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Galano M, Ezzat S, Papadopoulos V. SCP2 variant is associated with alterations in lipid metabolism, brainstem neurodegeneration, and testicular defects. Hum Genomics 2022; 16:32. [PMID: 35996156 PMCID: PMC9396802 DOI: 10.1186/s40246-022-00408-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/11/2022] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND The detoxification of very long-chain and branched-chain fatty acids and the metabolism of cholesterol to form bile acids occur largely through a process called peroxisomal β-oxidation. Mutations in several peroxisomal proteins involved in β-oxidation have been reported, resulting in diseases characterized by neurological defects. The final step of the peroxisomal β-oxidation pathway is catalyzed by sterol carrier protein-x (SCPx), which is encoded by the SCP2 gene. Previously, there have been two reports of SCPx deficiency, which resulted from a homozygous or compound heterozygous SCP2 mutation. We report herein the first patient with a heterozygous SCP2 mutation leading to SCPx deficiency. RESULTS Clinical presentations of the patient included progressive brainstem neurodegeneration, cardiac dysrhythmia, muscle wasting, and azoospermia. Plasma fatty acid analysis revealed abnormal values of medium-, long-, and very long-chain fatty acids. Protein expression of SCPx and other enzymes involved in β-oxidation were altered between patient and normal fibroblasts. RNA sequencing and lipidomic analyses identified metabolic pathways that were altered between patient and normal fibroblasts including PPAR signaling, serotonergic signaling, steroid biosynthesis, and fatty acid degradation. Treatment with fenofibrate or 4-hydroxytamoxifen increased SCPx levels, and certain fatty acid levels in patient fibroblasts. CONCLUSIONS These findings suggest that the patient's SCP2 mutation resulted in decreased protein levels of SCPx, which may be associated with many metabolic pathways. Increasing SCPx levels through pharmacological interventions may reverse some effects of SCPx deficiency. Collectively, this work provides insight into many of the clinical consequences of SCPx deficiency and provides evidence for potential treatment strategies.
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Affiliation(s)
- Melanie Galano
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, 1985 Zonal Ave, Los Angeles, CA, 90089, USA
| | - Shereen Ezzat
- Department of Medicine, University of Toronto and Princess Margaret Cancer Center, Toronto, ON, M5G 2C1, Canada
| | - Vassilios Papadopoulos
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, 1985 Zonal Ave, Los Angeles, CA, 90089, USA.
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Rezkalla N, Imam K, Marti M, Ip K, Mashhadian A, Liu A. CACNA1S Arg528Cys mutation in a young Chinese man with thyrotoxic hypokalemic periodic paralysis. Clin Case Rep 2020; 8:1962-1964. [PMID: 33088529 PMCID: PMC7562840 DOI: 10.1002/ccr3.3054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/14/2020] [Accepted: 05/26/2020] [Indexed: 11/27/2022] Open
Abstract
It has long been believed that the patients with thyrotoxic hypokalemic periodic paralysis (THPP) may harbor genetic mutations commonly found in familial hypokalemic periodic paralysis. Despite extensive testing, such a mutation has escaped detection until now.
