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TSC1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

TSC1 gene

The TSC1 gene produces hamartin, a tumor suppressor protein that regulates cell growth and division, preventing the formation of noncancerous tumors.

Normal Function

The TSC1 gene provides instructions for producing a protein called hamartin. Within cells, hamartin interacts with a protein called tuberin, which is produced from the TSC2 gene. These two proteins help control cell growth and division (proliferation) and cell size. Proteins that normally prevent cells from growing and dividing too fast or in an uncontrolled way are known as tumor suppressors. Hamartin and tuberin carry out their tumor suppressor function by interacting with and regulating a wide variety of other proteins.

Health Conditions Related to Genetic Changes

Lymphangioleiomyomatosis

TSC1 gene variants (also known as mutations) can cause a disorder called lymphangioleiomyomatosis (LAM), although variants in the TSC2 gene appear to be responsible for most cases of this disorder. This destructive lung disease is caused by the abnormal overgrowth of smooth muscle-like tissue in the lungs. It occurs almost exclusively in women, causing coughing, shortness of breath, chest pain, and lung collapse.

LAM can occur alone (isolated or sporadic LAM) or in combination with a condition called tuberous sclerosis complex. Researchers suggest that sporadic LAM can be caused by a random variant in the TSC1 gene that occurs very early in development. As a result, some of the body's cells have a normal version of the gene, while others have the altered version. This situation is called mosaicism. When a variant occurs in the other copy of the TSC1 gene in certain cells during a woman's lifetime (a somatic variant), she may develop LAM.

Tuberous sclerosis complex

Hundreds of variants in the TSC1 gene have been identified in individuals with tuberous sclerosis complex, a condition characterized by developmental problems and the growth of noncancerous (benign) tumors in many parts of the body. Most of these variants involve either small deletions or insertions of DNA in the TSC1 gene. Some variants create a premature stop signal in the instructions for making hamartin.

People with TSC1-related tuberous sclerosis complex are born with one altered copy of the TSC1 gene in each cell. A TSC1 gene change prevents the cell from making functional hamartin from that copy of the gene. Enough hamartin is usually produced from the other, normal copy of the TSC1 gene to regulate cell growth effectively. For some types of tumors to develop, a second variant involving the other copy of the gene must occur in certain cells during a person's lifetime.

When both copies of the TSC1 gene are altered in a particular cell, that cell cannot produce any functional hamartin. The loss of this protein allows the cell to grow and divide in an uncontrolled way to form a tumor. A shortage of hamartin also interferes with the normal development of certain cells. In people with TSC1-related tuberous sclerosis complex, a second TSC1 gene variant typically occurs in multiple cells over an affected person's lifetime. The loss of hamartin in different types of cells disrupts normal development and leads to the growth of tumors in many different organs and tissues.

Other disorders

Inherited variants in the TSC1 gene can cause a disorder known as focal cortical dysplasia of Taylor balloon cell type. This disorder involves malformations of the cerebrum, the large, frontal part of the brain that is responsible for thinking and learning. Focal cortical dysplasia causes severe recurrent seizures (epilepsy) in affected individuals.

Other Names for This Gene

  • hamartin
  • KIAA0243
  • TSC1_HUMAN
  • tuberous sclerosis 1

Frequently Asked Questions

For LAM, early signs often include shortness of breath, persistent cough, chest pain, or recurrent lung collapse (pneumothorax), especially in women. For TSC, symptoms vary widely but can include skin lesions (like facial angiofibromas), seizures, developmental delays, or benign tumors in organs like the brain, kidneys, or heart.
Diagnosis of LAM typically involves high-resolution computed tomography (HRCT) of the lungs to identify characteristic cysts. Lung function tests and a blood test for VEGF-D (vascular endothelial growth factor D) can also aid diagnosis. If TSC is not present, it's considered sporadic LAM.
For LAM, treatments include medications like sirolimus (rapamycin) to slow disease progression, oxygen therapy, and sometimes lung transplantation in severe cases. For TSC, management is individualized and may involve anti-seizure medications, surgical removal of tumors, or targeted therapies like mTOR inhibitors (e.g., everolimus) for specific manifestations.
If you have TSC, genetic testing for TSC1 (and TSC2) is highly recommended for diagnosis and family planning, as it's an autosomal dominant condition. For sporadic LAM, the risk to family members is generally low, but genetic counseling can help assess individual risks and discuss testing options, especially if there's any suspicion of mosaicism or a family history.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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