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TPM3 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

TPM3 gene

The TPM3 gene provides instructions for making slow muscle alpha-tropomyosin, a protein that regulates muscle contraction, and mutations in this gene are associated with several muscle disorders.

Normal Function

The TPM3 gene provides instructions for making a protein called slow muscle alpha (α)-tropomyosin, which is part of the tropomyosin protein family. Tropomyosin proteins regulate the tensing of muscle fibers (muscle contraction) by controlling the binding of two muscle proteins, myosin and actin. In non-muscle cells, tropomyosin proteins play a role in controlling cell shape.

Slow muscle α-tropomyosin is found in skeletal muscles, specifically in type I (slow twitch) fibers. Type I fibers are the primary component of skeletal muscles that are resistant to fatigue, such as those involved in posture.

Health Conditions Related to Genetic Changes

Cap myopathy

At least two TPM3 gene mutations have been identified in people with cap myopathy. These mutations (Arg168Cys or Arg168His) may interfere with normal actin-myosin binding, impairing muscle contraction and resulting in muscle weakness.

Congenital fiber-type disproportion

At least 10 mutations in the TPM3 gene have been found to cause congenital fiber-type disproportion, a disorder that causes general muscle weakness. These mutations are thought to impair the protein's ability to interact with myosin and actin within type I skeletal muscle fibers, disrupting muscle contraction.

Nemaline myopathy

Mutations in the TPM3 gene are also associated with nemaline myopathy. Affected individuals typically have muscle weakness throughout their body, including the muscles of the face, neck, and limbs, beginning at birth or in early childhood.

Other Names for This Gene

  • cytoskeletal tropomyosin TM30
  • FLJ41118
  • heat-stable cytoskeletal protein 30 kDa
  • hscp30
  • TM-5
  • TM3
  • TPM3_HUMAN
  • TRK
  • tropomyosin alpha-3 chain
  • tropomyosin gamma

Frequently Asked Questions

Cap myopathy is characterized by the presence of “cap” structures on muscle biopsy—dense, eosinophilic regions that overlay the periphery of some muscle fibers. Clinically, patients often have early‑onset distal weakness (especially in the hands and feet), foot drop, and mild facial weakness, but they usually retain the ability to walk independently. Unlike nemaline myopathy, respiratory involvement is uncommon, and serum creatine kinase (CK) levels are typically normal or only mildly elevated. These patterns, together with a TPM3‑specific genetic variant, help differentiate cap myopathy from other myopathies.
Therapy should focus on maintaining functional mobility while avoiding over‑exertion that could exacerbate muscle damage. Low‑impact aerobic activities such as swimming, stationary cycling, or assisted walking on a treadmill are beneficial. Stretching programs targeting the hip flexors, hamstrings, and neck muscles help prevent contractures. Occupational therapy can assist with fine‑motor tasks and adaptive equipment. Respiratory physiotherapy is advised if there are signs of reduced vital capacity, even though severe respiratory failure is less common in TPM3‑related disease.
Genetic testing is advised when a child presents with unexplained muscle weakness, especially if the weakness is predominant in type I (slow‑twitch) fibers, or when a muscle biopsy shows caps, nemaline rods, or fiber‑type disproportion. Testing is usually done via a targeted next‑generation sequencing panel for congenital myopathies, which includes TPM3, or by whole‑exome sequencing if the phenotype is atypical. A blood draw provides DNA, and results are returned within 4–6 weeks. Confirmatory Sanger sequencing may be required for variants of uncertain significance.
Most pathogenic TPM3 variants are inherited in an autosomal dominant manner, meaning a single altered copy of the gene can cause disease. If a parent carries a pathogenic TPM3 variant, each child has a 50 % chance of inheriting the mutation. De novo mutations (new in the child) also occur, accounting for many sporadic cases. Genetic counseling is recommended for families to discuss testing of the affected individual, parental carrier status, and options such as prenatal diagnosis or preimplantation genetic testing for future pregnancies.
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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