scholarly journals Molecular Mechanisms of Epileptic Encephalopathy Caused by KCNMA1 Loss-of-Function Mutations

2022 ◽  
Vol 12 ◽  
Author(s):  
Yu Yao ◽  
Dongxiao Qu ◽  
Xiaoping Jing ◽  
Yuxiang Jia ◽  
Qi Zhong ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Novel Mutation ◽  
Motor Impairment ◽  
Febrile Seizures ◽  
Epileptic Encephalopathy ◽  
Transcriptomic Analysis ◽  
Loss Of Function ◽  
Astrocyte Activation ◽  
Α Subunit ◽  
Imaging Results

The gene kcnma1 encodes the α-subunit of high-conductance calcium- and voltage-dependent K+ (BK) potassium channel. With the development of generation gene sequencing technology, many KCNMA1 mutants have been identified and are more closely related to generalized epilepsy and paroxysmal dyskinesia. Here, we performed a genetic screen of 26 patients with febrile seizures and identified a novel mutation of KCNMA1 (E155Q). Electrophysiological characterization of different KCNMA1 mutants in HEK 293T cells, the previously-reported R458T and E884K variants (not yet determined), as well as the newly-found E155Q variant, revealed that the current density amplitude of all the above variants was significantly smaller than that of the wild-type (WT) channel. All the above variants caused a positive shift of the I-V curve and played a role through the loss-of-function (LOF) mechanism. Moreover, the β4 subunit slowed down the activation of the E155Q mutant. Then, we used kcnma1 knockout (BK KO) mice as the overall animal model of LOF mutants. It was found that BK KO mice had spontaneous epilepsy, motor impairment, autophagic dysfunction, abnormal electroencephalogram (EEG) signals, as well as possible anxiety and cognitive impairment. In addition, we performed transcriptomic analysis on the hippocampus and cortex of BK KO and WT mice. We identified many differentially expressed genes (DEGs). Eight dysregulated genes [i.e., (Gfap and Grm3 associated with astrocyte activation) (Alpl and Nlrp10 associated with neuroinflammation) (Efna5 and Reln associated with epilepsy) (Cdkn1a and Nr4a1 associated with autophagy)] were validated by RT-PCR, which showed a high concordance with transcriptomic analysis. Calcium imaging results suggested that BK might regulate the autophagy pathway from TRPML1. In conclusion, our study indicated that newly-found point E155Q resulted in a novel loss-of-function variant and the dysregulation of gene expression, especially astrocyte activation, neuroinflammation and autophagy, might be the molecular mechanism of BK-LOF meditated epilepsy.

scholarly journals Goα Regulates Volatile Anesthetic Action in Caenorhabditis elegans

Genetics ◽  
2001 ◽  
Vol 158 (2) ◽  
pp. 643-655 ◽  
Author(s):  
Bruno van Swinderen ◽  
Laura B Metz ◽  
Laynie D Shebester ◽  
Jane E Mendel ◽  
Paul W Sternberg ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Novel Mutation ◽  
Volatile Anesthetic ◽  
Loss Of Function ◽  
Wild Type ◽  
Α Subunit ◽  
C Elegans ◽  
Missense Mutant ◽  
Anesthetic Action ◽  
Mutant Phenotypes

Abstract To identify genes controlling volatile anesthetic (VA) action, we have screened through existing Caenorhabditis elegans mutants and found that strains with a reduction in Go signaling are VA resistant. Loss-of-function mutants of the gene goa-1, which codes for the α-subunit of Go, have EC50s for the VA isoflurane of 1.7- to 2.4-fold that of wild type. Strains overexpressing egl-10, which codes for an RGS protein negatively regulating goa-1, are also isoflurane resistant. However, sensitivity to halothane, a structurally distinct VA, is differentially affected by Go pathway mutants. The RGS overexpressing strains, a goa-1 missense mutant found to carry a novel mutation near the GTP-binding domain, and eat-16(rf) mutants, which suppress goa-1(gf) mutations, are all halothane resistant; goa-1(null) mutants have wild-type sensitivities. Double mutant strains carrying mutations in both goa-1 and unc-64, which codes for a neuronal syntaxin previously found to regulate VA sensitivity, show that the syntaxin mutant phenotypes depend in part on goa-1 expression. Pharmacological assays using the cholinesterase inhibitor aldicarb suggest that VAs and GOA-1 similarly downregulate cholinergic neurotransmitter release in C. elegans. Thus, the mechanism of action of VAs in C. elegans is regulated by Goα, and presynaptic Goα-effectors are candidate VA molecular targets.

