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


Reviewed April 2014

What is the official name of the CTC1 gene?

The official name of this gene is “CTS telomere maintenance complex component 1.”

CTC1 is the gene's official symbol. The CTC1 gene is also known by other names, listed below.

What is the normal function of the CTC1 gene?

The CTC1 gene provides instructions for making a protein that plays an important role in structures known as telomeres, which are found at the ends of chromosomes. Telomeres are short, repetitive segments of DNA that help protect chromosomes from abnormally sticking together or breaking down (degrading). In most cells, telomeres become progressively shorter as the cell divides. After a certain number of cell divisions, the telomeres become so short that they trigger the cell to stop dividing or to self-destruct (undergo apoptosis).

The CTC1 protein works as part of a group of proteins known as the CST complex, which is involved in the maintenance of telomeres. This complex is part of the special machinery that some cells use to copy (replicate) telomeres so they do not become too short as cells divide. Studies suggest that the CTC1 protein may also have roles in DNA replication unrelated to telomeres, but these functions are not well understood.

How are changes in the CTC1 gene related to health conditions?

Coats plus syndrome - caused by mutations in the CTC1 gene

At least 20 mutations in the CTC1 gene have been identified in people with Coats plus syndrome. This disorder is characterized by an eye condition called Coats disease plus abnormalities of the brain, bones, gastrointestinal system, and other parts of the body.

Most people with Coats plus syndrome have a mutation in one copy of the CTC1 gene in each cell that eliminates the function of the CTC1 protein and a mutation in the other copy of the gene that reduces but does not eliminate the protein's function. This combination of mutations leaves only a small amount of functional CTC1 protein available to work as part of the CST complex. The resulting impairment of this complex affects the replication of telomeres, although the effect on telomere structure and function is unclear. Some studies have found that people with CTC1 gene mutations have abnormally short telomeres, while other studies have found no change in telomere length. Researchers are working to determine how telomeres are different in people with CTC1 gene mutations and how these changes could underlie the varied signs and symptoms of Coats plus syndrome.

Where is the CTC1 gene located?

Cytogenetic Location: 17p13.1

Molecular Location on chromosome 17: base pairs 8,224,821 to 8,248,095

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

The CTC1 gene is located on the short (p) arm of chromosome 17 at position 13.1.

The CTC1 gene is located on the short (p) arm of chromosome 17 at position 13.1.

More precisely, the CTC1 gene is located from base pair 8,224,821 to base pair 8,248,095 on chromosome 17.

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

Where can I find additional information about CTC1?

You and your healthcare professional may find the following resources about CTC1 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 CTC1 gene or gene products?

  • AAF132
  • AAF-132
  • alpha accessory factor 132
  • C17orf68
  • conserved telomere capping protein 1
  • CST complex subunit CTC1
  • FLJ22170
  • HBV DNAPTP1-transactivated protein B
  • RP11-849F2.8
  • tmp494178

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

What glossary definitions help with understanding CTC1?

apoptosis ; cell ; DNA ; DNA replication ; gastrointestinal ; gene ; mutation ; protein ; subunit ; syndrome ; telomere

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


  • Anderson BH, Kasher PR, Mayer J, Szynkiewicz M, Jenkinson EM, Bhaskar SS, Urquhart JE, Daly SB, Dickerson JE, O'Sullivan J, Leibundgut EO, Muter J, Abdel-Salem GM, Babul-Hirji R, Baxter P, Berger A, Bonafé L, Brunstom-Hernandez JE, Buckard JA, Chitayat D, Chong WK, Cordelli DM, Ferreira P, Fluss J, Forrest EH, Franzoni E, Garone C, Hammans SR, Houge G, Hughes I, Jacquemont S, Jeannet PY, Jefferson RJ, Kumar R, Kutschke G, Lundberg S, Lourenço CM, Mehta R, Naidu S, Nischal KK, Nunes L, Ounap K, Philippart M, Prabhakar P, Risen SR, Schiffmann R, Soh C, Stephenson JB, Stewart H, Stone J, Tolmie JL, van der Knaap MS, Vieira JP, Vilain CN, Wakeling EL, Wermenbol V, Whitney A, Lovell SC, Meyer S, Livingston JH, Baerlocher GM, Black GC, Rice GI, Crow YJ. Mutations in CTC1, encoding conserved telomere maintenance component 1, cause Coats plus. Nat Genet. 2012 Jan 22;44(3):338-42. doi: 10.1038/ng.1084. (
  • Chen LY, Majerská J, Lingner J. Molecular basis of telomere syndrome caused by CTC1 mutations. Genes Dev. 2013 Oct 1;27(19):2099-108. doi: 10.1101/gad.222893.113. (
  • Gu P, Chang S. Functional characterization of human CTC1 mutations reveals novel mechanisms responsible for the pathogenesis of the telomere disease Coats plus. Aging Cell. 2013 Dec;12(6):1100-9. doi: 10.1111/acel.12139. Epub 2013 Sep 4. (
  • NCBI Gene (
  • Polvi A, Linnankivi T, Kivelä T, Herva R, Keating JP, Mäkitie O, Pareyson D, Vainionpää L, Lahtinen J, Hovatta I, Pihko H, Lehesjoki AE. Mutations in CTC1, encoding the CTS telomere maintenance complex component 1, cause cerebroretinal microangiopathy with calcifications and cysts. Am J Hum Genet. 2012 Mar 9;90(3):540-9. doi: 10.1016/j.ajhg.2012.02.002. Epub 2012 Mar 1. (
  • Surovtseva YV, Churikov D, Boltz KA, Song X, Lamb JC, Warrington R, Leehy K, Heacock M, Price CM, Shippen DE. Conserved telomere maintenance component 1 interacts with STN1 and maintains chromosome ends in higher eukaryotes. Mol Cell. 2009 Oct 23;36(2):207-18. doi: 10.1016/j.molcel.2009.09.017. (


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: April 2014
Published: February 1, 2016