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Bayat A, Iavarone S, Miceli F, Jakobsen AV, Johannesen KM, Nikanorova M, Ploski R, Szymanska K, Flamini R, Cooper EC, Weckhuysen S, Taglialatela M, Møller RS. Phenotypic and functional assessment of two novel KCNQ2 gain-of-function variants Y141N and G239S and effects of amitriptyline treatment. Neurotherapeutics 2024; 21:e00296. [PMID: 38241158 PMCID: PMC10903081 DOI: 10.1016/j.neurot.2023.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 10/11/2023] [Indexed: 01/21/2024] Open
Abstract
While loss-of-function (LoF) variants in KCNQ2 are associated with a spectrum of neonatal-onset epilepsies, gain-of-function (GoF) variants cause a more complex phenotype that precludes neonatal-onset epilepsy. In the present work, the clinical features of three patients carrying a de novo KCNQ2 Y141N (n = 1) or G239S variant (n = 2) respectively, are described. All three patients had a mild global developmental delay, with prominent language deficits, and strong activation of interictal epileptic activity during sleep. Epileptic seizures were not reported. The absence of neonatal seizures suggested a GoF effect and prompted functional testing of the variants. In vitro whole-cell patch-clamp electrophysiological experiments in Chinese Hamster Ovary cells transiently-transfected with the cDNAs encoding Kv7.2 subunits carrying the Y141N or G239S variants in homomeric or heteromeric configurations with Kv7.2 subunits, revealed that currents from channels incorporating mutant subunits displayed increased current densities and hyperpolarizing shifts of about 10 mV in activation gating; both these functional features are consistent with an in vitro GoF phenotype. The antidepressant drug amitriptyline induced a reversible and concentration-dependent inhibition of current carried by Kv7.2 Y141N and G239S mutant channels. Based on in vitro results, amitriptyline was prescribed in one patient (G239S), prompting a significant improvement in motor, verbal, social, sensory and adaptive behavior skillsduring the two-year-treatment period. Thus, our results suggest that KCNQ2 GoF variants Y141N and G239S cause a mild DD with prominent language deficits in the absence of neonatal seizures and that treatment with the Kv7 channel blocker amitriptyline might represent a potential targeted treatment for patients with KCNQ2 GoF variants.
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Affiliation(s)
- Allan Bayat
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Filadelfia, Dianalund, Denmark; Department for Regional Health Research, University of Southern Denmark, Odense, Denmark; Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - Stefano Iavarone
- Section of Pharmacology, Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | - Francesco Miceli
- Section of Pharmacology, Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | - Anne V Jakobsen
- Department of Pediatrics, Danish Epilepsy Center, Filadelfia, Dianalund, Denmark
| | - Katrine M Johannesen
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Filadelfia, Dianalund, Denmark; Department of Genetics, University Hospital of Copenhagen, Rigshospitalet, Copenhagen, Denmark
| | - Marina Nikanorova
- Department of Pediatrics, Danish Epilepsy Center, Filadelfia, Dianalund, Denmark
| | - Rafal Ploski
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Krystyna Szymanska
- Department of Pediatric Neurology, Medical University of Warsaw, Warsaw, Poland
| | | | - Edward C Cooper
- Departments of Neurology, Neuroscience, and Molecular and Human Genetics, Baylor College of Medicine, Houston TX, USA
| | - Sarah Weckhuysen
- Applied and Translational Genomics Group, VIB-Center for Molecular Neurology, VIB, University of Antwerp, Antwerp, Belgium; Neurology Department, University Hospital Antwerp, Antwerp, Belgium; Translational Neurosciences, Faculty of Medicine and Health Science, University of Antwerp, Antwerp, Belgium; μNEURO Research Centre of Excellence, University of Antwerp, Antwerp, Belgium
| | - Maurizio Taglialatela
- Section of Pharmacology, Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | - Rikke S Møller
- Department of Epilepsy Genetics and Personalized Medicine, Danish Epilepsy Center, Filadelfia, Dianalund, Denmark; Department for Regional Health Research, University of Southern Denmark, Odense, Denmark
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Millevert C, Weckhuysen S. ILAE Genetic Literacy Series: Self-limited familial epilepsy syndromes with onset in neonatal age and infancy. Epileptic Disord 2023; 25:445-453. [PMID: 36939707 DOI: 10.1002/epd2.20026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 12/13/2022] [Accepted: 12/22/2022] [Indexed: 03/21/2023]
Abstract
The self-limited (familial) epilepsies with onset in neonates or infants, formerly called benign familial neonatal and/or infantile epilepsies, are autosomal dominant disorders characterized by neonatal- or infantile-onset focal motor seizures and the absence of neurodevelopmental complications. Seizures tend to remit during infancy or early childhood and are therefore called "self-limited". A positive family history for epilepsy usually suggests the genetic etiology, but incomplete penetrance and de novo inheritance occur. Here, we review the phenotypic spectrum and the genetic architecture of self-limited (familial) epilepsies with onset in neonates or infants. Using an illustrative case study, we describe important clues in recognition of these syndromes, diagnostic steps including genetic testing, management, and genetic counseling.