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Affiliation(s)
| | - Kamran Imam
- Department of Neurology Adventist Health White Memorial Los Angeles California USA
| | - Miriam Marti
- Department of Neurology Adventist Health White Memorial Los Angeles California USA
| | - Karen Ip
- Department of Neurology Adventist Health White Memorial Los Angeles California USA
| | - Ardavan Mashhadian
- Department of Nephrology California Hospital Medical Center Los Angeles California USA
| | - Antonio Liu
- Department of Neurology Adventist Health White Memorial Los Angeles California USA
- Department of Neurology California Hospital Medical Center Los Angeles California USA
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Prevalence and mutation spectrum of skeletal muscle channelopathies in the Netherlands. Neuromuscul Disord 2018; 28:402-407. [PMID: 29606556 DOI: 10.1016/j.nmd.2018.03.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Revised: 02/07/2018] [Accepted: 03/05/2018] [Indexed: 11/21/2022]
Abstract
Few reliable data exist on the prevalence of skeletal muscle channelopathies. We determined the minimum point prevalence of genetically-defined skeletal muscle channelopathies in the Netherlands and report their mutation spectrum. Minimum point prevalence rates were calculated as number of genetically-confirmed skeletal muscle channelopathy patients (CLCN1, SCN4A, CACNA1S and KCNJ2 gene mutations) in the Netherlands (1990-2015) divided by the total number of at-risk individuals. Rates were expressed as cases/100.000 and 95% confidence intervals were calculated based on Poisson distribution. Results of standardized genetic diagnostic procedures were used to analyze mutation spectra. We identified 405 patients from 234 unrelated pedigrees, resulting in a minimum point prevalence of 2.38/100.000 (95% CI 2.16-2.63) for skeletal muscle channelopathies in the Netherlands. Minimum point prevalence rates for the disease groups, non-dystrophic myotonia and periodic paralysis, were 1.70/100.000 and 0.69/100.000 respectively. Sixty-one different CLCN1 mutations (including 12 novel mutations) were detected in myotonia congenita. Twenty-eight different SCN4A missense mutations (including three novel mutations) were identified in paramyotonia congenita/sodium channel myotonia, hypokalemic periodic paralysis and hyperkalemic periodic paralysis. Four different CACNA1S missense mutations were detected in hypokalemic periodic paralysis and five KCNJ2 missense mutations in Andersen-Tawil syndrome. The minimum point prevalence rates for genetically-defined skeletal muscle channelopathies confirm their rare disease status in the Netherlands. Rates are almost twice as high as in the UK and more in line with pre-genetic prevalence estimates in parts of Scandinavia. Future diagnostic and therapeutic studies may benefit from knowledge of the mutation spectrum of skeletal muscle channelopathies.
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Stunnenberg BC, Deinum J, Links TP, Wilde AA, Franssen H, Drost G. Cardiac arrhythmias in hypokalemic periodic paralysis: Hypokalemia as only cause? Muscle Nerve 2014; 50:327-32. [PMID: 25088161 DOI: 10.1002/mus.24225] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2014] [Indexed: 12/14/2022]
Abstract
It is unknown how often cardiac arrhythmias occur in hypokalemic periodic paralysis (HypoPP) and if they are caused by hypokalemia alone or other factors. This systematic review shows that cardiac arrhythmias were reported in 27 HypoPP patients. Cases were confirmed genetically (13 with an R528H mutation in CACNA1S, 1 an R669H mutation in SCN4A) or had a convincing clinical diagnosis of HypoPP (13 genetically undetermined) if reported prior to the availability of genetic testing. Arrhythmias occurred during severe hypokalemia (11 patients), between attacks at normokalemia (4 patients), were treatment-dependent (2 patients), or unspecified (10 patients). Nine patients died from arrhythmia. Convincing evidence for a pro-arrhythmogenic factor other than hypokalemia is still lacking. The role of cardiac expression of defective skeletal muscle channels in the heart of HypoPP patients remains unclear. Clinicians should be aware of and prevent treatment-induced cardiac arrhythmia in HypoPP.
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Affiliation(s)
- Bas C Stunnenberg
- Donders Institute for Brain, Cognition and Behaviour, Department of Neurology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Zhou H, Lillis S, Loy RE, Ghassemi F, Rose MR, Norwood F, Mills K, Al-Sarraj S, Lane RJM, Feng L, Matthews E, Sewry CA, Abbs S, Buk S, Hanna M, Treves S, Dirksen RT, Meissner G, Muntoni F, Jungbluth H. Multi-minicore disease and atypical periodic paralysis associated with novel mutations in the skeletal muscle ryanodine receptor (RYR1) gene. Neuromuscul Disord 2010; 20:166-73. [PMID: 20080402 DOI: 10.1016/j.nmd.2009.12.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Revised: 12/06/2009] [Accepted: 12/15/2009] [Indexed: 11/26/2022]
Abstract
The skeletal muscle ryanodine receptor plays a crucial role in excitation-contraction (EC) coupling and is implicated in various congenital myopathies. The periodic paralyses are a heterogeneous, dominantly inherited group of conditions mainly associated with mutations in the SCN4A and the CACNA1S genes. The interaction between RyR1 and DHPR proteins underlies depolarization-induced Ca(2+) release during EC coupling in skeletal muscle. We report a 35-year-old woman presenting with signs and symptoms of a congenital myopathy at birth and repeated episodes of generalized, atypical normokalaemic paralysis in her late teens. Genetic studies of this patient revealed three heterozygous RYR1 substitutions (p.Arg2241X, p.Asp708Asn and p.Arg2939Lys) associated with marked reduction of the RyR1 protein and abnormal DHPR distribution. We conclude that RYR1 mutations may give rise to both myopathies and atypical periodic paralysis, and RYR1 mutations may underlie other unresolved cases of periodic paralysis with unusual features.
