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PEX12
peroxisomal biogenesis factor 12
PEX12 is located on the long (q) arm of chromosome 17, at band 17q12. Arm ratio per GRCh38 - banding schematic.
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Overview
PEX12 (peroxisomal biogenesis factor 12) encodes a peroxisomal membrane protein that plays a critical role in assembling functional peroxisomes. Peroxisomes are small organelles found in nearly all cells, where they carry out essential metabolic processes including the breakdown of very long-chain fatty acids and the synthesis of certain lipids. The PEX12 protein anchors in the peroxisomal membrane and facilitates the import of other proteins into the organelle interior. Disruption of PEX12 function prevents normal peroxisome formation, resulting in accumulation of toxic metabolic intermediates and severe multisystem disease. Pathogenic variants in this gene follow an autosomal recessive inheritance pattern, meaning both gene copies must carry a variant for disease to manifest.
What the gene does
The PEX12 protein functions as part of the peroxisomal protein import machinery, which transports newly synthesised enzymes from the cytoplasm into the peroxisome interior. PEX12 is embedded in the peroxisomal membrane, where it interacts with other peroxin proteins to form a complex that recognises cargo proteins destined for the peroxisome. The protein contains a zinc finger domain that mediates interactions with components of the import apparatus. Without functional PEX12, cells cannot build complete peroxisomes or properly stock them with the enzymes needed for metabolic reactions. This leads to accumulation of very long-chain fatty acids, defective bile acid synthesis, and impaired plasmalogen production. These metabolic derangements particularly affect tissues with high energy demands, including the brain, liver, and kidneys. The peroxisomal import process is tightly regulated, and PEX12 contributes to quality control mechanisms that ensure only correctly folded proteins enter the organelle.
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Chromosome location
PEX12 is located on chromosome 17 at position q12 (17q12). This chromosomal region contains multiple genes involved in diverse cellular processes. The gene comprises multiple exons that together encode a 359 amino acid protein. The genomic structure and regulatory elements controlling PEX12 expression have been characterised in various cell types, with the gene showing broad expression across tissues that rely on peroxisomal metabolism.
Protein structure
The PEX12 protein is 359 amino acids in length and contains a RING-type degenerate zinc finger domain spanning amino acids 304-343. This zinc finger region is located near the carboxy terminus and is essential for the protein's role in peroxisomal biogenesis. The RING domain mediates protein-protein interactions with other components of the peroxisomal import machinery. The protein also contains transmembrane segments that anchor it within the peroxisomal membrane, positioning the functional domains appropriately for cargo recognition and translocation. The structural organisation allows PEX12 to coordinate with other peroxins in assembling the complete import complex.
Key variants
Pathogenic variants in PEX12 are associated with Zellweger spectrum disorder, a group of autosomal recessive conditions affecting peroxisome function. Disease-causing variants include missense changes that disrupt protein folding or domain function, nonsense variants that produce truncated proteins, and splice site alterations affecting transcript processing. The severity of clinical manifestations can vary depending on residual PEX12 function, with complete loss of activity typically causing the most severe phenotype.
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.140C>G | p.Ser47Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.511del | p.Glu171fs | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.51_54del | p.Gln17fs | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.518G>A | p.Trp173Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.541dup | p.Tyr181fs | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.543C>A | p.Tyr181Ter | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.573_574dup | p.Leu192fs | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.808del | p.Gln270fs | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder type 3B |
c.842del | p.Thr281fs | Pathogenic/Likely pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
c.875_876del | p.Asn291_Ser292insTer | Pathogenic | ★★☆☆ | Peroxisome biogenesis disorder 3A (Zellweger) |
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
Biallelic pathogenic variants in PEX12 cause Zellweger spectrum disorder, which encompasses a range of severity from neonatal Zellweger syndrome to milder infantile Refsum disease. Affected individuals present with neurological impairment, liver dysfunction, distinctive facial features, and skeletal abnormalities. The disorder arises from defective peroxisome assembly, leading to accumulation of toxic metabolites and deficiency of essential lipid products. Clinical features may include hypotonia, seizures, developmental delay, hearing and vision loss, and feeding difficulties. Diagnosis is typically confirmed through biochemical testing showing elevated very long-chain fatty acids and genetic analysis identifying biallelic PEX12 variants.
- Zellweger spectrum disorder Dedicated page coming soon
Inheritance pattern
Conditions caused by pathogenic PEX12 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
PEX12 appears on multiple NHS Genomic Medicine Service gene panels with green ratings, reflecting strong evidence for its role in human disease. These panels include Peroxisomal disorders, Likely inborn error of metabolism, Inherited white matter disorders, Intellectual disability, Neonatal cholestasis, and Fetal anomalies. The gene's inclusion across diverse panels reflects the multisystem nature of peroxisomal disorders. Green classification indicates that PEX12 variants meet criteria for reporting in clinical diagnostic settings when identified in individuals with compatible clinical features.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What inheritance pattern does PEX12 follow?
PEX12-related conditions follow an autosomal recessive inheritance pattern. This means an individual must inherit a pathogenic variant from both parents to develop Zellweger spectrum disorder. Carriers with one variant typically do not show symptoms.
What are peroxisomes and why are they important?
Peroxisomes are small cellular compartments that break down very long-chain fatty acids, synthesise certain lipids including plasmalogens, and carry out other metabolic reactions. When peroxisomes fail to assemble properly due to PEX12 dysfunction, toxic metabolites accumulate and essential biochemical pathways are disrupted, affecting multiple organ systems.
How is Zellweger spectrum disorder diagnosed?
Diagnosis typically involves biochemical testing showing abnormal levels of very long-chain fatty acids, plasmalogen deficiency, and other peroxisomal metabolites, combined with genetic testing to identify pathogenic variants in PEX12 or other peroxisome biogenesis genes. Clinical features and family history also inform the diagnostic process.