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SEPTIN9 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SEPTIN9 gene

The SEPTIN9 gene provides instructions for creating the septin-9 protein, which plays a critical role in cell division and acts as a tumor suppressor.

Normal Function

The SEPTIN9 gene provides instructions for making a protein called septin-9, which belongs to a group of proteins called septins. Septins are involved in a process called cytokinesis, the step in cell division when the cytoplasm divides to form two separate cells. The septin-9 protein also acts as a tumor suppressor, regulating cell growth to prevent uncontrolled division.

The SEPTIN9 gene is found in cells throughout the body. Approximately 15 slightly different versions (isoforms) of the septin-9 protein may be produced. These isoforms interact with other septin proteins to perform their functions.

Health Conditions Related to Genetic Changes

Hereditary neuralgic amyotrophy

SEPTIN9 gene variants have been identified in individuals with hereditary neuralgic amyotrophy, a disorder characterized by episodes of nerve pain (neuralgia) and muscle wasting (amyotrophy) in the shoulders and arms. Key features include:

  • The most common variant replaces the amino acid arginine with tryptophan at position 88 (Arg88Trp or R88W).
  • Duplication of genetic material within the SEPTIN9 gene has also been identified.
  • These variants interfere with septin-9 function and may alter the distribution of isoforms, affecting the brachial plexus nerves.

Charcot-Marie-Tooth disease

MedlinePlus Genetics provides information about Charcot-Marie-Tooth disease.

Cancers

Changes in the activity (expression) of the SEPTIN9 gene are associated with certain cancers. Altered expression may enhance cancer-related events such as cell proliferation, cell movement, and angiogenesis (the development of new blood vessels that nourish a tumor). Increased production of specific septin-9 isoforms has been associated with breast and prostate cancers, as well as tumors of the ovary, pancreas, lung, kidney, liver, thyroid, and esophagus.

Other Names for This Gene

  • SEPT9
  • SEPT9_HUMAN
  • SeptD1
  • septin D1
  • SINT1

Frequently Asked Questions

Hereditary neuralgic amyotrophy associated with SEPTIN9 variants is generally inherited in an autosomal dominant pattern, meaning only one copy of the altered gene is sufficient to cause the condition. If a parent has the condition, there is a 50 percent chance of passing the variant to each child. Genetic counseling is recommended for affected individuals to discuss inheritance risks and testing options for at-risk relatives, particularly children who may exhibit early signs of nerve sensitivity or episodic pain.
No, SEPTIN9 gene changes are not currently used for routine cancer screening in the general population. While altered expression of the SEPTIN9 gene is associated with certain cancers like breast and prostate cancer, these changes are typically somatic (occurring in tumor cells) rather than germline (inherited). Current clinical guidelines do not recommend genetic testing for SEPTIN9 to predict cancer risk, and standard cancer screening protocols based on age, family history, and other risk factors remain the standard of care.
The variants causing hereditary neuralgic amyotrophy are germline mutations present in all cells of the body from conception, such as the R88W substitution, which disrupts normal septin-9 protein function in nerve cells. In contrast, SEPTIN9 changes associated with cancer are usually somatic alterations in gene expression or specific isoform production that occur within tumor cells to promote uncontrolled growth and angiogenesis. These cancer-related changes are not inherited and do not affect the function of healthy tissues like the brachial plexus.
Diagnosis typically begins with a clinical evaluation of recurrent episodes of severe shoulder and arm pain followed by muscle weakness and wasting. Genetic testing is required for confirmation, specifically looking for the Arg88Trp (R88W) mutation or duplications within the SEPTIN9 gene. Electromyography (EMG) and nerve conduction studies may also be used to assess the extent of nerve damage in the brachial plexus, but only genetic sequencing can definitively identify the underlying SEPTIN9 variant.
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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