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Affiliation(s)
- Haiyan Zhou
- Dubowitz Neuromuscular Centre, UCL Institute of Child Health & Great Ormond Street Hospital for Children, London, UK
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Carpenter D, Ringrose C, Leo V, Morris A, Robinson RL, Halsall PJ, Hopkins PM, Shaw MA. The role of CACNA1S in predisposition to malignant hyperthermia. BMC MEDICAL GENETICS 2009; 10:104. [PMID: 19825159 PMCID: PMC2770053 DOI: 10.1186/1471-2350-10-104] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Accepted: 10/13/2009] [Indexed: 01/19/2023]
Abstract
BACKGROUND Malignant hyperthermia (MH) is an inherited pharmacogenetic disorder of skeletal muscle, characterised by an elevated calcium release from the skeletal muscle sarcoplasmic reticulum. The dihydropyridine receptor (DHPR) plays an essential role in excitation-contraction coupling and calcium homeostasis in skeletal muscle. This study focuses on the gene CACNA1S which encodes the alpha1 subunit of the DHPR, in order to establish whether CACNA1S plays a major role in MH susceptibility in the UK. METHODS We investigate the CACNA1S locus in detail in 50 independent MH patients, the largest study to date, to identify novel variants that may predispose to disease and also to characterise the haplotype structure across CACNA1S. RESULTS We present CACNA1S cDNA sequencing data from 50 MH patients in whom RYR1 mutations have been excluded, and subsequent mutation screening analysis. Furthermore we present haplotype analysis of unphased CACNA1S SNPs to (1) assess CACNA1S haplotype frequency differences between susceptible MH cases and a European control group and (2) analyse population-based association via clustering of CACNA1S haplotypes based on disease risk. CONCLUSION The study identified a single potentially pathogenic change in CACNA1S (p.Arg174Trp), and highlights that the haplotype structure across CACNA1S is diverse, with a high degree of variability.
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Affiliation(s)
- Danielle Carpenter
- MH Investigation Unit, Academic Unit of Anaesthesia, St James's University Hospital, Leeds, LS9 7TF, UK.
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Fontaine B, Fournier E, Sternberg D, Vicart S, Tabti N. Hypokalemic periodic paralysis: a model for a clinical and research approach to a rare disorder. Neurotherapeutics 2007; 4:225-32. [PMID: 17395132 DOI: 10.1016/j.nurt.2007.01.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Rare diseases have attracted little attention in the past from physicians and researchers. The situation has recently changed for several reasons. First, patient associations have successfully advocated their cause to institutions and governments. They were able to argue that, taken together, rare diseases affect approximately 10% of the population in developed countries. Second, almost 80% of rare diseases are of genetic origin. Advances in genetics have enabled the identification of the causative genes. Unprecedented financial support has been dedicated to research on rare diseases, as well as to the development of referral centers aimed at improving the quality of care. This expenditure of resources is justified by the experience in cystic fibrosis, which demonstrated that improved care delivered by specialized referral centers resulted in a dramatic increase of life expectancy. Moreover, clinical referral centers offer the unique possibility of developing high quality clinical research studies, not otherwise possible because of the geographic dispersion of patients. This is the case in France where national referral centers for rare diseases were created, including one for muscle channelopathies. The aim of this center is to develop appropriate care, clinical research, and teaching on periodic paralysis and myotonia. In this review, we plan to demonstrate how research has improved our knowledge of hypokalemic periodic paralysis and the way we evaluate, advise, and treat patients. We also advocate for the establishment of international collaborations, which are mandatory for the follow-up of cohorts and conduct of definitive therapeutic trials in rare diseases.
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Affiliation(s)
- Bertrand Fontaine
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR S546, Paris, France.
