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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed June 2008

What is the official name of the TYMP gene?

The official name of this gene is “thymidine phosphorylase.”

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

What is the normal function of the TYMP gene?

The TYMP gene (previously known as ECGF1) provides instructions for making an enzyme called thymidine phosphorylase. Thymidine is a molecule known as a nucleoside, which (after a chemical modification) is used as a building block of DNA. Thymidine phosphorylase converts thymidine into two smaller molecules, 2-deoxyribose 1-phosphate and thymine. This chemical reaction is an important step in the breakdown of thymidine, which helps regulate the level of nucleosides in cells.

Thymidine phosphorylase plays an important role in maintaining the appropriate amount of thymidine in cell structures called mitochondria. Mitochondria convert the energy from food into a form that cells can use. Although most DNA is packaged in chromosomes within the nucleus, mitochondria also have a small amount of their own DNA (called mitochondrial DNA or mtDNA). Mitochondria use nucleosides, including thymidine, to build new molecules of mtDNA as needed.

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

mitochondrial neurogastrointestinal encephalopathy disease - caused by mutations in the TYMP gene

About 50 mutations in the TYMP gene have been identified in people with mitochondrial neurogastrointestinal encephalopathy (MNGIE) disease. TYMP mutations greatly reduce or eliminate the activity of thymidine phosphorylase. A shortage of this enzyme allows thymidine to build up to very high levels in the body. An excess of thymidine appears to be damaging to mtDNA, disrupting its usual maintenance and repair. As a result, mutations can accumulate in mtDNA, causing it to become unstable. Mitochondria may also have less mtDNA than usual (mtDNA depletion). These genetic changes impair the normal function of mitochondria. Although mtDNA abnormalities underlie the digestive and neurological problems characteristic of MNGIE disease, it is unclear how defective mitochondria cause the specific features of the disorder.

Where is the TYMP gene located?

Cytogenetic Location: 22q13.33

Molecular Location on chromosome 22: base pairs 50,525,752 to 50,530,085

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The TYMP gene is located on the long (q) arm of chromosome 22 at position 13.33.

The TYMP gene is located on the long (q) arm of chromosome 22 at position 13.33.

More precisely, the TYMP gene is located from base pair 50,525,752 to base pair 50,530,085 on chromosome 22.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about TYMP?

You and your healthcare professional may find the following resources about TYMP 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 TYMP gene or gene products?

  • ECGF1
  • endothelial cell growth factor 1 (platelet-derived)
  • gliostatin
  • hPD-ECGF
  • TdRPase
  • TP

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding TYMP?

breakdown ; cell ; depletion ; digestive ; DNA ; encephalopathy ; enzyme ; gene ; growth factor ; mitochondria ; molecule ; neurological ; nucleoside ; nucleus ; phosphate ; thymine

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Hirano M, Martí R, Spinazzola A, Nishino I, Nishigaki Y. Thymidine phosphorylase deficiency causes MNGIE: an autosomal recessive mitochondrial disorder. Nucleosides Nucleotides Nucleic Acids. 2004 Oct;23(8-9):1217-25. (
  • Hirano M, Nishigaki Y, Martí R. Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE): a disease of two genomes. Neurologist. 2004 Jan;10(1):8-17. Review. (
  • Lara MC, Valentino ML, Torres-Torronteras J, Hirano M, Martí R. Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE): biochemical features and therapeutic approaches. Biosci Rep. 2007 Jun;27(1-3):151-63. Review. (
  • Martí R, Nishigaki Y, Vilá MR, Hirano M. Alteration of nucleotide metabolism: a new mechanism for mitochondrial disorders. Clin Chem Lab Med. 2003 Jul;41(7):845-51. Review. (
  • Marti R, Spinazzola A, Nishino I, Andreu AL, Naini A, Tadesse S, Oliver JA, Hirano M. Mitochondrial neurogastrointestinal encephalomyopathy and thymidine metabolism: results and hypotheses. Mitochondrion. 2002 Nov;2(1-2):143-7. (
  • NCBI Gene (
  • Nishino I, Spinazzola A, Hirano M. MNGIE: from nuclear DNA to mitochondrial DNA. Neuromuscul Disord. 2001 Jan;11(1):7-10. Review. (
  • Nishino I, Spinazzola A, Hirano M. Thymidine phosphorylase gene mutations in MNGIE, a human mitochondrial disorder. Science. 1999 Jan 29;283(5402):689-92. (
  • Nishino I, Spinazzola A, Papadimitriou A, Hammans S, Steiner I, Hahn CD, Connolly AM, Verloes A, Guimarães J, Maillard I, Hamano H, Donati MA, Semrad CE, Russell JA, Andreu AL, Hadjigeorgiou GM, Vu TH, Tadesse S, Nygaard TG, Nonaka I, Hirano I, Bonilla E, Rowland LP, DiMauro S, Hirano M. Mitochondrial neurogastrointestinal encephalomyopathy: an autosomal recessive disorder due to thymidine phosphorylase mutations. Ann Neurol. 2000 Jun;47(6):792-800. (
  • Valentino ML, Martí R, Tadesse S, López LC, Manes JL, Lyzak J, Hahn A, Carelli V, Hirano M. Thymidine and deoxyuridine accumulate in tissues of patients with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). FEBS Lett. 2007 Jul 24;581(18):3410-4. Epub 2007 Jun 27. (


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? ( in the Handbook.

Reviewed: June 2008
Published: February 8, 2016