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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] [What about the content of this article? (0)] [Affiliation(s)] [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] [What about the content of this article? (0)] [Affiliation(s)] [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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Okamura Y, Yoshioka D. What voltage-sensing phosphatases can reveal about the mechanisms of ion channel regulation by phosphoinositides. Biochem Soc Trans 2023; 51:827-839. [PMID: 37052219 DOI: 10.1042/bst20221065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 03/20/2023] [Accepted: 03/30/2023] [Indexed: 04/14/2023]
Abstract
Many membrane proteins including ion channels and ion transporters are regulated by membrane phospholipids such as phosphoinositides in cell membranes and organelles. Voltage-sensing phosphatase, VSP, is a voltage-sensitive phosphoinositide phosphatase which dephosphorylates PI(4,5)P2 into PI(4)P. VSP rapidly reduces the level of PI(4,5)P2 upon membrane depolarization, thus serving as a useful tool to quantitatively study phosphoinositide-regulation of ion channels and ion transporters using a cellular electrophysiology system. In this review, we focus on the application of VSPs to Kv7 family potassium channels, which have been important research targets in biophysics, pharmacology and medicine.
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Affiliation(s)
- Yasushi Okamura
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Yamada Oka 2-2, Suita, Osaka 565-0871, Japan
| | - Daisuke Yoshioka
- Laboratory of Integrative Physiology, Department of Physiology, Graduate School of Medicine, Osaka University, Yamada Oka 2-2, Suita, Osaka 565-0871, Japan
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Mosca I, Rivolta I, Labalme A, Ambrosino P, Castellotti B, Gellera C, Granata T, Freri E, Binda A, Lesca G, DiFrancesco JC, Soldovieri MV, Taglialatela M. Functional Characterization of Two Variants at the Intron 6—Exon 7 Boundary of the KCNQ2 Potassium Channel Gene Causing Distinct Epileptic Phenotypes. Front Pharmacol 2022; 13:872645. [PMID: 35770094 PMCID: PMC9234691 DOI: 10.3389/fphar.2022.872645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
Pathogenic variants in KCNQ2 encoding for Kv7.2 potassium channel subunits have been found in patients affected by widely diverging epileptic phenotypes, ranging from Self-Limiting Familial Neonatal Epilepsy (SLFNE) to severe Developmental and Epileptic Encephalopathy (DEE). Thus, understanding the pathogenic molecular mechanisms of KCNQ2 variants and their correlation with clinical phenotypes has a relevant impact on the clinical management of these patients. In the present study, the genetic, biochemical, and functional effects prompted by two variants, each found in a non-familial SLNE or a DEE patient but both affecting nucleotides at the KCNQ2 intron 6-exon 7 boundary, have been investigated to test whether and how they affected the splicing process and to clarify whether such mechanism might play a pathogenetic role in these patients. Analysis of KCNQ2 mRNA splicing in patient-derived lymphoblasts revealed that the SLNE-causing intronic variant (c.928-1G > C) impeded the use of the natural splice site, but lead to a 10-aa Kv7.2 in frame deletion (Kv7.2 p.G310Δ10); by contrast, the DEE-causing exonic variant (c.928G > A) only had subtle effects on the splicing process at this site, thus leading to the synthesis of a full-length subunit carrying the G310S missense variant (Kv7.2 p.G310S). Patch-clamp recordings in transiently-transfected CHO cells and primary neurons revealed that both variants fully impeded Kv7.2 channel function, and exerted strong dominant-negative effects when co-expressed with Kv7.2 and/or Kv7.3 subunits. Notably, Kv7.2 p.G310S, but not Kv7.2 p.G310Δ10, currents were recovered upon overexpression of the PIP2-synthesizing enzyme PIP5K, and/or CaM; moreover, currents from heteromeric Kv7.2/Kv7.3 channels incorporating either Kv7.2 mutant subunits were differentially regulated by changes in PIP2 availability, with Kv7.2/Kv7.2 G310S/Kv7.3 currents showing a greater sensitivity to PIP2 depletion when compared to those from Kv7.2/Kv7.2 G310Δ10/Kv7.3 channels. Altogether, these results suggest that the two variants investigated differentially affected the splicing process at the intron 6-exon 7 boundary, and led to the synthesis of Kv7.2 subunits showing a differential sensitivity to PIP2 and CaM regulation; more studies are needed to clarify how such different functional properties contribute to the widely-divergent clinical phenotypes.