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Affiliation(s)
- Charissa Millevert
- Applied & Translational Neurogenomics Group, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium
- Department of Neurology, University Hospital, Antwerp, Belgium
| | - Sarah Weckhuysen
- Applied & Translational Neurogenomics Group, VIB Center for Molecular Neurology, VIB, Antwerp, Belgium
- Department of Neurology, University Hospital, Antwerp, Belgium
- μNEURO Research Centre of Excellence, University of Antwerp, Antwerp, Belgium
- Translational Neurosciences, Faculty of Medicine and Health Science, University of Antwerp, Antwerp, Belgium
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Ye J, Tang S, Miao P, Gong Z, Shu Q, Feng J, Li Y. Clinical analysis and functional characterization of KCNQ2-related developmental and epileptic encephalopathy. Front Mol Neurosci 2023; 16:1205265. [PMID: 37497102 PMCID: PMC10366601 DOI: 10.3389/fnmol.2023.1205265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 06/19/2023] [Indexed: 07/28/2023] Open
Abstract
Background Developmental and epileptic encephalopathy (DEE) is a condition characterized by severe seizures and a range of developmental impairments. Pathogenic variants in KCNQ2, encoding for potassium channel subunit, cause KCNQ2-related DEE. This study aimed to examine the relationships between genotype and phenotype in KCNQ2-related DEE. Methods In total, 12 patients were enrolled in this study for genetic testing, clinical analysis, and developmental evaluation. Pathogenic variants of KCNQ2 were characterized through a whole-cell electrophysiological recording expressed in Chinese hamster ovary (CHO) cells. The expression levels of the KCNQ2 subunit and its localization at the plasma membrane were determined using Western blot analysis. Results Seizures were detected in all patients. All DEE patients showed evidence of developmental delay. In total, 11 de novo KCNQ2 variants were identified, including 10 missense variants from DEE patients and one truncating variant from a patient with self-limited neonatal epilepsy (SeLNE). All variants were found to be loss of function through analysis of M-currents using patch-clamp recordings. The functional impact of variants on M-current in heteromericKCNQ2/3 channels may be associated with the severity of developmental disorders in DEE. The variants with dominant-negative effects in heteromeric channels may be responsible for the profound developmental phenotype. Conclusion The mechanism underlying KCNQ2-related DEE involves a reduction of the M-current through dominant-negative effects, and the severity of developmental disorders in DEE may be predicted by the impact of variants on the M-current of heteromericKCNQ2/3 channels.
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Affiliation(s)
- Jia Ye
- National Clinical Research Center for Child Health, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Siyang Tang
- Pediatric Department, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Pu Miao
- Pediatric Department, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Zhefeng Gong
- School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Qiang Shu
- Pediatric Department, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Jianhua Feng
- School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Yuezhou Li
- National Clinical Research Center for Child Health, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, China
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Potassium channelopathies associated with epilepsy-related syndromes and directions for therapeutic intervention. Biochem Pharmacol 2023; 208:115413. [PMID: 36646291 DOI: 10.1016/j.bcp.2023.115413] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023]
Abstract
A number of mutations to members of several CNS potassium (K) channel families have been identified which result in rare forms of neonatal onset epilepsy, or syndromes of which one prominent characteristic is a form of epilepsy. Benign Familial Neonatal Convulsions or Seizures (BFNC or BFNS), also referred to as Self-Limited Familial Neonatal Epilepsy (SeLNE), results from mutations in 2 members of the KV7 family (KCNQ) of K channels; while generally self-resolving by about 15 weeks of age, these mutations significantly increase the probability of generalized seizure disorders in the adult, in some cases they result in more severe developmental syndromes. Epilepsy of Infancy with Migrating Focal Seizures (EIMSF), or Migrating Partial Seizures of Infancy (MMPSI), is a rare severe form of epilepsy linked primarily to gain of function mutations in a member of the sodium-dependent K channel family, KCNT1 or SLACK. Finally, KCNMA1 channelopathies, including Liang-Wang syndrome (LIWAS), are rare combinations of neurological symptoms including seizure, movement abnormalities, delayed development and intellectual disabilities, with Liang-Wang syndrome an extremely serious polymalformative syndrome with a number of neurological sequelae including epilepsy. These are caused by mutations in the pore-forming subunit of the large-conductance calcium-activated K channel (BK channel) KCNMA1. The identification of these rare but significant channelopathies has resulted in a resurgence of interest in their treatment by direct pharmacological or genetic modulation. We will briefly review the genetics, biophysics and pharmacology of these K channels, their linkage with the 3 syndromes described above, and efforts to more effectively target these syndromes.
