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PEX13 Gene
PEX13 (Peroxisome Biogenesis Factor 13)
Overview
PEX13 encodes peroxin-13, a critical component of the peroxisomal translocation machinery required for import of matrix proteins into peroxisomes. As a member of the peroxin family of proteins, PEX13 functions as a docking factor at the peroxisomal membrane, facilitating the recognition and import of proteins bearing the peroxisomal targeting signal type 1 (PTS1).[@pex13_1999] Mutations in PEX13 cause peroxisome biogenesis disorders (PBDs), a spectrum of autosomal recessive conditions characterized by severe neurological impairment, developmental arrest, and often premature death. The gene is located on chromosome 2p15 and encodes a protein with an SH3 domain that mediates protein-protein interactions essential for peroxisomal import complex assembly.
<div class="infobox infobox-gene">
| Property | Value |
|----------|-------|
| Gene Symbol | PEX13 |
| Full Name | Peroxisome Biogenesis Factor 13 |
| Chromosomal Location | 2p15 |
| NCBI Gene ID | 5194 |
| OMIM ID | 603773 |
| Ensembl ID | ENSG00000131828 |
| UniProt ID | Q9UKV0 |
| Encoded Protein | Peroxin-13 (489 amino acids) |
| Protein Domain | SH3 domain (C-terminal) |
| Associated Diseases | Zellweger spectrum disorders, Neonatal adrenoleukodystrophy, Infantile Refsum disease |
| Inheritance | Autosomal recessive |
</div>
Molecular Function
Structure and Domains
...
PEX13 (Peroxisome Biogenesis Factor 13)
Overview
PEX13 encodes peroxin-13, a critical component of the peroxisomal translocation machinery required for import of matrix proteins into peroxisomes. As a member of the peroxin family of proteins, PEX13 functions as a docking factor at the peroxisomal membrane, facilitating the recognition and import of proteins bearing the peroxisomal targeting signal type 1 (PTS1).[@pex13_1999] Mutations in PEX13 cause peroxisome biogenesis disorders (PBDs), a spectrum of autosomal recessive conditions characterized by severe neurological impairment, developmental arrest, and often premature death. The gene is located on chromosome 2p15 and encodes a protein with an SH3 domain that mediates protein-protein interactions essential for peroxisomal import complex assembly.
<div class="infobox infobox-gene">
| Property | Value |
|----------|-------|
| Gene Symbol | PEX13 |
| Full Name | Peroxisome Biogenesis Factor 13 |
| Chromosomal Location | 2p15 |
| NCBI Gene ID | 5194 |
| OMIM ID | 603773 |
| Ensembl ID | ENSG00000131828 |
| UniProt ID | Q9UKV0 |
| Encoded Protein | Peroxin-13 (489 amino acids) |
| Protein Domain | SH3 domain (C-terminal) |
| Associated Diseases | Zellweger spectrum disorders, Neonatal adrenoleukodystrophy, Infantile Refsum disease |
| Inheritance | Autosomal recessive |
</div>
Molecular Function
Structure and Domains
PEX13 is an integral peroxisomal membrane protein composed of 489 amino acids with a predicted molecular mass of approximately 54 kDa. The protein contains several distinct structural features:
The SH3 domain of PEX13 has been structurally characterized and shown to bind proline-rich sequences in partner proteins, including Pex14p and the Pex5p receptor [@pex13_structure_2002]. This domain is critical for formation of the peroxisomal translocation pore and for recruiting cytosolic import factors to the membrane.
Peroxisomal Import Machinery
PEX13 functions at a critical hub in the peroxisomal protein import pathway. The current model involves:
PEX13 directly interacts with Pex5p through its SH3 domain, forming a stable docking complex that is essential for import efficiency. Studies in yeast and mammals have shown that PEX13 deficiency leads to accumulation of peroxisomal matrix proteins in the cytosol and severe impairment of peroxisome function [@peroxisome_import_2003].
Disease Associations
Peroxisome Biogenesis Disorders
Mutations in PEX13 are causative for peroxisome biogenesis disorders, a group of genetically heterogeneous conditions that represent the most severe spectrum of peroxisomal dysfunction. These disorders are characterized by:
- Zellweger syndrome (ZS): The most severe phenotype, presenting with profound neonatal hypotonia, craniofacial dysmorphism, severe developmental delay, neuronal migration defects, and often early death
- Neonatal adrenoleukodystrophy (NALD): Intermediate severity with later onset and somewhat slower progression
- Infantile Refsum disease (IRD): The mildest phenotype, with later onset and longer survival
A comprehensive genotype-phenotype analysis of PBDs has revealed that the nature and location of PEX13 mutations correlate with residual protein function and disease severity [@pbd_2005]. Patients with null mutations typically present with classical Zellweger syndrome, while those with missense mutations retaining partial function may have milder phenotypes.
