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CST3 gene

cystatin C

Normal Function

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).

Health Conditions Related to Genetic Changes

Hereditary cerebral amyloid angiopathy

At least one variant (also called a 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 variant that has been identified causes a form of the condition known as hereditary cerebral hemorrhage, Icelandic type or Icelandic type cerebral amyloid angiopathy. This variant 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, does not appear to have any health effects outside of the brain. In the brain, the amyloid deposits 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.

More About This Health Condition

Age-related macular degeneration

MedlinePlus Genetics provides information about Age-related macular degeneration

More About This Health Condition

Other Names for This Gene

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

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


  • Ghiso J, Jensson O, Frangione B. Amyloid fibrils in hereditary cerebral hemorrhage with amyloidosis of Icelandic type is a variant of gamma-trace basic protein (cystatin C). Proc Natl Acad Sci U S A. 1986 May;83(9):2974-8. doi: 10.1073/pnas.83.9.2974. Citation on PubMed
  • 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. Citation on PubMed
  • 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. doi: 10.1111/j.1750-3639.2006.tb00562.x. Citation on PubMed
  • Palsdottir A, Snorradottir AO, Thorsteinsson L. Hereditary cystatin C amyloid angiopathy: genetic, clinical, and pathological aspects. Brain Pathol. 2006 Jan;16(1):55-9. doi: 10.1111/j.1750-3639.2006.tb00561.x. Citation on PubMed
  • 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. doi: 10.1093/jnen/62.9.885. Citation on PubMed
  • 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. Erratum In: Acta Neuropathol. 2009 Aug;118(2):321. Citation on PubMed or Free article on PubMed Central

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