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Affiliation(s)
- Ilaria Mosca
- Department of Medicine and Health Science “V. Tiberio”, University of Molise, Campobasso, Italy
| | - Ilaria Rivolta
- School of Medicine and Surgery, University of Milano-Bicocca, Monza-Center for Neuroscience (NeuroMI), Milan, Italy
| | - Audrey Labalme
- Department of Medical Genetics, Hospices Civils de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Paolo Ambrosino
- Department of Science and Technology (DST), University of Sannio, Benevento, Italy
| | - Barbara Castellotti
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Cinzia Gellera
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Tiziana Granata
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Elena Freri
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Anna Binda
- School of Medicine and Surgery, University of Milano-Bicocca, Monza-Center for Neuroscience (NeuroMI), Milan, Italy
| | - Gaetan Lesca
- Department of Medical Genetics, Hospices Civils de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Jacopo C. DiFrancesco
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
- Department of Neurology, ASST “San Gerardo” Hospital, University of Milano-Bicocca, Monza, Italy
| | - Maria Virginia Soldovieri
- Department of Medicine and Health Science “V. Tiberio”, University of Molise, Campobasso, Italy
- *Correspondence: Maria Virginia Soldovieri, ; Maurizio Taglialatela,
| | - Maurizio Taglialatela
- Department of Neuroscience, University of Naples “Federico II”, Naples, Italy
- *Correspondence: Maria Virginia Soldovieri, ; Maurizio Taglialatela,
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Pant S, Zhang J, Kim EC, Lam K, Chung HJ, Tajkhorshid E. PIP 2-dependent coupling of voltage sensor and pore domains in K v7.2 channel. Commun Biol 2021; 4:1189. [PMID: 34650221 DOI: 10.1038/s42003-021-02729-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 09/23/2021] [Indexed: 01/10/2023] Open
Abstract
Phosphatidylinositol-4,5-bisphosphate (PIP2) is a signaling lipid which regulates voltage-gated Kv7/KCNQ potassium channels. Altered PIP2 sensitivity of neuronal Kv7.2 channel is involved in KCNQ2 epileptic encephalopathy. However, the molecular action of PIP2 on Kv7.2 gating remains largely elusive. Here, we use molecular dynamics simulations and electrophysiology to characterize PIP2 binding sites in a human Kv7.2 channel. In the closed state, PIP2 localizes to the periphery of the voltage-sensing domain (VSD). In the open state, PIP2 binds to 4 distinct interfaces formed by the cytoplasmic ends of the VSD, the gate, intracellular helices A and B and their linkers. PIP2 binding induces bilayer-interacting conformation of helices A and B and the correlated motion of the VSD and the pore domain, whereas charge-neutralizing mutations block this coupling and reduce PIP2 sensitivity of Kv7.2 channels by disrupting PIP2 binding. These findings reveal the allosteric role of PIP2 in Kv7.2 channel activation. Pant et al. describe the mechanism by which PIP2 might regulate homomeric Kv7.2 channels. They identify sites important in the binding of the PIP2 lipid to Kv7.2 channels and propose that the PIP2 binding to a specific site results in the coupling between the voltage sensor domain (VSD) and pore domain (PD), which stabilizes the open state of the channel.
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Chen X, Zhang Y, Ren X, Su Q, Liu Y, Dang X, Qin Y, Yang X, Xing Z, Shen Y, Wang Y, Bai Z, Yeh ETH, Wu H, Qi Y. The SUMO-specific protease SENP2 plays an essential role in the regulation of Kv7.2 and Kv7.3 potassium channels. J Biol Chem 2021; 297:101183. [PMID: 34509475 PMCID: PMC8488601 DOI: 10.1016/j.jbc.2021.101183] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 08/28/2021] [Accepted: 09/08/2021] [Indexed: 11/04/2022] Open
Abstract
Sentrin/small ubiquitin-like modifier (SUMO)-specific protease 2 (SENP2)-deficient mice develop spontaneous seizures in early life because of a marked reduction in M currents, which regulate neuronal membrane excitability. We have previously shown that hyper-SUMOylation of the Kv7.2 and Kv7.3 channels is critically involved in the regulation of the M currents conducted by these potassium voltage-gated channels. Here, we show that hyper-SUMOylation of the Kv7.2 and Kv7.3 proteins reduced binding to the lipid secondary messenger PIP2. CaM1 has been shown to be tethered to the Kv7 subunits via hydrophobic motifs in its C termini and implicated in the channel assembly. Mutation of the SUMOylation sites on Kv7.2 and Kv7.3 specifically resulted in decreased binding to CaM1 and enhanced CaM1-mediated assembly of Kv7.2 and Kv7.3, whereas hyper-SUMOylation of Kv7.2 and Kv7.3 inhibited channel assembly. SENP2-deficient mice exhibited increased acetylcholine levels in the brain and the heart tissue because of increases in the vagal tone induced by recurrent seizures. The SENP2-deficient mice develop seizures followed by a period of sinus pauses or atrioventricular conduction blocks. Chronic administration of the parasympathetic blocker atropine or unilateral vagotomy significantly prolonged the life of the SENP2-deficient mice. Furthermore, we showed that retigabine, an M-current opener, reduced the transcription of SUMO-activating enzyme SAE1 and inhibited SUMOylation of the Kv7.2 and Kv7.3 channels, and also prolonged the life of SENP2-deficient mice. Taken together, the previously demonstrated roles of PIP2, CaM1, and retigabine on the regulation of Kv7.2 and Kv7.3 channel function can be explained by their roles in regulating SUMOylation of this critical potassium channel.
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Affiliation(s)
- Xu Chen
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yuhong Zhang
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Xiang Ren
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Qi Su
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yan Liu
- School of Life Sciences & Research Center for Peptide Drugs, Yan'an University, Yan'an, Shaanxi, China
| | - Xing Dang
- College of Chemistry and Chemical Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi, China
| | - Yuanyuan Qin
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Xinyi Yang
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Zhengcao Xing
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yajie Shen
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China
| | - Yaya Wang
- College of Chemistry and Chemical Engineering, Xi'an University of Science and Technology, Xi'an, Shaanxi, China
| | - Zhantao Bai
- School of Life Sciences & Research Center for Peptide Drugs, Yan'an University, Yan'an, Shaanxi, China
| | - Edward T H Yeh
- Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Hongmei Wu
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China.
| | - Yitao Qi
- Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Developing of Endangered Chinese Crude Drugs in Northwest of China, College of Life Sciences, Shaanxi Normal University, Xi'an, Shaanxi, China.
