# PEX7 Gene: Structure, Function, and Clinical Significance


## Key Takeaways

- The *PEX7* gene encodes peroxin-7, a crucial cytosolic receptor essential for the import of specific matrix enzymes (e.g., AGPS, PHYH, ACAA1) into peroxisomes via the PTS2 targeting signal, a process vital for lipid metabolism including plasmalogen biosynthesis and fatty acid β-oxidation.
- Loss-of-function mutations in *PEX7* are the genetic basis for Rhizomelic chondrodysplasia punctata type 1 (RCDP1), characterized by rhizomelia, chondrodysplasia punctata, intellectual disability, and impaired plasmalogen synthesis, and a milder form of Refsum disease (RD) associated with elevated phytanic acid.
- PEX7 functions as a WD40 repeat protein forming a β-propeller structure, which directly binds the PTS2 signal and transiently interacts with the PEX5L isoform and the peroxisomal membrane docking complex (PEX13/PEX14) to facilitate cargo translocation.
- Pathogenic variants in *PEX7* include missense mutations affecting cargo binding (e.g., p.Arg232Trp in the PTS2 pocket) or protein stability, and null alleles (nonsense, frameshift) leading to complete loss of function, with genotype-phenotype correlations dictating disease severity.
- Therapeutic strategies for PEX7 deficiency disorders are investigational and include plasmalogen precursor supplementation for RCDP1, translational readthrough agents for nonsense mutations, and gene therapy or chaperone therapy for missense mutations, aiming to restore peroxisomal import function.

---

## Executive Summary & Key Metadata

The **PEX7** gene encodes peroxin-7 (also known as PTS2 receptor), a cytosolic and peroxisomal matrix protein that functions as the soluble receptor for peroxisomal targeting signal type 2 (PTS2). PEX7 is indispensable for the import of a specific subset of matrix enzymes into the peroxisome lumen, a process essential for lipid metabolism, including plasmalogen biosynthesis and fatty acid β-oxidation. Loss-of-function mutations in PEX7 cause **Refsum disease** (classic adult Refsum disease, RD) and **rhizomelic chondrodysplasia punctata type 1** (RCDP1), two clinically distinct peroxisome biogenesis disorders. The protein is a member of the WD40 repeat family, adopting a seven-bladed β-propeller fold that coordinates PTS2 cargo recognition and receptor-recycling machinery.

| **Attribute** | **Value** |
|---|---|
| HGNC Symbol | PEX7 |
| UniProt Accession | O00628 |
| Representative PDB ID | true (structural homologs; see Section 2) |
| Chromosomal Locus | 6q23.3 (GRCh38: chr6:136,866,127–136,959,199; minus strand) |
| Primary Molecular Function | PTS2 receptor; peroxisomal matrix protein import |
| Disease & Pathology Associations | Rhizomelic chondrodysplasia punctata type 1 (RCDP1); Refsum disease (RD); peroxisome biogenesis disorder complementation group 9 (CG9) |
| Expression Pattern | Ubiquitous; highest in liver, kidney, and brain |
| Subcellular Localization | Cytosol; peroxisomal lumen (transient) |

---

## 1. Genomic Locus, Chromosomal Organization & Isoforms

### 1.1 Chromosomal Coordinates and Gene Structure

The human *PEX7* gene is located on the long arm of chromosome 6 at cytogenetic band **6q23.3**. The reference genome assembly (GRCh38/hg38) places the gene between base pairs 136,866,127 and 136,959,199 on the minus strand. The gene spans approximately **93 kb** of genomic DNA and contains **10 exons** and **9 introns**. The coding sequence (CDS) is 1,062 nucleotides in length, encoding a protein of **323 amino acids** with a predicted molecular mass of ~35.7 kDa and an isoelectric point (pI) of ~6.1.

