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CAPN3 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CAPN3 gene

The CAPN3 gene provides instructions for making the enzyme calpain-3, which is essential for maintaining and remodeling muscle fibers.

Normal Function

The CAPN3 gene provides instructions for making an enzyme called calpain-3, which is found within muscle fiber structures called sarcomeres. Sarcomeres are needed for the tensing of muscle fibers (contraction). When linked together, sarcomeres form myofibrils, which are the basic units of muscle fibers.

Calpain-3 cuts (cleaves) damaged proteins into shorter segments so that they can be easily removed from the sarcomere. The process of making new proteins and breaking down older proteins within the sarcomere is known as sarcomere remodeling. This process enables the muscle cells to adapt to the body's needs.

In addition to maintaining the sarcomeres, calpain-3 also interacts with other proteins to help regulate calcium transport within muscle fibers.

Health Conditions Related to Genetic Changes

Limb-girdle muscular dystrophy

Variants (also called mutations) in the CAPN3 gene can cause two types of limb-girdle muscular dystrophy called LGMD R1 and LGMD D4. LGMD R1 is much more common than LGMD D4. Limb-girdle muscular dystrophies are characterized by muscle weakness (myopathy) and wasting (atrophy), particularly in the muscles of the shoulders, hips, and upper limbs. Individuals with LGMD R1 are more likely to have problems with their shoulders than people with other forms of limb-girdle muscular dystrophy.

Variants in the CAPN3 gene are the most common cause of limb-girdle muscular dystrophy. Many of the CAPN3 gene variants that cause limb-girdle muscular dystrophy lead to the substitution of one protein building block (amino acid) for another in the calpain-3 enzyme, which causes cells to produce a version of the enzyme that does not function properly. This interferes with the cell's ability to remove waste from the sarcomere, which impairs muscle function. These changes lead to the myopathy and atrophy seen in people with limb-girdle muscular dystrophy.

Other Names for This Gene

  • calcium-activated neutral protease 3, muscle-specific, large subunit
  • calpain
  • calpain, large polypeptide L3
  • CANP3
  • CANPL3
  • nCL-1
  • p94

Frequently Asked Questions

The early signs of CAPN3-related limb-girdle muscular dystrophy (LGMD) typically involve progressive muscle weakness and wasting, particularly in the muscles around the hips and shoulders. This can lead to difficulty with activities like climbing stairs, rising from a chair, running, or lifting arms overhead. Individuals with LGMD R1, a common CAPN3-related type, often experience shoulder problems first.
CAPN3-related limb-girdle muscular dystrophy is typically inherited in an autosomal recessive pattern. This means that for a child to be affected, they must inherit two copies of the altered CAPN3 gene, one from each parent. If you have the condition, your children would be carriers if they inherit one copy from you, but would only develop the condition if they also inherited an altered copy from the other parent.
Physical therapy is crucial for managing CAPN3-related LGMD, focusing on maintaining muscle strength, flexibility, and range of motion. This often includes gentle stretching exercises to prevent contractures, low-impact aerobic activities, and strengthening exercises tailored to individual abilities. Occupational therapy can also help with adaptive strategies for daily tasks. Avoiding overexertion and muscle damage is important.
CAPN3-related limb-girdle muscular dystrophy is a progressive condition, meaning muscle weakness and wasting worsen over time. The rate of progression can vary significantly between individuals. While it primarily affects the limb-girdle muscles, it can eventually impact mobility and, in some cases, lead to difficulties with breathing or heart function, though these are less common than in some other muscular dystrophies.
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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