A research group from the Viral Vector Core Center, Gunma University Initiative for Advanced Research (GIAR) , has developed a compact genetic switch that selectively targets inhibitory neurons and successfully suppresses seizures in multiple mouse models of epilepsy. The technology, based on a newly developed 410-bp promoter called cmGAD67, may provide a foundation for future gene therapies for drug-resistant epilepsy.
The results of this study were published online in Molecular Therapy, the official journal of the American Society of Gene & Cell Therapy (ASGCT).
1.Highlights
- Developed cmGAD67, a compact 410-bp promoter that drives highly selective gene expression in inhibitory neurons.
- Achieved both high expression strength and cell type specificity, overcoming key limitations of conventional inhibitory neuron-specific promoters.
- Enabled selective targeting of inhibitory neurons using AAV-mediated gene delivery.
- AAV-mediated expression of GAD65 under the control of cmGAD67 suppressed seizures in multiple mouse models of epilepsy.
- Provides a promising platform for the development of gene therapies for drug-resistant epilepsy and other neurological disorders involving excitation–inhibition imbalance.
2.Background
Epilepsy is one of the most common neurological disorders, affecting approximately 50 million people worldwide. Although anti-seizure medications can control seizures in many patients, about one-third continue to experience seizures despite treatment and are classified as having drug-resistant epilepsy. These patients often face substantial challenges in daily life, highlighting the need for new therapeutic approaches.
Recent advances in adeno-associated virus (AAV)-mediated gene therapy have created new opportunities for the treatment of neurological disorders. Because epileptic seizures result from excessive neuronal excitation and an imbalance between excitatory and inhibitory neural activity, selectively enhancing inhibitory neuronal function represents a promising therapeutic strategy.
However, existing inhibitory neuron-specific promoters are generally large and often exhibit insufficient expression strength. Their large size consumes valuable AAV packaging capacity, while limited promoter activity can restrict therapeutic gene expression. These challenges have hindered the development of efficient inhibitory neuron-targeted gene therapies.
To address these limitations, we developed cmGAD67, a compact and highly active promoter that selectively drives gene expression in inhibitory neurons, and evaluated its potential for AAV-based gene therapy for drug-resistant epilepsy.
3.Research Findings
The research team first analyzed regulatory regions of the GAD67 gene, which is selectively expressed in inhibitory neurons, and developed a compact promoter named cmGAD67. Despite its small size of only 410 base pairs, cmGAD67 exhibited stronger transcriptional activity than previously reported inhibitory neuron-specific promoters while maintaining high cell type specificity.
To evaluate its performance in vivo, the researchers delivered cmGAD67-driven reporter genes to the mouse brain using AAV vectors. More than 90% of transgene-expressing cells were inhibitory neurons, demonstrating highly selective targeting. The promoter efficiently drove gene expression in major inhibitory neuron subtypes, including parvalbumin-positive and somatostatin-positive interneurons.
The team next generated an AAV vector expressing GAD65, a key enzyme involved in GABA synthesis, under the control of cmGAD67. Following administration to multiple mouse models of epilepsy, treated animals showed increased GABA production, reduced epileptiform brain activity, decreased seizure severity, and improved survival compared with control groups.
Importantly, no obvious adverse effects on locomotor activity or general behavior were observed. These findings demonstrate that cmGAD67 provides a powerful platform for selective inhibitory neuron targeting and support its potential application in gene therapy for drug-resistant epilepsy.
4.Future Prospects
The compact size, strong transcriptional activity, and high inhibitory neuron specificity of cmGAD67 make it a promising regulatory element for AAV-based gene therapies targeting neurological disorders. By minimizing the space required within the AAV genome, cmGAD67 allows greater flexibility for incorporating therapeutic genes and additional regulatory components.
The research team is currently evaluating the performance and safety of cmGAD67-based gene therapy approaches in non-human primates, including marmosets, with the goal of advancing toward clinical translation. Future studies will focus on establishing long-term efficacy and safety in models of drug-resistant epilepsy.
Beyond epilepsy, abnormalities in the balance between neuronal excitation and inhibition have been implicated in a variety of neurological and neuropsychiatric disorders. Therefore, cmGAD67 may serve as a versatile platform for developing next-generation gene therapies and for investigating inhibitory neural circuits in the brain.
The researchers hope that this technology will ultimately contribute to the development of safer and more precise gene therapies for patients with currently untreatable neurological diseases.
5.Funding information
This research was supported by the following programs:
AMED (Japan Agency for Medical Research and Development/Strategic Research Program for Brain Sciences (SRPBS) / Brain Mapping by Integrated Neurotechnologies for Disease Studies (Brain/MINDS)) (Project Number Brain/MINDS 2.0 and JP24wm0625103)
JSPS (Japan Society for the Promotion of Science/ Grants-in-Aid for Scientific Research) (20K06906/24K10022, 22K06454/24H01221, and 23H02791)
Next-GIP (JPMJSP2146)
GIAR Viral Vector Core Center Research Fundings
6.Publication Information
Title: A compact GAD67 promoter enables inhibitory neuron–targeted AAV gene therapy for seizure suppression
Authors:Yuuki Fukai1,2,Ayumu Konno1,2, Nobutake Hosoi2, Karin Miyakawa2, Ryosuke Kaneko3, Hirokazu Hirai 1,2
1 Gunma University Initiative for Advanced Research, Gunma University, Maebashi, Gunma 371-8511, Japan.
2 Department of Neurophysiology & Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan
3 Medical Genetics Research Center, Nara Medical University, 840 Shijo-Cho, Kashihara, Nara 634-8521, Japan
Journal: Molecular Therapy
DOI:10.1016/j.ymthe.2026.06.007
Publication date: June 25, 2026, 11:00(EDT) ( June 26,2026,0:00 (JST))
Contact Information
【For research-related inquiries】
Gunma University Initiative for Advanced Research (GIAR)-Viral Vector Core Center
E-mail: hirai[at] gunma-u.ac.jp
Website: GIAR Viral Vector Core Center
Department of Neurophysiology & Neural Repair, Gunma University Graduate School of Medicine
【For media inquiries】
Gunma University Research Promotion Division
GIAR Support Office
E-mail: kk-kensui4[at] ml.gunma-u.ac.jp
【Related Website】
Eurek Alert! https://www.eurekalert.org/
GIAR Viral Vector Core Center
Department of Neurophysiology & Neural Repair, Gunma University Graduate School of Medicine