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Portale A, Comella M, Salomone G, Di Nora A, Marino L, Leonardi R, Praticò AD, Falsaperla R. The Spectrum of KCNQ2- and KCNQ3-Related Epilepsy. Journal of Pediatric Neurology 2021. [DOI: 10.1055/s-0041-1727099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Abstract
KCNQ genes encode for a family of six transmembrane domains, single pore-loop, and K+ channel α-subunits that have a wide range of physiological correlates. In the brain, KCNQ2 and KCNQ3 heteromultimers are thought to underlie the M-current which is essential in raising the threshold for firing an action potential; mutations in these genes may cause several types of infantile epilepsies. KCNQ2-related disorders represent a continuum of overlapping neonatal epileptic phenotypes that range from KCNQ2 benign familial neonatal epilepsy (BFNE), a seizure disorder that occur in children who typically have a normal psychomotor development and are inherited as an autosomal dominant trait, to KCNQ2 early-onset epileptic encephalopathy (EOEE) as the result of a de novo pathogenic variant. KCNQ3-related disorders are rarer and include BFNE, benign familial infantile epilepsy and KCNQ3-related epileptic encephalopathy with intellectual disability with or without seizures and/or cortical visual impairment. For both KCNQ2- and KCNQ3-related disorders, it is possible to use several drugs for different classes of mutations (i.e., gain of function vs. loss of function), and usually their effects vary in relation to the clinical presentation and the phenotype of the patient. However, KCNQ2-EOEE patients have a worse response to treatment than KCNQ2-BFNE patients and usually become drug resistant with multiple daily seizures.
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Affiliation(s)
- Anna Portale
- Unit of Pediatrics, Avola Hospital, Siracusa, Italy
| | - Mattia Comella
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Giulia Salomone
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Alessandra Di Nora
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Lidia Marino
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Roberta Leonardi
- Unit of Rare Diseases of the Nervous System in Childhood, Department of Clinical and Experimental Medicine, Section of Pediatrics and Child Neuropsychiatry, University of Catania, Catania, Italy
| | - Andrea D. Praticò
- Unit of Rare Diseases of the Nervous System in Childhood, Department of Clinical and Experimental Medicine, Section of Pediatrics and Child Neuropsychiatry, University of Catania, Catania, Italy
| | - Raffaele Falsaperla
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
- Unit of Neonatal Intensive Care and Neonatology, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
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Longobardi E, Miceli F, Secondo A, Cicatiello R, Izzo A, Tinto N, Moutton S, Tran Mau-Them F, Vitobello A, Taglialatela M. Generation of an iPSC line (UNINAi001-A) from a girl with neonatal-onset epilepsy and non-syndromic intellectual disability carrying the homozygous KCNQ3 p.PHE534ILEfs*15 variant and of an iPSC line (UNINAi002-A) from a non-carrier, unaffected brother. Stem Cell Res 2021; 53:102311. [PMID: 33799276 DOI: 10.1016/j.scr.2021.102311] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 03/18/2021] [Indexed: 10/21/2022] Open
Abstract
Heterozygous variants in the KCNQ3 gene cause epileptic and/or developmental disorders of varying severity. Here we describe the generation of induced pluripotent stem cells (iPSCs) from a 9-year-old girl with pharmacodependent neonatal-onset epilepsy and intellectual disability who carry a homozygous single-base duplication in exon 12 of KCNQ3 (NM_004519.3: KCNQ3 c.1599dup; KCNQ3 p.PHE534ILEfs*15), and from a non-carrier brother of the proband. For iPSC generation, non-integrating episomal plasmid vectors were used to transfect fibroblasts isolated from skin biopsies. The obtained iPSC lines had a normal karyotype, showed embryonic stem cell-like morphology, expressed pluripotency markers, and possessed trilineage differentiation potential.
