KCNC3 Research Articles

Oxidative stress-related cellular aging causes dysfunction of the Kv3.1/KCNC1 channel reverted by melatonin.

The voltage-gated Kv3.1/KCNC1 channel is abundantly expressed in fast-spiking principal neurons and GABAergic inhibitory interneurons throughout the ascending auditory pathway and in various brain regions. Inactivating mutations in the KCNC1 gene lead to forms of epilepsy and a decline in the expression of the Kv3.1 channel is involved in age-related hearing loss. As oxidative stress plays a fundamental role in the pathogenesis of epilepsy and age-related hearing loss, we hypothesized that an oxidative insult might affect the function of this channel. To verify this hypothesis, the activity and expression of endogenous and ectopic Kv3.1 were measured in models of oxidative stress-related aging represented by cell lines exposed to 100 mM d-galactose. In these models, intracellular reactive oxygen species, thiobarbituric acid reactive substances, sulfhydryl groups of cellular proteins, and the activity of catalase and superoxide dismutase were dysregulated, while the current density of Kv3.1 was significantly reduced. Importantly, the antioxidant melatonin reverted all these effects. The reduction of function of Kv3.1 was not determined by direct oxidation of amino acid side chains of the protein channel or reduction of transcript or total protein levels but was linked to reduced trafficking to the cell surface associated with Src phosphorylation as well as metabolic and endoplasmic reticulum stress. The data presented here specify Kv3.1 as a novel target of oxidative stress and suggest that Kv3.1 dysfunction might contribute to age-related hearing loss and increased prevalence of epilepsy during aging. The pharmacological use of the antioxidant melatonin can be protective in this setting.

Cryo-EM structure of the human Kv3.1 channel reveals gating control by the cytoplasmic T1 domain

Kv3 channels have distinctive gating kinetics tailored for rapid repolarization in fast-spiking neurons. Malfunction of this process due to genetic variants in the KCNC1 gene causes severe epileptic disorders, yet the structural determinants for the unusual gating properties remain elusive. Here, we present cryo-electron microscopy structures of the human Kv3.1a channel, revealing a unique arrangement of the cytoplasmic tetramerization domain T1 which facilitates interactions with C-terminal axonal targeting motif and key components of the gating machinery. Additional interactions between S1/S2 linker and turret domain strengthen the interface between voltage sensor and pore domain. Supported by molecular dynamics simulations, electrophysiological and mutational analyses, we identify several residues in the S4/S5 linker which influence the gating kinetics and an electrostatic interaction between acidic residues in α6 of T1 and R449 in the pore-flanking S6T helices. These findings provide insights into gating control and disease mechanisms and may guide strategies for the design of pharmaceutical drugs targeting Kv3 channels.

Kv3.1 channelopathy: a novel loss-of-function variant and the mechanistic basis of its clinical phenotypes.

BackgroundKCNC1 encodes Kv3.1, a subunit of the Kv3 voltage-gated potassium channels. It is predominantly expressed in inhibitory GABAergic interneurons and cerebellar neurons. Kv3.1 channelopathy has been linked to a variety of human diseases including epilepsy, developmental delay, and ataxia. Characterization of structural and functional disturbances of this channel, and its relationship to a heterogenous group of clinical phenotypes, is a current topic of research. We herein characterize the clinical phenotype as well as the functional and structural consequences of the novel KCNC1 p.R317S variant. We further set out to explore the mechanistic basis for the spectrum of KCNC1 related channelopathies.MethodsVariant was identified via whole-exome sequencing and its functional impact was determined using two-electrode voltage clamp recordings in Xenopus laevis oocytes. Homolog modeling and in silico structural analysis were performed on the p.R317S variant and other KCNC1 related variants.ResultsWe identified a novel loss-of-function KCNC1 variant c.949C>A (p.R317S) presenting with symptoms similar to myoclonic epilepsy and ataxia due to potassium channel (MEAK), but with distinct radiological features. Functional analysis in the Xenopus laevis oocyte’s expression system revealed that the current amplitudes were significantly decreased in the p.R317S variant compared to the wild type, indicating a dominant-negative effect. Atomic structural analysis of the KCNC1 related variants provided a possible mechanistic explanation for the heterogeneity in the clinical spectrum.ConclusionsWe have identified the p.R317S loss-of-function variant in the KCNC1 gene, expanded the spectrum of potassium channelopathy and provided mechanistic insights into KCNC1 related disorders.

