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CTNS gene

cystinosin, lysosomal cystine transporter

Normal Function

The CTNS gene provides instructions for making a protein called cystinosin. This protein is located in the membrane of lysosomes, which are compartments in the cell that digest and recycle materials. Proteins digested inside lysosomes are broken down into smaller building blocks, called amino acids. The amino acids are then moved out of lysosomes by transport proteins. Cystinosin is a transport protein that specifically moves the amino acid cystine out of the lysosome.

Health Conditions Related to Genetic Changes


More than 80 different mutations that are responsible for causing cystinosis have been identified in the CTNS gene. The most common mutation is a deletion of a large part of the CTNS gene (sometimes referred to as the 57-kb deletion), resulting in the complete loss of cystinosin. This deletion is responsible for approximately 50 percent of cystinosis cases in people of European descent. Other mutations result in the production of an abnormally short protein that cannot carry out its normal transport function. Mutations that change very small regions of the CTNS gene may allow the transporter protein to retain some of its usual activity, resulting in a milder form of cystinosis.

More About This Health Condition

Other Names for This Gene

  • Cystinosis
  • PQLC4

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases


  • Anikster Y, Shotelersuk V, Gahl WA. CTNS mutations in patients with cystinosis. Hum Mutat. 1999;14(6):454-8. doi: 10.1002/(SICI)1098-1004(199912)14:63.0.CO;2-H. Citation on PubMed
  • Bendavid C, Kleta R, Long R, Ouspenskaia M, Muenke M, Haddad BR, Gahl WA. FISH diagnosis of the common 57-kb deletion in CTNS causing cystinosis. Hum Genet. 2004 Nov;115(6):510-4. doi: 10.1007/s00439-004-1170-2. Epub 2004 Sep 9. Citation on PubMed
  • Haq MR, Kalatzis V, Gubler MC, Town MM, Antignac C, Van't Hoff WG, Woolf AS. Immunolocalization of cystinosin, the protein defective in cystinosis. J Am Soc Nephrol. 2002 Aug;13(8):2046-51. doi: 10.1097/ Citation on PubMed
  • Kalatzis V, Antignac C. Cystinosis: from gene to disease. Nephrol Dial Transplant. 2002 Nov;17(11):1883-6. doi: 10.1093/ndt/17.11.1883. No abstract available. Citation on PubMed
  • Kalatzis V, Nevo N, Cherqui S, Gasnier B, Antignac C. Molecular pathogenesis of cystinosis: effect of CTNS mutations on the transport activity and subcellular localization of cystinosin. Hum Mol Genet. 2004 Jul 1;13(13):1361-71. doi: 10.1093/hmg/ddh152. Epub 2004 May 5. Citation on PubMed
  • Servais A, Moriniere V, Grunfeld JP, Noel LH, Goujon JM, Chadefaux-Vekemans B, Antignac C. Late-onset nephropathic cystinosis: clinical presentation, outcome, and genotyping. Clin J Am Soc Nephrol. 2008 Jan;3(1):27-35. doi: 10.2215/CJN.01740407. Citation on PubMed or Free article on PubMed Central
  • Touchman JW, Anikster Y, Dietrich NL, Maduro VV, McDowell G, Shotelersuk V, Bouffard GG, Beckstrom-Sternberg SM, Gahl WA, Green ED. The genomic region encompassing the nephropathic cystinosis gene (CTNS): complete sequencing of a 200-kb segment and discovery of a novel gene within the common cystinosis-causing deletion. Genome Res. 2000 Feb;10(2):165-73. doi: 10.1101/gr.10.2.165. Citation on PubMed or Free article on PubMed Central
  • Town M, Jean G, Cherqui S, Attard M, Forestier L, Whitmore SA, Callen DF, Gribouval O, Broyer M, Bates GP, van't Hoff W, Antignac C. A novel gene encoding an integral membrane protein is mutated in nephropathic cystinosis. Nat Genet. 1998 Apr;18(4):319-24. doi: 10.1038/ng0498-319. Citation on PubMed
  • Wamelink MM, Struys EA, Jansen EE, Levtchenko EN, Zijlstra FS, Engelke U, Blom HJ, Jakobs C, Wevers RA. Sedoheptulokinase deficiency due to a 57-kb deletion in cystinosis patients causes urinary accumulation of sedoheptulose: elucidation of the CARKL gene. Hum Mutat. 2008 Apr;29(4):532-6. doi: 10.1002/humu.20685. Citation on PubMed

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.