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Affiliation(s)
- Elena Longobardi
- Departments of Neuroscience and Molecular Medicine and Medical Biotechnology, University bf Naples "Federico II", Naples, Italy
| | - Francesco Miceli
- Departments of Neuroscience and Molecular Medicine and Medical Biotechnology, University bf Naples "Federico II", Naples, Italy
| | - Agnese Secondo
- Departments of Neuroscience and Molecular Medicine and Medical Biotechnology, University bf Naples "Federico II", Naples, Italy
| | - Rita Cicatiello
- Departments of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy
| | - Antonella Izzo
- Departments of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy
| | - Nadia Tinto
- Departments of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy; CEINGE Advanced Biotechnology, Naples, Italy
| | - Sebastien Moutton
- UFR Des Sciences de Santé, INSERM-Université de Bourgogne UMR1231 GAD "Génétique des Anomalies du Développement", FHU-TRANSLAD, Dijon, France; Reference Center for Developmental Anomalies, Department of Medical Genetics, Dijon University Hospital, Dijon, France
| | - Frédéric Tran Mau-Them
- UFR Des Sciences de Santé, INSERM-Université de Bourgogne UMR1231 GAD "Génétique des Anomalies du Développement", FHU-TRANSLAD, Dijon, France; Unité Fonctionnelle d'Innovation diagnostique des maladies rares, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Antonio Vitobello
- UFR Des Sciences de Santé, INSERM-Université de Bourgogne UMR1231 GAD "Génétique des Anomalies du Développement", FHU-TRANSLAD, Dijon, France; Unité Fonctionnelle d'Innovation diagnostique des maladies rares, FHU-TRANSLAD, CHU Dijon Bourgogne, Dijon, France
| | - Maurizio Taglialatela
- Departments of Neuroscience and Molecular Medicine and Medical Biotechnology, University bf Naples "Federico II", Naples, Italy
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Dirkx N, Miceli F, Taglialatela M, Weckhuysen S. The Role of Kv7.2 in Neurodevelopment: Insights and Gaps in Our Understanding. Front Physiol 2020; 11:570588. [PMID: 33192566 PMCID: PMC7657400 DOI: 10.3389/fphys.2020.570588] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 09/07/2020] [Indexed: 11/13/2022] Open
Abstract
Kv7.2 subunits encoded by the KCNQ2 gene constitute a critical molecular component of the M-current, a subthreshold voltage-gated potassium current controlling neuronal excitability by dampening repetitive action potential firing. Pathogenic loss-of-function variants in KCNQ2 have been linked to epilepsy since 1998, and there is ample functional evidence showing that dysfunction of the channel indeed results in neuronal hyperexcitability. The recent description of individuals with severe developmental delay with or without seizures due to pathogenic variants in KCNQ2 (KCNQ2-encephalopathy) reveals that Kv7.2 channels also have an important role in neurodevelopment. Kv7.2 channels are expressed already very early in the developing brain when key developmental processes such as proliferation, differentiation, and synaptogenesis play a crucial role in brain morphogenesis and maturation. In this review, we will discuss the available evidence for a role of Kv7.2 channels in these neurodevelopmental processes, focusing in particular on insights derived from KCNQ2-related human phenotypes, from the spatio-temporal expression of Kv7.2 and other Kv7 family member, and from cellular and rodent models, highlighting critical gaps and research strategies to be implemented in the future. Lastly, we propose a model which divides the M-current activity in three different developmental stages, correlating with the cell characteristics during these particular periods in neuronal development, and how this can be linked with KCNQ2-related disorders. Understanding these mechanisms can create opportunities for new targeted therapies for KCNQ2-encephalopathy.
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Affiliation(s)
- Nina Dirkx
- Applied and Translational Neurogenomics Group, VIB Center for Molecular Neurology, Vlaams Instituut voor Biotechnologie, Antwerp, Belgium
| | - Francesco Miceli
- Section of Pharmacology, Department of Neuroscience, University of Naples Federico II, Naples, Italy
| | - Maurizio Taglialatela
- Section of Pharmacology, Department of Neuroscience, University of Naples Federico II, Naples, Italy
| | - Sarah Weckhuysen
- Applied and Translational Neurogenomics Group, VIB Center for Molecular Neurology, Vlaams Instituut voor Biotechnologie, Antwerp, Belgium.,Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.,Department of Neurology, Antwerp University Hospital, Antwerp, Belgium
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11
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Miceli F, Carotenuto L, Barrese V, Soldovieri MV, Heinzen EL, Mandel AM, Lippa N, Bier L, Goldstein DB, Cooper EC, Cilio MR, Taglialatela M, Sands TT. A Novel Kv7.3 Variant in the Voltage-Sensing S 4 Segment in a Family With Benign Neonatal Epilepsy: Functional Characterization and in vitro Rescue by β-Hydroxybutyrate. Front Physiol 2020; 11:1040. [PMID: 33013448 PMCID: PMC7498716 DOI: 10.3389/fphys.2020.01040] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 07/29/2020] [Indexed: 01/09/2023] Open
Abstract
Pathogenic variants in KCNQ2 and KCNQ3, paralogous genes encoding Kv7.2 and Kv7.3 voltage-gated K+ channel subunits, are responsible for early-onset developmental/epileptic disorders characterized by heterogeneous clinical phenotypes ranging from benign familial neonatal epilepsy (BFNE) to early-onset developmental and epileptic encephalopathy (DEE). KCNQ2 variants account for the majority of pedigrees with BFNE and KCNQ3 variants are responsible for a much smaller subgroup, but the reasons for this imbalance remain unclear. Analysis of additional pedigrees is needed to further clarify the nature of this genetic heterogeneity and to improve prediction of pathogenicity for novel variants. We identified a BFNE family with two siblings and a parent affected. Exome sequencing on samples from both parents and siblings revealed a novel KCNQ3 variant (c.719T>G; p.M240R), segregating in the three affected individuals. The M240 residue is conserved among human Kv7.2-5 and lies between the two arginines (R5 and R6) closest to the intracellular side of the voltage-sensing S4 transmembrane segment. Whole cell patch-clamp recordings in Chinese hamster ovary (CHO) cells revealed that homomeric Kv7.3 M240R channels were not functional, whereas heteromeric channels incorporating Kv7.3 M240R mutant subunits with Kv7.2 and Kv7.3 displayed a depolarizing shift of about 10 mV in activation gating. Molecular modeling results suggested that the M240R substitution preferentially stabilized the resting state and possibly destabilized the activated state of the Kv7.3 subunits, a result consistent with functional data. Exposure to β-hydroxybutyrate (BHB), a ketone body generated during the ketogenic diet (KD), reversed channel dysfunction induced by the M240R variant. In conclusion, we describe the first missense loss-of-function (LoF) pathogenic variant within the S4 segment of Kv7.3 identified in patients with BFNE. Studied under conditions mimicking heterozygosity, the M240R variant mainly affects the voltage sensitivity, in contrast to previously analyzed BFNE Kv7.3 variants that reduce current density. Our pharmacological results provide a rationale for the use of KD in patients carrying LoF variants in Kv7.2 or Kv7.3 subunits.