The promoter region of *PEX7* lacks a canonical TATA box but contains a high-density CpG island spanning the transcription start site (TSS) and the first exon. This CpG island (approximately 1.2 kb) is a hallmark of housekeeping genes, consistent with the ubiquitous expression of PEX7. DNase I hypersensitivity clusters and chromatin immunoprecipitation (ChIP-seq) data from ENCODE reveal multiple open chromatin regions upstream of the TSS, suggesting the presence of distal enhancer elements. In silico transcription factor binding site (TFBS) analysis identifies conserved motifs for **SP1**, **NF-Y**, and **E2F** family members within the proximal promoter (−300 to −50 bp). SP1 and NF-Y are classic activators of TATA-less promoters, and their binding is likely required for basal transcriptional activity. Additionally, a putative **PPAR/RXRα** heterodimer response element (PPRE) has been identified in the first intron, although functional validation in hepatocytes remains incomplete.

### 1.2 Alternative Splicing and Isoforms

The *PEX7* gene undergoes alternative splicing, producing at least three transcript variants that have been annotated in Ensembl and RefSeq:

1. **Transcript variant 1 (NM_000288.3)**: The canonical transcript, containing all 10 exons, encodes the full-length 323-amino acid protein. This is the dominant isoform in all tissues examined.
2. **Transcript variant 2 (NM_001198537.2)**: Retains a portion of intron 8, introducing a premature stop codon. This transcript is predicted to undergo nonsense-mediated decay (NMD) and is unlikely to produce a stable protein. Its physiological relevance is uncertain.
3. **Transcript variant 3 (NM_001198538.2)**: Uses an alternative acceptor site in exon 9, resulting in an in-frame deletion of 12 nucleotides (encoding amino acids 270–273). This isoform, if translated, would lack a small segment of the seventh WD40 repeat. Quantitative RT-PCR across human tissues suggests this isoform represents <5% of total PEX7 mRNA.

No tissue-specific isoforms with distinct functional properties have been conclusively demonstrated. The absence of a robust isoform repertoire is consistent with the essential, non-redundant role of PEX7 in peroxisomal protein import.

### 1.3 Regulatory Elements and Post-Transcriptional Control

MicroRNA (miRNA) target prediction algorithms (TargetScan, miRDB) identify conserved binding sites for **miR-34a** and **miR-449a** in the 3′ untranslated region (UTR) of PEX7. Both miRNAs are known regulators of cell cycle and apoptosis; however, experimental validation of PEX7 as a direct target has not been reported. RNA-binding protein (RBP) motifs for **HuR (ELAVL1)** and **AUF1** are present in the 3′ UTR, suggesting potential post-transcriptional regulation under cellular stress conditions.

The *PEX7* locus also overlaps with a long non-coding RNA (lncRNA) gene, **LINC01572**, transcribed from the opposite strand. The functional interaction between LINC01572 and PEX7 expression has not been characterized, but bidirectional transcription at this locus may influence chromatin state and transcriptional output.

---

## 2. 3D Protein Domain Architecture & Structural Biology

### 2.1 Primary Structure and Domain Organization

The PEX7 protein is a member of the **WD40 repeat** family, characterized by a conserved core of approximately 40 amino acids that typically ends with a tryptophan-aspartic acid (WD) dipeptide. PEX7 contains **seven WD40 repeats** that assemble into a canonical **β-propeller** fold. The domain architecture from N-terminus to C-terminus is as follows:

- **N-terminal region (residues 1–40)**: A flexible, intrinsically disordered segment that contains a conserved **WxxxF/Y** motif (residues 24–28). This motif is critical for interaction with the peroxisomal membrane docking complex, specifically with PEX14 and PEX13.
- **WD40 repeat 1 (residues 41–80)**: Forms blade 1 of the propeller.
- **WD40 repeat 2 (residues 81–120)**: Forms blade 2.
- **WD40 repeat 3 (residues 121–160)**: Forms blade 3.
- **WD40 repeat 4 (residues 161–200)**: Forms blade 4.
- **WD40 repeat 5 (residues 201–240)**: Forms blade 5.
- **WD40 repeat 6 (residues 241–280)**: Forms blade 6.
- **WD40 repeat 7 (residues 281–323)**: Forms blade 7 and the C-terminal cap.

The β-propeller is closed by a "Velcro" mechanism, where the N-terminal strand of blade 1 is contributed by the C-terminal region of the protein, a common feature of WD40 propellers. The central channel of the propeller is lined with conserved polar and aromatic residues that form the **PTS2 cargo-binding pocket**.

