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Affiliation(s)
- Tiziana Granata
- Department of Pediatric Neuroscience, Fondazione IRCCS Instituto Neurologico Carlo Besta, Milan, Italy.
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DePaoli-Roach AA, Segvich DM, Meyer CM, Rahimi Y, Worby CA, Gentry MS, Roach PJ. Laforin and malin knockout mice have normal glucose disposal and insulin sensitivity. Hum Mol Genet 2011; 21:1604-10. [PMID: 22186021 DOI: 10.1093/hmg/ddr598] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Lafora disease is a fatal, progressive myoclonus epilepsy caused in ~90% of cases by mutations in the EPM2A or EPM2B genes. Characteristic of the disease is the formation of Lafora bodies, insoluble deposits containing abnormal glycogen-like material in many tissues, including neurons, muscle, heart and liver. Because glycogen is important for glucose homeostasis, the aberrant glycogen metabolism in Lafora disease might disturb whole-body glucose handling. Indeed, Vernia et al. [Vernia, S., Heredia, M., Criado, O., Rodriguez de Cordoba, S., Garcia-Roves, P.M., Cansell, C., Denis, R., Luquet, S., Foufelle, F., Ferre, P. et al. (2011) Laforin, a dual-specificity phosphatase involved in Lafora disease, regulates insulin response and whole-body energy balance in mice. Hum. Mol. Genet., 20, 2571-2584] reported that Epm2a-/- mice had enhanced glucose disposal and insulin sensitivity, leading them to suggest that laforin, the Epm2a gene product, is involved in insulin signaling. We analyzed 3-month- and 6-7-month-old Epm2a-/- mice and observed no differences in glucose tolerance tests (GTTs) or insulin tolerance tests (ITTs) compared with wild-type mice of matched genetic background. At 3 months, Epm2b-/- mice also showed no differences in GTTs and ITTs. In the 6-7-month-old Epm2a-/- mice, there was no evidence for increased insulin stimulation of the phosphorylation of Akt, GSK-3 or S6 in skeletal muscle, liver and heart. From metabolic analyses, these animals were normal with regard to food intake, oxygen consumption, energy expenditure and respiratory exchange ratio. By dual-energy X-ray absorptiometry scan, body composition was unaltered at 3 or 6-7 months of age. Echocardiography showed no defects of cardiac function in Epm2a-/- or Epm2b-/- mice. We conclude that laforin and malin have no effect on whole-body glucose metabolism and insulin sensitivity, and that laforin is not involved in insulin signaling.
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Affiliation(s)
- Anna A DePaoli-Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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53
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Rubboli G, Franceschetti S, Berkovic SF, Canafoglia L, Gambardella A, Dibbens LM, Riguzzi P, Campieri C, Magaudda A, Tassinari CA, Michelucci R. Clinical and neurophysiologic features of progressive myoclonus epilepsy without renal failure caused by SCARB2 mutations. Epilepsia 2011; 52:2356-63. [PMID: 22050460 DOI: 10.1111/j.1528-1167.2011.03307.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE Mutations of the SCARB2 gene cause action myoclonus renal failure syndrome (AMRF), a rare condition that combines progressive myoclonus epilepsy (PME) with severe renal dysfunction. We describe the clinical and neurophysiologic features of PME associated with SCARB2 mutations without renal impairment. METHODS Clinical and neurophysiologic investigations, including wakefulness and sleep electroencephalography (EEG), polygraphic recording (with jerk-locked back-averaging and analysis of the EEG-EMG (electromyography) relationship by coherence spectra and phase calculation), multimodal evoked potentials, and electromyography were performed on five Italian patients with SCARB2 mutations. KEY FINDINGS The main clinical features were adolescent-young adulthood onset, progressive action myoclonus, ataxia, absence of cognitive deterioration and, in most cases, epilepsy. The severity of the epilepsy could vary from uncontrolled seizures and status epilepticus in patients with adolescent onset to absent or rare seizures in patients with adult onset. Relevant neurophysiologic findings were a pronounced photosensitivity and massive action myoclonus associated with rhythmic myoclonic jerks at a frequency of 12-20 Hz, clinically resembling a postural tremor. The cortical origin of rhythmic myoclonus was demonstrated mainly by coherence and phase analysis of EEG-EMG signals indicating a significant EEG-EMG coupling and a direct corticospinal transfer. SIGNIFICANCE Our patients with SCARB2 mutations showed the clinical and neurophysiologic phenotype of PME, in which epilepsy could be extremely severe, extending the spectrum reported in the typical AMRF syndrome. Patients with PME of unknown origin of adolescent or young adult onset, with these neurophysiologic features, should be tested for SCARB2 mutations, even in the absence of renal impairment.