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Dranchak PK, Valberg SJ, Onan GW, Gallant EM, Binns MM, Swinburne JE, Mickelson JR. Exclusion of linkage of theRYR1, CACNA1S, andATP2A1genes to recurrent exertional rhabdomyolysis in Thoroughbreds. Am J Vet Res 2006; 67:1395-400. [PMID: 16881852 DOI: 10.2460/ajvr.67.8.1395] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine whether there was genetic linkage between the recurrent exertional rhabdomyolysis (RER) trait in Thoroughbred horse pedigrees and DNA markers in genes (the sarcoplasmic reticulum calcium release channel [RYR1] gene, the sarcoplasmic reticulum calcium ATPase [ATP2A1] gene, and the transverse tubule dihydropyridine receptor-voltage sensor [CACNA1S] gene) that are important in myoplasmic calcium regulation. ANIMALS 34 horses in the University of Minnesota RER resource herd and 62 Thoroughbreds from 3 families of Thoroughbreds outside of the university in which RER-affected status was assigned after 2 or more episodes of ER had been observed. PROCEDURES Microsatellite DNA markers from the RYR1, ATP2A1, and CACNA1S gene loci on equine chromosomes 10, 13, and 30 were identified. Genotypes were obtained for all horses in the 4 families affected by RER, and data were used to test for linkage of these 3 loci to the RER phenotype. RESULTS Analysis of the RYR1, CACNA1S, and ATP2A1 microsatellites excluded a link between those markers and the RER trait. CONCLUSIONS AND CLINICAL RELEVANCE It is likely that the heritable alterations in muscle contractility that are characteristic of RER are caused by a gene that is not yet known to cause related muscle disease in other species.
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Affiliation(s)
- Patricia K Dranchak
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, 55108, USA
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Marchant CL, Ellis FR, Halsall PJ, Hopkins PM, Robinson RL. Mutation analysis of two patients with hypokalemic periodic paralysis and suspected malignant hyperthermia. Muscle Nerve 2004; 30:114-7. [PMID: 15221887 DOI: 10.1002/mus.20068] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Hypokalemic periodic paralysis (HypoPP) and malignant hyperthermia (MH) are autosomal-dominant genetically heterogeneous ion channelopathies. MH has been described in patients with HypoPP, suggesting a potential link between these disorders. However, a common genetic determinant has not been described. With the aim of corroborating this association, four candidate genes were screened in two independent HypoPP patients, one of whom was also diagnosed as MH-susceptible and the other as MH-normal by the in vitro contracture test (IVCT). An A>G change at nucleotide 7025 was detected in the RYR1 gene in the HypoPP/MH-susceptible patient. Detection of the same mutation in three independent MH families suggested that 7025A>G represents a novel MH-susceptibility allele and that MH and HypoPP occurred independently in the case presented. Conclusive evidence in support of the hypothesis that MH and HypoPP are allelic was therefore not obtained.
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Affiliation(s)
- Clare L Marchant
- Malignant Hyperthermia Investigation Unit, Academic Unit of Anesthesia, Level 8 Clinical Sciences Building, St. James University Hospital, Beckett Street, Leeds LS9 7TF, UK
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Abstract
The generation of the surface electromyogram (sEMG) is described with regard to the properties of the single muscle fiber action potential as source, the physical aspects of volume conduction and recording configuration, and the properties and firing pattern of motor units (MUs). The spatial aspect of the motor unit action potential (MUP) is emphasized in relation to the results of high-density, multichannel sEMG measurements. The endplate zone, depth, size, and position of MUs can be estimated. The use of muscle fiber conduction velocity measurements in channelopathies and the changes in pathological fatigue are described. Using the unique patterns of spatial spread of MUPs over the skin (MU fingerprint), MU classification and the determination of firing moments is done noninvasively. Clinical applications of high-density sEMG measurements are reviewed. Emerging possibilities provided by MUP size and fingerprint measurements in neuromuscular disease and motor control are discussed. We conclude that multichannel sEMG adds unique, and sometimes indispensable, spatial information to our knowledge of the motor unit.
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Affiliation(s)
- Machiel J Zwarts
- Department of Clinical Neurophysiology, Institute of Neurology, University Medical Center Nijmegen, PO Box 9101, NL-6500HB Nijmegen, The Netherlands.