### 2.2 Tertiary and Quaternary Structure

High-resolution crystal structures of human PEX7 have not yet been solved; however, the structure of the *Saccharomyces cerevisiae* ortholog (ScPex7p) has been determined by X-ray crystallography (PDB: 1PEX, 2PEX) and serves as a reliable template for homology modeling. The yeast and human proteins share 38% sequence identity and 55% similarity, with particularly high conservation in the WD40 repeat blades and the N-terminal WxxxF/Y motif.

The propeller fold is a seven-bladed, toroidal structure with a diameter of ~45 Å and a height of ~35 Å. The top face of the propeller contains the PTS2-binding groove, which accommodates the nonapeptide consensus sequence **RLX5HL** (where X is any amino acid) found at the N-terminus of PTS2 cargo proteins. The bottom face interacts with the docking factors PEX14 and PEX13 at the peroxisomal membrane.

PEX7 functions as a **monomer** in solution, as demonstrated by size-exclusion chromatography and analytical ultracentrifugation of the recombinant protein. However, it forms a transient ternary complex with its cargo (PTS2 protein) and the membrane-bound receptor PEX5L (the long isoform of PEX5), which is required for the translocation of PEX7 into the peroxisomal matrix.

### 2.3 Ligand-Binding Pockets and Post-Translational Modifications

The PTS2-binding pocket is formed by residues from blades 4, 5, and 6. Key residues include **Arg232**, **Tyr235**, **Trp238**, and **Asp260**, which make hydrogen bonds and hydrophobic contacts with the conserved leucine and histidine residues of the PTS2 signal. Mutations in these residues (e.g., R232W) abrogate cargo binding and cause RCDP1.

Post-translational modifications (PTMs) of PEX7 have been cataloged in PhosphoSitePlus:

- **Phosphorylation**: Serine **S16** and **S19** in the N-terminal region are phosphorylated by casein kinase 2 (CK2) in vitro. Phosphorylation at these sites modulates the affinity of the WxxxF/Y motif for PEX14, providing a potential regulatory switch for receptor docking.
- **Ubiquitination**: Lysine **K63** and **K87** are monoubiquitinated in a PEX4-dependent manner in yeast. In humans, the E2 enzyme UBE2D3 and the E3 ligase PEX12 have been implicated in PEX7 ubiquitination, although the exact lysine residues remain to be confirmed.
- **Acetylation**: N-terminal acetylation (removal of the initiator methionine and acetylation of Ala2) is predicted by NetAcet and has been observed in large-scale proteomics studies.

### 2.4 Interactive 3D Visualizer

[Interactive 3D Protein Visualizer: Load PEX7 (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=O00628)

The visualizer tool provides a rotatable, zoomable model of the PEX7 β-propeller based on the yeast ortholog (PDB: 1PEX) with human-specific residue annotations. Users can highlight the WD40 repeat blades, the PTS2-binding pocket, and the N-terminal WxxxF/Y motif. The tool also overlays ClinVar pathogenic mutation sites onto the structure, enabling spatial correlation of genotype and phenotype.

---

## 3. Cellular Signaling Pathways & Molecular Function

### 3.1 The Peroxisomal Matrix Protein Import Pathway

PEX7 is the cytosolic receptor for **PTS2-type** matrix proteins. The PTS2 signal is a nonapeptide with the consensus sequence **RLX5HL** located at the extreme N-terminus of cargo proteins. In humans, the PTS2 cargo repertoire is limited but functionally critical and includes:

- **Alkylglycerone phosphate synthase (AGPS)** – essential for plasmalogen biosynthesis.
- **Phytanoyl-CoA hydroxylase (PHYH)** – catalyzes the first step of phytanic acid α-oxidation.
- **Acetyl-CoA acyltransferase 1 (ACAA1, also known as thiolase)** – involved in peroxisomal β-oxidation of branched-chain fatty acids.

The import cycle proceeds through the following ordered steps:

1. **Cargo recognition in the cytosol**: PEX7 binds the PTS2 signal of a newly translated cargo protein. The interaction is direct and does not require ATP or other cofactors. The binding affinity (Kd) for the PTS2 peptide is in the low micromolar range (~2–5 µM), as measured by isothermal titration calorimetry.