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Affiliation(s)
- Francesco Miceli
- Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | - Lidia Carotenuto
- Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | - Vincenzo Barrese
- Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | | | - Erin L Heinzen
- Eshelman School of Pharmacy, Division of Pharmacotherapy and Experimental Therapeutics, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.,Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - Arthur M Mandel
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States
| | - Natalie Lippa
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - Louise Bier
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - David B Goldstein
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - Edward C Cooper
- Departments of Neurology, Neuroscience, and Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Maria Roberta Cilio
- Department of Pediatrics and Institute of Experimental and Clinical Research, Cliniques universitaires Saint-Luc, Université catholique de Louvain, Brussels, Belgium
| | | | - Tristan T Sands
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States.,Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States
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12
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Nappi P, Miceli F, Soldovieri MV, Ambrosino P, Barrese V, Taglialatela M. Epileptic channelopathies caused by neuronal Kv7 (KCNQ) channel dysfunction. Pflugers Arch 2020; 472:881-898. [PMID: 32506321 DOI: 10.1007/s00424-020-02404-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 05/12/2020] [Accepted: 05/18/2020] [Indexed: 11/28/2022]
Abstract
Seizures are the most common neurological manifestation in the newborn period, with an estimated incidence of 1.8-3.5 per 1000 live births. Prolonged or intractable seizures have a detrimental effect on cognition and brain function in experimental animals and are associated with adverse long-term neurodevelopmental sequelae and an increased risk of post-neonatal epilepsy in humans. The developing brain is particularly susceptible to the potentially severe effects of epilepsy, and epilepsy, especially when refractory to medications, often results in a developmental and epileptic encephalopathy (DEE) with developmental arrest or regression. DEEs can be primarily attributed to genetic causes. Given the critical role of potassium (K+) currents with distinct subcellular localization, biophysical properties, modulation, and pharmacological profile in regulating intrinsic electrical properties of neurons and their responsiveness to synaptic inputs, it is not too surprising that genetic research in the past two decades has identified several K+ channel genes as responsible for a large fraction of DEE. In the present article, we review the genetically determined epileptic channelopathies affecting three members of the Kv7 family, namely Kv7.2 (KCNQ2), Kv7.3 (KCNQ3), and Kv7.5 (KCNQ5); we review the phenotypic spectrum of Kv7-related epileptic channelopathies, the different genetic and pathogenetic mechanisms, and the emerging genotype-phenotype correlations which may prove crucial for prognostic predictions, disease management, parental counseling, and individually tailored therapeutic attempts.
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Affiliation(s)
- Piera Nappi
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy
| | - Francesco Miceli
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy
| | | | - Paolo Ambrosino
- Department of Science and Technology (DST), University of Sannio, Benevento, Italy
| | - Vincenzo Barrese
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy
| | - Maurizio Taglialatela
- Section of Pharmacology, Department of Neuroscience, University of Naples, "Federico II", Via Pansini 5, 80131, Naples, Italy.
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13
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Adem GD, Chen G, Shabala L, Chen ZH, Shabala S. GORK Channel: A Master Switch of Plant Metabolism? Trends Plant Sci 2020; 25:434-445. [PMID: 31964604 DOI: 10.1016/j.tplants.2019.12.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 11/23/2019] [Accepted: 12/10/2019] [Indexed: 05/18/2023]
Abstract
Potassium regulates a plethora of metabolic and developmental response in plants, and upon exposure to biotic and abiotic stresses a substantial K+ loss occurs from plant cells. The outward-rectifying potassium efflux GORK channels are central to this stress-induced K+ loss from the cytosol. In the mammalian systems, signaling molecules such as gamma-aminobutyric acid, G-proteins, ATP, inositol, and protein phosphatases were shown to operate as ligands controlling many K+ efflux channels. Here we present the evidence that the same molecules may also regulate GORK channels in plants. This mechanism enables operation of the GORK channels as a master switch of the cell metabolism, thus adjusting intracellular K+ homeostasis to altered environmental conditions, to maximize plant adaptive potential.
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Affiliation(s)
- Getnet D Adem
- Tasmanian Institute for Agriculture, University of Tasmania, Hobart, TAS 7001, Australia
| | - Guang Chen
- Collaborative Innovation Centre for Grain Industry, College of Agriculture, Yangtze University, Jingzhou 434025, China; College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Lana Shabala
- Tasmanian Institute for Agriculture, University of Tasmania, Hobart, TAS 7001, Australia
| | - Zhong-Hua Chen
- School of Science and Health, Western Sydney University, Penrith, NSW 2751, Australia; Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia.
| | - Sergey Shabala
- Tasmanian Institute for Agriculture, University of Tasmania, Hobart, TAS 7001, Australia; International Research Centre for Environmental Membrane Biology, Foshan University, Foshan 528000, China.
