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Sci Rep. 2015 Oct 19;5:15199. doi: 10.1038/srep15199.

De novo KCNB1 mutations in infantile epilepsy inhibit repetitive neuronal firing.

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Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan.
Department of Pediatrics, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan.
Epilepsy Center, Schneider's Children Medical Center, Petah Tiqwa, Israel.
Department of Pediatrics, Yamagata University Faculty of Medicine, Yamagata, Japan.


The voltage-gated Kv2.1 potassium channel encoded by KCNB1 produces the major delayed rectifier potassium current in pyramidal neurons. Recently, de novo heterozygous missense KCNB1 mutations have been identified in three patients with epileptic encephalopathy and a patient with neurodevelopmental disorder. However, the frequency of KCNB1 mutations in infantile epileptic patients and their effects on neuronal activity are yet unknown. We searched whole exome sequencing data of a total of 437 patients with infantile epilepsy, and found novel de novo heterozygous missense KCNB1 mutations in two patients showing psychomotor developmental delay and severe infantile generalized seizures with high-amplitude spike-and-wave electroencephalogram discharges. The mutation located in the channel voltage sensor (p.R306C) disrupted sensitivity and cooperativity of the sensor, while the mutation in the channel pore domain (p.G401R) selectively abolished endogenous Kv2 currents in transfected pyramidal neurons, indicating a dominant-negative effect. Both mutants inhibited repetitive neuronal firing through preventing production of deep interspike voltages. Thus KCNB1 mutations can be a rare genetic cause of infantile epilepsy, and insufficient firing of pyramidal neurons would disturb both development and stability of neuronal circuits, leading to the disease phenotypes.

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