in vivo 28: 1193-1196 (2014)

Juvenile Myoclonic Epilepsy Is Not Associated with the DRPLA in a European Population

CHRISTOS YAPIJAKIS1,2, STERGIOS GATZONIS3, SOTIRIOS YOUROUKOS4, VASILIKI KOLLIA2, STELLA KARACHRISTIANOU5 and MARIA ANAGNOSTOULI1

1First Department of Neurology, Eginition Hospital, University of Athens Medical School, Athens, Greece; 2Cephalogenetics Research Center, Athens, Greece; 3Department of Neurosurgery, University of Athens Medical School, Evangelismos Hospital, Athens, Greece; 4First Department of Pediatrics, Agia Sophia Hospital, University of Athens Medical School, Athens, Greece; 5Third Department of Neurology, Papanikolaou Hospital, Aristotelian University of Thessaloniki Medical School, Thessaloniki, Greece

Abstract. Background: Juvenile myoclonic epilepsy (JME), of generalized epilepsy (2-4). It is distinguished from other is an early-onset inherited generalized epilepsy which generalized epilepsies by its onset in early adolescence and displays genetic heterogeneity, with at least 10 known loci. the observation of myoclonic jerks, which are not necessarily Another neurogenetic disease, dentato-rubro-pallido-luysian a prelude to a major seizure and usually occur in the atrophy (DRPLA) presents three clinical phenotypes, one of morning, upon awakening (3, 5). The presentation of all JME which in Japanese displays many similarities to JME. Aim: cases seems to belong in a defined clinical spectrum The purpose of this study was to investigate whether the according to the diagnostic criteria of the International DRPLA gene is associated with JME in Caucasians. League Against Epilepsy (6, 7). Patients and Methods: The CAG repeat polymorphism in the Nevertheless, JME displays genetic heterogeneity, with at DRPLA gene, which is expanded in patients with DRPLA, least 10 loci identified so far, on 6p21, 15q14, was examined with polymerase chain reaction amplification 2q23.3, 5q34, 1p36.33, Xp11.3, 5q12-q14, 6p12.2, 3q27.1, in 107 individuals of Greek origin, including 24 patients with and 2q33-q36 (8-17). Very few patients with JME have been sporadic and 8 with familial JME, 25 healthy relatives and found to have recessive which have been reported 50 healthy controls. Results: The repeat sizes of all studied in four encoding calcium channel voltage-dependent individuals were within the normal range. Discussion: These beta-4 subunit (CACNB4) on 2q23.3, gamma-aminobutyric results seem to exclude the DRPLA gene as a major acid A receptor alpha-1 (GABRA1) on 5q34, gamma- candidate gene for JME in this European population. aminobutyric acid A receptor delta (GABRD) on 1p36.33, and chloride channel 2 (CLCN2) on 3q27.1 (10-12, 16). The spectrum of epilepsy types varies wildly and the Since JME is characterized by genetic heterogeneity with prognosis for different entities is quite diverse. Among the multiple involved genes with seemingly limited contribution epileptic syndromes in which the main feature includes to pathogenesis, there might also be other contributing genes. myoclonic seizures, juvenile myoclonic epilepsy (JME) is One such gene might be the dentato-rubro-pallido-luysian regarded as the most common and well-delineated entity, atrophy (DRPLA) gene, which resides on 12p13 (18,19). In affecting about 26% of all individuals with idiopathic this gene, a trinucleotide repeat expansion causes dentato- generalized epilepsy (1). JME is an early-onset inherited type rubro-pallido-luysian atrophy (MIM 125370), the juvenile type of which displays clinical similarities to JME (20, 21). A (CAG)n repeat, which is found in 7-23 copies in the normal population, is expanded to more than 48 repeats in Correspondence to: Professor Christos Yapijakis, DMD, MS, Ph.D., patients with autosomal dominant neurodegenerative DRPLA First Department of Neurology, Eginition Hospital, University of (18,19). DRPLA is considered extremely rare in Europeans, Athens Medical School, 74 Vas. Sophias 11528 Athens, Greece. Tel: but it is much more common in Japanese (18-25). The +30 2107289125, Fax: +30 2109431972, e-mail cyapijakis_ua_gr@ disease presents three clinical phenotypes (20, 26) associated yahoo.com with age of onset: late adult (ataxia, choreoathetosis and Key Words: Juvenile myoclonic epilepsy, dentato-rubro-pallido- dementia but no epilepsy), early adult (similar to late adult, luysian atrophy, DRPLA, trinucleotide repeat, Greek population. including epilepsy), and juvenile (initially myoclonus

