BACKGROUND: Progressive Myoclonic Epilepsy (PME) is a group of rare diseases that are difficult to differentiate from one another based on phenotypical characteristics.
METHODS: We report a case of PME type 7 due to a pathogenic variant in KCNC1 with myoclonus improvement after epileptic seizures.
CONCLUSIONS: Myoclonus improvement after seizures may be a clue to the diagnosis of Progressive Myoclonic Epilepsy type 7.

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.

Small-molecule modulators of diverse voltage-gated K+ (Kv) channels may help treat a wide range of neurological disorders. However, developing effective modulators requires understanding of their mechanism of action. We apply an orthogonal approach to elucidate the mechanism of action of an imidazolidinedione derivative (AUT5), a highly selective positive allosteric modulator of Kv3.1 and Kv3.2 channels. AUT5 modulation involves positive cooperativity and preferential stabilization of the open state. The cryo-EM structure of the Kv3.1/AUT5 complex at a resolution of 2.5 Å reveals four equivalent AUT5 binding sites at the extracellular inter-subunit interface between the voltage-sensing and pore domains of the channel\'s tetrameric assembly. Furthermore, we show that the unique extracellular turret regions of Kv3.1 and Kv3.2 essentially govern the selective positive modulation by AUT5. High-resolution apo and bound structures of Kv3.1 demonstrate how AUT5 binding promotes turret rearrangements and interactions with the voltage-sensing domain to favor the open conformation.

Developmental and epileptic encephalopathies (DEE) are severe neurodevelopmental disorders characterized by recurrent, usually early-onset, epileptic seizures accompanied by developmental impairment often related to both underlying genetic etiology and abnormal epileptiform activity. Today, next-generation sequencing technologies (NGS) allow us to sequence large portions of DNA quickly and with low costs. The aim of this study is to evaluate the use of whole-exome sequencing (WES) as a first-line molecular genetic test in a sample of subjects with DEEs characterized by early-onset drug-resistant epilepsies, associated with global developmental delay and/or intellectual disability (ID). We performed 82 WESs, identifying 35 pathogenic variants with a detection rate of 43%. The identified variants were highlighted on 29 different genes including, 3 new candidate genes (KCNC2, STXBP6, DHRS9) for DEEs never identified before. In total, 23 out of 35 (66%) de novo variants were identified. The most frequently identified type of inheritance was autosomal dominant de novo (60%) followed by autosomal recessive in homozygosity (17%) and heterozygosity (11%), autosomal dominant inherited from parental mosaicism (6%) and X-linked dominant de novo (6%). The most frequent mutations identified were missense (75%) followed by frameshift deletions (16%), frameshift duplications (5%), and splicing mutations (3%). Considering the results obtained in the present study we support the use of WES as a form of first-line molecular genetic testing in DEEs.

De novo heterozygous variants in KCNC2 encoding the voltage-gated potassium (K+) channel subunit Kv3.2 are a recently described cause of developmental and epileptic encephalopathy (DEE). A de novo variant in KCNC2 c.374G > A (p.Cys125Tyr) was identified via exome sequencing in a patient with DEE. Relative to wild-type Kv3.2, Kv3.2-p.Cys125Tyr induces K+ currents exhibiting a large hyperpolarizing shift in the voltage dependence of activation, accelerated activation, and delayed deactivation consistent with a relative stabilization of the open conformation, along with increased current density. Leveraging the cryogenic electron microscopy (cryo-EM) structure of Kv3.1, molecular dynamic simulations suggest that a strong π-π stacking interaction between the variant Tyr125 and Tyr156 in the α-6 helix of the T1 domain promotes a relative stabilization of the open conformation of the channel, which underlies the observed gain of function. A multicompartment computational model of a Kv3-expressing parvalbumin-positive cerebral cortex fast-spiking γ-aminobutyric acidergic (GABAergic) interneuron (PV-IN) demonstrates how the Kv3.2-Cys125Tyr variant impairs neuronal excitability and dysregulates inhibition in cerebral cortex circuits to explain the resulting epilepsy.

Inhibitory parvalbumin (PV) interneurons regulate the activity of neural circuits within brain regions involved in emotional processing, including the prefrontal cortex (PFC). Recently, rodent studies have implicated a stress-induced increase in prefrontal PV neuron activity in the development of anxiety behaviors, particularly in females. However, the mechanisms through which stress increases activity of prefrontal PV neurons remain unknown. The fast-spiking properties of PV neurons in part come from their expression of voltage-gated potassium (K+) ion channels, particularly Kv3.1 channels. We therefore suggest that stress-induced changes in Kv3.1 channels contribute to the appearance of an anxious phenotype following chronic stress in female mice. Here, we first showed that unpredictable chronic mild stress (UCMS) increased expression of Kv3.1 channels on prefrontal PV neurons in female mice, a potential mechanism underlying the previously observed hyperactivity of these neurons after stress. We then showed that female mice deficient in Kv3.1 channels displayed resilience to UCMS-induced anxiety-like behaviors. Altogether, our findings implicate Kv3.1 channels in the development of anxiety-like behaviors following UCMS, particularly in females, providing a novel mechanism to understand sex-specific vulnerabilities to stress-induced psychopathologies.