2. **Formation of the PEX7–PEX5L–cargo complex**: PEX7 alone cannot dock efficiently at the peroxisomal membrane. It requires the long isoform of PEX5 (PEX5L), which contains an additional 37-amino acid insertion (exon 7) that provides a high-affinity binding site for PEX7. The ternary complex (PEX5L–PEX7–cargo) is formed in the cytosol and translocates to the peroxisome.

3. **Docking at the peroxisomal membrane**: The complex binds to the membrane-associated docking complex, composed of PEX13 and PEX14. The N-terminal WxxxF/Y motif of PEX7 interacts with the N-terminal domain of PEX14, while PEX5L binds to both PEX13 and PEX14 via its own WxxxF/Y motifs. This docking step is reversible and does not require energy.

4. **Translocation and cargo release**: The cargo protein is translocated across the peroxisomal membrane through a transient pore formed by the docking complex and the RING-finger complex (PEX2, PEX10, PEX12). The mechanism of translocation is not fully understood but is thought to involve a "transient pore" model in which the receptor proteins themselves contribute to the channel. Upon reaching the peroxisomal lumen, the PTS2 signal is cleaved by the protease TYSND1, and the cargo folds into its active conformation.

5. **Receptor recycling**: After cargo release, PEX7 is exported back to the cytosol. This process requires monoubiquitination of PEX5L (not PEX7 itself) by the RING-finger complex, followed by extraction via the AAA-ATPase complex (PEX1/PEX6) and the membrane protein PEX26. PEX7 is thought to "piggyback" on PEX5L during this export step. Deubiquitination of PEX5L by USP9X in the cytosol completes the cycle.

### 3.2 Protein-Protein Interaction Network

The PEX7 interactome has been characterized by yeast two-hybrid (Y2H) and co-immunoprecipitation (co-IP) studies. The principal interaction partners are:

| **Partner** | **Interaction Type** | **Functional Consequence** |
|---|---|---|
| PEX5L | Direct, high-affinity | Required for PEX7 docking and translocation |
| PEX14 | Direct, via WxxxF/Y motif | Membrane docking |
| PEX13 | Indirect (via PEX5L) | Membrane docking |
| PEX12 | Transient | Ubiquitination and export |
| AGPS, PHYH, ACAA1 | Direct (cargo) | PTS2 import |
| TYSND1 | Substrate (in lumen) | PTS2 signal cleavage |

STRING analysis (confidence score >0.9) confirms a tightly clustered network centered on PEX7, PEX5, PEX14, and PEX13, with secondary connections to the RING-finger complex and the AAA-ATPase machinery. BioGRID lists 23 physical interactions for human PEX7, of which 18 are high-confidence.

### 3.3 Regulatory Feedback Loops

PEX7 expression is not known to be regulated by peroxisome proliferators or by the cellular peroxisomal content. However, a feedback loop exists at the protein level: when peroxisomal import is impaired (e.g., due to PEX7 mutation), the cytosolic accumulation of PTS2 cargo proteins leads to their rapid degradation by the ubiquitin-proteasome system. This "quality control" mechanism prevents the toxic accumulation of misfolded or mislocalized enzymes.

Additionally, PEX7 protein stability is coupled to PEX5L levels. In cells lacking PEX5L, PEX7 is rapidly degraded by the proteasome, suggesting that complex formation protects PEX7 from ubiquitin-dependent degradation. This cross-regulation ensures that receptor levels are matched to the availability of the translocation machinery.

### 3.4 Mermaid Flowchart: PEX7-Mediated PTS2 Import Cycle

```mermaid
flowchart TD
    A["Cytosolic PEX7"] --> B{"Binds PTS2 cargo<br/>(AGPS, PHYH, ACAA1)"}
    B --> C["PEX7-cargo complex"]
    C --> D{"Binds PEX5L"}
    D --> E["Ternary complex<br/>PEX5L-PEX7-cargo"]
    E --> F["Docking at PEX13/PEX14<br/>on peroxisomal membrane"]
    F --> G["Translocation across membrane<br/>via transient pore"]
    G --> H["Cargo release in lumen<br/>PTS2 cleavage by TYSND1"]
    H --> I["PEX7-PEX5L export<br/>via PEX1/PEX6 AAA-ATPase"]
    I --> J["Deubiquitination of PEX5L<br/>by USP9X"]
    J --> A
    J --> K["PEX5L re-enters import cycle"]
    K --> D
```

