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Reviewed June 2008
What is the official name of the CSTB gene?
The official name of this gene is “cystatin B.”
CSTB is the gene's official symbol. The CSTB gene is also known by other names, listed below.
Read more about gene names and symbols on the About page.
What is the normal function of the CSTB gene?
The CSTB gene provides instructions for making a protein called cystatin B. This protein reduces the activity of (inhibits) enzymes called cathepsins. Cathepsins help break down certain proteins in the lysosomes (compartments in the cell that digest and recycle materials). While the specific function of cystatin B is unclear, it may help protect the cells' proteins from cathepsins that leak out of the lysosomes.
One region of the CSTB gene has a particular repeating sequence of 12 DNA building blocks (nucleotides) written as CCCCG-CCCCG-CG. This sequence, called a dodecamer repeat, is usually repeated two or three times within a part of the gene that helps regulate cystatin B protein production.
How are changes in the CSTB gene related to health conditions?
Where is the CSTB gene located?
Cytogenetic Location: 21q22.3
Molecular Location on chromosome 21: base pairs 43,773,665 to 43,776,375
(Homo sapiens Annotation Release 107, GRCh38.p2) (
The CSTB gene is located on the long (q) arm of chromosome 21 at position 22.3.
More precisely, the CSTB gene is located from base pair 43,773,665 to base pair 43,776,375 on chromosome 21.
See How do geneticists indicate the location of a gene? in the Handbook.
Where can I find additional information about CSTB?
You and your healthcare professional may find the following resources about CSTB 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 CSTB gene or gene products?
See How are genetic conditions and genes named? in the Handbook.
Where can I find general information about genes?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding CSTB?
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (12 links)
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.