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GJB1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

GJB1 gene

The GJB1 gene encodes the connexin 32 protein, which is vital for nerve impulse transmission and the maintenance of myelin in the nervous system.

Normal Function

The GJB1 gene provides instructions for making a protein called gap junction beta 1, also known as connexin 32 (Cx32). This protein forms gap junctions, which are channels that allow ions, nutrients, and signaling molecules to pass between neighboring cells. Connexin 32 is particularly important in the peripheral nervous system, where it is found in Schwann cells, and in the central nervous system, where it is found in oligodendrocytes. These cells produce myelin, the fatty substance that insulates nerve fibers and ensures efficient transmission of nerve impulses.

Health Conditions Related to Genetic Changes

Charcot-Marie-Tooth disease

Pathogenic variants in the GJB1 gene cause Charcot-Marie-Tooth disease type X (CMTX1). This disorder damages peripheral nerves, leading to muscle weakness and sensory loss in the hands and feet.

The mechanisms of these variants include:

  • Substitution of amino acids in the connexin 32 protein.
  • Failure of the protein to reach the cell membrane.
  • Production of an altered protein that breaks down quickly or fails to form functional channels.

The resulting loss of functional gap junctions impairs the activity of Schwann cells and disrupts myelin production, which hinders nerve impulse transmission. While peripheral nerves are most severely affected, some individuals may also experience mild central nervous system symptoms due to the loss of myelin in the brain.

Other Names for This Gene

  • CMTX
  • CMTX1
  • connexin 32
  • CX32

Frequently Asked Questions

Because the GJB1 gene is located on the X chromosome, males who inherit a pathogenic variant have only one copy of the gene and typically experience the full, severe form of the disease. Symptoms often begin in childhood or adolescence with progressive weakness and sensory loss in the feet and legs, leading to foot drop, high arches, and difficulty walking. Females, who have two X chromosomes, usually have one normal copy that partially compensates for the affected one. As a result, female carriers often have milder symptoms, which may not appear until later in life, or they may remain asymptomatic, though they can still pass the variant to their children.
Diagnosis is confirmed through genetic testing, typically a targeted gene panel or whole exome sequencing that looks for pathogenic variants in the GJB1 gene. The process usually involves a simple blood draw or saliva sample. It is important to note that genetic testing can identify the specific mutation, but it does not always predict the exact severity of symptoms, as environmental factors and other genetic modifiers can play a role. A genetic counselor can help interpret the results and discuss implications for family members, including the option for carrier testing for female relatives.
Management focuses on preserving mobility and preventing joint deformities. Patients are strongly advised to wear ankle-foot orthoses (AFOs) to support weak ankles and prevent tripping. Regular physical therapy is crucial to maintain muscle strength and flexibility, with a focus on low-impact exercises like swimming or cycling to avoid over-stressing the legs. Additionally, foot care is critical; patients should inspect their feet daily for blisters or sores because reduced sensation can lead to unnoticed injuries that become infected. Avoiding high-impact activities that cause excessive fatigue is also recommended to manage energy levels throughout the day.
While there is no cure for CMTX1, some substances can exacerbate nerve damage or fatigue. Patients should be cautious with medications that have neurotoxic side effects, such as certain chemotherapy drugs or high doses of vitamin B6, which can cause peripheral neuropathy. Additionally, extreme temperatures can sometimes worsen sensory symptoms or muscle cramping. It is generally recommended to avoid smoking, as it reduces blood flow to the extremities, which can further compromise nerve health and skin integrity in the feet.
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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