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Affiliation(s)
- Guido Rubboli
- Neurology Unit, IRCCS Institute of Neurological Sciences, Bologna, Italy.
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54
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Are there errors in glycogen biosynthesis and is laforin a repair enzyme? FEBS Lett 2011; 585:3216-8. [PMID: 21930129 DOI: 10.1016/j.febslet.2011.09.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 09/03/2011] [Accepted: 09/07/2011] [Indexed: 11/23/2022]
Abstract
Glycogen, a branched polymer of glucose, is well known as a cellular reserve of metabolic energy and/or biosynthetic precursors. Besides glucose, however, glycogen contains small amounts of covalent phosphate, present as C2 and C3 phosphomonoesters. Current evidence suggests that the phosphate is introduced by the biosynthetic enzyme glycogen synthase as a rare alternative to its normal catalytic addition of glucose units. The phosphate can be removed by the laforin phosphatase, whose mutation causes a fatal myoclonus epilepsy called Lafora disease. The hypothesis is that glycogen phosphorylation can be considered a catalytic error and laforin a repair enzyme.
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55
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Polajnar M, Žerovnik E. Impaired autophagy: a link between neurodegenerative diseases and progressive myoclonus epilepsies. Trends Mol Med 2011; 17:293-300. [DOI: 10.1016/j.molmed.2011.02.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 02/22/2011] [Accepted: 02/25/2011] [Indexed: 01/29/2023]
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56
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Corbett MA, Schwake M, Bahlo M, Dibbens LM, Lin M, Gandolfo LC, Vears DF, O'Sullivan JD, Robertson T, Bayly MA, Gardner AE, Vlaar AM, Korenke GC, Bloem BR, de Coo IF, Verhagen JMA, Lehesjoki AE, Gecz J, Berkovic SF. A mutation in the Golgi Qb-SNARE gene GOSR2 causes progressive myoclonus epilepsy with early ataxia. Am J Hum Genet 2011; 88:657-63. [PMID: 21549339 DOI: 10.1016/j.ajhg.2011.04.011] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2011] [Revised: 04/13/2011] [Accepted: 04/14/2011] [Indexed: 11/30/2022] Open
Abstract
The progressive myoclonus epilepsies (PMEs) are a group of predominantly recessive disorders that present with action myoclonus, tonic-clonic seizures, and progressive neurological decline. Many PMEs have similar clinical presentations yet are genetically heterogeneous, making accurate diagnosis difficult. A locus for PME was mapped in a consanguineous family with a single affected individual to chromosome 17q21. An identical-by-descent, homozygous mutation in GOSR2 (c.430G>T, p.Gly144Trp), a Golgi vesicle transport gene, was identified in this patient and in four apparently unrelated individuals. A comparison of the phenotypes in these patients defined a clinically distinct PME syndrome characterized by early-onset ataxia, action myoclonus by age 6, scoliosis, and mildly elevated serum creatine kinase. This p.Gly144Trp mutation is equivalent to a loss of function and results in failure of GOSR2 protein to localize to the cis-Golgi.
