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TCIRG1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

TCIRG1 gene

The TCIRG1 gene provides instructions for a protein subunit essential for bone remodeling, and mutations in this gene are a primary cause of osteopetrosis.

Normal Function

The TCIRG1 gene provides instructions for making one part, the a3 subunit, of a large protein complex known as a vacuolar H+-ATPase (V-ATPase). V-ATPases are a group of similar complexes that act as pumps to move positively charged hydrogen atoms (protons) across membranes. This movement of protons helps regulate the relative acidity (pH) of cells and their surrounding environment.

The V-ATPases containing the a3 subunit play an essential role in specialized cells called osteoclasts. These cells break down bone tissue as part of the normal process of bone remodeling, in which old bone is removed and new bone is created to replace it. On the surface of osteoclasts, V-ATPases are embedded in a specialized, highly folded membrane called the ruffled border. The ruffled border faces the surface of bone, where it helps form a tightly sealed compartment between the osteoclast and the bone surface. V-ATPases pump protons into the compartment, making it very acidic, which is necessary to break down bone.

Health Conditions Related to Genetic Changes

Osteopetrosis

More than 60 mutations in the TCIRG1 gene have been identified in people with osteopetrosis. These mutations cause the most severe form of the disorder, autosomal recessive osteopetrosis (ARO).

Many TCIRG1 gene mutations change how the gene's instructions are used to make the a3 subunit of V-ATPase, or lead to the production of an abnormally short version of the subunit. Studies suggest that most of these mutations eliminate the function of the a3 subunit. Without the a3 subunit, V-ATPases cannot pump protons out of osteoclasts. As a result, the compartment between the ruffled border and the bone surface is not acidified, and bone cannot be broken down. When old bone is not broken down as new bone is formed, bones throughout the skeleton become unusually dense and structurally abnormal, making them prone to fracture.

Other Names for This Gene

  • Atp6i
  • ATP6N1C
  • ATP6V0A3
  • ATPase, H+ transporting, 116kD
  • OC-116
  • OC-116 kDa
  • OC-116kDa
  • OC116
  • OPTB1
  • osteoclastic proton pump 116 kDa subunit
  • specific 116-kDa vacuolar proton pump subunit
  • Stv1
  • T cell immune response cDNA7 protein
  • T-cell immune regulator 1
  • T-cell immune regulator 1, ATPase H+ transporting V0 subunit a3
  • T-cell immune response cDNA 7
  • T-cell immune response cDNA7 protein
  • T-cell, immune regulator 1, ATPase, H+ transporting, lysosomal V0 protein a
  • T-cell, immune regulator 1, ATPase, H+ transporting, lysosomal V0 protein A3
  • T-cell, immune regulator 1, ATPase, H+ transporting, lysosomal V0 subunit A3
  • TIRC7
  • V-ATPase 116 kDa
  • V-ATPase 116-kDa
  • V-type proton ATPase 116 kDa subunit a
  • V-type proton ATPase 116 kDa subunit a isoform 3
  • vacuolar proton translocating ATPase 116 kDa subunit A
  • Vph1
  • VPP3_HUMAN

Frequently Asked Questions

Osteopetrosis caused by TCIRG1 gene mutations, specifically autosomal recessive osteopetrosis (ARO), is often severe and can manifest early in life. Key symptoms result from abnormally dense, brittle bones and include frequent fractures, bone pain, and impaired bone marrow function leading to anemia, easy bruising/bleeding, and recurrent infections. The increased bone density can also compress nerves, causing vision or hearing loss, and can lead to an enlarged liver and spleen. A parent should suspect this condition if their infant or young child experiences multiple unexplained fractures, has unusual paleness, frequent infections, or shows signs of developmental delays or neurological issues.
s TCIRG1-related osteopetrosis is an autosomal recessive disorder, both parents must be carriers of a mutated TCIRG1 gene to have an affected child. Carriers typically do not show symptoms. For each pregnancy, if both parents are carriers, there is a 25% chance of having a child with osteopetrosis, a 50% chance of having a child who is an unaffected carrier, and a 25% chance of having a child who inherits two normal copies of the gene. Genetic counseling is highly recommended for families with a history of TCIRG1-related osteopetrosis to understand these risks and explore options like prenatal diagnosis or preimplantation genetic diagnosis for future pregnancies.
Diagnosis of osteopetrosis typically begins with imaging studies like X-rays, which reveal abnormally dense bones. Blood tests may show signs of bone marrow failure, such as anemia or low platelet counts. To confirm the specific genetic cause, molecular genetic testing of the TCIRG1 gene is performed. This test analyzes a blood or saliva sample to identify mutations within the gene, which helps differentiate ARO from other forms of osteopetrosis and guides treatment and prognosis.
The primary treatment for severe TCIRG1-related osteopetrosis is hematopoietic stem cell transplantation (HSCT), often referred to as a bone marrow transplant. This procedure can replace the dysfunctional osteoclasts with healthy ones, allowing for proper bone remodeling. Other treatments are supportive, including managing fractures, treating infections, and addressing neurological complications. Without successful HSCT, the long-term outlook for severe ARO can be poor due to complications like bone marrow failure, recurrent infections, and neurological damage. With successful transplantation, the prognosis significantly improves, though ongoing medical management is often required.
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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