The 1674+11C>T polymorphism of CHRNA4 is associated with juvenile myoclonic epilepsy

Open ArchivePublished:July 06, 2009DOI:https://doi.org/10.1016/j.seizure.2009.06.007

      Abstract

      The α4 subunit gene (CHRNA4) of the neuronal nicotinic acetylcholine receptor (nAChR), linked to an idiopathic partial epilepsy, autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), may also play a key role in the development of the idiopathic generalized epilepsy syndrome (IGE), juvenile myoclonic epilepsy (JME). This study was designed to explore an association of four polymorphisms of the CHRNA4 with JME in Polish children and young patients. The study included 92 JME patients and 222 unrelated healthy individuals. In each group the frequencies of the CHRNA4 c.555C>T, c.594C>T, 1674+11C>T, and 1674+14A>G polymorphisms were determined using PCR-RFLP analyses. An association between the 1674+11C>T polymorphism of the CHRNA4 and JME was evidenced. Allele T (the risk factor) appeared with a significantly higher frequency in the JME patients than in the controls (p = 0.0299). The patients harboring the 1674+11CT+TT genotypes showed an increased risk of JME (CT+TT versus CC: OR = 1.925; 95% CI = 1.021–3.629; p = 0.0408). No association was found for the other CHRNA4 polymorphisms tested. The CHRNA4 1674+11C>T polymorphism may be a susceptibility factor for epilepsy, and its higher frequency in patients with juvenile myoclonic epilepsy suggests that the CHRNA4 may be one of the candidate genes for this epileptic syndrome.