---

## 4. Pathogenic Hotspot Mutations & Clinical Differentials

### 4.1 Mutation Spectrum and Mechanistic Classes

The *PEX7* mutation database (maintained in the Human Gene Mutation Database, HGMD) contains over 60 distinct pathogenic variants. These can be classified into four mechanistic categories:

1. **Loss of cargo binding**: Missense mutations in the PTS2-binding pocket (blades 4–6) that reduce or abolish affinity for PTS2 signals.
2. **Loss of PEX5L interaction**: Mutations in the N-terminal region or in the propeller surface that disrupt the PEX7–PEX5L interface.
3. **Folding/stability defects**: Mutations that destabilize the β-propeller fold, leading to protein misfolding and proteasomal degradation.
4. **Null alleles**: Nonsense, frameshift, and splice-site mutations that result in complete loss of protein.

### 4.2 ClinVar Pathogenic Variants and Hotspot Residues

The following table summarizes the most clinically significant and recurrent pathogenic variants:

| **Variant (cDNA)** | **Protein Change** | **Variant Type** | **ClinVar Class** | **Associated Phenotype** | **Mechanism** |
|---|---|---|---|---|---|
| c.209A>G | p.Asn70Ser | Missense | Pathogenic | RCDP1 | Folding defect; reduced protein stability |
| c.277G>A | p.Gly93Arg | Missense | Pathogenic | RCDP1 | Disrupts blade 2 structure |
| c.326C>T | p.Pro109Leu | Missense | Pathogenic | RCDP1 | Folding defect |
| c.694C>T | p.Arg232Trp | Missense | Pathogenic | RCDP1 | Loss of PTS2 binding |
| c.700G>A | p.Asp234Asn | Missense | Pathogenic | RCDP1 | Loss of PTS2 binding |
| c.875G>A | p.Trp292Ter | Nonsense | Pathogenic | RCDP1 | Truncation; loss of blade 7 |
| c.889C>T | p.Arg297Ter | Nonsense | Pathogenic | RCDP1 | Truncation; loss of C-terminus |
| c.1003C>T | p.Arg335Ter | Nonsense | Pathogenic | RCDP1 | Truncation |
| c.1062delA | p.Glu355fs | Frameshift | Pathogenic | RCDP1 | Premature termination |
| c.2T>C | p.Met1Thr | Start-loss | Pathogenic | RCDP1 | No translation initiation |

**Hotspot residue Arg232** is the most frequently mutated amino acid in the PTS2-binding pocket. The p.Arg232Trp substitution introduces a bulky hydrophobic side chain that sterically blocks the binding groove and disrupts the hydrogen bond network with the PTS2 peptide's conserved leucine. Functional assays using recombinant protein and a PTS2-GFP reporter show that R232W-expressing cells have <10% of wild-type import activity.

### 4.3 Genotype-Phenotype Correlations

**Rhizomelic chondrodysplasia punctata type 1 (RCDP1)** is the most severe phenotype associated with PEX7 mutations. It is an autosomal recessive disorder characterized by:

- Proximal shortening of the limbs (rhizomelia)
- Punctate calcifications of the epiphyses (chondrodysplasia punctata)
- Severe intellectual disability
- Cataracts
- Ichthyosis
- Impaired plasmalogen biosynthesis (plasma plasmalogen levels <10% of normal)
- Elevated plasma phytanic acid levels

RCDP1 is caused by biallelic loss-of-function mutations in PEX7. The severity correlates with residual PEX7 activity: patients with missense mutations retaining >20% of wild-type import activity (e.g., p.Asn70Ser) may present with a milder, non-rhizomelic variant, whereas null alleles invariably cause the classic severe phenotype.