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Miceli F, Millevert C, Soldovieri MV, Mosca I, Ambrosino P, Carotenuto L, Schrader D, Lee HK, Riviello J, Hong W, Risen S, Emrick L, Amin H, Ville D, Edery P, de Bellescize J, Michaud V, Van-Gils J, Goizet C, Willemsen MH, Kleefstra T, Møller RS, Bayat A, Devinsky O, Sands T, Korenke GC, Kluger G, Mefford HC, Brilstra E, Lesca G, Milh M, Cooper EC, Taglialatela M, Weckhuysen S. KCNQ2 R144 variants cause neurodevelopmental disability with language impairment and autistic features without neonatal seizures through a gain-of-function mechanism. EBioMedicine 2022; 81:104130. [PMID: 35780567 PMCID: PMC9254340 DOI: 10.1016/j.ebiom.2022.104130] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 06/08/2022] [Accepted: 06/10/2022] [Indexed: 01/10/2023] Open
Abstract
Background Prior studies have revealed remarkable phenotypic heterogeneity in KCNQ2-related disorders, correlated with effects on biophysical features of heterologously expressed channels. Here, we assessed phenotypes and functional properties associated with KCNQ2 missense variants R144W, R144Q, and R144G. We also explored in vitro blockade of channels carrying R144Q mutant subunits by amitriptyline. Methods Patients were identified using the RIKEE database and through clinical collaborators. Phenotypes were collected by a standardized questionnaire. Functional and pharmacological properties of variant subunits were analyzed by whole-cell patch-clamp recordings. Findings Detailed clinical information on fifteen patients (14 novel and 1 previously published) was analyzed. All patients had developmental delay with prominent language impairment. R144Q patients were more severely affected than R144W patients. Infantile to childhood onset epilepsy occurred in 40%, while 67% of sleep-EEGs showed sleep-activated epileptiform activity. Ten patients (67%) showed autistic features. Activation gating of homomeric Kv7.2 R144W/Q/G channels was left-shifted, suggesting gain-of-function effects. Amitriptyline blocked channels containing Kv7.2 and Kv7.2 R144Q subunits. Interpretation Patients carrying KCNQ2 R144 gain-of-function variants have developmental delay with prominent language impairment, autistic features, often accompanied by infantile- to childhood-onset epilepsy and EEG sleep-activated epileptiform activity. The absence of neonatal seizures is a robust and important clinical differentiator between KCNQ2 gain-of-function and loss-of-function variants. The Kv7.2/7.3 channel blocker amitriptyline might represent a targeted treatment. Funding Supported by FWO, GSKE, KCNQ2-Cure, Jack Pribaz Foundation, European Joint Programme on Rare Disease 2020, the Italian Ministry for University and Research, the Italian Ministry of Health, the European Commission, the University of Antwerp, NINDS, and Chalk Family Foundation.