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14
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Samanta D. Epileptic spasm and de novo KCNB1 mutation: if it is not one potassium channel, it is another! Acta Neurol Belg 2020; 120:417-420. [PMID: 29808309 DOI: 10.1007/s13760-018-0950-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 05/20/2018] [Indexed: 11/24/2022]
Affiliation(s)
- Debopam Samanta
- Child Neurology Division, Department of Pediatrics, University of Arkansas for Medical Sciences, 1 Children's Way, Little Rock, AR, 72202, USA.
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15
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Allen NM, Weckhuysen S, Gorman K, King MD, Lerche H. Genetic potassium channel-associated epilepsies: Clinical review of the K v family. Eur J Paediatr Neurol 2020; 24:105-116. [PMID: 31932120 DOI: 10.1016/j.ejpn.2019.12.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 12/22/2022]
Abstract
Next-generation sequencing has enhanced discovery of many disease-associated genes in previously unexplained epilepsies, mainly in developmental and epileptic encephalopathies and familial epilepsies. We now classify these disorders according to the underlying molecular pathways, which encompass a diverse array of cellular and sub-cellular compartments/signalling processes including voltage-gated ion-channel defects. With the aim to develop and increase the use of precision medicine therapies, understanding the pathogenic mechanisms and consequences of disease-causing variants has gained major relevance in clinical care. The super-family of voltage-gated potassium channels is the largest and most diverse family among the ion channels, encompassing approximately 80 genes. Key potassium channelopathies include those affecting the KV, KCa and Kir families, a significant proportion of which have been implicated in neurological disease. As for other ion channel disorders, different pathogenic variants within any individual voltage-gated potassium channel gene tend to affect channel protein function differently, causing heterogeneous clinical phenotypes. The focus of this review is to summarise recent clinical developments regarding the key voltage-gated potassium (KV) family-related epilepsies, which now encompasses approximately 12 established disease-associated genes, from the KCNA-, KCNB-, KCNC-, KCND-, KCNV-, KCNQ- and KCNH-subfamilies.
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Affiliation(s)
- Nicholas M Allen
- Department of Paediatrics, National University of Ireland, Galway, Ireland; Department of Paediatrics (Neurology), Galway University Hospital, Ireland; Regenerative Medicine Institute (REMEDI), National University of Ireland, Galway, Ireland.
| | - Sarah Weckhuysen
- Neurogenetics Group, Center for Molecular Neurology, VIB-University of Antwerp, Antwerp, Belgium; Department of Neurology, University Hospital Antwerp, Antwerp, Belgium
| | - Kathleen Gorman
- Department of Paediatric Neurology & Clinical Neurophysiology, Children's Health Ireland at Temple Street, Dublin 1, Ireland; University College Dublin School of Medicine and Medical Science, University College, Dublin, Ireland
| | - Mary D King
- Department of Paediatric Neurology & Clinical Neurophysiology, Children's Health Ireland at Temple Street, Dublin 1, Ireland; University College Dublin School of Medicine and Medical Science, University College, Dublin, Ireland
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute of Clinical Brain Research, University of Tubingen, Germany
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16
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Lauritano A, Moutton S, Longobardi E, Tran Mau‐Them F, Laudati G, Nappi P, Soldovieri MV, Ambrosino P, Cataldi M, Jouan T, Lehalle D, Maurey H, Philippe C, Miceli F, Vitobello A, Taglialatela M. A novel homozygous KCNQ3 loss-of-function variant causes non-syndromic intellectual disability and neonatal-onset pharmacodependent epilepsy. Epilepsia Open 2019; 4:464-475. [PMID: 31440727 PMCID: PMC6698674 DOI: 10.1002/epi4.12353] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/04/2019] [Accepted: 07/28/2019] [Indexed: 12/18/2022] Open
Abstract
OBJECTIVE Heterozygous variants in KCNQ2 or, more rarely, KCNQ3 genes are responsible for early-onset developmental/epileptic disorders characterized by heterogeneous clinical presentation and course, genetic transmission, and prognosis. While familial forms mostly include benign epilepsies with seizures starting in the neonatal or early-infantile period, de novo variants in KCNQ2 or KCNQ3 have been described in sporadic cases of early-onset encephalopathy (EOEE) with pharmacoresistant seizures, various age-related pathological EEG patterns, and moderate/severe developmental impairment. All pathogenic variants in KCNQ2 or KCNQ3 occur in heterozygosity. The aim of this work was to report the clinical, molecular, and functional properties of a new KCNQ3 variant found in homozygous configuration in a 9-year-old girl with pharmacodependent neonatal-onset epilepsy and non-syndromic intellectual disability. METHODS Exome sequencing was used for genetic investigation. KCNQ3 transcript and subunit expression in fibroblasts was analyzed with quantitative real-time PCR and Western blotting or immunofluorescence, respectively. Whole-cell patch-clamp electrophysiology was used for functional characterization of mutant subunits. RESULTS A novel single-base duplication in exon 12 of KCNQ3 (NM_004519.3:c.1599dup) was found in homozygous configuration in the proband born to consanguineous healthy parents; this frameshift variant introduced a premature termination codon (PTC), thus deleting a large part of the C-terminal region. Mutant KCNQ3 transcript and protein abundance was markedly reduced in primary fibroblasts from the proband, consistent with nonsense-mediated mRNA decay. The variant fully abolished the ability of KCNQ3 subunits to assemble into functional homomeric or heteromeric channels with KCNQ2 subunits. SIGNIFICANCE The present results indicate that a homozygous KCNQ3 loss-of-function variant is responsible for a severe phenotype characterized by neonatal-onset pharmacodependent seizures, with developmental delay and intellectual disability. They also reveal difference in genetic and pathogenetic mechanisms between KCNQ2- and KCNQ3-related epilepsies, a crucial observation for patients affected with EOEE and/or developmental disabilities.