0258-851X/2014 $2.00+.40 1193 in vivo 28: 1193-1196 (2014) epilepsy, but later ataxia, dementia or pyramidal signs may PCR products were separated lengthwise by 6% polyacrylamide gel occur). The observed clinical phenotype is related to length electrophoresis. A phage M13 sequencing ladder was of the expanded trinucleotide repeats. electrophoresed in parallel as a marker in order to accurately determine the size of the (CAG) repeat alleles. After vacuum Since in Japanese patients the juvenile type of DRPLA n drying of the gel, the radioactive bands were revealed by displays similar phenotypic features and age of onset to JME, autoradiography. the question is whether the (CAG)n repeat in the DRPLA gene might be associated with this myoclonic epileptic syndrome, Results and Discussion at least in a subset of Europeans with JME. There are several paradigms of allelic mutations within a gene which cause The observed sizes of the (CAG)n repeat alleles of the different disorders with some common features. For example, studied heaIthy Greeks (9-20 copies, median=15, N=100) point mutations in the calcium channel alpha-1A isoform 4 were in a range comparable to other studied European and (CACNL1A4) gene may cause either familial hemiplegic Asian populations (18, 19, 22, 23, 30). The repeat alleles of migraine or episodic ataxia type 2, while a (CAG)n repeat the patients and their relatives were all in the normal range, expansion in the same gene is associated with spinocerebellar as defined by the studied normal Greek population. The ataxia type 6 (27). Interestingly, the variable length of a patients had 9-20 repeats (median=16, N=64), while their trinucleotide repeat may also be associated with different relatives had 9-19 repeats (median=15, N=50). disorders, as in the case of DRPLA and autosomal recessive In conclusion, there was no indication of an expanded or spastic paraplegia (18, 19, 28). The latter is caused by an intermediate size of alleles in our sample of patients with homozygosity of intermediate-size alleles of the (CAG)n JME. In addition, in two of the studied families, two patients repeat in the DRPLA gene. with JME had the same two (CAG)n alleles as their healthy In order to investigate whether the (CAG)n repeat in the brothers. We consider this finding as evidence against DRPLA gene might be associated with JME, at least in a linkage of JME and DRPLA. subset of Europeans, we examined this repeat with standard JME is considered to be a phenotype included in the molecular techniques in Greek patients with JME. In spectrum of idiopathic generalized epilepsy, which is a addition, we examined some of their healthy relatives and common complex disease with an almost exclusively genetic healthy controls from the Greek population. etiology, but with variable phenotypes (31). Varying combinations of several interacting genes may result in Materials and Methods clinical phenotypes such as juvenile absence epilepsy, epilepsy with generalized tonic clonic seizures, or JME. In Blood samples were collected from 107 individuals of Greek origin, support of this hypothesis, the same cys104phe in after informed consent. The studied individuals included 32 patients the CACNB4 gene has been found in patients with diverse with JME (24 with sporadic and 8 with familial disorder), 25 of phenotypes, such as rare juvenile atypical prolonged their healthy relatives (parents, brothers and sisters) and 50 healthy absences with occasional tonic-clonic seizures, and episodic controls. The diagnosis of JME was established at University ataxia with recurrent episodes of vertigo, truncal ataxia and Departments of Neurology (Athens and Thessaloniki) and of dysarthria (10). Pediatrics (Athens), based on the patients’ clinical profile, history Therefore, it seems that the clinical features of myoclonic and electroencephalogram findings (EEG), according to specifically described inclusion/exclusion criteria of the International League jerks and ataxia may be included in the clinical spectrum of Against Epilepsy (29). both idiopathic generalized epilepsy and DRPLA. The two The age of the patients ranged between 14-34 years (median=21 disorders share some clinical similarities, possibly due to years) and the age at onset of the disease was 11-18 years overlapping molecular pathogenic mechanisms. Interestingly, (median=15 years). Regarding their gender, 26 (81%) were female it is well documented that the signal transduction pathways and six (19%) were male. Most cases were sporadic (N=24), while involving both the DRPLA and JME-related ion in four families there were two affected children born to normal channels CACNB4 and CLCN2 lead to activation of the parents, suggesting autosomal recessive inheritance. The relatives of the patients with JME were free of idiopathic transcription factor cAMP-response element-binding protein epilepsy or other neurological disorder, had normal EEG spikes and (CREB) (32-34). their age ranged from 11 to 54 years (median=40 years). The In the present study, we investigated the hypothesis that controls were free of any neurological disorder and their age varied the (CAG)n repeat might be associated with JME at least in from 25 to 62 years (median=43 years). a subset of Europeans. Our results provide evidence for Total DNA was extracted from blood samples using a standard exclusion of the DRPLA gene as a major candidate gene for NaCl technique. The polymorphic (CAG) repeat of the DRPLA n juvenile myoclonic epilepsy in Europeans. Additional studies gene was studied using standard molecular methodology, as previously described (19). Briefly, the region containing the repeat of more DNA samples of Caucasian patients with JME are was amplified using primers (VBC Genomics, Wien, Austria) and necessary in order to strengthen this point beyond any radioactive polymerase chain reaction (PCR) conditions and the reasonable doubt.