      Keywords

      1. Introduction

      Idiopathic generalized epilepsies (IGEs) belong to a group of epilepsies with no apparent structural brain damage or neurological abnormalities, and they are mainly due to genetic factors. Patients with IGEs are prone to recurrent seizures, which occur both in childhood and in adolescence. Common IGE forms, such as: juvenile myoclonic epilepsy (JME), childhood absence epilepsy (CAE), juvenile absence epilepsy (JAE), and epilepsy with generalized tonic–clonic seizures (EGTCS), follow complex inheritance patterns.
      • Berkovic S.F.
      • Howell R.A.
      • Hay D.A.
      • Hopper J.L.
      Epilepsies in twins: genetics of the major epilepsy syndromes.
      In most cases identification of genes that underlie predisposition to IGEs is difficult because of clinical and genetic heterogeneity of this group of epilepsies,
      • Cossette P.
      • Liu L.
      • Brisebois K.
      • Dong H.
      • Lortie A.
      • Vanasse M.
      • et al.
      Mutation of GABRA1 in an autosomal dominant form of juvenile myoclonic epilepsy.
      and only a few susceptibility genes have been identified so far.
      • Cossette P.
      • Liu L.
      • Brisebois K.
      • Dong H.
      • Lortie A.
      • Vanasse M.
      • et al.
      Mutation of GABRA1 in an autosomal dominant form of juvenile myoclonic epilepsy.
      • Engel J.
      A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology.
      • Haug K.
      • Warnstedt M.
      • Alekov A.K.
      • Sander T.
      • Ramírez A.
      • Poser B.
      • et al.
      Mutations in CLCN2 encoding a voltage-gated chloride channel are associated with idiopathic generalized epilepsies.
      Among four IGE subtypes, JME appears genetically more distinct, and in many families autosomal dominant inheritance is apparent.
      • Haug K.
      • Warnstedt M.
      • Alekov A.K.
      • Sander T.
      • Ramírez A.
      • Poser B.
      • et al.
      Mutations in CLCN2 encoding a voltage-gated chloride channel are associated with idiopathic generalized epilepsies.
      This epileptic syndrome is characterized by myoclonic tonic–clonic and absence seizures. It has been found that the risk of developing either JME or related IGEs is higher in relatives of probands with JME, and different subtypes of IGE may coexist within a single family.
      • Cossette P.
      • Liu L.
      • Brisebois K.
      • Dong H.
      • Lortie A.
      • Vanasse M.
      • et al.
      Mutation of GABRA1 in an autosomal dominant form of juvenile myoclonic epilepsy.
      • Marini C.
      • Scheffer I.E.
      • Crossland K.M.
      • Grinton B.E.
      • Phillips F.L.
      • McMahon J.M.
      • et al.
      Genetic architecture of idiopathic generalized epilepsy: clinical genetic analysis of 55 multiplex families.
      Chromosomal regions harboring genes encoding the nAChRs were tested for linkage to the juvenile myoclonic epilepsy and strong evidence had been presented that the EJM2 locus, in which the gene encoding the α7 subunit (CHRNA7) is located, contributes to the genetic susceptibility to the JME trait.
      • Elmslie F.V.
      • Rees M.
      • Williamson M.P.
      • Kerr M.
      • Kjeldsen M.J.
      • Pang K.A.
      • et al.
      Genetic mapping of a major susceptibility locus for juvenile myoclonic epilepsy on chromosome 15q.
      • Taske N.L.
      • Williamson M.P.
      • Makoff A.
      • Bate L.
      • Curtis D.
      • Kerr M.
      • et al.
      Evaluation of the positional candidate gene CHRNA7 at the juvenile myoclonic epilepsy locus (EJM2) on chromosome 15q13-14.
      Mutations of the ion channel genes encoding subunits of nAChR are associated with the familial forms of partial epilepsies classified as autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), but some polymorphisms of the gene coding for the α4 subunit (CHRNA4) also confer genetic susceptibility to the common subtypes of IGE.
      • Steinlein O.
      • Sander T.
      • Stoodt J.
      • Kretz R.
      • Janz D.
      • Propping P.
      Possible association of a silent polymorphism in the neuronal nicotinic acetylcholine receptor subunit alpha4 with common idiopathic generalized epilepsies.
      • Lee C.C.
      • Chou I.C.
      • Tsai C.H.
      • Wan L.
      • Shu Y.A.
      • Tsai Y.
      • et al.
      Association of idiopathic generalized epilepsy with polymorphisms in the neuronal nicotinic acetylcholine receptor subunits.
      • Chioza B.
      • Goodwin H.
      • Blower J.
      • McCormick D.
      • Nashef L.
      • Asherson P.
      • et al.
      Failure to replicate association between the gene for the neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) and IGE.
      • Haider M.Z.
      • Habeeb Y.
      • Al-Nakkas E.
      • Al-Anzi H.
      • Zaki M.
      • Al-Tawari A.
      • et al.
      Lack of an association between candidate gene loci and idiopathic generalized epilepsy in Kuwaiti Arab children.
      Suggestive evidence for the Caucasian population came from one of the CHRNA4 polymorphisms, c.594C>T (SNP 1044394), investigated in a group of IGE probands, comprising CAE, JAE and JME patients.
      • Steinlein O.
      • Sander T.
      • Stoodt J.
      • Kretz R.
      • Janz D.
      • Propping P.
      Possible association of a silent polymorphism in the neuronal nicotinic acetylcholine receptor subunit alpha4 with common idiopathic generalized epilepsies.
      Recently, another silent polymorphism within the CHRNA4 (Ser543Ser) have been linked to the group of IGEs in the Taiwanese population.
      • Lee C.C.
      • Chou I.C.
      • Tsai C.H.
      • Wan L.
      • Shu Y.A.
      • Tsai Y.
      • et al.
      Association of idiopathic generalized epilepsy with polymorphisms in the neuronal nicotinic acetylcholine receptor subunits.
      Two other CHRNA4 polymorphisms, 1674+11C>T (SNP 45442394) and 1674+14A>G (SNP 3827020), located within intron5 of the CHRNA4, are distinguishable by the presence of restriction sites for SsiI or Sty.
      • Dorszewska J.
      • Florczak J.
      • Rozycka A.
      • Jaroszewska-Kolecka J.
      • Trzeciak W.H.
      • Kozubski W.
      Polymorphisms of the CHRNA4 gene encoding the alpha4 subunit of nicotinic acetylcholine receptor as related to the oxidative DNA damage and the level of apoptotic proteins in lymphocytes of the patients with Alzheimer's disease.
      It has been suggested that the CHRNA4 polymorphisms or putative sequence variants situated near the CHRNA4 locus, confer susceptibility to the common IGE syndromes. In view of a possible association between the CHRNA4 variants and IGEs, we decided to analyze four of these polymorphisms in our sample comprising the JME patients.