Changing Landscape of Dravet Syndrome Management: An Overview

2020 ◽  
Vol 51 (02) ◽  
pp. 135-145 ◽  
Author(s):  
Debopam Samanta
Keyword(s):  
Motor Impairment ◽  
Current Treatment ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Loss Of Function ◽  
Unexpected Death ◽  
Autistic Behavior ◽  
Behavioral Abnormalities ◽  
Treatment Paradigm ◽  
Antisense Oligonucleotide Therapy

AbstractDravet syndrome (DS), previously known as severe myoclonic epilepsy of infancy, is a severe developmental and epileptic encephalopathy caused by loss-of-function mutations in one copy of SCN1A (haploinsufficiency), located on chromosome 2q24, with decreased function of Nav1.1 sodium channels in GABAergic inhibitory interneurons. Pharmacoresistant seizures in DS start in the infancy in the form of hemiclonic febrile status epilepticus. Later, other intractable seizure types develop including myoclonic seizures. Early normal development in infancy evolves into moderate to severe intellectual impairment, motor impairment, behavioral abnormalities, and later a characteristic crouching gait. Clobazam, valproate, levetiracetam, topiramate, zonisamide, ketogenic diet, and vagus nerve stimulation had been shown to be effective, but even with polytherapy, only 10% of patients get adequate seizure control. The author provides a narrative review of the current treatment paradigm as well as recent advances in the management of DS based on a comprehensive literature review (MEDLINE using PubMed and OvidSP vendors with appropriate keywords to incorporate recent evidence), personal practice, and experience. In recent years, the treatment paradigm of DS is changing with the approval of pharmaceutical-grade cannabidiol oil and stiripentol. Another novel antiepileptic drug (AED), fenfluramine, had also shown excellent efficacy in phase 3 studies of DS. However, these AEDs primarily control seizures without addressing the underlying pathogenesis and other important common comorbidities such as cognitive impairment, autistic behavior, neuropsychiatric abnormalities, and motor impairment including crouching gait. Several agents targeted for DS are in the developmental stage: TAK935, lorcaserin, clemizole, huperzine analog, ataluren, selective sodium channel modulators and activators, antisense oligonucleotide therapy, and adenoviral vector therapy. As DS is associated with a high risk of sudden unexpected death in epilepsy, seizure detection devices can be used in this population for testing and clinical validation of these devices.

SCN1A and Its Related Epileptic Phenotypes

2021 ◽  
Author(s):  
Federica Sullo ◽  
Elisa Pasquetti ◽  
Francesca Patanè ◽  
Manuela Lo Bianco ◽  
Simona D. Marino ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Neurological Disorders ◽  
Wide Spectrum ◽  
Febrile Seizures ◽  
Epileptic Encephalopathy ◽  
Dravet Syndrome ◽  
Behavioral Alterations ◽  
Α Subunit ◽  
Hyperactivity Disorder ◽  
Whole Exome

AbstractEpilepsy is one of the most common neurological disorders, with a lifetime incidence of 1 in 26. Approximately two-thirds of epilepsy has a substantial genetic component in its etiology. As a result, simultaneous screening for mutations in multiple genes and performing whole exome sequencing (WES) are becoming very frequent in the clinical evaluation of children with epilepsy. In this setting, mutations in voltage-gated sodium channel (SCN) α-subunit genes are the most commonly identified cause of epilepsy, with sodium channel genes (i.e., SCN1A, SCN2A, SCN8A) being the most frequently identified causative genes. SCN1A mutations result in a wide spectrum of epilepsy phenotypes ranging from simple febrile seizures to Dravet syndrome, a severe epileptic encephalopathy. In case of mutation of SCN1A, it is also possible to observe behavioral alterations, such as impulsivity, inattentiveness, and distractibility, which can be framed in an attention deficit hyperactivity disorder (ADHD) like phenotype. Despite more than 1,200 SCN1A mutations being reported, it is not possible to assess a clear phenotype–genotype correlations. Treatment remains a challenge and seizure control is often partial and transitory.