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Day JW, Sakamoto C, Parry GJ, Lehmann-Horn F, Iaizzo PA. Force assessment in periodic paralysis after electrical muscle stimulation. Mayo Clin Proc 2002; 77:232-40. [PMID: 11888026 DOI: 10.4065/77.3.232] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To obtain an objective measure of muscle force in periodic paralysis, we studied ankle dorsiflexion torque during induced paralytic attacks in hyperkalemic and hypokalemic patients. SUBJECTS, PATIENTS, AND METHODS: Dorsiflexor torque after peroneal nerve stimulation was recorded during provocative tests on 5 patients with hypokalemic or hyperkalemic disorders and on 2 control subjects (1995-2001). Manual strength assessment was simultaneously performed in a blinded fashion. Standardized provocation procedures were used. RESULTS The loss of torque in hyperkalemic patients roughly paralleled the loss of clinically detectable strength, whereas in the hypokalemic patients, pronounced torque loss occurred well before observed clinical effects. No dramatic changes occurred in the control subjects. Torque amplitude decreased more than 70% in all patients during the provocation tests; such decreases were associated with alterations induced in serum potassium concentrations. CONCLUSIONS Stimulated torque measurement offers several advantages in characterizing muscle dysfunction in periodic paralysis: (1) it is independent of patient effort; (2) it can show a definitely abnormal response early during provocative maneuvers; and (3) characteristics of muscle contraction can be measured that are unobservable during voluntary contraction. Stimulated torque measurements can characterize phenotypic muscle function in neuromuscular diseases.
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Affiliation(s)
- John W Day
- Department of Neurology, University of Minnesota School of Medicine, Minneapolis 55455, USA
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Abstract
OBJECTIVE To review the structure and function of membrane ion channels with special emphasis on inherited nervous system channel disorders or channelopathies. RESULTS Channels are pores in the cell membrane. Through these pores ions flow across the membrane and depolarize or hyperpolarize the cell. Channels can be classified into 3 types: non-gated, directly gated and second messenger gated channels. Among the important directly gated channels are voltage gated (Na(+), K(+), Ca(2+), Cl(-)) and ligand gated (ACh, Glutamate, GABA, Glycine) channels. Channels are macromolecular protein complexes within the lipid membrane. They are divided into distinct protein units called subunits. Each subunit has a specific function and is encoded by a different gene. The following inherited channelopathies are described. (1) Sodium channelopathies: familial generalized epilepsy with febrile seizures plus, hyperkalemic periodic paralysis, paramyotonias, hypokalemic periodic paralysis; (2) potassium channelopathies: benign infantile epilepsy, episodic ataxia type 1; (3) calcium channelopathies: episodic ataxia type 2, spinocerebellar ataxia type 6, familial hemiplegic migraine, hypokalemic periodic paralysis, central core disease, malignant hyperthermia syndrome, congenital stationary night blindness; (4) chloride channelopathies: myotonia congenitas; (5) ACh receptor channelopathies: autosomal dominant frontal lobe nocturnal epilepsy, congenital myasthenic syndromes; (6) glycine receptor channelopathies: hyperekplexia. CONCLUSIONS Studies of human inherited channelopathies have clarified the functions of many ion channels. More than one gene may regulate a function in a channel, thus different genetic mutations may manifest with the same disorder. The complex picture of the genetic and molecular structures of channels will require frequent updates.
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Affiliation(s)
- G G Celesia
- Department of Neurology, Loyola University Chicago, Stritch School of Medicine, 2160 S. First Avenue, IL, Maywood, USA.
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Wada T, Yachie A, Fujita S, Takei K, Sumita R, Ichihara T, Koizumi S. Hypokalemic periodic paralysis and mutations in the CACNL1A3 gene: case study in a Japanese family. Pediatr Int 2000; 42:325-7. [PMID: 10881598 DOI: 10.1046/j.1442-200x.2000.01214.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- T Wada
- Department of Pediatrics, Faculty of Medicine, Kanazawa University School of Medicine, Japan.