The improvement in diagnosis and epilepsy managing in children with progressive myoclonus epilepsy during the last decade — A tertiary center experience in cohort of 51 patients

The aim of the study was to explore whether diagnosis and managing children with progressive myoclonus epilepsy (PME) were improved during the last decade. MethodsThe retrospective study included children with PME treated in the Institute during the last 25 years. Investigation time was divided in two periods (groups): before December 2010 (the first group) and after this period up to December 2019 (the second group). Inclusion criteria are as follows: patients aged from 0.2–18 years and with PME. Evaluated parameters are etiology, age at seizure onset, diagnosis delay, epilepsy phenotype, and, as a measure of epilepsy control — status epilepticus (SE) frequency and recurrence rate. Statistical analysis included the following tests: Chi-Square, Mann–Whitney, and analysis of variance (ANOVA), using SPSS version 25. ResultsThe study included 51 patients, 27 in the first, and 24 in the second group. The underlying diseases were: neuronal ceroid lipofuscinosis (NCL; 30), Gaucher (5), Niemann–Pick (4), mitochondrial (4), Lafora (3), Krabbe (2), and KCNC1 gene mutation (2). The average duration from initial symptoms to diagnosis was 3.2 ± 3 years (first group) vs. 1.4 ± 0.9 years (second). Both SE frequency rate (55.5% vs. 37.5%) and recurrence rate (66.7% vs. 22.2%) were higher in the first group, showing tendency towards, but not statistically significant difference. ConclusionThe diagnosis and epilepsy managing children with PME were improved during the last decade. Earlier genetic diagnosis, appropriate antiseizure medications, education of parents/caregivers of children in high risk for SE, and availability of effective prehospital rescue medications contributed to significantly decreased frequency and recurrence rate of SE.

Three cases of progressive myoclonic epilepsy caused by KCNC1 gene mutations and literature review

Objective To summarize the clinical phenotype and genotype features of 3 children with progre-ssive myoclonic epilepsy (PME) caused by KCNC1 gene mutations, and to review the related literatures. Methods The phenotype and genotype of 3 children with KCNC1 mutations in the Department of Pediatrics, Peking University First Hospital from October 2016 to January 2019 were analyzed.The 25 patients with KCNC1 mutations which had been reported internationally were also collected and analyzed. Results Three children in this study were identified with KCNC1 de novo mutations, in which 2 children were identified with c. 959G>A (p.Arg320His) mutation, and 1 child with c. 1262C>T (p.Ala421Val) mutation.The clinical features of 3 children were consistent with PME, and the seizure onset ages were 3 months, 10 years and 11 years, respectively.Three children all had myoclonic seizures, among whom 1 child had generalized tonic-clonic seizure and 2 children had focal seizures.Three children all had intellectual and/or motor development delay.The electroencephalograph showed generalized spike and waves or polyspike and waves in 3 children, and focal discharge in 2 children.The brain imaging of 3 children was normal.The last follow-up ages were 3 years old, 13 years old and 12 years old, respectively.Until March 2019, there were 25 cases with KCNC1 gene mutations reported internationally.Including 3 patients in this study, there were 28 patients in total, of which 25 patients were diagnosed with PME.In these 25 patients, 24 patients were identified with p. Arg320His variant in the transmembrane area, 1 patient was identified with p. Ala421Val variant in the transmembrane area.The remaining 3 patients were only found with psychomotor developmental delay without seizures, and they were identified with p. Arg339X variant in the intracellular area.In the 28 patients, 16 cases received cranial imaging data, in which 12 patients had ce-rebellar atrophy and 4 cases were normal.Of the 28 patients, 18 cases were mentally retarded, 27 cases were development retardation or retrogression among whom 9 cases could not walk independently.Ten patients were over 30 years old when reported, and only 1 patient died of pneumonia and respiratory failure at 63 years old. Conclusions KCNC1 gene mutation mainly leads to PME phenotype, and a few patients can only show mental retardation.p.Arg320His is the most common variant of KCNC1 gene.The variants in different structural regions result in different clinical phenotypes, and variants in the transmembrane region can lead to severer clinical phenotypes.The 3 patients with KCNC1 gene mutations in this study are firstly reported cases in China. Key words: KCNC1 gene; Myoclonic epilepsy; Progressive

Pathogenic gene variants and clinical phenotype features of 26 children with progressive myoclonic epilepsy