Neurological Manifestations
The neurological consequences of PEX13 mutations stem from peroxisomal dysfunction in the central nervous system:
Clinical studies of patients with PEX13 mutations have documented severe developmental delay, hypotonia, seizures, and visual impairment [@pbd_review_2011]. Neuroimaging typically reveals polymicrogyria, ventricular enlargement, and white matter abnormalities.
Connection to Neurodegenerative Diseases
Beyond rare PBDs, PEX13 and peroxisomal dysfunction are increasingly implicated in common neurodegenerative diseases:
Alzheimer's Disease
Multiple lines of evidence connect peroxisomal dysfunction to AD pathogenesis:
Parkinson's Disease
Peroxisomal dysfunction is also implicated in PD pathogenesis:
Other Neurodegenerative Conditions
Peroxisomal dysfunction has been implicated in:
- Huntington's disease: PBD gene variants modify disease progression
- Amyotrophic lateral sclerosis: Peroxisomal markers are altered in motor neurons
- Multiple sclerosis: Demyelination involves peroxisomal dysfunction
Expression Patterns
Tissue Distribution
PEX13 is expressed in virtually all tissues, with highest levels in tissues requiring high peroxisomal activity:
| Tissue | Expression Level |
|--------|------------------|
| Brain (cortex) | High |
| Liver | Very high |
| Kidney | High |
| Heart | Moderate |
| Skeletal muscle | Moderate |
| Lung | Moderate |
Brain Expression
Within the brain, PEX13 shows region-specific expression patterns:
Studies in neuronal cell lines have demonstrated that PEX13 expression is developmentally regulated, with increased expression during neuronal differentiation [@pex13_neuronal_2021]. This suggests that peroxisomal biogenesis is particularly important during neuronal maturation.
Therapeutic Implications
Current Treatment Approaches
There is currently no cure for PBDs caused by PEX13 mutations. Management is supportive and includes:
Emerging Therapeutic Strategies
Research efforts are focused on developing novel therapies:
Research Directions
Current research areas include:
- iPSC models: Generation of patient-derived induced pluripotent stem cells for drug screening
- CRISPR-based therapies: Gene editing approaches to correct PEX13 mutations
- Peroxisome regeneration: Understanding mechanisms to promote peroxisome biogenesis in post-mitotic neurons
- Cross-correction strategies: Exploiting intercellular peroxisome transfer between cells
Gene Variants
Known Pathogenic Variants
Over 50 pathogenic variants in PEX13 have been described:
| Variant Type | Examples | Phenotype |
|--------------|----------|-----------|
| Nonsense | p.R200X, p.W403X | Severe (ZS) |
| Missense | p.G235R, p.Y346C | Variable |
| Frameshift | c.1234delC, c.2106insT | Severe (ZS) |
| Splice site | c.1815+1G>A | Variable |
| Large deletions | Exon 5-8 deletion | Severe |
Genotype-phenotype correlations indicate that variants resulting in complete loss of function (null alleles) cause classical Zellweger syndrome, while hypomorphic variants (partial function) can result in milder phenotypes [@pex13_splicing_2023].
Interactions and Pathways
Protein-Protein Interactions
PEX13 interacts with multiple components of the peroxisomal import machinery:
Signaling Pathways
PEX13 intersects with several important cellular pathways:
Cross-References
- [Peroxisome Signaling Pathway in Neurodegeneration](/mechanisms/peroxisome-signaling-pathway-neurodegeneration)
- [Peroxisome Dysfunction](/mechanisms/peroxisome-dysfunction)
- [Zellweger Spectrum Disorders](/diseases/zellweger-spectrum-disorders)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [PEX1 Gene](/genes/pex1)
- [PEX5 Gene](/genes/pex5)
- [PEX6 Gene](/genes/pex6)
- [Catalase Protein](/proteins/catalase-protein)
- [Plasmalogen Metabolism](/mechanisms/plasmalogen-metabolism-neurodegeneration)
Research History and Key Discoveries
Early Discovery (1990s)
The PEX13 gene was first identified in the late 1990s through genetic studies of patients with peroxisome biogenesis disorders. Initial studies focused on the identification of the gene through positional cloning and complementation assays. The first pathogenic mutations were described in 1999, establishing PEX13 as a cause of Zellweger syndrome [@pex13_1999]. Early biochemical characterization revealed that PEX13-deficient cells showed a complete absence of peroxisomal matrix proteins, highlighting the essential role of PEX13 in the import pathway.