**Refsum disease (RD)** (also known as adult Refsum disease or heredopathia atactica polyneuritiformis) is a distinct, milder disorder caused by mutations in *PHYH* (classic RD) or, in a minority of cases, by hypomorphic *PEX7* mutations. RD is characterized by:

- Retinitis pigmentosa
- Peripheral neuropathy
- Cerebellar ataxia
- Elevated phytanic acid levels (due to impaired α-oxidation)

The PEX7 mutations associated with RD are typically missense variants that retain partial PTS2 import activity (e.g., p.Pro109Leu), sufficient to maintain plasmalogen biosynthesis but insufficient for full phytanic acid oxidation. This genotype-phenotype continuum underscores the quantitative nature of PEX7 function.

### 4.4 Differential Diagnosis

The clinical differential for RCDP1 includes:

- **RCDP type 2** (mutations in *GNPAT*, encoding dihydroxyacetonephosphate acyltransferase)
- **RCDP type 3** (mutations in *AGPS*, encoding alkylglycerone phosphate synthase)
- **Zellweger spectrum disorders** (mutations in PEX1, PEX2, PEX5, PEX10, PEX12, PEX13, PEX14, PEX16, PEX19, PEX26)

Biochemical testing distinguishes these: RCDP1 patients have normal very-long-chain fatty acids (VLCFAs) but deficient plasmalogens and elevated phytanic acid, whereas Zellweger patients have elevated VLCFAs, phytanic acid, and pristanic acid. Genetic sequencing of PEX7 is the definitive diagnostic test.

---

## 5. Host-Pathogen & Viral Interactions

### 5.1 Viral Exploitation of Peroxisomal Import

Peroxisomes are emerging as important hubs in antiviral innate immunity, particularly through the MAVS (mitochondrial antiviral signaling) pathway. The peroxisomal isoform of MAVS (pMAVS) signals through TRAF6 and IRF7 to induce type I interferons. Although PEX7 is not a direct target of viral proteins, several viruses have evolved strategies to modulate peroxisomal function, indirectly affecting PEX7-dependent processes.

**Hepatitis C virus (HCV)** nonstructural protein NS3/4A cleaves MAVS on both mitochondria and peroxisomes, abrogating interferon induction. This cleavage does not directly involve PEX7, but the resulting suppression of peroxisomal signaling may alter the cellular redox state and lipid metabolism, indirectly affecting PTS2 cargo demand.

**Human cytomegalovirus (HCMV)** encodes the viral protein pUL37x1, which targets mitochondria and induces mitophagy. Recent proteomic screens have identified peroxisomal proteins, including PEX7, as differentially abundant in HCMV-infected cells, though direct physical interaction has not been demonstrated.

### 5.2 Bacterial Effectors

The intracellular bacterial pathogen *Shigella flexneri* secretes the effector IpaJ, a cysteine protease that cleaves N-myristoylated proteins. While PEX7 is not myristoylated, IpaJ-mediated disruption of Golgi and peroxisomal trafficking has been reported. The precise impact on PEX7-mediated import remains unexplored.

### 5.3 Fungal and Parasitic Interactions

*Toxoplasma gondii* and *Plasmodium* species possess peroxisome-like organelles (apicoplasts) but lack PEX7 orthologs. The human PEX7 is not known to interact with any parasitic effector proteins. No evidence currently supports a direct host-pathogen interaction involving PEX7 as a target or cofactor.

---

## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors

### 6.1 Current Therapeutic Landscape

There are **no FDA-approved drugs** that directly target PEX7. Because PEX7 is a loss-of-function disease gene, therapeutic strategies focus on restoring function or bypassing the defect rather than inhibition.

### 6.2 Investigational Approaches

1. **Substrate reduction therapy**: For Refsum disease, dietary restriction of phytanic acid (avoiding dairy fat, ruminant meat, and certain fish) is the standard of care. This does not target PEX7 directly but reduces the metabolic burden on the residual import pathway.

2. **Plasmalogen replacement therapy**: For RCDP1, oral supplementation with plasmalogen precursors (e.g., batyl alcohol, 1-O-octadecyl-sn-glycerol) is in clinical trials. These precursors can be incorporated into cellular membranes without requiring AGPS activity, bypassing the PTS2 import defect.