      2. Methods

      2.1 Subjects

      The subjects of the study were 92 unrelated Polish children and young patients in whom JME was diagnosed, and 222 healthy volunteers. Probands were patients of the Department of Developmental Neurology of University of Medical Sciences in Poznan. All patients were Caucasians aged 6–26 years, and fulfilled diagnostic criteria for JME of the International Classification of Epileptic Syndromes. Healthy individuals, born in Poland, aged 15–35 with no history of any epilepsy syndromes and neurological disorders served as controls. Written consents from all adult patients and parents of the children were obtained, and the local Ethic Review Committee approved the study protocol.

      2.2 Genotyping

      The CHRNA4 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay, using published PCR primers.
      • Dorszewska J.
      • Florczak J.
      • Rozycka A.
      • Jaroszewska-Kolecka J.
      • Trzeciak W.H.
      • Kozubski W.
      Polymorphisms of the CHRNA4 gene encoding the alpha4 subunit of nicotinic acetylcholine receptor as related to the oxidative DNA damage and the level of apoptotic proteins in lymphocytes of the patients with Alzheimer's disease.
      The amplification was followed by restriction digestion with the FokI (c.555C>T; SNP 1044393), CfoI (c.594C>T; SNP 1044394), SsiI (1674+11C>T; SNP 45442394), and StyI (1674+14A>G; SNP 3827020). Digested PCR products were directly analyzed by electrophoresis either on 2% agarose or 10% polyacrylamide gels, and each allele was identified according to its size.

      2.3 Statistical analysis

      The genotype and allele frequencies of the CHRNA4 polymorphisms in the JME patients were compared with the healthy individuals using a case–control study design. Significance was evaluated by Chi-square or Fisher exact test. Odds ratios and 95% confidence intervals were estimated using an online implementation for deviation from Hardy–Weinberg equilibrium and tests for association (http://ihg2.helmholtz-muenchen.de/cgi-bin/hw/hwa1.pl). In all cases, p < 0.05 was considered as statistically significant.