The pathogenesis of schizophrenia is believed to involve combined dysfunctions of many proteins including microtubule-associated protein 6 (MAP6) and Kv3.1 voltage-gated K+ (Kv) channel, but their relationship and functions in behavioral regulation are often not known. Here we report that MAP6 stabilizes Kv3.1 channels in parvalbumin-positive (PV+ ) fast-spiking GABAergic interneurons, regulating behavior. MAP6-/- and Kv3.1-/- mice display similar hyperactivity and avoidance reduction. Their proteins colocalize in PV+ interneurons and MAP6 deletion markedly reduces Kv3.1 protein level. We further show that two microtubule-binding modules of MAP6 bind the Kv3.1 tetramerization domain with high affinity, maintaining the channel level in both neuronal soma and axons. MAP6 knockdown by AAV-shRNA in the amygdala or the hippocampus reduces avoidance or causes hyperactivity and recognition memory deficit, respectively, through elevating projection neuron activity. Finally, knocking down Kv3.1 or disrupting the MAP6-Kv3.1 binding in these brain regions causes avoidance reduction and hyperactivity, consistent with the effects of MAP6 knockdown. Thus, disrupting this conserved cytoskeleton-membrane interaction in fast-spiking neurons causes different degrees of functional vulnerability in various neural circuits.

Owing to the heterogeneity of Alzheimer\'s disease (AD), its pathogenic mechanisms are yet to be fully elucidated. Evidence suggests an important role of metabolism in the pathophysiology of AD. Herein, we identified the metabolism-related AD subtypes and feature genes.
The AD datasets were obtained from the Gene Expression Omnibus database and the metabolism-relevant genes were downloaded from a previously published compilation. Consensus clustering was performed to identify the AD subclasses. The clinical characteristics, correlations with metabolic signatures, and immune infiltration of the AD subclasses were evaluated. Feature genes were screened using weighted correlation network analysis (WGCNA) and processed via Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses. Furthermore, three machine-learning algorithms were used to narrow down the selection of the feature genes. Finally, we identified the diagnostic value and expression of the feature genes using the AD dataset and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis.
Three AD subclasses were identified, namely Metabolism Correlated (MC) A (MCA), MCB, and MCC subclasses. MCA contained signatures associated with high AD progression and may represent a high-risk subclass compared with the other two subclasses. MCA exhibited a high expression of genes related to glycolysis, fructose, and galactose metabolism, whereas genes associated with the citrate cycle and pyruvate metabolism were downregulated and associated with high immune infiltration. Conversely, MCB was associated with citrate cycle genes and exhibited elevated expression of immune checkpoint genes. Using WGCNA, 101 metabolic genes were identified to exhibit the strongest association with poor AD progression. Finally, the application of machine-learning algorithms enabled us to successfully identify eight feature genes, which were employed to develop a nomogram model that could bring distinct clinical benefits for patients with AD. As indicated by the AD datasets and qRT-PCR analysis, these genes were intimately associated with AD progression.
Metabolic dysfunction is associated with AD. Hypothetical molecular subclasses of AD based on metabolic genes may provide new insights for developing individualized therapy for AD. The feature genes highly correlated with AD progression included GFAP, CYB5R3, DARS, KIAA0513, EZR, KCNC1, COLEC12, and TST.

Complex motor skills in vertebrates require specialized upper motor neurons with precise action potential (AP) firing. To examine how diverse populations of upper motor neurons subserve distinct functions and the specific repertoire of ion channels involved, we conducted a thorough study of the excitability of upper motor neurons controlling somatic motor function in the zebra finch. We found that robustus arcopallialis projection neurons (RAPNs), key command neurons for song production, exhibit ultranarrow spikes and higher firing rates compared to neurons controlling non-vocal somatic motor functions (dorsal intermediate arcopallium [AId] neurons). Pharmacological and molecular data indicate that this striking difference is associated with the higher expression in RAPNs of high threshold, fast-activating voltage-gated Kv3 channels, that likely contain Kv3.1 (KCNC1) subunits. The spike waveform and Kv3.1 expression in RAPNs mirror properties of Betz cells, specialized upper motor neurons involved in fine digit control in humans and other primates but absent in rodents. Our study thus provides evidence that songbirds and primates have convergently evolved the use of Kv3.1 to ensure precise, rapid AP firing in upper motor neurons controlling fast and complex motor skills.

Raspberry ketone (RK; [4-(4-hydroxyphenyl)-2-butanone]) is a synthetic flavoring agent and dietary supplement for weight control. This study investigated the metabolic signature of oral doses of RK that prevent weight gain or promote loss of righting reflex (LORR) in C57Bl/6J mice. Daily RK 200 mg/kg prevented high-fat diet (HFD; 45% Kcal fat) fed weight gain (∼8% reduction) over 35 days. RNA-seq of inguinal white adipose tissue (WAT) performed in males revealed 12 differentially expressed genes. Apelin (Apln) and potassium voltage-gated channel subfamily C member (Kcnc3) expression were elevated with HFD and normalized with RK dosing, which was confirmed by qPCR. Acute RK 640 mg/kg produced a LORR with a <5 min onset with a >30 min duration. Acute RK 200 mg/kg increased gene expression of Apln, Kcnc3, and nuclear factor erythroid 2-related factor 2 (Nrf2), but reduced acetyl-COA carboxylase (Acc1) and NAD(P)H quinone dehydrogenase 1 (Nqo1) in inguinal WAT. Acute RK 640 mg/kg elevated interleukin 6 (Il 6) and heme oxygenase 1 (Hmox1) expression, but reduced Nrf2 in inguinal and epididymal WAT. Our findings suggest that RK has a dose-dependent metabolic signature in WAT associated with either weight control or LORR.