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


Reviewed May 2012

What is the official name of the CST3 gene?

The official name of this gene is “cystatin C.”

CST3 is the gene's official symbol. The CST3 gene is also known by other names, listed below.

What is the normal function of the CST3 gene?

The CST3 gene provides instructions for making a protein called cystatin C. This protein is part of a family of proteins called cysteine protease inhibitors that help control several types of chemical reactions by blocking (inhibiting) the activity of certain enzymes. Cystatin C inhibits the activity of enzymes called cathepsins that cut apart other proteins in order to break them down.

Cystatin C is found in biological fluids, such as blood. Its levels are especially high in the fluid that surrounds and protects the brain and spinal cord (the cerebrospinal fluid or CSF).

How are changes in the CST3 gene related to health conditions?

hereditary cerebral amyloid angiopathy - caused by mutations in the CST3 gene

At least one mutation in the CST3 gene has been found to cause hereditary cerebral amyloid angiopathy, a condition characterized by stroke and a decline in intellectual function (dementia), which begins in mid-adulthood. The CST3 gene mutation that has been identified causes a form of hereditary cerebral amyloid angiopathy known as the Icelandic type. This mutation replaces the protein building block (amino acid) leucine with the amino acid glutamine at position 68 in the cystatin C protein (written as Leu68Gln or L68Q). This abnormal cystatin C protein is less stable and is more prone to cluster together (aggregate) than the normal protein. The aggregated protein forms clumps called amyloid deposits that accumulate in the blood vessel walls primarily in the brain, but also in blood vessels in other areas of the body such as the skin, spleen, and lymph nodes. The accumulation of these amyloid deposits, known as plaques, does not appear to have any health effects outside of the brain. In the brain, the amyloid plaques replace the muscle fibers and elastic fibers that give blood vessels flexibility, causing them to become weak and prone to breakage. Such a break in the brain causes bleeding (hemorrhagic stroke), which can lead to brain damage and dementia.

Where is the CST3 gene located?

Cytogenetic Location: 20p11.21

Molecular Location on chromosome 20: base pairs 23,627,897 to 23,638,048

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

The CST3 gene is located on the short (p) arm of chromosome 20 at position 11.21.

The CST3 gene is located on the short (p) arm of chromosome 20 at position 11.21.

More precisely, the CST3 gene is located from base pair 23,627,897 to base pair 23,638,048 on chromosome 20.

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

Where can I find additional information about CST3?

You and your healthcare professional may find the following resources about CST3 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 CST3 gene or gene products?

  • cystatin 3
  • cystatin-3
  • cystatin-C
  • cystatin-C precursor
  • gamma-trace
  • neuroendocrine basic polypeptide
  • post-gamma-globulin

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

What glossary definitions help with understanding CST3?

aggregate ; amino acid ; amyloid ; cysteine ; dementia ; elastic ; gene ; glutamine ; hemorrhagic stroke ; hereditary ; leucine ; lymph ; mutation ; precursor ; protease ; protein

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


  • Kolodziejczyk R, Michalska K, Hernandez-Santoyo A, Wahlbom M, Grubb A, Jaskolski M. Crystal structure of human cystatin C stabilized against amyloid formation. FEBS J. 2010 Apr;277(7):1726-37. doi: 10.1111/j.1742-4658.2010.07596.x. Epub 2010 Feb 19. (
  • Levy E, Jaskolski M, Grubb A. The role of cystatin C in cerebral amyloid angiopathy and stroke: cell biology and animal models. Brain Pathol. 2006 Jan;16(1):60-70. Review. (
  • NCBI Gene (
  • Palsdottir A, Snorradottir AO, Thorsteinsson L. Hereditary cystatin C amyloid angiopathy: genetic, clinical, and pathological aspects. Brain Pathol. 2006 Jan;16(1):55-9. Review. (
  • Revesz T, Ghiso J, Lashley T, Plant G, Rostagno A, Frangione B, Holton JL. Cerebral amyloid angiopathies: a pathologic, biochemical, and genetic view. J Neuropathol Exp Neurol. 2003 Sep;62(9):885-98. Review. (
  • Revesz T, Holton JL, Lashley T, Plant G, Frangione B, Rostagno A, Ghiso J. Genetics and molecular pathogenesis of sporadic and hereditary cerebral amyloid angiopathies. Acta Neuropathol. 2009 Jul;118(1):115-30. doi: 10.1007/s00401-009-0501-8. Epub 2009 Feb 19. Review. Erratum in: Acta Neuropathol. 2009 Aug;118(2):321. (


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: May 2012
Published: February 1, 2016