      3. Results

      The data for genotype distribution and allele frequencies of CHRNA4 c.555C>T, c.594C>T, 1674+11C>T, and 1674+14A>G polymorphisms for the patients and the controls are shown in Table 1. Distribution of these polymorphisms was consistent with Hardy–Weinberg equilibrium in the patients and in the control group. No significant differences were observed in either the frequency of the CHRNA4 c.555C>T, c.594C>T, and 1674+14A>G genotypes or alleles between the patients and the controls. The CC, CT and TT genotype distribution of the CHRNA4 c.555C>T polymorphism was, respectively, 83%, 17%, and 0% for the patients, and 80%, 19%, and 1% for the controls. There were no TT genotypes in the patients. The derived allele frequencies for the C and T alleles were 91% and 9% in the patients, and 90% and 10% in the controls. Studies on the c.594C>T CHRNA4 polymorphism showed similar results (see Table 1). The genotype frequencies in the probands were 90% (CC) and 10% (CT), and in the controls: 88% (CC) and 12% (CT). No 594TT homozygotes were identified in each group. The allele frequencies in the patients and the controls were 95% (C) and 5% (T), and 94% (C), and 6% (T), respectively. Analyses of the 1674+14A>G polymorphism also revealed that genotype and allelic frequency did not differ between the patients and the control group (see Table 1).
      Table 1Localization, genotype and allele frequencies of the CHRNA4 polymorphisms in JME patients and control subjects.
      Polymorphism positionGenotypesNumber of genotypes (%)Genotype pVAL (χ2 test)AllelesNumber of alleles (%)Allele pVAL
      JMEControlsJMEControlsχ2 testFisher's exact test
      555 bp FokI (Exon5)CC76 (83%)110 (80%)0.676C168 (0.91)246 (0.90)0.5870.630
      CT16 (17%)26 (19%)T16 (0.09)28 (0.10)
      TT01 (1%)Σ184274
      594 bp CfoI (Exon5)CC83 (90%)120 (88%)0.539C175 (0.95)257 (0.94)0.5500.680
      CT9 (10%)17 (12%)T9 (0.05)17 (0.06)
      TT00Σ184274
      1674+11 bp SsiI (Intron5)CC72 (78%)194 (87%)0.041*C163 (0.89)416 (0.94)0.029*0.034*
      CT19 (21%)28 (13%)T21 (0.11)28 (0.06)
      TT1 (1%)0Σ184444
      1674+14 bp StyI (Intron5)AA31 (34%)52 (38%)0.722A114 (0.62)174 (0.64)0.7370.768
      AG52 (56%)70 (51%)G70 (0.38)100 (0.36)
      GG9 (10%)15(11%)Σ184274
      On the contrary, the 1674+11C>T polymorphism in the patients showed a significant difference when compared to the healthy individuals. The frequency of the T allele of the 1674+11C>T polymorphism in the JME group was higher than that in the control group (p = 0.0299). Moreover, no TT genotype was found among the healthy individuals (see Table 1). We also undertook the test for association, using the 1674+11T as a risk allele (see Table 2). The odds ratios (ORs) and the confidence intervals (CIs) were calculated for each genotype and compared with the homozygous one for the genotype of higher frequency among controls, which was set as the reference genotype. When the 1674+11CC genotype was used as the reference, the combined 1674+11CT+TT genotypes were associated with significantly higher risk of JME (OR = 1.925; CI = 1.021–3.629, p = 0.0408).
      Table 2The tests for association
      The tests for association were adapted from http://ihg2.helmholtz-muenchen.de/cgi-bin/hw/hwa2.pl.
      of CHRNA4 polymorphisms in JME patients and control subjects.
      PolymorphismAllele freq. differenceHeterozygousHomozygousAllele positivity
      CHRNA4Ssi 1674+11Risk allele T
      JME[C] vs. [T][CC] vs. [CT][CC] vs. [TT][CC] vs. [CT+TT]
      Odds ratio = 1.914, C.I. = [1.057–3.467], χ2 = 4.72, p = 0.02988Odds ratio = 1.828, C.I. = [0.962–3.475], χ2 = 3.46, p = 0.06301Odds ratio = 8.048, C.I. = [0.324–199.818], χ2 = 2.67, p = 0.10242Odds ratio = 1.925, C.I. = [1.021–3.629], χ2 = 4.18, p = 0.04082
      a The tests for association were adapted from http://ihg2.helmholtz-muenchen.de/cgi-bin/hw/hwa2.pl.