1194 Yapijakis et al: The DRPLA Gene and Juvenile Myoclonic Epilepsy

References 16 Saint-Martin C, Gauvain G, Teodorescu G, Gourfinkel-An I, Fedirko E, Weber YG, Maljevic S, Ernst JP, Garcia-Olivares J, 1 Camfield CS, Striano P and Camfield PR: Epidemiology of Fahlke C, Nabbout R, LeGuern E, Lerche H, Poncer JC and juvenile myoclonic epilepsy. Epilepsy Behav 1: S15-17, 2013. Depienne C: Two novel CLCN2 mutations accelerating chloride 2 Panayiotopoulos CP and Obeid T: Juvenile myoclonic epilepsy: channel deactivation are associated with idiopathic generalized an autosomal recessive disease. Ann Neurol 25: 440-443, 1989. epilepsy. Hum Mutat 30: 397-405, 2009. 3 Alfradique I and Vasconcelos MM: Juvenile myoclonic epilepsy. 17 Ratnapriya R, Vijai J, Kadandale JS, Iyer RS, Radhakrishnan K Arq Neuropsiquiatr 65: 1266-1271, 2007. and Anand A: A locus for juvenile myoclonic epilepsy maps to 4 Genton P, Thomas P, Kasteleijn-Nolst Trenité DG, Medina MT 2q33-q36. Hum Genet 128: 123-130, 2010. and Salas-Puig J: Clinical aspects of juvenile myoclonic 18 Koide R, Ikeuchi T, Onodera O, Tanaka H, Igarashi S, Endo K, epilepsy. Epilepsy Behav 1: S8-14, 2013. Takahashi H, Kondo R, Ishikawa A, Hayashi T, Saito M, 5 Oguni H, Mukahira K, Oguni M, Uehara T, Su YH, Izumi T and Tomoda A, Naito H, Ikuta F and Tsuji S: Unstable expansion of Fukuyama Y: Video-polygraphic analysis of myoclonic seizures CAG repeat in hereditary dentatorubral-pallidoluysian atrophy in juvenile myoclonic epilepsy. Epilepsia 35: 307-316, 1994. (DRPLA). Nat Genet 6: 9-13, 1994. 6 Panayiotopoulos CP: The new ILAE report on terminology and 19 Nagafuchi S, Yanagisawa H, Sato K, Shirayama T, Ohsaki E, concepts for organization of epileptic seizures: a clinician's Bundo M, Takeda T, Tadokoro K, Kondo I, Murayama N, critical view and contribution. Epilepsia 52: 2155-2160, 2011. Tanaka Y, Kikushima H, Umino K, Kurosawa H, Furukawa T, 7 Shorvon SD: The etiologic classification of epilepsy. Epilepsia Nihei K, Inoue T, Sano A, Komure O, Takahashi M, Yoshizawa 52: 1052-1057, 2011. T, Kanazawa I and Yamada M: Dentatorubral and pallidoluysian 8 Greenberg DA, Delgado-Escueta AV, Widelitz H, Sparkes RS, atrophy expansion of an unstable CAG trinucleotide on Treiman L, Maldonado HM, Park MS and Terasaki PI: Juvenile 12p. Nat Genet 6: 14-18, 1994. myoclonic epilepsy (JME) may be linked to the BF and HLA loci 20 Takahashi H, Ohama E, Naito H, Takeda S, Nakashima S, on human chromosome 6. Am J Med Genet 31: 185-192, 1988. Makifuchi T and Ikuta F: Hereditary dentatorubral- 9 Elmslie FV, Rees M, Williamson MP, Kerr M, Kjeldsen MJ, pallidoluysian atrophy: clinical and pathologic variants in a Pang KA, Sundqvist A, Friis ML, Chadwick D, Richens A, family. Neurology 38: 1065-1070, 1988. Covanis A, Santos M, Arzimanoglou A, Panayiotopoulos CP, 21 Naito H and Oyanagi S: Familial myoclonus epilepsy and Curtis D, Whitehouse WP and Gardiner RM: Genetic mapping choreoathetosis: hereditary dentatorubral-pallidoluysian atrophy. of a major susceptibility locus for juvenile myoclonic epilepsy Neurology 32: 798-807, 1982. on chromosome 15q. Hum Mol Genet 6: 1329-1334, 1997. 