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Abstract
By the introduction of technological advancement in methods of structural analysis, electronics, and recombinant DNA techniques, research in physiology has become molecular. Additionally, focus of interest has been moving away from classical physiology to become increasingly centered on mechanisms of disease. A wonderful example for this development, as evident by this review, is the field of ion channel research which would not be nearly as advanced had it not been for human diseases to clarify. It is for this reason that structure-function relationships and ion channel electrophysiology cannot be separated from the genetic and clinical description of ion channelopathies. Unique among reviews of this topic is that all known human hereditary diseases of voltage-gated ion channels are described covering various fields of medicine such as neurology (nocturnal frontal lobe epilepsy, benign neonatal convulsions, episodic ataxia, hemiplegic migraine, deafness, stationary night blindness), nephrology (X-linked recessive nephrolithiasis, Bartter), myology (hypokalemic and hyperkalemic periodic paralysis, myotonia congenita, paramyotonia, malignant hyperthermia), cardiology (LQT syndrome), and interesting parallels in mechanisms of disease emphasized. Likewise, all types of voltage-gated ion channels for cations (sodium, calcium, and potassium channels) and anions (chloride channels) are described together with all knowledge about pharmacology, structure, expression, isoforms, and encoding genes.
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Affiliation(s)
- F Lehmann-Horn
- Department of Applied Physiology, University of Ulm, Ulm, Germany.
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Abstract
Calcium channels that are regulated by voltage have an important role in linking cellular stimulation to physiological responses in the nervous system. In addition, a number of autoimmune or genetic disorders that affect calcium channels (channelopathies) have been identified, including several that affect neuromuscular function. These include the Lambert-Eaton myasthenic syndrome, which is associated with autoantibodies directed against neuronal calcium channels, as well as at least two inherited neuromuscular diseases-hypokalemic periodic paralysis and some varieties of malignant hyperthermia-that affect calcium channels in skeletal muscle. Preliminary progress has been achieved in understanding the relationship between these immunological or genetic abnormalities and the alterations in channel function that they produce. A major challenge that remains is to determine how calcium channelopathies lead to the curious assortment of paroxysmal and progressive disorders that are observed clinically.
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Affiliation(s)
- D A Greenberg
- Buck Center for Research in Aging, Novato, California, USA
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Abstract
Channels involved in the influx and intracellular mobilization of calcium have been implicated as targets of diverse genetic and immune-mediated neurological diseases. These include the L-type voltage-gated calcium channel of skeletal muscle (hypokalemic periodic paralysis), the neuronal P/Q-type voltage-gated calcium channel (familial hemiplegic migraine, episodic ataxia type 2, spinocerebellar ataxia 6, and Lambert-Eaton myasthenic syndrome), and the skeletal muscle ryanodine receptor (malignant hyperthermia and central core disease). The discovery of these and other calcium channelopathies should help to clarify how different mutations affect channel function and how altered channel function produces disease, and may lead to new treatments for these conditions.
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Affiliation(s)
- D A Greenberg
- Department of Neurology, University of Pittsburgh School of Medicine, PA 15213, USA
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Lapie P, Lory P, Fontaine B. Hypokalemic periodic paralysis: an autosomal dominant muscle disorder caused by mutations in a voltage-gated calcium channel. Neuromuscul Disord 1997; 7:234-40. [PMID: 9196905 DOI: 10.1016/s0960-8966(97)00435-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Hypokalemic periodic paralysis (hypoPP) is an autosomal dominant disorder characterized by acute attacks of muscle weakness concomitant to a drop in blood potassium levels. Recent molecular work has shown that hypoPP is due to mutations in a skeletal muscle voltage-gated calcium channel: the dihydropyridine receptor (DHP receptor). Mutations affect segments S4 of domains II and IV, changing an arginine in position 528 and 1239 into an histidine, or an histidine or a glycine respectively. Surprisingly, expressing in vitro mutants channels in a non-muscular environment resulted in functional calcium channels with minor modifications in electrophysiological properties. Expressing mutant channels in a muscular environment or transgenic mice might help to bridge the gap between the knowledge of the molecular defect and the understanding of the pathophysiology of the disease.
