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Genetics Home Reference: your guide to understanding genetic conditions
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PEX7

Reviewed July 2010

What is the official name of the PEX7 gene?

The official name of this gene is “peroxisomal biogenesis factor 7.”

PEX7 is the gene's official symbol. The PEX7 gene is also known by other names, listed below.

What is the normal function of the PEX7 gene?

The PEX7 gene provides instructions for making a protein called peroxisomal biogenesis factor 7, which is part of a group known as the peroxisomal assembly (PEX) proteins. Within cells, PEX proteins are responsible for importing certain enzymes into structures called peroxisomes. The enzymes in these sac-like compartments break down many different substances, including fatty acids and certain toxic compounds. They are also important for the production (synthesis) of fats (lipids) used in digestion and in the nervous system.

Peroxisomal biogenesis factor 7 transports several enzymes that are essential for the normal assembly and function of peroxisomes. The most important of these enzymes is alkylglycerone phosphate synthase (produced from the AGPS gene). This enzyme is required for the synthesis of specialized lipid molecules called plasmalogens, which are present in cell membranes throughout the body. Peroxisomal biogenesis factor 7 also transports the enzyme phytanoyl-CoA hydroxylase (produced from the PHYH gene). This enzyme helps process a type of fatty acid called phytanic acid, which is obtained from the diet. Phytanic acid is broken down through a multistep process into smaller molecules that the body can use for energy.

Does the PEX7 gene share characteristics with other genes?

The PEX7 gene belongs to a family of genes called WDR (WD repeat domain containing).

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.

How are changes in the PEX7 gene related to health conditions?

Refsum disease - caused by mutations in the PEX7 gene

Mutations in the PEX7 gene cause a small percentage of all cases of Refsum disease. The three mutations known to be responsible for this condition reduce the activity of peroxisomal biogenesis factor 7, which disrupts the import of several critical enzymes (including phytanoyl-CoA hydroxylase) into peroxisomes. Without enough of these enzymes, peroxisomes cannot break down fatty acids and other substances effectively.

In people with Refsum disease, a shortage of phytanoyl-CoA hydroxylase prevents peroxisomes from breaking down phytanic acid. Instead, this substance gradually builds up in the body's tissues. Over time, the accumulation of phytanic acid becomes toxic to cells. It is unclear, however, how an excess of this substance affects vision and smell and causes the other specific features of Refsum disease.

rhizomelic chondrodysplasia punctata - caused by mutations in the PEX7 gene

More than three dozen mutations in the PEX7 gene have been found to cause rhizomelic chondrodysplasia punctata type 1 (RCDP1). These mutations tend to be more severe than the mutations that cause Refsum disease. The genetic changes associated with RCDP1 often lead to a completely nonfunctional version of peroxisomal biogenesis factor 7 or prevent cells from making any of this protein. The most common mutation responsible for RCDP1 replaces the amino acid leucine at protein position 292 with a premature stop signal in the instructions for making peroxisomal biogenesis factor 7 (written as Leu292Ter or L292X). This mutation leads to a nonfunctional version of the protein.

The PEX7 gene mutations responsible for RCDP1 prevent peroxisomal biogenesis factor 7 from transporting critical enzymes, particularly alkylglycerone phosphate synthase, into peroxisomes. A shortage of alkylglycerone phosphate synthase prevents the synthesis of plasmalogens. Problems with the production of these lipid molecules appear to cause the signs and symptoms of RCDP1. However, researchers are still working to determine how a lack of plasmalogens leads to skeletal abnormalities, intellectual disability, and the other features of this condition.

Where is the PEX7 gene located?

Cytogenetic Location: 6q23.3

Molecular Location on chromosome 6: base pairs 136,822,219 to 136,913,933

The PEX7 gene is located on the long (q) arm of chromosome 6 at position 23.3.

The PEX7 gene is located on the long (q) arm of chromosome 6 at position 23.3.

More precisely, the PEX7 gene is located from base pair 136,822,219 to base pair 136,913,933 on chromosome 6.

See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.

Where can I find additional information about PEX7?