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Affiliation(s)
- Mark A Corbett
- Genetics and Molecular Pathology, SA Pathology, Adelaide, Australia
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57
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Pong AW, Pal DK, Chung WK. Developments in molecular genetic diagnostics: an update for the pediatric epilepsy specialist. Pediatr Neurol 2011; 44:317-27. [PMID: 21481738 DOI: 10.1016/j.pediatrneurol.2011.01.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 08/31/2010] [Accepted: 01/31/2011] [Indexed: 02/02/2023]
Abstract
The contributions of genetic influences in both rare and common epilepsies are rapidly being elucidated, and neurologists routinely consider genetic testing in the workup of numerous epilepsy syndromes. Trends in patient attitudes and developments in clinical molecular diagnostics will increase interest in, and the availability of genetic tests for, genetic evaluations of epilepsies. We review recent and planned developments in clinical genetic testing platforms, including their indications, strengths, and limitations. We discuss genome-wide microarray methods (i.e., methods to detect copy number variations), karyotypes, and sequence-based testing. We outline the general approach to genetic evaluations of epilepsy, emphasizing the importance of clinical evaluations, and provide online clinical resources. Finally, we present potential social, legal, and financial barriers to genetic evaluations, and discuss concerns regarding clinical utility and recurrence risk. This review provides a practical overview of molecular diagnostics for the neurologist in the genetic evaluation of epilepsies in 2011.
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Affiliation(s)
- Amanda W Pong
- Department of Neurology, Neurological Institute, Columbia University Medical Center, Columbia University, New York, New York 10032, USA.
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58
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Sims KB, Cole AJ, Sherman JC, Caruso PA, Snuderl M. Case records of the Massachusetts General Hospital. Case 8-2011. A 32-year-old woman with seizures and cognitive decline. N Engl J Med 2011; 364:1062-74. [PMID: 21410375 DOI: 10.1056/nejmcpc1013927] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Katherine B Sims
- Department of Neurology, Massachusetts General Hospital, Boston, USA
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59
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Characterization of severe action myoclonus in sialidoses. Epilepsy Res 2011; 94:86-93. [DOI: 10.1016/j.eplepsyres.2011.01.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 01/10/2011] [Accepted: 01/23/2011] [Indexed: 11/20/2022]
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60
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Lehesjoki AE, Gardiner RM. Unverricht-Lundborg disease and ceroid lipofuscinoses. Epilepsia 2010. [DOI: 10.1111/j.1528-1167.2010.02862.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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61
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Abstract
We consider recent developments in disorders affecting three areas of metabolism: glycogen, fatty acids, and the mitochondrial respiratory chain. Among the glycogenoses, new attention has been directed to defects of glycogen synthesis resulting in absence rather than excess of muscle glycogen ("aglycogenosis"). These include defects of glycogen synthetase and defects of glycogenin, the primer of glycogen synthesis. Considerable progress also has been made in our understanding of alterations of glycogen metabolism that result in polyglucosan storage. Among the disorders of lipid metabolism, mutations in the genes encoding two triglyceride lipases acting hand in hand cause severe generalized lipid storage myopathy, one associated with ichthyosis (Chanarin-Dorfman syndrome), the other dominated by juvenile-onset weakness. For the mitochondrial myopathies, we discuss the importance of homoplasmic mitochondrial DNA mutations and review the rapid progress made in our understanding of the coenzyme Q(10) deficiencies, which are often treatable.
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Affiliation(s)
- Salvatore DiMauro
- Department of Neurology, College of Physicians and Surgeons, Columbia University Medical Center, Room 4-424B, 630 West 168th Street, New York, NY 10032, USA.
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Visani E, Minati L, Canafoglia L, Gilioli I, Granvillano A, Varotto G, Aquino D, Fazio P, Bruzzone MG, Franceschetti S, Panzica F. Abnormal ERD/ERS but Unaffected BOLD Response in Patients with Unverricht–Lundborg Disease During Index Extension: A Simultaneous EEG-fMRI Study. Brain Topogr 2010; 24:65-77. [DOI: 10.1007/s10548-010-0167-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 11/08/2010] [Indexed: 11/24/2022]
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63
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Glycogen synthesis in brain and astrocytes is inhibited by chronic lithium treatment. Neurosci Lett 2010; 482:128-32. [DOI: 10.1016/j.neulet.2010.07.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 07/06/2010] [Accepted: 07/08/2010] [Indexed: 02/06/2023]
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Insights into the mechanism of polysaccharide dephosphorylation by a glucan phosphatase. Proc Natl Acad Sci U S A 2010; 107:15312-3. [PMID: 20724661 DOI: 10.1073/pnas.1010573107] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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65
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Abstract
Lafora disease is a rare, fatal, autosomal recessive, progressive myoclonic epilepsy. It may also be considered as a disorder of carbohydrate metabolism because of the formation of polyglucosan inclusion bodies in neural and other tissues due to abnormalities of the proteins laforin or malin. The condition is characterized by epilepsy, myoclonus and dementia. Diagnostic findings on MRI and neurophysiological testing are not definitive and biopsy or genetic studies may be required. Therapy in Lafora disease is currently limited to symptomatic management of the epilepsy, myoclonus and intercurrent complications. With a greater understanding of the pathophysiological processes involved, there is justified hope for future therapies.
