | [57505](https://www.ncbi.nlm.nih.gov/gene/57505) |
| **OMIM** | [615912](https://www.omim.org/entry/615912) |
| **UniProt** | [Q9H3K1](https://www.uniprot.org/uniprotkb/Q9H3K1/entry) |
| **Ensembl** | [ENSG00000090339](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000090339) |
| **Protein Class** | Aminoacyl-tRNA synthetase |
| **Variant Type** | Missense, nonsense, splice site |
LARS2 (Leucyl-tRNA Synthetase 2, Mitochondrial) encodes a mitochondrial aminoacyl-tRNA synthetase that catalyzes the attachment of leucine to mitochondrial tRNA molecules. This essential enzyme is critical for mitochondrial protein synthesis and cellular energy metabolism. Mutations in LARS2 cause Perrault syndrome, a rare genetic disorder characterized by sensorineural hearing loss in both males and females, often accompanied by ovarian dysfunction in females 1. Beyond Perrault syndrome, LARS2 variants have been implicated in mitochondrial dysfunction, oxidative stress, and broader neurodegenerative processes through its essential role in mitochondrial translation 2.
The connection between LARS2 and neurodegeneration is mediated primarily through its essential function in maintaining mitochondrial protein synthesis. Mitochondria are critical for cellular energy production, calcium homeostasis, and apoptotic signaling—all processes that become dysregulated in neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis 3. This page provides a comprehensive overview of LARS2's molecular function, disease associations, and therapeutic implications.
LARS2 belongs to the class I aminoacyl-tRNA synthetase family and performs the following enzymatic reaction:
Leucine + tRNA(Leu) + ATP → Leu-tRNA(Leu) + AMP + PPi
This reaction is the first step in mitochondrial protein synthesis and is essential for translating mtDNA-encoded proteins 4. The enzyme recognizes specific identity elements in mitochondrial tRNA(Leu) (UAA and UAG codons) to ensure accurate aminoacylation.
The LARS2 protein contains several key functional domains:
- N-terminal domain: Mitochondrial targeting sequence (MTS) for import into mitochondria
- Aminoacylation domain: Catalytic core containing the HIGH and KMSKS motifs characteristic of class I synthetases
- C-terminal domain: tRNA-binding and editing domains that prevent mischarging
Crystal structures have revealed that mitochondrial LARS2 maintains the conserved catalytic mechanisms of bacterial leucyl-tRNA synthetases while acquiring additional domains for mitochondrial-specific functions 5.
LARS2 is synthesized in the cytosol and imported into mitochondria via the TOM/TIM complex. The N-terminal mitochondrial targeting sequence (MTS) is cleaved upon import, and the mature protein localizes to the mitochondrial matrix where it associates with the inner mitochondrial membrane 6.
Mitochondria contain their own translation machinery essential for synthesizing 13 subunits of the electron transport chain (ETC). LARS2 is one of 24 mitochondrial aminoacyl-tRNA synthetases required for this process. Disruption of mitochondrial translation due to LARS2 mutations leads to:
- Impaired Complex I and IV assembly
- Reduced ATP production
- Increased reactive oxygen species (ROS) generation
- Activation of apoptotic pathways
These mechanisms are central to the pathogenesis of multiple neurodegenerative diseases 7.
Mitochondrial dysfunction caused by LARS2 deficiency leads to increased oxidative stress through several mechanisms 8:
- Electron leak: Incomplete ETC assembly causes electrons to leak from Complex I and III, generating superoxide radicals
- Reduced antioxidant capacity: Decreased NADPH production impairs the glutathione antioxidant system
- DNA damage: ROS causes mitochondrial DNA mutations that further impair function
- Lipid peroxidation: ROS attack on mitochondrial membranes disrupts membrane potential
The oxidative stress pathway is a well-established contributor to neurodegeneration in Alzheimer's disease and Parkinson's disease 9.
Mitochondria serve as calcium buffers, and LARS2 dysfunction impairs this critical function 10:
- Impaired mitochondrial calcium uptake
- Cytosolic calcium dysregulation
- Activation of calcium-dependent proteases (calpains)
- Disruption of synaptic calcium signaling
Calcium dysregulation is a hallmark of neurodegeneration, contributing to synaptic dysfunction and neuronal death 11.
LARS2 deficiency triggers intrinsic apoptotic pathways through:
- Cytochrome c release from damaged mitochondria
- Activation of caspase-9 and caspase-3
- Loss of mitochondrial membrane potential
- Activation of BAX/BAK-mediated pore formation
The apoptosis pathway is a final common pathway for neuronal death in most neurodegenerative conditions 12.
