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Functional and pharmacological investigation of novel and de novo KCND3 variants identified in patients with neurodevelopmental disorders

Journal of Human Genetics (2025)Cite this article

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Abstract

Sudden unexpected death in epilepsy (SUDEP) is one of the most frequent causes of death in patients with epilepsy, though the pathogenesis of SUDEP has not been well elucidated. Here, we report novel heterozygous KCND3 variants, p.V401L and p.V401M, identified in young patients with refractory epilepsy (RE) and neurodevelopmental disorders, and the functional properties of these variants. We aimed to investigate the electrophysiological changes in de novo KCND3 variants and analyse the pharmacological effects of quinidine on these variants. Chinese hamster ovary (CHO) cells were transiently co-transfected with wild-type (WT) and/or variant KCND3 and Kcnip2. Transient outward potassium currents (Ito) were recorded using the whole-cell patch-clamp method. The inhibitory effect of quinidine on Ito was evaluated. In electrophysiological analysis, CHO cells expressing the variant channels showed a significant increase in current density compared with those expressing WT channels. The Ito activation curves were shifted significantly to the left, and significantly slower inactivation time constants were observed in both variant channels. Recovery from inactivation of the variant channels was significantly slower than that of WT. Quinidine suppressed Ito in a concentration-dependent manner and accelerated the slow inactivation of variant channels. In conclusion, de novo KCND3 variants identified in patients with RE and neurodevelopmental disorders showed gain and loss of function effects on Ito. These patients may be at risk of developing early repolarization syndrome, leading to SUDEP. Increased Ito was suppressed by quinidine, suggesting that it may be an effective therapy for RE and possibly for preventing SUDEP.

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Data availability

The datasets used and/or analysed in the current study will be available from the corresponding author upon reasonable request.

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Acknowledgements

The authors would like to thank Editage [http://www.editage.com] for editing and reviewing this manuscript for English language. We gratefully acknowledge Ms.Tanimoto Madoka for the technical contribution to the experimental works.

Funding

This study was supported by a grant-in-aid for Scientific Research, Ministry of Education, Culture, Sports, Science, and Technology of Japan for BT and TK (Grant-in-Aid for Research Activity Start-up No.22K20906 and Grant-in-Aid for Early-Career Scientists No. 19K17593 and No. 24K19074), a grant from the Kawano Paediatric Foundation, and a grant from the Senshin Medical Research Foundation for SO. The study funders had no role in the study design, data collection, management, analysis, or interpretation of the data, or the preparation, revision, or decision to submit the manuscript.

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Authors and Affiliations

  1. Medical Genome Center, National Cerebral and Cardiovascular Center, Suita, Japan

    Byambajav Tserenlkham, Koichiro Takayama, Dimitar P. Zankov, Keiko Sonoda & Seiko Ohno

  2. Laboratory of Epidemiology and Prevention, Kobe Pharmaceutical University, Kobe, Japan

    Byambajav Tserenlkham

  3. Division of Child Neurology, Stanford University School of Medicine, Stanford, CA, USA

    William B. Gallentine

  4. Department of Neurology, Stanford University School of Medicine, Stanford, CA, USA

    William B. Gallentine

  5. Pediatric Epilepsy Center, Stanford University School of Medicine, Stanford, CA, USA

    William B. Gallentine

  6. Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX, USA

    Vishnu Anand Cuddapah

  7. Division of Neurology and Developmental Neuroscience, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA

    Vishnu Anand Cuddapah

  8. Division of Translational Medicine and Human Genetics, the Hospital of the University of Pennsylvania, Philadelphia, PA, USA

    Stacey Cohen

  9. Genetic Diagnostic Laboratory University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA

    Stacey Cohen

  10. Department of Cardiovascular Medicine, Shiga University of Medical Science, Otsu, Japan

    Minoru Horie & Seiko Ohno

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  1. Byambajav Tserenlkham
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  2. Koichiro Takayama
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Correspondence to Seiko Ohno.

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Tserenlkham, B., Takayama, K., Zankov, D.P. et al. Functional and pharmacological investigation of novel and de novo KCND3 variants identified in patients with neurodevelopmental disorders. J Hum Genet (2025). https://doi.org/10.1038/s10038-025-01423-0

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