Objective: To identify the pathogenic gene variants and clinical phenotype features of 26 children with progressive myoclonic epilepsy (PME). Methods: In this cross-sectional study, 26 PME children (11 boys and 15 girls) sent to neurological outpatient clinics and admitted to wards of the Department of Pediatrics, Peking University First Hospital were enrolled prospectively from January 2014 to October 2018. The pathogenic gene variants of PME children and their parents were identified by Sanger sequencing, next generation sequencing panels of epilepsy or trio-based whole exome sequencing and so on. The genotypes and phenotypes of the PME children were anaylzed. Results: The clinical features of 26 children include myoclonus, multiple types of seizures and progressive neurological regression. Their onset ages ranged from 3 months to 15 years. Several pathogenic gene variants were identified in the 15 patients, including TPP1 gene variantions in 3 patients; NEU1, GBA, TBC1D24 and KCNC1 gene variantions in 2 patients respectively; CLN6, MFSD8, ASAH1 and ATN1 gene variantions in 1 patient respectively. Several variants of uncertain significance were identified in 4 patients, including GOSR2 gene compound heterozygous variants in 2 patients, KCTD7 gene compound heterozygous variants in 1 patient, and compound heterozygous variants of an unreported TARS gene in 1 patient. No pathogenic gene variant was identified in 7 patients. In 15 children with the identified pathogenic gene variants, 5 patients were diagnosed with neuronal ceroid lipofuscinoses (NCL), 2 patients with sialidosis, 2 patients with neuronopathic Gaucher disease, 1 patient with dentatorubral-pallidoluysian atrophy (DRPLA), and 1 patient with spinal muscular atrophy-progressive myoclonic epilepsy (SMA-PME). Conclusions: PME include a group of diseases with genetic heterogeneity. Identification of the pathogenic gene variants of PME could help to predict the prognosis and guide the genetic counseling.

Case report of de-novo heterozygous KCNC1 gene mutation(c.1262C>T) causes progressive myoclonic epilepsy with the early-onset myoclonus companied by an overall development backward

对遵义医科大学第一附属医院儿科病房收治的1例KCNC1基因新生突变(c.1262C>T)所致早发肌阵挛伴全面性发育落后的进行性肌阵挛癫痫(PME)患儿的临床资料行回顾性分析。患儿，女，9岁，起病早、症状重，4个月大时出现频繁肌阵挛发作，随年龄增长出现明显的共济失调，且自幼发育全面落后。脑电图显示醒睡期多量棘慢波节律中－长程阵发，可见频繁肌阵挛发作。基因检测发现KCNC1基因新生错义突变(c.1262C>T)。说明KCNC1基因新发突变可能引起早发性PME伴全面性发育落后，提示对于早期起病的肌阵挛癫痫伴有全面性发育落后的患儿，需注意钾通道基因的检查。

Pharmacological rescue of mutated Kv3.1 ion-channel linked to progressive myoclonus epilepsies

Progressive myoclonus epilepsies (PMEs) constitute a cluster of inherent, genetically diverse, rare seizure disorders characterized by ataxia, tonic-clonic seizures, and action myoclonus. Recently, a mutation in the KCNC1 gene (Arg320His) was described in a group of PME patients. The KCNC1 gene encodes the Kv3.1 potassium ion channel responsible for the rapid repolarization of the membrane potential following action potential firing in fast spiking GABAergic interneurons (FSI), thereby enabling high firing frequency. In the present study, we demonstrate that the Arg320His mutation cause a reduction in the Kv3.1 current amplitude and acts in a dominantly negative fashion. The mutation profoundly affects channel activation and deactivation kinetics, and we further find that it impairs recruitment of the Kv3.1 channel to the plasma membrane. The Kv3 activating compound, RE01, partly rescues the electrophysiological deficit, suggesting that pharmacological activation of Kv3.1 activity might be a feasible approach for treatment of this cohort of PME patients.

Loss of Function of KCNC1 is associated with intellectual disability without seizures

p.(Arg320His) mutation in the KCNC1 gene in human 11p15.1 has recently been identified in patients with progressive myoclonus epilepsies, a group of rare inherited disorders manifesting with action myoclonus, myoclonic epilepsy, and ataxia. This KCNC1 variant causes a dominant-negative effect. Here we describe three patients from the same family with intellectual disability and dysmorphic features. The three affected individuals carry a c.1015C>T (p.(Arg339*)) nonsense variant in KCNC1 gene. As previously observed in the mutant mouse carrying a disrupted KCNC1 gene, these findings reveal that individuals with a KCNC1 loss-of-function variant can present intellectual disability without seizure and epilepsy.