Structural Studies (2000s)
The 2000s saw significant advances in understanding PEX13 structure. The crystal structure of the SH3 domain was solved in 2002, revealing the molecular basis for protein-protein interactions [@pex13_structure_2002]. Subsequent studies used mutagenesis to map critical residues involved in PEX5 binding and peroxisomal targeting. These structural insights informed the development of small molecule correctors for missense mutations.
Connection to Neurodegeneration (2010s)
A major paradigm shift occurred in the 2010s when researchers began connecting peroxisomal dysfunction to common neurodegenerative diseases. Post-mortem brain studies revealed reduced peroxisome numbers in AD and PD brains [@peroxisome_ad_2008; @peroxisome_pd_2013]. The discovery that PEX10 mutations could influence α-synuclein aggregation provided a direct mechanistic link between peroxins and PD pathogenesis [@pex10_alpha_syn_2013].
Current Research (2020s)
The current era is characterized by:
- Single-cell sequencing to understand cell-type-specific peroxisomal function
- iPSC models of PBDs for drug screening
- Gene therapy approaches using AAV vectors
- Understanding peroxisome-mitochondria crosstalk in neurodegeneration
Model Systems
Yeast Models
Saccharomyces cerevisiae and Pichia pastoris have been invaluable for studying PEX13 function. The yeast ortholog (PEX13p) is structurally and functionally conserved, allowing deletion mutants to reveal essential functions. Key findings from yeast include:
- Identification of the docking complex composition
- Characterization of Pex5p recycling mechanism
- Understanding of peroxisome quality control
Mouse Models
Several Pex13 knockout mouse models have been generated:
- Complete knockout: Embryonic lethal, with severe developmental defects
- Conditional knockout: Brain-specific deletion leads to neurodegeneration
- Hypomorphic alleles: Model milder PBD phenotypes
These models reproduce key features of human PBDs and are used for therapeutic testing.
Cell Culture Models
Primary cell cultures from patients and iPSC-derived cells provide relevant disease models:
- Fibroblasts: Patient-derived fibroblasts show characteristic peroxisomal defects
- Neurons: iPSC-derived neurons reveal neuronal-specific vulnerabilities
- Organoids: Brain organoids allow study of development and interaction
Clinical Management
Diagnostic Approach
Diagnosis of PEX13-related disorders involves:
Standard of Care
Current management includes:
Monitoring and Follow-up
Patients require regular monitoring of:
- Neurological status and developmental progress
- Liver function tests
- VLCFA levels
- Visual and auditory function
- Growth parameters
Future Perspectives
Gene Therapy Advances
Gene therapy represents the most promising approach for PEX13-related disorders:
Clinical trials are expected to begin within the next 5 years.
Small Molecule Therapies
Drug repurposing screens have identified potential therapeutics:
- PPAR agonists: Fenofibrate promotes peroxisome proliferation
- HDAC inhibitors: Valproic acid may enhance peroxisomal function
- Antioxidants: N-acetylcysteine reduces oxidative stress
- Autophagy inducers: Rapamycin may enhance peroxisome biogenesis
Biomarker Development
Biomarker research aims to:
- Identify early diagnostic markers
- Track disease progression
- Monitor treatment response
- Predict clinical outcomes
Pathophysiological Mechanisms
Peroxisomal Matrix Protein Import Defects
The primary pathophysiological consequence of PEX13 mutations is the failure to import peroxisomal matrix proteins. This leads to:
Specifically, the absence of peroxisomal matrix proteins causes:
- Failure of fatty acid β-oxidation
- Impaired plasmalogen synthesis
- Defective cholesterol biosynthesis
- Dysregulated pipecolic acid metabolism
Lipid Metabolism Dysregulation
Peroxisomes play essential roles in lipid metabolism:
Very Long-Chain Fatty Acid (VLCFA) Metabolism:
- PEX13 deficiency prevents VLCFA β-oxidation
- VLCFAs accumulate in plasma and tissues
- VLCFAs incorporate into membrane phospholipids
- Altered membrane properties affect neuronal function
- Peroxisomes are the primary site of plasmalogen synthesis
- Plasmalogens are essential for myelin structure
- Synaptic membranes require plasmalogens for function
- Deficiency leads to demyelination and synaptic loss
- Peroxisomal steps in primary bile acid synthesis are blocked