V. The epithelial sodium channel and its implication in human diseases

1999 ◽  
Vol 276 (3) ◽  
pp. G567-G571 ◽  
Author(s):  
Edith Hummler ◽  
Jean-Daniel Horisberger
Keyword(s):  
Distal Colon ◽  
Loss Of Function ◽  
Newborn Mice ◽  
Α Subunit ◽  
Salt Wasting ◽  
Lung Fluid ◽  
Wasting Syndrome ◽  
Rate Limiting Step ◽  
Γ Subunit ◽  
Rate Limiting

The epithelial Na+ channel (ENaC) controls the rate-limiting step in the process of transepithelial Na+ reabsorption in the distal nephron, the distal colon, and the airways. Hereditary salt-losing syndromes have been ascribed to loss of function mutations in the α-, β-, or γ-ENaC subunit genes, whereas gain of function mutations (located in the COOH terminus of the β- or γ-subunit) result in hypertension due to Na+ retention (Liddle’s syndrome). In mice, gene-targeting experiments have shown that, in addition to the kidney salt-wasting phenotype, ENaC was essential for lung fluid clearance in newborn mice. Disruption of the α-subunit resulted in a complete abolition of ENaC-mediated Na+ transport, whereas knockout of the β- or γ-subunit had only minor effects on fluid clearance in lung. Disruption of each of the three subunits resulted in a salt-wasting syndrome similar to that observed in humans.

scholarly journals Maturation of the Na,K-ATPase in the Endoplasmic Reticulum in Health and Disease

2021 ◽  
Author(s):  
Vitalii Kryvenko ◽  
Olga Vagin ◽  
Laura A. Dada ◽  
Jacob I. Sznajder ◽  
István Vadász
Keyword(s):  
Endoplasmic Reticulum ◽  
Intracellular Signaling ◽  
Loss Of Function ◽  
Α Subunit ◽  
Rate Limiting Step ◽  
Atpase Subunits ◽  
A Cell ◽  
Health And Disease ◽  
And Function ◽  
Rate Limiting

Abstract The Na,K-ATPase establishes the electrochemical gradient of cells by driving an active exchange of Na+ and K+ ions while consuming ATP. The minimal functional transporter consists of a catalytic α-subunit and a β-subunit with chaperon activity. The Na,K-ATPase also functions as a cell adhesion molecule and participates in various intracellular signaling pathways. The maturation and trafficking of the Na,K-ATPase include co- and post-translational processing of the enzyme in the endoplasmic reticulum (ER) and the Golgi apparatus and subsequent delivery to the plasma membrane (PM). The ER folding of the enzyme is considered as the rate-limiting step in the membrane delivery of the protein. It has been demonstrated that only assembled Na,K-ATPase α:β-complexes may exit the organelle, whereas unassembled, misfolded or unfolded subunits are retained in the ER and are subsequently degraded. Loss of function of the Na,K-ATPase has been associated with lung, heart, kidney and neurological disorders. Recently, it has been shown that ER dysfunction, in particular, alterations in the homeostasis of the organelle, as well as impaired ER-resident chaperone activity may impede folding of Na,K-ATPase subunits, thus decreasing the abundance and function of the enzyme at the PM. Here, we summarize our current understanding on maturation and subsequent processing of the Na,K-ATPase in the ER under physiological and pathophysiological conditions. Graphic Abstract

scholarly journals Circular RNA mmu_circ_0005019 inhibits fibrosis of cardiac fibroblasts and reverses electrical remodeling of cardiomyocytes