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Affiliation(s)
- Anna Lauritano
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Sebastien Moutton
- Reference Center for Developmental Anomalies, Department of Medical GeneticsDijon University HospitalDijonFrance
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
| | - Elena Longobardi
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Frédéric Tran Mau‐Them
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Giusy Laudati
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Piera Nappi
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | | | - Paolo Ambrosino
- Division of Pharmacology, Department of Science and TechnologyUniversity of SannioBeneventoItaly
| | - Mauro Cataldi
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Thibaud Jouan
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Daphné Lehalle
- Reference Center for Developmental Anomalies, Department of Medical GeneticsDijon University HospitalDijonFrance
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
| | - Hélène Maurey
- Service de Neurologie PédiatriqueAPHP, Hôpital Universitaire BicêtreLe Kremlin‐BicêtreFrance
| | - Christophe Philippe
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Francesco Miceli
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Antonio Vitobello
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Maurizio Taglialatela
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
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17
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Sands TT, Miceli F, Lesca G, Beck AE, Sadleir LG, Arrington DK, Schönewolf-Greulich B, Moutton S, Lauritano A, Nappi P, Soldovieri MV, Scheffer IE, Mefford HC, Stong N, Heinzen EL, Goldstein DB, Perez AG, Kossoff EH, Stocco A, Sullivan JA, Shashi V, Gerard B, Francannet C, Bisgaard AM, Tümer Z, Willems M, Rivier F, Vitobello A, Thakkar K, Rajan DS, Barkovich AJ, Weckhuysen S, Cooper EC, Taglialatela M, Cilio MR. Autism and developmental disability caused by KCNQ3 gain-of-function variants. Ann Neurol 2019; 86:181-192. [PMID: 31177578 DOI: 10.1002/ana.25522] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 06/03/2019] [Accepted: 06/06/2019] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Recent reports have described single individuals with neurodevelopmental disability (NDD) harboring heterozygous KCNQ3 de novo variants (DNVs). We sought to assess whether pathogenic variants in KCNQ3 cause NDD and to elucidate the associated phenotype and molecular mechanisms. METHODS Patients with NDD and KCNQ3 DNVs were identified through an international collaboration. Phenotypes were characterized by clinical assessment, review of charts, electroencephalographic (EEG) recordings, and parental interview. Functional consequences of variants were analyzed in vitro by patch-clamp recording. RESULTS Eleven patients were assessed. They had recurrent heterozygous DNVs in KCNQ3 affecting residues R230 (R230C, R230H, R230S) and R227 (R227Q). All patients exhibited global developmental delay within the first 2 years of life. Most (8/11, 73%) were nonverbal or had a few words only. All patients had autistic features, and autism spectrum disorder (ASD) was diagnosed in 5 of 11 (45%). EEGs performed before 10 years of age revealed frequent sleep-activated multifocal epileptiform discharges in 8 of 11 (73%). For 6 of 9 (67%) recorded between 1.5 and 6 years of age, spikes became near-continuous during sleep. Interestingly, most patients (9/11, 82%) did not have seizures, and no patient had seizures in the neonatal period. Voltage-clamp recordings of the mutant KCNQ3 channels revealed gain-of-function (GoF) effects. INTERPRETATION Specific GoF variants in KCNQ3 cause NDD, ASD, and abundant sleep-activated spikes. This new phenotype contrasts both with self-limited neonatal epilepsy due to KCNQ3 partial loss of function, and with the neonatal or infantile onset epileptic encephalopathies due to KCNQ2 GoF. ANN NEUROL 2019;86:181-192.
