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

CTS gene family

Reviewed February 2009

What are the CTS genes?

Genes in the CTS gene family provide instructions for producing proteins called cathepsins. Cathepsins function as proteases, which means that they cut apart other proteins. Cathepsins are found in many types of cells and are typically located in lysosomes, compartments within cells that digest and recycle different types of molecules.

There are currently 23 known genes in the human CTS gene family. The genes in this family are designated by the letters CTS and an additional letter specific to that particular gene, for example CTSA and CTSL. The gene family includes multiple versions of CTSL; these genes are designated CTSL1, CTSL2, and CTSL3. Additionally, CTS genes that are similar to the CTSL genes have been named CTSLL (for CTSL-like) and are designated CTSLL1 through CTSLL7.

Cathepsins are involved in many different processes in cells and tissues. For example, they play roles in the self-destruction of cells (apoptosis), the formation of new blood vessels (angiogenesis), and cell growth and division (proliferation). Cathepsins are also involved in the normal functioning of the immune system and the breakdown and removal (resorption) of bone tissue that is no longer needed.

Changes in CTS genes have been associated with several complex diseases including rheumatoid arthritis, Alzheimer disease, and osteoporosis. Additionally, mutations in the CTSA gene cause a condition called galactosialidosis, which is characterized by skeletal malformations, an eye abnormality, and other health problems. Studies suggest that increased activity (expression) of cathepsins may also play a role in several types of cancer.

Which genes are included in the CTS gene family?

The HUGO Gene Nomenclature Committee (HGNC) provides an index of gene families ( and their member genes.

Genetics Home Reference summarizes the normal function and health implications of these members of the CTS gene family: CTSA, CTSD, and CTSF.

What conditions are related to genes in the CTS gene family?

Genetics Home Reference includes these conditions related to genes in the CTS gene family:

  • congenital neuronal ceroid lipofuscinosis
  • galactosialidosis
  • Kufs disease

Where can I find additional information about the CTS gene family?

You may find the following resources about the CTS gene family helpful.

  • Eurekah Bioscience Collection: Functions of Lysosomal Proteases ( (U.S. National Library of Medicine)

What glossary definitions help with understanding the CTS gene family?

angiogenesis ; apoptosis ; arthritis ; breakdown ; cancer ; cell ; cysteine ; gene ; immune system ; osteoporosis ; proliferation ; protease ; serine ; tissue

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


These sources were used to develop the Genetics Home Reference summary for the CTS gene family.

  • Joyce JA, Hanahan D. Multiple roles for cysteine cathepsins in cancer. Cell Cycle. 2004 Dec;3(12):1516-619. Epub 2004 Dec 6. Review. (
  • Nomura T, Katunuma N. Involvement of cathepsins in the invasion, metastasis and proliferation of cancer cells. J Med Invest. 2005 Feb;52(1-2):1-9. Review. (
  • Turk V, Turk B, Turk D. Lysosomal cysteine proteases: facts and opportunities. EMBO J. 2001 Sep 3;20(17):4629-33. Review. (
  • Stoka V, Turk B, Turk V. Lysosomal cysteine proteases: structural features and their role in apoptosis. IUBMB Life. 2005 Apr-May;57(4-5):347-53. Review. (


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: February 2009
Published: February 8, 2016