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Na Wu ◽  
Chengying Li ◽  
Bin Xu ◽  
Ying Xiang ◽  
Xiaoyue Jia ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Cardiac Fibroblasts ◽  
Circular Rna ◽  
Protective Role ◽  
Luciferase Reporter ◽  
Loss Of Function ◽  
Candidate Target ◽  
Paired Control ◽  
Reporter Assays ◽  
And Migration

Abstract Background Circular RNA (circRNA) have been reported to play important roles in cardiovascular diseases including myocardial infarction and heart failure. However, the role of circRNA in atrial fibrillation (AF) has rarely been investigated. We recently found a circRNA hsa_circ_0099734 was significantly differentially expressed in the AF patients atrial tissues compared to paired control. We aim to investigate the functional role and molecular mechanisms of mmu_circ_0005019 which is the homologous circRNA in mice of hsa_circ_0099734 in AF. Methods In order to investigate the effect of mmu_circ_0005019 on the proliferation, migration, differentiation into myofibroblasts and expression of collagen of cardiac fibroblasts, and the effect of mmu_circ_0005019 on the apoptosis and expression of Ito, INA and SK3 of cardiomyocytes, gain- and loss-of-function of cell models were established in mice cardiac fibroblasts and HL-1 atrial myocytes. Dual-luciferase reporter assays and RIP were performed to verify the binding effects between mmu_circ_0005019 and its target microRNA (miRNA). Results In cardiac fibroblasts, mmu_circ_0005019 showed inhibitory effects on cell proliferation and migration. In cardiomyocytes, overexpression of mmu_circ_0005019 promoted Kcnd1, Scn5a and Kcnn3 expression. Knockdown of mmu_circ_0005019 inhibited the expression of Kcnd1, Kcnd3, Scn5a and Kcnn3. Mechanistically, mmu_circ_0005019 exerted biological functions by acting as a miR-499-5p sponge to regulate the expression of its target gene Kcnn3. Conclusions Our findings highlight mmu_circ_0005019 played a protective role in AF development and might serve as an attractive candidate target for AF treatment.

scholarly journals Production, characterization, and cross-reactivity of a polyclonal antibody against Arabidopsis TARGET OF RAPAMYCIN

2019 ◽  
Vol 62 (1) ◽  
Author(s):  
Gyeong-Im Shin ◽  
Sun Young Moon ◽  
Song Yi Jeong ◽  
Myung Geun Ji ◽  
Joon-Yung Cha ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Cross Reactivity ◽  
Target Of Rapamycin ◽  
Loss Of Function ◽  
Anticancer Activities ◽  
Purification Method ◽  
E Coli ◽  
Related Family ◽  
Large Gene ◽  
Truncated Variants

AbstractTARGET OF RAPAMYCIN (TOR), a member of the phosphatidylinositol 3-kinase-related family of protein kinases, is encoded by a single, large gene and is evolutionarily conserved in all eukaryotes. TOR plays a role as a master regulator that integrates nutrient, energy, and stress signaling to orchestrate development. TOR was first identified in yeast mutant screens, as its mutants conferred resistance to rapamycin, an antibiotic with immunosuppressive and anticancer activities. In Arabidopsis thaliana, the loss-of-function tor mutant displays embryo lethality, but the precise mechanisms of TOR function are still unknown. Moreover, a lack of reliable molecular and biochemical assay tools limits our ability to explore TOR functions in plants. Here, we produced a polyclonal α-TOR antibody using two truncated variants of TOR (1–200 and 1113–1304 amino acids) as antigens because recombinant full-length TOR is challenging to express in Escherichia coli. Recombinant His-TOR1−200 and His-TOR1113−1304 proteins were individually expressed in E. coli, and a mixture of proteins (at a 1:1 ratio) was used for immunizing rabbits. Antiserum was purified by an antigen-specific purification method, and the purified polyclonal α-TOR antibody successfully detected endogenous TOR proteins in wild-type Arabidopsis and TOR orthologous in major crop plants, including tomato, maize, and alfalfa. Moreover, our α-TOR antibody is useful for coimmunoprecipitation assays. In summary, we generated a polyclonal α-TOR antibody that detects endogenous TOR in various plant species. Our antibody could be used in future studies to determine the precise molecular mechanisms of TOR, which has largely unknown multifunctional roles in plants.