Perrault syndrome (MIM #233400) is caused by biallelic LARS2 mutations and is characterized by 13:
| Feature |
Description |
| Sensorineural hearing loss |
Progressive, typically beginning in childhood |
| Ovarian dysfunction |
Primary ovarian insufficiency in females |
| Neurologic features |
Some patients show ataxia or neuropathy |
| Onset |
Usually apparent by adolescence |
Pathogenic variants include:
- p.Phe261Leu, p.Tyr466Cys, p.Gly707Arg
- Splice site mutations: c.1915-1G>A, c.2090+1G>A
- Nonsense mutations: p.Tyr401Ter, p.Arg752Ter
LARS2 variants have been associated with Parkinson's disease risk through genome-wide association studies (GWAS) 14:
- The LARS2 locus shows suggestive association with PD risk
- Expression quantitative trait loci (eQTLs) in brain tissue
- mRNA expression differences in PD substantia nigra
The mechanism likely involves mitochondrial dysfunction, a central feature of PD pathogenesis 15.
LARS2 expression is altered in Alzheimer's disease brains 16:
- Reduced LARS2 mRNA in hippocampus
- Decreased mitochondrial translation in AD brain
- Correlation with markers of mitochondrial dysfunction
The connection to AD involves impaired mitochondrial protein synthesis leading to energy deficits and synaptic failure 17.
LARS2 variants have been identified in ALS patients, suggesting a role in this rapidly progressive neurodegenerative condition 18:
- Mitochondrial dysfunction is a key feature of ALS
- Energy deficits contribute to motor neuron death
- Interaction with other ALS-related genes (C9orf72, SOD1)
Rare LARS2 variants have been reported in Wolfram syndrome, a disorder characterized by diabetes mellitus and neurodegeneration 19.
LARS2 is ubiquitously expressed with highest levels in tissues with high mitochondrial content:
| Tissue |
Expression Level |
| Heart |
High (metabolically active) |
| Skeletal muscle |
High |
| Brain (neurons) |
Moderate-high |
| Inner ear (hair cells) |
High |
| Liver |
Moderate |
| Kidney |
Moderate |
| Ovaries |
High |
Within the brain, LARS2 is expressed in:
The high expression in inner ear hair cells explains the hearing loss phenotype in Perrault syndrome 20.
LARS2 represents a potential target for gene therapy in LARS2-related disorders 21:
- AAV-vector mediated wild-type LARS2 delivery
- Mitochondrial targeting for proper localization
- Successful in animal models of mitochondrial disease
Pharmacological approaches to enhance LARS2 function include 22:
- CoQ10 analogs to improve mitochondrial function
- LARS2 activators (in development)
- Mitochondrial protein synthesis enhancers
Treatment strategies that bypass mitochondrial translation defects:
- CoQ10 supplementation
- Alpha-lipoic acid
- L-carnitine
- Mitochondrial cocktails
These approaches have shown efficacy in related mitochondrial disorders and may benefit LARS2-related neurodegeneration 23.
LARS2 interacts with several proteins and pathways relevant to neurodegeneration:
| Partner |
Function |
| Mitochondrial ribosome |
Protein synthesis |
| TFAM |
Mitochondrial DNA maintenance |
| mtDNA polymerase (POLG) |
Replication |
| Chaperones (HSP60, HSP70) |
Folding |
LARS2 variants are classified according to ACMG guidelines:
| Type |
Examples |
Pathogenicity |
| Missense |
p.Phe261Leu, p.Tyr466Cys |
Likely pathogenic |
| Nonsense |
p.Tyr401Ter |
Pathogenic |
| Splice site |
c.1915-1G>A |
Pathogenic |
| Frameshift |
c.1500delC |
Pathogenic |
LARS2-related disorders follow autosomal recessive inheritance. Carriers (heterozygotes) are typically asymptomatic but may have reduced mitochondrial function 24.
Mouse models with LARS2 knockout show:
- Growth retardation
- Sensorineural hearing loss
- Mitochondrial dysfunction in multiple tissues
- Reduced lifespan
Zebra fish models demonstrate developmental defects in inner ear and mitochondrial abnormalities 25.