You and your healthcare professional may find the following resources about PEX7 helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the PEX7 gene or gene products?

  • peroxin-7
  • peroxisomal PTS2 receptor
  • peroxisome targeting signal 2 receptor
  • PEX7_HUMAN
  • PTS2R

See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What glossary definitions help with understanding PEX7?

acids ; amino acid ; cell ; CoA ; digestion ; disability ; enzyme ; fatty acids ; gene ; leucine ; lipid ; mutation ; nervous system ; oxidation ; peroxisomes ; phosphate ; protein ; receptor ; synthesis ; toxic

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).

References

  • Braverman N, Chen L, Lin P, Obie C, Steel G, Douglas P, Chakraborty PK, Clarke JT, Boneh A, Moser A, Moser H, Valle D. Mutation analysis of PEX7 in 60 probands with rhizomelic chondrodysplasia punctata and functional correlations of genotype with phenotype. Hum Mutat. 2002 Oct;20(4):284-97. (http://www.ncbi.nlm.nih.gov/pubmed/12325024?dopt=Abstract)
  • Braverman N, Steel G, Lin P, Moser A, Moser H, Valle D. PEX7 gene structure, alternative transcripts, and evidence for a founder haplotype for the frequent RCDP allele, L292ter. Genomics. 2000 Jan 15;63(2):181-92. (http://www.ncbi.nlm.nih.gov/pubmed/10673331?dopt=Abstract)
  • Braverman N, Steel G, Obie C, Moser A, Moser H, Gould SJ, Valle D. Human PEX7 encodes the peroxisomal PTS2 receptor and is responsible for rhizomelic chondrodysplasia punctata. Nat Genet. 1997 Apr;15(4):369-76. (http://www.ncbi.nlm.nih.gov/pubmed/9090381?dopt=Abstract)
  • Gene Review: Refsum Disease (http://www.ncbi.nlm.nih.gov/books/NBK1353/)
  • Gene Review: Rhizomelic Chondrodysplasia Punctata Type 1 (http://www.ncbi.nlm.nih.gov/books/NBK1270/)
  • Jansen GA, Waterham HR, Wanders RJ. Molecular basis of Refsum disease: sequence variations in phytanoyl-CoA hydroxylase (PHYH) and the PTS2 receptor (PEX7). Hum Mutat. 2004 Mar;23(3):209-18. Review. (http://www.ncbi.nlm.nih.gov/pubmed/14974078?dopt=Abstract)
  • Motley AM, Brites P, Gerez L, Hogenhout E, Haasjes J, Benne R, Tabak HF, Wanders RJ, Waterham HR. Mutational spectrum in the PEX7 gene and functional analysis of mutant alleles in 78 patients with rhizomelic chondrodysplasia punctata type 1. Am J Hum Genet. 2002 Mar;70(3):612-24. Epub 2002 Jan 7. (http://www.ncbi.nlm.nih.gov/pubmed/11781871?dopt=Abstract)
  • NCBI Gene (http://www.ncbi.nlm.nih.gov/gene/5191)
  • Van den Brink DM, Brites P, Haasjes J, Wierzbicki AS, Mitchell J, Lambert-Hamill M, de Belleroche J, Jansen GA, Waterham HR, Wanders RJ. Identification of PEX7 as the second gene involved in Refsum disease. Adv Exp Med Biol. 2003;544:69-70. (http://www.ncbi.nlm.nih.gov/pubmed/14713215?dopt=Abstract)
  • van den Brink DM, Wanders RJ. Phytanic acid: production from phytol, its breakdown and role in human disease. Cell Mol Life Sci. 2006 Aug;63(15):1752-65. Review. (http://www.ncbi.nlm.nih.gov/pubmed/16799769?dopt=Abstract)
  • Wanders RJ, Komen JC. Peroxisomes, Refsum's disease and the alpha- and omega-oxidation of phytanic acid. Biochem Soc Trans. 2007 Nov;35(Pt 5):865-9. Review. (http://www.ncbi.nlm.nih.gov/pubmed/17956234?dopt=Abstract)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: July 2010
Published: August 18, 2014