scholarly journals Fibrillar α-synuclein induces neurotoxic astrocyte activation via RIP kinase signaling and NF-κB

2021 ◽  
Vol 12 (8) ◽  
Author(s):  
Tsui-Wen Chou ◽  
Nydia P. Chang ◽  
Medha Krishnagiri ◽  
Aisha P. Patel ◽  
Marissa Lindman ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Biology ◽  
Molecular Mechanisms ◽  
Neurodegenerative Disorder ◽  
Neuronal Cell ◽  
Dopamine Neurons ◽  
Functional Markers ◽  
Kinase Signaling ◽  
Astrocyte Activation ◽  
Transcriptional Responses

AbstractParkinson’s disease (PD) is a neurodegenerative disorder characterized by the death of midbrain dopamine neurons. The pathogenesis of PD is poorly understood, though misfolded and/or aggregated forms of the protein α-synuclein have been implicated in several neurodegenerative disease processes, including neuroinflammation and astrocyte activation. Astrocytes in the midbrain play complex roles during PD, initiating both harmful and protective processes that vary over the course of the disease. However, despite their significant regulatory roles during neurodegeneration, the cellular and molecular mechanisms that promote pathogenic astrocyte activity remain mysterious. Here, we show that α-synuclein preformed fibrils (PFFs) induce pathogenic activation of human midbrain astrocytes, marked by inflammatory transcriptional responses, downregulation of phagocytic function, and conferral of neurotoxic activity. These effects required the necroptotic kinases RIPK1 and RIPK3, but were independent of MLKL and necroptosis. Instead, both transcriptional and functional markers of astrocyte activation occurred via RIPK-dependent activation of NF-κB signaling. Our study identifies a previously unknown function for α-synuclein in promoting neurotoxic astrocyte activation, as well as new cell death-independent roles for RIP kinase signaling in the regulation of glial cell biology and neuroinflammation. Together, these findings highlight previously unappreciated molecular mechanisms of pathologic astrocyte activation and neuronal cell death with implications for Parkinsonian neurodegeneration.

scholarly journals A Novel Mutation of ATP7B Gene in a Case of Wilson Disease

Medicina ◽  
2021 ◽  
Vol 57 (2) ◽  
pp. 123
Author(s):  
Cigdem Yuce Kahraman ◽  
Ali Islek ◽  
Abdulgani Tatar ◽  
Özlem Özdemir ◽  
Adil Mardinglu ◽  
...  
Keyword(s):  
Wilson Disease ◽  
Novel Mutation ◽  
Molecular Genetic ◽  
Molecular Genetic Analysis ◽  
Compound Heterozygous ◽  
Atp7b Gene ◽  
Loss Of Function ◽  
Clinical Presentations ◽  
The Family ◽  
The Brain

Wilson disease (WD) (OMIM# 277900) is an autosomal recessive inherited disorder characterized by excess copper (Cu) storage in different human tissues, such as the brain, liver, and the corneas of the eyes. It is a rare disorder that occurs in approximately 1 in 30,000 individuals. The clinical presentations of WD are highly varied, primarily consisting of hepatic and neurological conditions. WD is caused by homozygous or compound heterozygous mutations in the ATP7B gene. The diagnosis of the disease is complicated because of its heterogeneous phenotypes. The molecular genetic analysis encourages early diagnosis, treatment, and the opportunity to screen individuals at risk in the family. In this paper, we reported a case with a novel, hotspot-located mutation in WD. We have suggested that this mutation in the ATP7B gene might contribute to liver findings, progressing to liver failure with a loss of function effect. Besides this, if patients have liver symptoms in childhood and/or are children of consanguineous parents, WD should be considered during the evaluation of the patients.

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