According to Charcot-Marie-Tooth News, a recent case study found that a variation of the SEPT9 gene could contribute to the development of Charcot-Marie-Tooth disease. Read the full findings in BMC Medical Genetics.
Charcot-Marie-Tooth Disease
Charcot-Marie-Tooth disease (CMT) is a rare, inherited neurological disorder. It affects peripheral nerves (nerves outside of the spinal cord and brain).
Genetic mutations cause CMT. A large majority of demyelinating CMT is caused by a mutated PMP22 gene. Other genetic mutations leading to CMT development include the MPZ, MFN2, and GJB1 genes. One of the reasons why this recent study is so interesting is because it found a gene mutation contributing to Charcot-Marie-Tooth disease outside of the expected variants.
The genes affected by CMT usually communicate with the muscles. So when these gene variants appear, it causes nerve degeneration and muscle weakness. Symptoms of CMT include difficulty with fine motor skills, leg and foot deformities, muscle weakness, and muscle atrophy in the hands. Learn more about Charcot-Marie-Tooth disease.
SEPT9 Research Findings
Researchers examined a woman who visited the hospital complaining of sensory issues and progressive muscle weakness. Her symptoms began 15 years prior, at age 40. An examination found that she was experiencing:
- Muscle weakness
- Lowered tendon reflexes
- Muscle tremors
- A foot deformity in which the foot has a high arch
- Low sensitivity in her legs and feet
- A loss of coordination
- Issues with cognition, focus, and memory
When doctors also found peripheral nerve damage, the woman was diagnosed with Charcot-Marie-Tooth disease. Various members of her family were also symptomatic. Out of her three children, one had cerebral palsy, one had no symptoms, and one had similar physical and cognitive problems. Her father and older brother had similar physical, cognitive, and nerve-based problems.
Because of the familial component, researchers decided to sequence the patient’s genome. They found a mutation in the SEPT9 gene. SEPT9 normally creates septin-9, a protein that plays a role in cell division, movement, and tumor suppression. Surprisingly, and intriguingly, this mutation has never before been found or reported in patients with Charcot-Marie-Tooth disease. However, SEPT9 mutations have been linked to hereditary neuralgic amyotrophy.
Altogether, researchers now believe that SEPT9 variants could be a risk factor for Charcot-Marie-Tooth disease. However, more research is still needed.