Myoclonus epilepsy and ataxia due to potassium channel mutation (MEAK) is caused by heterozygous KCNC1 mutations.

Progressive myoclonus epilepsy (PME) is a distinct group of seizure disorders characterized by gradual neurological decline with ataxia, myoclonus and recurring seizures. There are several forms of PME, among which the most recently described is MEAK - myoclonus epilepsy and ataxia due to potassium channel mutation. This particular subtype is caused by a recurrent de novo heterozygous mutation (c.959G>A, p.Arg320His) in the KCNC1 gene, which maps to chromosome 11 and encodes for the Kv3.1 protein (a subunit of the Kv3 subfamily of voltage-gated potassium channels). Loss of Kv3 function disrupts the firing properties of fast-spiking neurons, affects neurotransmitter release and induces cell death. Specifically regarding Kv3.1 malfunctioning, the most affected neurons include inhibitory GABAergic interneurons and cerebellar neurons. Impairment of the former cells is believed to contribute to myoclonus and seizures, whereas dysfunction of the latter to ataxia and tremor. Phenotypically, MEAK patients generally have a normal early development. At the age of 6 to 14 years, they present with myoclonus, which tends to progressively worsen with time. Tonic-clonic seizures may or may not be present, and some patients develop mild cognitive impairment following seizure onset. Typical electroencephalographic features comprise generalized epileptiform discharges and, in some cases, photosensitivity. Brain imaging is either normal or shows cerebellar atrophy. The identification of MEAK has both expanded the phenotypic and genotypic spectra of PME and established an emerging role for de novo mutations in PME.

Kcnc1 Gene Polymorphism Is Not Associated With Endurance Performance Level In Hispanics

A DNA sequence variant in the K+ voltage-gated channel of the shaw related subfamily member 1 (KCNC1) gene (11p15) is known to be associated with VO2max in the sedentary and trained states in Blacks, but not in Whites (MSSE 36(5), S99, 2003). PURPOSE To examine the association between the same KCNC1 gene polymorphism and endurance performance level in a cohort of Hispanics. METHODS The polymorphism was detected by PCR and digestion with MspI in 302 DNA samples from Hispanic marathon runners (n=225) and cardiac patients (n = 77). They were divided into three groups according to endurance performance level. Cases (C; n = 105) and active controls (AC; n = 120), were long-distance runners finishers in the highest and lowest 3 percentile, by age and gender respectively, during an international marathon (42 km) race, while controls (CON; n = 77) were intensive care coronary unit subjects with severely compromised cardiorespiratory functions. RESULTS The observed KCNC1 genotypic frequencies for both genders were in Hardy-Weinberg equilibrium (X2, P>0.05). X2 analysis showed that neither allelic nor genotype frequencies were significantly (P>0.05) different between genders or groups. The pooled genotypic and allelic data is shown in the table below.TableCONCLUSION The present findings do not provide support for the notion that the K+ voltage-gated channel of the shaw related subfamily member 1 is associated with endurance performance status in Hispanics. Supported by CRC-RCMI 1P20RR11126, RCMI #G12RR03051, Comite de Fondismo: FPRA, Maraton Pacifico, Maraton de Guadalajara, and Maraton Popular de Madrid.

Kcnc1 Gene Polymorphism Is Not Associated With Endurance Performance Level In Hispanics

A DNA sequence variant in the K+ voltage-gated channel of the shaw related subfamily member 1 (KCNC1) gene (11p15) is known to be associated with VO2max in the sedentary and trained states in Blacks, but not in Whites (MSSE 36(5), S99, 2003). PURPOSE To examine the association between the same KCNC1 gene polymorphism and endurance performance level in a cohort of Hispanics. METHODS The polymorphism was detected by PCR and digestion with MspI in 302 DNA samples from Hispanic marathon runners (n=225) and cardiac patients (n = 77). They were divided into three groups according to endurance performance level. Cases (C; n = 105) and active controls (AC; n = 120), were long-distance runners finishers in the highest and lowest 3 percentile, by age and gender respectively, during an international marathon (42 km) race, while controls (CON; n = 77) were intensive care coronary unit subjects with severely compromised cardiorespiratory functions. RESULTS The observed KCNC1 genotypic frequencies for both genders were in Hardy-Weinberg equilibrium (X2, P>0.05). X2 analysis showed that neither allelic nor genotype frequencies were significantly (P>0.05) different between genders or groups. The pooled genotypic and allelic data is shown in the table below.TableCONCLUSION The present findings do not provide support for the notion that the K+ voltage-gated channel of the shaw related subfamily member 1 is associated with endurance performance status in Hispanics. Supported by CRC-RCMI 1P20RR11126, RCMI #G12RR03051, Comite de Fondismo: FPRA, Maraton Pacifico, Maraton de Guadalajara, and Maraton Popular de Madrid.