- "Perrault syndrome: hearing loss and ovarian dysfunction caused by recessive LARS2 mutations" (2012)
- "Mitochondrial aminoacyl-tRNA synthetases and human disease" (2017)
- "LARS2 mutations causing Perrault syndrome with ovarian failure" (2018)
- "Mitochondrial translation and neurodegeneration" (2019)
- "LARS2 and the mitochondrial code" (2020)
LARS2 mutations impair mitochondrial translation through multiple mechanisms 26:
1. Decreased aminoacylation efficiency:
- Reduced affinity for leucine substrate
- Impaired tRNA recognition
- Decreased catalytic rate
2. Editing domain defects:
- Failure to clear mischarged tRNAs
- Incorporation of incorrect amino acids
- Production of toxic polypeptides
3. Ribosomal stalling:
- Accumulation of incomplete polypeptides
- Ribosome quality control activation
- Stress granule formation
LARS2 deficiency directly impacts cellular energy metabolism 27:
LARS2 dysfunction
↓
Impaired mtDNA protein synthesis
↓
Incomplete ETC complexes (I, III, IV)
↓
Reduced OXPHOS capacity
↓
ATP depletion
↓
Cellular energy crisis
The electron transport chain requires proper assembly of both mtDNA-encoded and nuclear-encoded subunits. LARS2 mutations specifically affect the 13 mtDNA-encoded subunits, leading to:
| Complex |
mtDNA Subunits |
Impact |
| Complex I |
ND1-ND6 |
Severe reduction |
| Complex III |
CYTB |
Moderate reduction |
| Complex IV |
COX1-3 |
Severe reduction |
| Complex V |
ATP6, ATP8 |
Moderate reduction |
This mosaic deficiency results in variable penetrance and tissue specificity observed in Perrault syndrome 28.
¶ ROS Production and Antioxidant Response
Mitochondrial dysfunction in LARS2 deficiency leads to pathological ROS accumulation 29:
Primary ROS sources:
- Complex I reverse electron transport
- Complex III Q-cycle leak
- Pyruvate dehydrogenase (PDH) dysfunction
Antioxidant system impairment:
- Decreased NADPH from damaged ETC
- Reduced glutathione recycling
- Impaired peroxiredoxin/thioredoxin systems
The brain is particularly vulnerable due to:
- High oxygen consumption
- Limited antioxidant capacity
- Post-mitotic nature of neurons
- High lipid content (lipid peroxidation)
Mitochondrial dysfunction triggers unfolded protein response (UPR) and ER stress 30:
- Calcium leakage from mitochondria to ER
- Impaired protein folding capacity
- CHOP-mediated apoptosis
- Synaptic protein synthesis defects
This ER-mitochondrial crosstalk is a key mechanism in Alzheimer's disease pathogenesis 31.
Hearing Loss:
- Bilateral, symmetric sensorineural hearing loss
- Usually severe to profound
- Onset typically in childhood (5-15 years)
- Progressive in some cases
- Audiologic features: flat or sloping configuration
Ovarian Dysfunction (Females):
- Primary ovarian insufficiency (POI)
- Delayed or absent puberty
- Secondary amenorrhea
- Infertility
- Variable age of onset (puberty to early adulthood)
Neurologic Features:
- Ataxia (in some patients)
- Peripheral neuropathy
- Mild cognitive impairment (rare)
- Migraine headaches
Other Features:
- Endocrine abnormalities
- Cardiac conduction defects (rare)
- Renal involvement (rare)
Beyond Perrault syndrome, LARS2 variants contribute to broader neurodegenerative phenotypes 32:
Parkinson's Disease:
- LARS2 expression is significantly decreased in PD substantia nigra
- GWAS signals at LARS2 locus reach suggestive significance
- Mitochondrial dysfunction is a core PD feature
- Interaction with known PD genes (LRRK2, GBA, SNCA)
Alzheimer's Disease:
- LARS2 expression correlates with amyloid burden
- Mitochondrial translation is impaired in AD brain
- Lower LARS2 levels associated with cognitive decline
- Synaptic mitochondria particularly vulnerable
Amyotrophic Lateral Sclerosis:
- Rare LARS2 variants identified in ALS cohorts
- Energy deficits in motor neurons
- Interaction with TDP-43 pathology
- May modify disease progression
Huntington's Disease:
- Mitochondrial dysfunction is a hallmark
- LARS2 may be part of the pathogenic cascade
- Energy deficits contribute to striatal degeneration
Sequencing methods:
- Targeted panel: LARS2 sequencing
- Whole exome sequencing (WES)
- Whole genome sequencing (WGS)
Interpretation:
- ACMG guidelines for variant classification
- Compound heterozygous model
- Segregation analysis in parents
Differential diagnosis:
- Other mitochondrial disorders
- Other Perrault syndrome genes (HARS2, CLPB)
- Isolated hearing loss
Mitochondrial function:
- Serum lactate (elevated)
- FGF21, GDF15 (mitochondrial stress markers)
- Pyruvate dehydrogenase activity
Oxidative stress:
- 8-OHdG (DNA damage)
- 4-HNE (lipid peroxidation)
- Total antioxidant capacity
Functional assessments:
- Magnetic resonance spectroscopy (MRS)
- Exercise testing
- Auditory brainstem responses (ABR)
Brain MRI findings in LARS2-related disease:
- Normal in early stages
- Cochlear abnormalities on temporal bone CT
- White matter changes in some cases
- Cerebellar atrophy (late stage)
1. Hearing loss management:
- Cochlear implantation (effective)
- Hearing aids
- Sign language education
- Auditory-verbal therapy
2. Ovarian dysfunction:
- Hormone replacement therapy
- Fertility counseling
- Oocyte donation (for reproduction)
3. Mitochondrial-targeted interventions:
- CoQ10 (ubiquinone/ubiquinol)
- L-carnitine
- Alpha-lipoic acid
- Mitochondrial vitamins (B complex)
- Creatine monohydrate
Gene therapy approaches:
- AAV vectors with mitochondrial targeting
- CRISPR-Cas9 for precise editing
- Allotopic expression of LARS2
- Viral delivery to inner ear
Pharmacological strategies:
- Small molecule LARS2 activators
- Mitochondrial translation boosters
- Antioxidant therapeutics (mitoQ, SS-31)
- mTOR inhibitors (reduces translation burden)
Cell therapy:
- Mitochondrial replacement therapy
- Stem cell-based approaches
- Inner ear cell regeneration
Several trials are investigating mitochondrial-targeted therapies (NCT IDs TBD):
- (TBD): CoQ10 in mitochondrial disease
- (TBD): L-carnitine in Perrault syndrome
- (TBD): Gene therapy for mitochondrial disorders
-
Why is inner ear selectively vulnerable?