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Affiliation(s)
- Thomas S Monaghan
- Department of Neurology and Neuroscience, Beaumont Hospital and Royal College of Surgeons in Ireland, Dublin 9, Ireland
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66
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Siqueira LFM. Progressive myoclonic epilepsies: review of clinical, molecular and therapeutic aspects. J Neurol 2010; 257:1612-9. [DOI: 10.1007/s00415-010-5641-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Accepted: 06/21/2010] [Indexed: 11/24/2022]
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67
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Steinlein OK. Gene polymorphisms and their role in epilepsy treatment and prognosis. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:109-18. [PMID: 20556360 DOI: 10.1007/s00210-010-0531-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 05/27/2010] [Indexed: 12/16/2022]
Abstract
The human genome carries an enormous number of genetic variants, many of them of functional consequence. In epilepsy, they are likely to be involved in drug-specific treatment efficacy, unwanted or even toxic drug reactions, teratogenic risks in pregnancy as well as in the long-term prognosis of patients with epilepsy. As in many other disorders with a complex genetic background, the associated genetic variants that could be verified successfully in replication studies are still only a few. However, new techniques and improved research strategies are likely to increase their number in the foreseeable future, although at a much slower pace as initially expected.
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Affiliation(s)
- Ortrud K Steinlein
- Institute of Human Genetics, University Hospital, Ludwig-Maximilians-University of Munich, Goethestr. 29, 80336, Munich, Germany.
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68
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DePaoli-Roach AA, Tagliabracci VS, Segvich DM, Meyer CM, Irimia JM, Roach PJ. Genetic depletion of the malin E3 ubiquitin ligase in mice leads to lafora bodies and the accumulation of insoluble laforin. J Biol Chem 2010; 285:25372-81. [PMID: 20538597 DOI: 10.1074/jbc.m110.148668] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Approximately 90% of cases of Lafora disease, a fatal teenage-onset progressive myoclonus epilepsy, are caused by mutations in either the EPM2A or the EPM2B genes that encode, respectively, a glycogen phosphatase called laforin and an E3 ubiquitin ligase called malin. Lafora disease is characterized by the formation of Lafora bodies, insoluble deposits containing poorly branched glycogen or polyglucosan, in many tissues including skeletal muscle, liver, and brain. Disruption of the Epm2b gene in mice resulted in viable animals that, by 3 months of age, accumulated Lafora bodies in the brain and to a lesser extent in heart and skeletal muscle. Analysis of muscle and brain of the Epm2b(-/-) mice by Western blotting indicated no effect on the levels of glycogen synthase, PTG (type 1 phosphatase-targeting subunit), or debranching enzyme, making it unlikely that these proteins are targeted for destruction by malin, as has been proposed. Total laforin protein was increased in the brain of Epm2b(-/-) mice and, most notably, was redistributed from the soluble, low speed supernatant to the insoluble low speed pellet, which now contained 90% of the total laforin. This result correlated with elevated insolubility of glycogen and glycogen synthase. Because up-regulation of laforin cannot explain Lafora body formation, we conclude that malin functions to maintain laforin associated with soluble glycogen and that its absence causes sequestration of laforin to an insoluble polysaccharide fraction where it is functionally inert.
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Affiliation(s)
- Anna A DePaoli-Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5122, USA.
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