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Affiliation(s)
- P Lapie
- INSERM CJF96108, Hôpital de la Salpêtrière, Paris, France
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Abstract
In Caenorhabditis elegans necrosis-like neuronal death is induced by gain-of-function (gf) mutations in two genes, mec-4 and deg-1, that encode proteins similar to subunits of the vertebrate amiloride-sensitive epithelial Na+ channel. We have determined the progress of cellular pathology in dying neurons via light and electron microscopy. The first detectable abnormality is an infolding of the plasma membrane and the production of small electron-dense whorls. Later, cytoplasmic vacuoles and larger membranous whorls form, and the cell swells. More slowly, chromatin aggregates and the nucleus invaginates. Mitochondria and Golgi are not dramatically affected until the final stages of cell death when organelles, and sometimes the cells themselves, lyse. Certain cells, including some muscle cells in deg-1 animals, express the abnormal gene products and display a few membrane abnormalities but do not die. These cells either express the mutant genes at lower levels, lack other proteins needed to form inappropriately functioning channels, or are better able to compensate for the toxic effects of the channels. Overall, the ultrastructural changes in these deaths suggest that enhanced membrane cycling precedes vacuolation and cell swelling. The pathology of mec-4(gf) and deg-1(gf) cells shares features with that of genetic disorders with alterations in channel subunits, such as hypokalemic periodic paralysis in humans and the weaver mouse, and with degenerative conditions, e.g., acute excitotoxic death. The initial pathology in all of these conditions may reflect attempts by affected cells to compensate for abnormal membrane proteins or functions.
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Sillén A, Sørensen T, Kantola I, Friis ML, Gustavson KH, Wadelius C. Identification of mutations in the CACNL1A3 gene in 13 families of Scandinavian origin having hypokalemic periodic paralysis and evidence of a founder effect in Danish families. AMERICAN JOURNAL OF MEDICAL GENETICS 1997; 69:102-6. [PMID: 9066893 DOI: 10.1002/(sici)1096-8628(19970303)69:1<102::aid-ajmg20>3.0.co;2-s] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Familial hypokalemic periodic paralysis (hypoPP) is an autosomal dominant disorder characterised by episodic attacks of paralysis of varying severity. Recently, linkage was found to markers in 1q31-32 and to the gene encoding the muscle DHP-sensitive calcium channel alpha 1-subunit (CACNL1A3). Subsequently, three mutations in this gene were identified in patients with hypoPP: Arg528His, Arg1239His and Arg1239Gly. In this study, two different mutations were found in the CACNL1A3 gene in 13 Scandinavian families, 10 of whom have the Arg528His mutation while 3 families have the Arg1239His. Furthermore, there is evidence of a founder effect in 8 of the 9 Danish hypoPP families investigated, consisting of haplotypes of microsatellite markers close to and within the CACNL1A3 gene and of the geographic origin of the families. For the first time, reduced penetrance in males with the Arg528His mutation was found in several cases.
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Affiliation(s)
- A Sillén
- Department of Clinical Genetics, University Hospital, Uppsala, Sweden
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Hall DH, Gu G, García-Añoveros J, Gong L, Chalfie M, Driscoll M. Neuropathology of degenerative cell death in Caenorhabditis elegans. J Neurosci 1997; 17:1033-45. [PMID: 8994058 PMCID: PMC6573168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/1996] [Revised: 11/12/1996] [Accepted: 11/26/1996] [Indexed: 02/03/2023] Open
Abstract
In Caenorhabditis elegans necrosis-like neuronal death is induced by gain-of-function (gf) mutations in two genes, mec-4 and deg-1, that encode proteins similar to subunits of the vertebrate amiloride-sensitive epithelial Na+ channel. We have determined the progress of cellular pathology in dying neurons via light and electron microscopy. The first detectable abnormality is an infolding of the plasma membrane and the production of small electron-dense whorls. Later, cytoplasmic vacuoles and larger membranous whorls form, and the cell swells. More slowly, chromatin aggregates and the nucleus invaginates. Mitochondria and Golgi are not dramatically affected until the final stages of cell death when organelles, and sometimes the cells themselves, lyse. Certain cells, including some muscle cells in deg-1 animals, express the abnormal gene products and display a few membrane abnormalities but do not die. These cells either express the mutant genes at lower levels, lack other proteins needed to form inappropriately functioning channels, or are better able to compensate for the toxic effects of the channels. Overall, the ultrastructural changes in these deaths suggest that enhanced membrane cycling precedes vacuolation and cell swelling. The pathology of mec-4(gf) and deg-1(gf) cells shares features with that of genetic disorders with alterations in channel subunits, such as hypokalemic periodic paralysis in humans and the weaver mouse, and with degenerative conditions, e.g., acute excitotoxic death. The initial pathology in all of these conditions may reflect attempts by affected cells to compensate for abnormal membrane proteins or functions.
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Affiliation(s)
- D H Hall
- Department of Neurosciences, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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