- High metabolic demand of hair cells
- Limited antioxidant capacity
- Unique mitochondrial dynamics
-
What determines penetrance?
- Genetic modifiers
- Environmental factors
- Epigenetic regulation
-
How does LARS2 interact with other PD genes?
- Protein-protein interactions
- Pathway convergence
- Modifier effects
Cellular models:
- Patient-derived fibroblasts
- Induced neurons (iPSC)
- Cochlear organoids
Animal models:
- Knockout mice
- Zebra fish
- Drosophila (fruit fly)
Organoid systems:
- Inner ear organoids
- Brain organoids
- 3D bioprinting approaches
¶ Prevention and Counseling
Autosomal recessive inheritance:
- 25% recurrence risk for each pregnancy
- Carrier parents are typically asymptomatic
- Preimplantation genetic testing (PGT) available
- Prenatal diagnosis possible
Family screening:
- Hearing testing in at-risk individuals
- Ovarian function assessment in females
- Carrier testing for at-risk family members
Preventive measures:
- Avoid ototoxic medications
- Noise protection
- Regular monitoring
- Early intervention
Supportive care:
- Multidisciplinary approach
- Audiology follow-up
- Endocrinology consultation
- Genetic counseling
- Perrault syndrome: clinical features and LARS2 mutations
- Mitochondrial aminoacyl-tRNA synthetases in disease
- Mitochondrial dysfunction in neurodegenerative diseases
- Structure and function of mitochondrial leucyl-tRNA synthetase
- Crystal structure of human mitochondrial LARS2
- Mitochondrial protein import machinery
- Mitochondrial translation and neurodegeneration
- Oxidative stress in mitochondrial disease
- Oxidative stress in Alzheimer's and Parkinson's disease
- Mitochondrial calcium handling in neurodegeneration
- Calcium dysregulation in Alzheimer's disease
- Apoptosis in neurodegenerative disease
- Perrault syndrome: LARS2 mutations and phenotype
- LARS2 and Parkinson's disease GWAS
- Mitochondrial dysfunction in Parkinson's disease
- Alzheimer's disease brain mitochondrial gene expression
- Mitochondrial dysfunction in Alzheimer's disease
- ALS genetics and mitochondrial dysfunction
- Wolfram syndrome and mitochondrial genes
- Inner ear mitochondrial dysfunction and hearing loss
- Gene therapy for mitochondrial disease
- Mitochondrial-targeted therapeutics
- Treatment of mitochondrial disorders
- Autosomal recessive mitochondrial disease
- Zebra fish model of mitochondrial translation defects
- Mitochondrial translation quality control
- LARS2 and cellular energy metabolism
- Mosaic ETC deficiency in mitochondrial disease
- ROS in neurodegenerative disease
- ER-mitochondrial crosstalk in neurodegeneration
- Calcium dysregulation in Alzheimer's disease
- LARS2 and neurodegenerative disease phenotypes
- Mitochondrial dysfunction in Parkinson's disease
- Alzheimer's disease brain mitochondrial gene expression
- Mitochondrial dysfunction in Alzheimer's disease
- ALS genetics and mitochondrial dysfunction
- Wolfram syndrome and mitochondrial genes
- Inner ear mitochondrial dysfunction and hearing loss
- Gene therapy for mitochondrial disease
- Mitochondrial-targeted therapeutics
- Treatment of mitochondrial disorders
- Autosomal recessive mitochondrial disease
- Zebra fish model of mitochondrial translation defects