KCNC1 Gene Polymorphism and OV2max

0710 The K+ voltage-gated channel of the shaw-related subfamily member 1 (KCNC1) gene (11p15), encodes for a voltage-gated K+ channel that serves as an oxygen sensor in*uencing pulmonary artery smooth muscle (PASM) cells excitability in hypoxic conditions, such as high intensity physical activity. PURPOSE: We examined the hypothesis of association between a G\A transition in the KCNC1 gene and OV2max in the sedentary (SS) and trained (TS) states, as well as in response (Δ) to 20-wk endurance-training (ET). METHODS: Pre- and Post-ET VO2 was measured by progressive exercise tests on a cycle ergometer. The polymorphism was detected by PCR and digestion with MspI in 777 DNA samples from the HERITAGE Family Study (Blacks = 275 and Whites = 502). RESULTS: Genotypic distributions were in Hardy- Weinberg equilibrium. χ2 indicated that genotype frequencies were different between races (P <0.0001) but not between genders (p>0.05). ANCOVA revealed statistically significant genotype effects for SS OV2max (P = 0.04) and TS OV2max (P = 0.01) values adjusted for age, gender and body mass. In Blacks only, homozygotes for the rare A allele had significantly higher SS (2329 ± 44 mL/min) and TS OV2max (2729 ± 45 mL/min) than both GG homozygotes (SS = 2314 ± 40 mL/min; TS = 2683 ± 43 mL/min) and GA heterozygotes (SS = 2241 ± 36 mL/min; TS = 2614 ± 36 mL/min). CONCLUSIONS: These findings suggest that DNA sequence variation in the KCNC1 gene is part of the complex genotype associated with OV2max in the sedentary and trained states in Blacks, but not in Whites. Supported by several grants from NHLBI of NIH, CRC-RCMI #1P20RR11126, and RCMI #G12RR03051.

KCNC1 Gene Polymorphism and OV2max

0710 The K+ voltage-gated channel of the shaw-related subfamily member 1 (KCNC1) gene (11p15), encodes for a voltage-gated K+ channel that serves as an oxygen sensor in*uencing pulmonary artery smooth muscle (PASM) cells excitability in hypoxic conditions, such as high intensity physical activity. PURPOSE: We examined the hypothesis of association between a G\A transition in the KCNC1 gene and OV2max in the sedentary (SS) and trained (TS) states, as well as in response (Δ) to 20-wk endurance-training (ET). METHODS: Pre- and Post-ET VO2 was measured by progressive exercise tests on a cycle ergometer. The polymorphism was detected by PCR and digestion with MspI in 777 DNA samples from the HERITAGE Family Study (Blacks = 275 and Whites = 502). RESULTS: Genotypic distributions were in Hardy- Weinberg equilibrium. χ2 indicated that genotype frequencies were different between races (P <0.0001) but not between genders (p>0.05). ANCOVA revealed statistically significant genotype effects for SS OV2max (P = 0.04) and TS OV2max (P = 0.01) values adjusted for age, gender and body mass. In Blacks only, homozygotes for the rare A allele had significantly higher SS (2329 ± 44 mL/min) and TS OV2max (2729 ± 45 mL/min) than both GG homozygotes (SS = 2314 ± 40 mL/min; TS = 2683 ± 43 mL/min) and GA heterozygotes (SS = 2241 ± 36 mL/min; TS = 2614 ± 36 mL/min). CONCLUSIONS: These findings suggest that DNA sequence variation in the KCNC1 gene is part of the complex genotype associated with OV2max in the sedentary and trained states in Blacks, but not in Whites. Supported by several grants from NHLBI of NIH, CRC-RCMI #1P20RR11126, and RCMI #G12RR03051.