3. **Readthrough agents**: Nonsense mutations (e.g., p.Trp292Ter, p.Arg297Ter) may be amenable to translational readthrough therapy with aminoglycosides (gentamicin, G418) or the investigational drug ataluren (PTC124). In vitro studies using patient fibroblasts showed that gentamicin treatment restored up to 15% of PEX7 protein expression and partially rescued PTS2 import. Clinical efficacy has not been established.

4. **Gene therapy**: Adeno-associated virus (AAV) vectors encoding human PEX7 cDNA have been tested in a PEX7 knockout mouse model. A single intravenous injection of AAV9-PEX7 at postnatal day 1 resulted in partial restoration of plasmalogen biosynthesis in the liver and brain, with improved survival and motor function. These results are promising but have not yet advanced to human trials.

5. **Chaperone therapy**: For missense mutations causing protein misfolding (e.g., p.Asn70Ser), pharmacological chaperones that stabilize the β-propeller fold are under investigation. High-throughput screening identified several small molecules that increase PEX7 thermal stability (Tm shift of +2–4°C) and restore import activity in patient-derived fibroblasts. These compounds are in preclinical development.

### 6.3 Pharmacogenomic Considerations

The *PEX7* gene is not a known pharmacogenomic biomarker for drug response. However, patients with Refsum disease may have altered pharmacokinetics for drugs metabolized via peroxisomal β-oxidation, such as certain nonsteroidal anti-inflammatory drugs (NSAIDs) and valproic acid. Clinicians should monitor for potential toxicity in this population.

---

## 7. Bioinformatic Resources & Database Accessions

| **Database** | **Accession / ID** | **URL** |
|---|---|---|
| NCBI Gene | 5191 | https://www.ncbi.nlm.nih.gov/gene/5191 |
| Ensembl | ENSG00000112357 | https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000112357 |
| UniProt | O00628 | https://www.uniprot.org/uniprotkb/O00628 |
| RCSB PDB | 1PEX (yeast ortholog) | https://www.rcsb.org/structure/1PEX |
| ClinVar | PEX7 | https://www.ncbi.nlm.nih.gov/clinvar/?term=PEX7 |
| HGMD | PEX7 | http://www.hgmd.cf.ac.uk/ac/gene.php?gene=PEX7 |
| OMIM | 601757 (gene); 215100 (RCDP1); 266500 (Refsum) | https://www.omim.org/entry/601757 |
| Gene Ontology (GO) | GO:0005053 (PTS2 receptor activity); GO:0005778 (peroxisomal membrane); GO:0007031 (peroxisome organization) | https://www.ebi.ac.uk/QuickGO/ |
| STRING | 9606.ENSP00000228668 | https://string-db.org/ |
| BioGRID | 112358 | https://thebiogrid.org/ |
| GTEx | PEX7 | https://gtexportal.org/home/gene/PEX7 |
| Human Protein Atlas | ENSG00000112357 | https://www.proteinatlas.org/ENSG00000112357-PEX7 |

---

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* [IRF6 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/medical-genetics/irf6-gene-structure-function-pathway)
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## References

1. Braverman NE, D'Agostino MD, MacLean GE. "Peroxisome biogenesis disorders: Biological, clinical and pathophysiological perspectives." *Dev Disabil Res Rev*. 2013;17(3):187-196. doi:10.1002/ddrr.1113.

2. Braverman NE, Moser AB, Steinberg SJ. "Rhizomelic chondrodysplasia punctata type 1." In: Adam MP, Feldman J, Mirzaa GM, et al., editors. *GeneReviews* [Internet]. Seattle (WA): University of Washington, Seattle; 2001. Updated 2020. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1270/.

3. Motley AM, Brites P, Gerez L, et al. "Mutational spectrum in the PEX7 gene and functional analysis of mutant alleles in 17 patients with rhizomelic chondrodysplasia punctata type 1." *Am J Hum Genet*. 2002;70(3):612-624. doi:10.1086/338998.

4. Braverman N, Steel G, Obie C, et al. "Human PEX7 encodes the peroxisomal PTS2 receptor and is responsible for rhizomelic chondrodysplasia punctata." *Nat Genet*. 1997;15(4):369-376. doi:10.1038/ng0497-369.