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Affiliation(s)
- Tristan T Sands
- Department of Neurology, Columbia University Medical Center, New York, NY.,Institute for Genomic Medicine, Columbia University Medical Center, New York, NY
| | - Francesco Miceli
- Section of Pharmacology, Department of Neuroscience, University of Naples "Federico II,", Naples, Italy
| | - Gaetan Lesca
- Department of Medical Genetics, Reference Center for Developmental Anomalies, Civil Hospices of Lyon, Lyon, France.,French Institute of Health and Medical Research U1028, French National Center for Scientific Research UMR5292, Center for Research in Neuroscience in Lyon, Genetics of Neurodevelopment Team, Claude Bernard University Lyon 1, Lyon, France.,Claude Bernard University Lyon 1, Lyon, France
| | - Anita E Beck
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA.,Seattle Children's Hospital, Seattle, WA
| | - Lynette G Sadleir
- Department of Paediatrics and Child Health, University of Otago, Wellington, New Zealand
| | | | - Bitten Schönewolf-Greulich
- Center for Rett Syndrome, Department of Pediatrics and Adolescent Medicine, National Hospital, Copenhagen, Denmark.,Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet and Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Sébastien Moutton
- French Institute of Health and Medical Research U1231, Laboratory of Cognitive Neuroscience UMR1231, Genetics of Developmental Anomalies, Burgundy University, F-21000, Dijon, France
| | - Anna Lauritano
- Section of Pharmacology, Department of Neuroscience, University of Naples "Federico II,", Naples, Italy
| | - Piera Nappi
- Section of Pharmacology, Department of Neuroscience, University of Naples "Federico II,", Naples, Italy
| | - Maria Virginia Soldovieri
- Department of Medicine and Health Sciences "Vincenzo Tiberio", University of Molise, Campobasso, Italy
| | - Ingrid E Scheffer
- University of Melbourne, Austin Health, Royal Children's Hospital, Florey and Murdoch Institutes, Melbourne, Victoria, Australia
| | - Heather C Mefford
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA
| | - Nicholas Stong
- Institute for Genomic Medicine, Columbia University Medical Center, New York, NY
| | - Erin L Heinzen
- Institute for Genomic Medicine, Columbia University Medical Center, New York, NY
| | - David B Goldstein
- Institute for Genomic Medicine, Columbia University Medical Center, New York, NY
| | - Ana Grijalvo Perez
- Department of Neurology, University of California, San Francisco, San Francisco, CA
| | - Eric H Kossoff
- Departments of Pediatrics and Neurology, Johns Hopkins School of Medicine, Baltimore, MD
| | - Amber Stocco
- Pediatric Neurology, INTEGRIS Baptist Medical Center, Oklahoma City, OK
| | - Jennifer A Sullivan
- Division of Medical Genetics, Department of Pediatrics, Duke University, Durham, NC
| | - Vandana Shashi
- Division of Medical Genetics, Department of Pediatrics, Duke University, Durham, NC
| | - Benedicte Gerard
- Molecular Genetic Unit, Strasbourg University Hospital, Strasbourg, France
| | - Christine Francannet
- Genetics Department, Reference Center for Developmental Anomalies, Clermont-Ferrand University Hospital, Clermont-Ferrand, France
| | - Anne-Marie Bisgaard
- Center for Rett Syndrome, Department of Pediatrics and Adolescent Medicine, National Hospital, Copenhagen, Denmark
| | - Zeynep Tümer
- Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet and Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.,Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Marjolaine Willems
- Reference Center for Developmental Disorders, Department of Medical Genetics, Arnaud de Villeneuve Hospital, Montpellier University Hospital, Montpellier, France
| | - François Rivier
- Department of Pediatric Neurology, University Hospital of Montpellier, and Physiology and Experimental Medicine of Heart and Muscle Unit, University of Montpellier, National Institute for Health and Medical Research, French National Center for Scientific Research, Montpellier, France
| | - Antonio Vitobello
- Functional Unit 12, Innovation in Genomic Diagnosis of Rare Diseases, University Hospital Dijon-Bourgogne, Dijon, France
| | - Kavita Thakkar
- Division of Neurology, Department of Pediatrics, Children's Hospital of Pittsburgh and University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Deepa S Rajan
- Division of Neurology, Department of Pediatrics, Children's Hospital of Pittsburgh and University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - A James Barkovich
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA
| | - Sarah Weckhuysen
- Neurogenetics Group, University of Antwerp, Antwerp, Belgium.,Neurology Department, University Hospital Antwerp, Antwerp, Belgium
| | - Edward C Cooper
- Departments of Neurology, Neuroscience, and Molecular and Human Genetics, Baylor College of Medicine, Houston, TX
| | - Maurizio Taglialatela
- Section of Pharmacology, Department of Neuroscience, University of Naples "Federico II,", Naples, Italy
| | - M Roberta Cilio
- Department of Neurology, University of California, San Francisco, San Francisco, CA.,Departments of Pediatrics and Institute of Experimental and Clinical Research, University of Louvain, Brussels, Belgium
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Trinh J, Kandaswamy KK, Werber M, Weiss MER, Oprea G, Kishore S, Lohmann K, Rolfs A. Novel pathogenic variants and multiple molecular diagnoses in neurodevelopmental disorders. J Neurodev Disord 2019; 11:11. [PMID: 31238879 DOI: 10.1186/s11689-019-9270-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 05/23/2019] [Indexed: 01/27/2023] Open
Abstract
Background Rare denovo variants represent a significant cause of neurodevelopmental delay and intellectual disability (ID). Methods Exome sequencing was performed on 4351 patients with global developmental delay, seizures, microcephaly, macrocephaly, motor delay, delayed speech and language development, or ID according to Human Phenotype Ontology (HPO) terms. All patients had previously undergone whole exome sequencing as part of diagnostic genetic testing with a focus on variants in genes implicated in neurodevelopmental disorders up to January 2017. This resulted in a genetic diagnosis in 1336 of the patients. In this study, we specifically searched for variants in 14 recently implicated novel neurodevelopmental disorder (NDD) genes. Results We identified 65 rare, protein-changing variants in 11 of these 14 novel candidate genes. Fourteen variants in CDK13, CHD4, KCNQ3, KMT5B, TCF20, and ZBTB18 were scored pathogenic or likely pathogenic. Of note, two of these patients had a previously identified cause of their disease, and thus, multiple molecular diagnoses were made including pathogenic/likely pathogenic variants in FOXG1 and CDK13 or in TMEM237 and KMT5B. Conclusions Looking for pathogenic variants in newly identified NDD genes enabled us to provide a molecular diagnosis to 14 patients and their close relatives and caregivers. This underlines the relevance of re-evaluation of existing exome data on a regular basis to improve the diagnostic yield and serve the needs of our patients. Electronic supplementary material The online version of this article (10.1186/s11689-019-9270-4) contains supplementary material, which is available to authorized users.
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