22 Norremolle A, Nielsen JE, Sørensen SA and Hasholt L: Elongated 10 Escayg A, De Waard M, Lee DD, Bichet D, Wolf P, Mayer T, CAG repeats of the B37 gene in a Danish family with dentato- Johnston J, Baloh R, Sander T and Meisler MH: Coding and rubro-pallido-luysian atrophy. Hum Genet 95: 313-318, 1995. noncoding variation of the human calcium-channel beta4-subunit 23 Warner TT, Williams LD, Walker RW, Flinter F, Robb SA, gene CACNB4 in patients with idiopathic generalized epilepsy Bundey SE, Honavar M and Harding AE: A clinical and and episodic ataxia. Am J Hum Genet 66: 1531-1539, 2000. molecular genetic study of dentatorubropallidoluysian atrophy 11 Cossette P, Liu L, Brisebois K, Dong H, Lortie A, Vanasse M, in four European families. Ann Neurol 37: 452-459, 1995. Saint-Hilaire JM, Carmant L, Verner A, Lu WY, Wang YT and 24 Licht DJ and Lynch DR: Juvenile dentatorubral-pallidoluysian Rouleau GA: Mutation of GABRA1 in an autosomal dominant atrophy: new clinical features. Pediatr Neurol 26: 51-54, 2002. form of juvenile myoclonic epilepsy. Nat Genet 31: 184-189, 25 Vinton A, Fahey MC, O'Brien TJ, Shaw J, Storey E, Gardner RJ, 2002. Mitchell PJ, Du Sart D and King JO: Dentatorubral- 12 Dibbens LM, Feng HJ, Richards MC, Harkin LA, Hodgson BL, pallidoluysian atrophy in three generations, with clinical courses Scott D, Jenkins M, Petrou S, Sutherland GR, Scheffer IE, from nearly asymptomatic elderly to severe juvenile, in an Berkovic SF, Macdonald RL and Mulley JC: GABRD encoding Australian family of Macedonian descent. Am J Med Genet A a protein for extra- or peri-synaptic GABAA receptors is a 136: 201-204, 2005. susceptibility locus for generalized epilepsies. Hum Mol Genet 26 Yamada M: Dentatorubral-pallidoluysian atrophy (DRPLA). 13: 1315-1319, 2004. Neuropathology 30: 453-457, 2010. 13 Gu W, Sander T, Heils A, Lenzen KP and Steinlein OK: A new 27 Robbins MS, Lipton RB, Laureta EC and Grosberg BM: CACNA1A EF-hand containing gene EFHC2 on Xp11.4: tentative evidence nonsense mutation is associated with basilar-type migraine and for association with juvenile myoclonic epilepsy. Epilepsy Res episodic ataxia type 2. Headache 49: 1042-1046, 2009. 66: 91-98, 2005. 28 Kurohara K, Kuroda Y, Maruyama H, Kawakami H, Yukitake M, 14 Kapoor A, Ratnapriya R, Kuruttukulam G and Anand A: A novel Matsui M and Nakamura S: Homozygosity for an allele carrying genetic locus for juvenile myoclonic epilepsy at chromosome intermediate CAG repeats in the dentatorubral-pallidoluysian 5q12-q14. Hum Genet 121: 655-662, 2007. atrophy (DRPLA) gene results in spastic paraplegia. Neurology 15 Medina MT, Suzuki T, Alonso ME, Durón RM, Martínez-Juárez 48: 1087-1090, 1997. IE, Bailey JN, Bai D, Inoue Y, Yoshimura I, Kaneko S, Montoya 29 Panayiotopoulos CP, Obeid T and Tahan AR: Juvenile myoclonic MC, Ochoa A, Prado AJ, Tanaka M, Machado-Salas J, Fujimoto epilepsy: a five-year prospective study. Epilepsia 35: 285-296, S, Ito M, Hamano S, Sugita K, Ueda Y, Osawa M, Oguni H, 1994. Rubio-Donnadieu F, Yamakawa K and Delgado-Escueta AV: 30 Muñoz E, Milà M, Sánchez A, Latorre P, Ariza A, Codina M, Novel mutations in myoclonin1/EFHC1 in sporadic and familial Ballesta F and Tolosa E: Dentatorubropallidoluysian atrophy in juvenile myoclonic epilepsy. Neurology 70(22 Pt 2): 2137-2144, a Spanish family: a clinical, radiological, pathological, and 2008. genetic study. J Neurol Neurosurg Psychiatry 67: 811-814, 1999.

