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CTNNB1 gene
URL of this page: https://medlineplus.gov/genetics/gene/ctnnb1/

CTNNB1 gene

catenin beta 1

Normal Function

The CTNNB1 gene provides instructions for making a protein called beta-catenin. This protein is present in many types of cells and tissues. It is primarily found at junctions that connect neighboring cells (adherens junctions). Beta-catenin plays an important role in sticking cells together (cell adhesion) and in communication between cells.

The beta-catenin protein is also an essential part of the Wnt signaling pathway. Certain proteins in this pathway attach (bind) to beta-catenin, which triggers a multistep process that allows the protein to move into the cell nucleus. Once in the nucleus, beta-catenin interacts with other proteins to control the activity (expression) of specific genes. The Wnt signaling pathway promotes the growth and division (proliferation) of cells and helps determine the specialized functions a cell will have (differentiation). Wnt signaling is known to be involved in many aspects of development before birth. In adult tissues, this pathway plays a role in the maintenance and renewal of stem cells, which are cells that help repair tissue damage and can give rise to other types of cells.

Among its many activities, beta-catenin appears to play an important role in the normal function of hair follicles, which are specialized structures in the skin where hair growth occurs. This protein is active in cells that make up a part of the hair follicle known as the matrix. These cells divide and mature to form the different components of the hair follicle and the hair shaft. As matrix cells divide, the hair shaft is pushed upward and extends beyond the skin.

Health Conditions Related to Genetic Changes

Desmoid tumor

Variants (also called mutations) in the CTNNB1 gene can cause a type of aggressive but noncancerous (benign) growth called a desmoid tumor. These rare tumors arise from connective tissue, which provides strength and flexibility to structures such as bones, ligaments, and muscles. The tumors are often found in the abdomen, shoulders, upper arms, or upper legs. The CTNNB1 gene variants that cause desmoid tumors are somatic, which means they are acquired during a person's lifetime and are present only in tumor cells. Somatic variants are not inherited.

The CTNNB1 gene variants that cause desmoid tumors usually occur in a region of the gene called exon 3. These variants lead to changes in single protein building blocks (amino acids) in the beta-catenin protein. This altered version of the beta-catenin protein is not broken down when it is no longer needed. As a result, the protein builds up within cells. Excess beta-catenin promotes the uncontrolled proliferation of cells, allowing for the formation of desmoid tumors.

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Pilomatricoma

Somatic variants in the CTNNB1 gene have been found to cause pilomatricomas, which are benign skin tumors that are associated with hair follicles.

The CTNNB1 gene variants found in pilomatricomas are described as "gain-of-function variants." They cause the beta-catenin protein to be turned on all of the time (constitutively active), which leads to the abnormal activation of certain genes. These genes increase the proliferation and differentiation of cells that are associated with the hair follicle matrix. The cells divide too quickly and in an uncontrolled way, leading to the formation of a pilomatricoma.

Almost all pilomatricomas are benign, but a very small percentage are cancerous (malignant). The malignant version of this tumor is known as a pilomatrix carcinoma. Like pilomatricomas, pilomatrix carcinomas have somatic variants in the CTNNB1 gene. It is unclear why some of these tumors are malignant while most others are not.

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Wilms tumor

Variants in the CTNNB1 gene have been found in Wilms tumor, a rare form of kidney cancer that occurs almost exclusively in children. These variants are somatic and occur only in the kidney cells that give rise to the tumor. The CTNNB1 gene variants that cause Wilms tumor result in an overly active protein. This overactive beta-catenin protein increases Wnt signaling, which leads to the unchecked proliferation of kidney cells and tumor development.

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Aldosterone-producing adenoma

MedlinePlus Genetics provides information about Aldosterone-producing adenoma

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Familial exudative vitreoretinopathy

MedlinePlus Genetics provides information about Familial exudative vitreoretinopathy

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Ovarian cancer

MedlinePlus Genetics provides information about Ovarian cancer

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Other cancers

Somatic variants in the CTNNB1 gene have been identified in several other types of cancer. These include liver, thyroid, ovarian, and skin cancers, as well as cancer of the large intestine (colon) and rectum (collectively known as colorectal cancer), cancer of the lining of the uterus (endometrial cancer), and a type of brain tumor called a medulloblastoma. Studies suggest that gain-of-function variants in the CTNNB1 gene prevent the breakdown of beta-catenin when it is no longer needed, which allows the protein to accumulate within cells. The excess beta-catenin moves into the cell nucleus and promotes the unchecked proliferation of cells, allowing cancerous tumors to develop.

Because variants in the CTNNB1 gene can cause normal cells to become cancerous, the CTNNB1 gene belongs to a class of genes known as oncogenes. Sometimes, variants in other oncogenes occur together with CTNNB1 gene variants to cause cancer. It is not well understood why variants in the CTNNB1 gene are associated with several different types of malignant and benign tumors.

Other disorders

Variants in the CTNNB1 gene have been found to cause a neurodevelopmental disorder that is characterized by mild to profound intellectual disabilities. Individuals with CTNNB1 neurodevelopmental disorder can also have vision problems. Some affected indviduals have exudative vitreoretinopathy, an eye disorder that causes vision loss that worsens over time. Additional signs and symptoms can include movement problems, an unusually small head size (microcephaly), behavioral issues, feeding difficulties, slow growth before birth, and a side-to-side curvature of the spine (scoliosis). 

CTNNB1 neurodevelopmental disorder is caused by a variant in one copy of the CTNNB1 gene that is present in all cells throughout the body. The variant causes cells to produce a version of the beta-catenin protein that is not functional. A decrease in functional beta-catenin protein likely impairs the ability of cells to adhere to and interact with each other. This impaired function appears to particularly affect brain cells' ability to grow and connect with other brain cells. As a result, the brain does not develop as it should, which causes intellectual disabilities and the other signs and symptoms of CTNNB1 neurodevelopmental disorder.

Other Names for This Gene

  • beta-catenin
  • catenin beta-1
  • CTNB1_HUMAN
  • CTNNB

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

References

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