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Singh SP, William M, Malavia M, Chu XP. Behavior of KCNQ Channels in Neural Plasticity and Motor Disorders. MEMBRANES 2022; 12:membranes12050499. [PMID: 35629827 PMCID: PMC9143857 DOI: 10.3390/membranes12050499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/26/2022] [Accepted: 05/03/2022] [Indexed: 02/01/2023]
Abstract
The broad distribution of voltage-gated potassium channels (VGKCs) in the human body makes them a critical component for the study of physiological and pathological function. Within the KCNQ family of VGKCs, these aqueous conduits serve an array of critical roles in homeostasis, especially in neural tissue. Moreover, the greater emphasis on genomic identification in the past century has led to a growth in literature on the role of the ion channels in pathological disease as well. Despite this, there is a need to consolidate the updated findings regarding both the pharmacotherapeutic and pathological roles of KCNQ channels, especially regarding neural plasticity and motor disorders which have the largest body of literature on this channel. Specifically, KCNQ channels serve a remarkable role in modulating the synaptic efficiency required to create appropriate plasticity in the brain. This role can serve as a foundation for clinical approaches to chronic pain. Additionally, KCNQ channels in motor disorders have been utilized as a direction for contemporary pharmacotherapeutic developments due to the muscarinic properties of this channel. The aim of this study is to provide a contemporary review of the behavior of these channels in neural plasticity and motor disorders. Upon review, the behavior of these channels is largely dependent on the physiological role that KCNQ modulatory factors (i.e., pharmacotherapeutic options) serve in pathological diseases.
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Arredondo K, Myers C, Hansen-Kiss E, Mathew MT, Jayaraman V, Siemon A, Bartholomew D, Herman GE, Mori M. Phenotypic Spectrum in a Family Sharing a Heterozygous KCNQ3 Variant. J Child Neurol 2022; 37:517-523. [PMID: 35384780 DOI: 10.1177/08830738221089741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND AND PURPOSE Mutations in KCNQ3 have classically been associated with benign familial neonatal and infantile seizures and more recently identified in patients with neurodevelopmental disorders and abnormal electroencephalogram (EEG) findings. We present 4 affected patients from a family with a pathogenic mutation in KCNQ3 with a unique constellation of clinical findings. METHODS A family of 3 affected siblings and mother sharing a KCNQ3 pathogenic variant are described, including clinical history, genetic results, and EEG and magnetic resonance imaging (MRI) findings. RESULTS This family shows a variety of clinical manifestations, including neonatal seizures, developmental delays, autism spectrum disorder, and anxiety. One child developed absence epilepsy, 2 children have infrequent convulsive seizures that have persisted into childhood, and their parent developed adult-onset epilepsy. An underlying c.1091G>A (R364H) variant in KCNQ3 was found in all affected individuals. CONCLUSIONS The phenotypic variability of KCNQ3 channelopathies continues to expand as more individuals and families are described, and the variant identified in this family adds to the understanding of the manifestations of KCNQ3-related disorders.
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Affiliation(s)
- Kristen Arredondo
- Department of Pediatrics, 12306The Ohio State University, Columbus, OH, USA
- Division of Pediatric Neurology, 2650Nationwide Children's Hospital, Columbus, OH, USA
| | - Cortlandt Myers
- Division of Genetic & Genomic Medicine, 2650Nationwide Children's Hospital, Columbus, OH, USA
| | - Emily Hansen-Kiss
- Department of Diagnostic & Biomedical Sciences, 12340University of Texas Health Science Center at Houston, School of Dentistry, Houston, TX, USA
| | - Mariam T Mathew
- Department of Pediatrics, 12306The Ohio State University, Columbus, OH, USA
- Institute for Genomic Medicine, 2650Nationwide Children's Hospital, Columbus, OH, USA
| | - Vijayakumar Jayaraman
- Institute for Genomic Medicine, 2650Nationwide Children's Hospital, Columbus, OH, USA
| | - Amy Siemon
- Division of Genetic & Genomic Medicine, 2650Nationwide Children's Hospital, Columbus, OH, USA
| | - Dennis Bartholomew
- Department of Pediatrics, 12306The Ohio State University, Columbus, OH, USA
- Division of Genetic & Genomic Medicine, 2650Nationwide Children's Hospital, Columbus, OH, USA
| | - Gail E Herman
- Department of Pediatrics, 12306The Ohio State University, Columbus, OH, USA
- Division of Genetic & Genomic Medicine, 2650Nationwide Children's Hospital, Columbus, OH, USA
| | - Mari Mori
- Department of Pediatrics, 12306The Ohio State University, Columbus, OH, USA
- Division of Genetic & Genomic Medicine, 2650Nationwide Children's Hospital, Columbus, OH, USA