- Accumulation of C27-bile acid intermediates
- Liver dysfunction results from bile acid toxicity
Oxidative Stress and Neuroinflammation
Peroxisomal dysfunction leads to oxidative stress:
Neuroinflammation is a secondary consequence:
- Microglial activation in response to neuronal damage
- Astrocyte reactivity and astrocytosis
- Cytokine release (IL-1β, IL-6, TNF-α)
- Blood-brain barrier disruption
Mitochondrial Dysfunction
Peroxisome-mitochondria crosstalk is essential for cellular health:
PEX13 deficiency causes secondary mitochondrial dysfunction:
- Reduced oxidative phosphorylation
- Increased mitochondrial ROS production
- Altered mitochondrial morphology
- Enhanced susceptibility to apoptotic stimuli
Cellular Vulnerability
Specific cell types show heightened vulnerability:
Neurons:
- High metabolic demands make neurons dependent on peroxisomal function
- Peroxisomes are particularly abundant in neurons
- Axonal transport requires proper peroxisomal function
- Synaptic terminals have high peroxisome density
- Myelin production requires massive lipid synthesis
- Plasmalogens are essential myelin components
- White matter is preferentially affected in PBDs
- High fatty acid turnover in photoreceptor outer segments
- Peroxisomes are essential for photoreceptor function
- Retinal degeneration is common in PBDs
Experimental Evidence
Cell Biology Studies
Key experimental findings from cell biology:
Animal Model Studies
Mouse models have provided crucial insights:
Human Studies
Clinical observations confirm experimental findings:
Comparative Genomics
Evolutionary Conservation
PEX13 is evolutionarily conserved:
| Species | Gene | Identity |
|---------|------|----------|
| Human | PEX13 | Reference |
| Mouse | Pex13 | 91% |
| Zebrafish | pex13 | 78% |
| D. melanogaster | Pex13 | 62% |
| C. elegans | pex-13 | 54% |
| S. cerevisiae | PEX13 | 41% |
Orthologs and Paralogs
- PEX13 orthologs: Present in all eukaryotes
- PEX13-related proteins: No close paralogs in humans
- Domain conservation: SH3 domain is highly conserved
- Functional conservation: Can complement yeast pex13 mutants
Public Health and Epidemiology
Disease Prevalence
Peroxisome biogenesis disorders:
- Incidence: 1 in 100,000 to 1 in 150,000 births
- PEX13 accounts for ~5% of PBDs
- More common in populations with high consanguinity
Economic Burden
PBDs impose significant healthcare costs:
- Extensive diagnostic workup
- Chronic supportive care
- Frequent hospitalizations
- Specialized dietary requirements
Genetic Counseling
Family planning considerations:
- Autosomal recessive inheritance
- 25% recurrence risk for carrier parents
- Carrier testing available
- Preimplantation genetic diagnosis option
External Links
- [Ensembl: ENSG00000131828](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000131828)
- [NCBI Gene: PEX13](https://www.ncbi.nlm.nih.gov/gene/?term=PEX13)
- [GeneCards: PEX13](https://www.genecards.org/cgi-bin/carddisp.pl?gene=PEX13)
- [OMIM: 603773](https://omim.org/603773)
- [UniProt: Q9UKV0](https://www.uniprot.org/uniprot/Q9UKV0)
- [UCSC Genome Browser](https://genome.ucsc.edu/cgi-bin/hgTracks?db=hg38&position=chr2:61000000-62000000)
Pathway Diagram
References
See Also
Related Hypotheses:
- [Astrocytic Lipoxin A4 Pathway Restoration via ALOX15 Gene Therapy](/hypotheses/h-ac55ff26)
- [CYP46A1 Overexpression Gene Therapy](/hypotheses/h-2600483e)
- [Lipid raft composition changes in synaptic neurodegeneration](/analysis/SDA-2026-04-01-gap-lipid-rafts-2026-04-01)
- [Neuroinflammation resolution mechanisms and pro-resolving mediators](/analysis/SDA-2026-04-01-gap-014)
- [Circuit-level neural dynamics in neurodegeneration](/analysis/SDA-2026-04-02-26abc5e5f9f2)
Pathway Diagram
The following diagram shows the key molecular relationships involving PEX13 Gene discovered through SciDEX knowledge graph analysis:
▸Metadataorigin_type: v1_polymorphic_backfill
| slug | genes-pex13 |
| kg_node_id | PEX13 |
| entity_type | gene |
| origin_type | v1_polymorphic_backfill |
| source_table | wiki_pages |
| wiki_page_id | wp-26acccf3e9a7 |
| __merged_from | {'merged_at': '2026-05-13', 'unprefixed_id': 'genes-pex13'} |
| _schema_version | 1 |
No provenance edges found
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[PEX13 Gene](http://scidex.ai/artifact/wiki-genes-pex13)
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