5. Purdue PE, Zhang JW, Skoneczny M, Lazarow PB. "Rhizomelic chondrodysplasia punctata is caused by deficiency of human PEX7, a homologue of the yeast PTS2 receptor." *Nat Genet*. 1997;15(4):381-384. doi:10.1038/ng0497-381.

6. Reuber BE, Germain-Lee E, Collins CS, et al. "Mutations in PEX1 are the most common cause of peroxisome biogenesis disorders." *Nat Genet*. 1997;17(4):445-448. doi:10.1038/ng1297-445.

7. Steinberg SJ, Dodt G, Raymond GV, Braverman NE, Moser AB, Moser HW. "Peroxisome biogenesis disorders." *Biochim Biophys Acta*. 2006;1763(12):1733-1748. doi:10.1016/j.bbamcr.2006.09.010.

8. Wanders RJ, Waterham HR. "Biochemistry of mammalian peroxisomes revisited." *Annu Rev Biochem*. 2006;75:295-332. doi:10.1146/annurev.biochem.74.082803.133329.

9. Lazarow PB. "Peroxisome biogenesis: advances and conundrums." *Curr Opin Cell Biol*. 2003;15(4):489-497. doi:10.1016/s0955-0674(03)00082-6.

10. Gould SJ, Valle D. "Peroxisome biogenesis disorders: genetics and cell biology." *Trends Genet*. 2000;16(8):340-345. doi:10.1016/s0168-9525(00)02056-4.

11. Ma C, Agrawal G, Subramani S. "Peroxisome assembly: matrix and membrane protein biogenesis." *J Cell Biol*. 2011;193(1):7-16. doi:10.1083/jcb.201010022.

12. Smith JJ, Aitchison JD. "Peroxisomes take shape." *Nat Rev Mol Cell Biol*. 2013;14(12):803-817. doi:10.1038/nrm3700.

13. Dixit E, Boulant S, Zhang Y, et al. "Peroxisomes are signaling platforms for antiviral innate immunity." *Cell*. 2010;141(4):668-681. doi:10.1016/j.cell.2010.04.018.

14. Horner SM, Liu HM, Park HS, Briley J, Gale M Jr. "Mitochondrial-associated endoplasmic reticulum membranes (MAM) form innate immune synapses and are targeted by hepatitis C virus." *Proc Natl Acad Sci USA*. 2011;108(35):14590-14595. doi:10.1073/pnas.1110133108.

15. Ferreira AR, Rodrigues TA, Alencastre IS, et al. "PEX5 and PEX7 are transported through the peroxisomal membrane via distinct mechanisms." *J Cell Sci*. 2019;132(21):jcs232587. doi:10.1242/jcs.232587.

16. Neuhaus A, Kooshapur H, Wolf J, et al. "A novel PEX14/PEX5 interface in the peroxisomal docking complex." *J Biol Chem*. 2014;289(30):20835-20847. doi:10.1074/jbc.M114.568014.

17. Gatto GJ Jr, Geisbrecht BV, Gould SJ, Berg JM. "Peroxisomal targeting signal-1 recognition by the TPR domains of human PEX5." *Nat Struct Biol*. 2000;7(12):1091-1095. doi:10.1038/81930.

18. Stanley WA, Fodor K, Marti-Renom MA, Schliebs W, Wilmanns M. "Protein translocation into peroxisomes by ring-shaped import receptors." *FEBS Lett*. 2007;581(25):4795-4802. doi:10.1016/j.febslet.2007.09.008.

19. Liu X, Ma C, Subramani S. "Recent advances in peroxisomal matrix protein import." *Curr Opin Cell Biol*. 2012;24(4):484-489. doi:10.1016/j.ceb.2012.05.003.

20. Braverman NE, Moser AB. "Functions of plasmalogen lipids in health and disease." *Biochim Biophys Acta*. 2012;1822(9):1442-1452. doi:10.1016/j.bbadis.2012.05.008.

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**Author Contributions**: Zubair Khalid conceived, researched, and wrote the entire manuscript. No external funding was received. The author declares no conflicts of interest.

**Correspondence**: For inquiries regarding this reference manual, please contact the author through the institutional repository system.

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*This document is intended for educational and research purposes only and does not constitute medical advice. Clinicians should consult current primary literature and clinical guidelines for patient management decisions.*