Researchers Identify CD99L2 As A New Gene Linked To X-Linked Spastic Ataxia

Researchers in Germany have identified a previously overlooked gene that helps explain a rare neurological movement disorder. By examining the DNA of 2,811 people with unexplained ataxia, hereditary spastic paraplegia, and dystonia, the team linked variants in the CD99L2 gene to X-linked spastic ataxia. The findings were published in the journal Nature Communications.

Until now, CD99L2 was primarily associated with immune system function, and its role in the nervous system was unknown. The new study shows that the gene is crucial for communication between nerve cells. This discovery provides a long-awaited explanation for a subset of patients whose symptoms could not be traced to previously known disease genes.

How CD99L2 Shapes Brain Signaling

Scientists at Ruhr University Bochum discovered that the CD99L2 gene encodes a protein that interacts with CAPN1, a calcium-dependent protease. CAPN1 has already been linked to hereditary spastic paraplegia and ataxia, suggesting that both proteins operate within the same biological pathway. Laboratory experiments showed that CD99L2 plays an important role in maintaining normal signaling at neuronal synapses.

According to the researchers, disease-causing variants in CD99L2 disrupt the production of a functional protein and interfere with its interaction with CAPN1. Patient-derived cells showed clear abnormalities in synaptic signaling and neuronal communication. Reduced activation of CAPN1 appears to disrupt critical cellular pathways, which likely contributes to the movement problems observed in affected individuals.

Combining Genetics With Functional Research

The project combined large-scale genetic analysis with detailed cellular studies. Investigators in Tübingen, led by Dr. Tobias Haack, conducted genome-wide diagnostic testing in a large cohort of patients with rare movement disorders. This approach identified CD99L2 as a strong candidate gene in several previously unexplained cases of X-linked spastic ataxia.

Follow-up research in Bochum, led by Dr. Jonasz Weber, examined how the identified variants affect cellular function. By studying patient-derived cells and experimental model systems, the team demonstrated that the mutations impair synaptic activity. The researchers argue that combining genetic findings with functional neuroscience is essential for establishing reliable disease mechanisms linked to newly discovered variants.

Understanding Spastic Ataxia

Spastic ataxia refers to a group of rare neurodegenerative disorders characterized by a combination of coordination difficulties, muscle stiffness, and weakness. The symptoms result from damage affecting the cerebellum and motor pathways within the central nervous system. The age at which symptoms appear and the rate of disease progression can vary considerably depending on the underlying genetic cause.

Identifying CD99L2 as a disease-associated gene may improve diagnostic testing for families affected by X-linked spastic ataxia. Clinicians could soon add this gene to targeted sequencing panels used to investigate unexplained cases of spastic ataxia and related neurological syndromes. Earlier and more accurate diagnoses may help guide genetic counseling and support future clinical research.

Potential Implications For Future Treatments

The findings also expand scientific understanding of how synaptic signaling contributes to neurodegenerative disease. By clarifying the role of the CD99L2–CAPN1 pathway, researchers have identified a new target for investigating potential therapeutic approaches.

Although current treatment options remain largely focused on symptom management, the study provides an important foundation for future work aimed at modifying the underlying disease process. Further research will be needed to determine whether therapies targeting this pathway could eventually help slow or prevent neurological decline in affected patients.