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31 Durner M, Keddache MA, Tomasini L, Shinnar S, Resor SR, 33 Khosravani H and Zamponi GW: Voltage-gated calcium channels Cohen J, Harden C, Moshe SL, Rosenbaum D, Kang H, and idiopathic generalized epilepsies. Physiol Rev 86: 941-966. Ballaban-Gil K, Hertz S, Labar DR, Luciano D, Wallace S, 2006. Yohai D, Klotz I, Dicker E and Greenberg DA: Genome scan of 34 Beaumont TL, Yao B, Shah A, Kapatos G and Loeb JA: Layer- idiopathic generalized epilepsy: evidence for major susceptibility specific CREB target gene induction in human neocortical gene and modifying genes influencing the seizure type. Ann epilepsy. J Neurosci 32: 14389-14401, 2012. Neurol 49: 328-335, 2001. 32 Nucifora FC Jr, Sasaki M, Peters MF, Huang H, Cooper JK, Yamada M, Takahashi H, Tsuji S, Troncoso J, Dawson VL, Dawson TM and Ross CA: Interference by huntingtin and Received August 5, 2014 atrophin-1 with CBP-mediated transcription leading to cellular Revised September 5, 2014 toxicity. Science 291: 2423-2428, 2001. Accepted September 5, 2014

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