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Vanoye CG, Desai RR, Ji Z, Adusumilli S, Jairam N, Ghabra N, Joshi N, Fitch E, Helbig KL, McKnight D, Lindy AS, Zou F, Helbig I, Cooper EC, George AL. High-throughput evaluation of epilepsy-associated KCNQ2 variants reveals functional and pharmacological heterogeneity. JCI Insight 2022; 7:156314. [PMID: 35104249 PMCID: PMC8983144 DOI: 10.1172/jci.insight.156314] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Hundreds of genetic variants in KCNQ2 encoding the voltage-gated potassium channel KV7.2 are associated with early onset epilepsy and/or developmental disability, but the functional consequences of most variants are unknown. Absent functional annotation for KCNQ2 variants hinders identification of individuals who may benefit from emerging precision therapies. We employed automated patch clamp recordings to assess at, to our knowledge, an unprecedented scale the functional and pharmacological properties of 79 missense and 2 inframe deletion KCNQ2 variants. Among the variants we studied were 18 known pathogenic variants, 24 mostly rare population variants, and 39 disease-associated variants with unclear functional effects. We analyzed electrophysiological data recorded from 9,480 cells. The functional properties of 18 known pathogenic variants largely matched previously published results and validated automated patch clamp for this purpose. Unlike rare population variants, most disease-associated KCNQ2 variants exhibited prominent loss-of-function with dominant-negative effects, providing strong evidence in support of pathogenicity. All variants responded to retigabine, although there were substantial differences in maximal responses. Our study demonstrated that dominant-negative loss-of-function is a common mechanism associated with missense KCNQ2 variants. Importantly, we observed genotype-dependent differences in the response of KCNQ2 variants to retigabine, a proposed precision therapy for KCNQ2 developmental and epileptic encephalopathy.
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Affiliation(s)
- Carlos G. Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Reshma R. Desai
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Zhigang Ji
- Departments of Neurology, Neuroscience, Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Sneha Adusumilli
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Nirvani Jairam
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Nora Ghabra
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Nishtha Joshi
- Departments of Neurology, Neuroscience, Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Eryn Fitch
- The Epilepsy NeuroGenetics Initiative (ENGIN), and,Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Katherine L. Helbig
- The Epilepsy NeuroGenetics Initiative (ENGIN), and,Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | | | | | | | - Ingo Helbig
- The Epilepsy NeuroGenetics Initiative (ENGIN), and,Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.,Department of Neurology, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania, USA
| | - Edward C. Cooper
- Departments of Neurology, Neuroscience, Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Alfred L. George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.,Center for Pharmacogenomics, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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Xiong J, Chen S, Chen B, Zhang W, Chen C, Deng X, He F, Zhang C, Yang L, Wang Y, Peng J, Yin F. A novel KCNQ2 missense variant in non-syndromic intellectual disability causes mild gain-of-function of Kv7.2 channel. Clin Chim Acta 2022; 530:74-80. [PMID: 35247435 DOI: 10.1016/j.cca.2022.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 03/01/2022] [Indexed: 11/26/2022]
Abstract
BACKGROUND Heterozygous variants of KCNQ2 can cause KCNQ2 associated neurodevelopmental disorder, mainly are benign (familial) neonatal or infantile epilepsy (B(F)NE or B(F)IE) and early-onset epileptic encephalopathy (EOEE). Moreover, some intermediate phenotypes, including intellectual disability (ID), and myokymia are related to the gene. METHODS We collected a non-syndromic ID male patient with a novel KCNQ2 missense variant. Whole cell electrophysiology, western blotting, and immunofluorescence were adopted to analyze the variant's functional alterations. RESULTS The patient presented with global developmental delay since his infancy. He still had profound ID but did not have epilepsy at the adolescence. The de novo KCNQ2 variant p.R75C (NM_172107) in the NH2 domain identified here showed a slightly hyperpolarized shift of activation curves and larger current density in homomeric configurations, which could be abolished in co-expression with Kv7.2 or Kv7.3 wild-type. Western blotting and immunocytochemistry supported that the expression of variant p.R75C is lower than the Kv7.2 wild-type. The findings indicated variant p.R75C cause mild gain-of-function (GOF) of Kv7.2 channel. CONCLUSIONS We report a non-syndromic ID patient with a KCNQ2 mild GOF variant, adding evidence for this rare clinical phenotype in the disorder. We propose that individuals with KCNQ2 GOF variants are prone to have cognitive impairments.
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Affiliation(s)
- Juan Xiong
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Shimeng Chen
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Baiyu Chen
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Wen Zhang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Chen Chen
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Xiaolu Deng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Fang He
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Ciliu Zhang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Lifen Yang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Ying Wang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Fei Yin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China; Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China.
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