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

SACS gene

The SACS gene provides instructions for producing the protein sacsin, which is essential for organizing cellular structures in the brain and muscles.

Normal Function

The SACS gene produces a protein called sacsin. While its specific function is not fully understood, it is found in the brain, skeletal muscles, and skin. Research indicates that sacsin helps organize proteins into bundles called intermediate filaments, which provide strength and support to cells.

In neurons, these filaments—specifically neurofilaments—form the structural framework for axons. Axons are extensions of nerve cells that are essential for transmitting nerve impulses to other neurons and muscle cells.

Health Conditions Related to Genetic Changes

Autosomal recessive spastic ataxia of Charlevoix-Saguenay

Mutations in the SACS gene cause autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). This condition affects muscle movement and is characterized by:

  • Spasticity: Abnormal tensing of the muscles.
  • Cerebellar ataxia: Problems with balance and coordination.
  • Peripheral neuropathy: Weakness and reduced sensation in the arms and legs.

In the Charlevoix-Saguenay region of Quebec, Canada, two specific mutations are common:

  • 6594delT: A deletion of a DNA building block (thymine) found in over 90 percent of local cases.
  • C5254T: A substitution of one nucleotide for another.

Both mutations result in an abnormally short, nonfunctional sacsin protein. Outside of Quebec, mutations are typically unique to individuals or families. These mutations lead to an unstable protein that fails to organize intermediate filaments properly, particularly in neurons. This disruption of neuronal signaling is believed to cause the signs and symptoms of ARSACS.

Frequently Asked Questions

Since ARSACS is autosomal recessive, an individual must inherit two copies of a mutated SACS gene (one from each parent) to develop the condition. If you have ARSACS, all your children will inherit one copy of the mutated gene and will be carriers. If you are a carrier (meaning you have one mutated copy but do not have the disease), and your partner is also a carrier, there is a 25% chance with each pregnancy that your child will inherit two mutated copies and develop ARSACS, a 50% chance they will be a carrier, and a 25% chance they will not inherit any mutated copies. Genetic counseling is highly recommended for affected individuals and their families to understand inheritance patterns and reproductive risks.
Diagnosis of ARSACS typically involves a thorough neurological examination to assess muscle movement, balance, coordination, and sensation. Imaging tests like an MRI of the brain and spinal cord can reveal characteristic changes. Nerve conduction studies and electromyography might be used to evaluate peripheral neuropathy. The definitive diagnosis is made through genetic testing, which analyzes the SACS gene for specific mutations, such as the common 6594delT or C5254T mutations found in the Charlevoix-Saguenay region, or other unique variants.
The first signs of ARSACS typically appear in early childhood, often between ages 2 and 5. Parents might notice delays in motor development, such as difficulty learning to walk, an unsteady or clumsy gait (ataxia), or frequent falls. Other early indicators can include abnormal muscle stiffness (spasticity), particularly in the legs, and difficulties with balance and coordination. If you observe these persistent symptoms, especially if there's a family history of similar issues, you should consult a pediatrician or neurologist.
There is currently no cure for ARSACS, so treatment focuses on managing symptoms and improving quality of life. Physical therapy is crucial to maintain muscle strength, flexibility, and balance, and to reduce spasticity. Occupational therapy can help with daily living activities. Medications may be prescribed to alleviate spasticity. Assistive devices like walkers, braces, or wheelchairs may become necessary as the condition progresses. Regular follow-ups with a neurologist and other specialists are important for comprehensive care.
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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