      4. Discussion

      Genes encoding the nAChR subunits had recently emerged as the candidates for idiopathic epilepsies. Significant evidence for linkage of JME was found to polymorphic loci within the region on chromosome 15q14, in which the CHRNA7 is localized.
      • Elmslie F.V.
      • Rees M.
      • Williamson M.P.
      • Kerr M.
      • Kjeldsen M.J.
      • Pang K.A.
      • et al.
      Genetic mapping of a major susceptibility locus for juvenile myoclonic epilepsy on chromosome 15q.
      • Taske N.L.
      • Williamson M.P.
      • Makoff A.
      • Bate L.
      • Curtis D.
      • Kerr M.
      • et al.
      Evaluation of the positional candidate gene CHRNA7 at the juvenile myoclonic epilepsy locus (EJM2) on chromosome 15q13-14.
      Two independent investigations, however, have failed to confirm these findings.
      • Sander T.
      • Schulz H.
      • Vieira-Saeker A.M.
      • Bianchi A.
      • Sailer U.
      • Bauer G.
      • et al.
      Evaluation of a putative major susceptibility locus for juvenile myoclonic epilepsy on chromosome 15q14.
      • Darner M.
      • Shinnar S.
      • Resor S.R.
      • Moshe S.L.
      • Rosenbaum D.
      • Cohen J.
      • et al.
      No evidence for a major susceptibility locus for juvenile myoclonic epilepsy on chromosome 15q.
      On the other hand, several mutations of the CHRNA4 gene were associated with ADNFLE.
      • Picard F.
      • Bruel D.
      • Servent D.
      • Saba W.
      • Fruchart-Gaillard C.
      • Schöllhorn-Peyronneau M.A.
      • et al.
      Alteration of the in vivo nicotinic receptor density in ADNFLE patients: a PET study.
      Since the c.851C>T (S284L) mutation of the CHRNA4 was identified in a Caucasian family with ADNFLE,
      • Rozycka A.
      • Skorupska E.
      • Kostyrko A.
      • Trzeciak W.H.
      Evidence for S284L mutation of the CHRNA4 in a white family with autosomal dominant nocturnal frontal lobe epilepsy.
      we decided to study the linkage of four CHRNA4 polymorphisms with JME in a sample from the Polish population. Two of these polymorphisms, c.555C>T and c.594C>T, are located in exon5, and two other, 1674+11C>T and 1674+14A>G, are within intron5 of the CHRNA4. To date, all of these polymorphisms, except the 1674+11C>T, had been studied in epilepsy, and in a single report.
      • Steinlein O.
      • Sander T.
      • Stoodt J.
      • Kretz R.
      • Janz D.
      • Propping P.
      Possible association of a silent polymorphism in the neuronal nicotinic acetylcholine receptor subunit alpha4 with common idiopathic generalized epilepsies.
      only one, the c.594C>T polymorphism, was associated with IGE. In this study, the c.594C>T polymorphism had previously been associated with the common subtypes of IGE, but no distinction between JME or absence epilepsies was made.
      • Steinlein O.
      • Sander T.
      • Stoodt J.
      • Kretz R.
      • Janz D.
      • Propping P.
      Possible association of a silent polymorphism in the neuronal nicotinic acetylcholine receptor subunit alpha4 with common idiopathic generalized epilepsies.
      The frequency of the T-allele was higher in the entire group of IGE patients (0.085) compared to the healthy individuals (0.027). However, case–control and family-based study, made by Chioza et al.
      • Chioza B.
      • Goodwin H.
      • Blower J.
      • McCormick D.
      • Nashef L.
      • Asherson P.
      • et al.
      Failure to replicate association between the gene for the neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) and IGE.
      in 182 Caucasian patients with IGEs (JME, JAE and CAE), as well as in 178 controls, has not implicated the CHRNA4 c.594C>T polymorphism in susceptibility to epilepsy.
      • Chioza B.
      • Goodwin H.
      • Blower J.
      • McCormick D.
      • Nashef L.
      • Asherson P.
      • et al.
      Failure to replicate association between the gene for the neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) and IGE.
      In this study, the allele frequencies of the 594T polymorphism in IGE probands and controls were virtually the same (0.05 and 0.04, respectively). In our study no significant differences in the T-allele distribution between the patients (0.05) and the control group (0.06) were discerned, and no homozygous 594TT genotype was found in the patients as well as in the control group. Also the c.555C>T polymorphism was not associated with JME, one of the IGE subtypes, similar to that reported for the Kuwaiti Arab children with IGEs (CC = 85%, CT = 14%, TT = 1%).
      • Haider M.Z.
      • Habeeb Y.
      • Al-Nakkas E.
      • Al-Anzi H.
      • Zaki M.
      • Al-Tawari A.
      • et al.
      Lack of an association between candidate gene loci and idiopathic generalized epilepsy in Kuwaiti Arab children.
      The allele frequencies of the c.555C>T polymorphism in our control group (C = 90%, T = 10%), however, were lower than that reported in other Caucasian populations, where the C allele was found in 70% and the T allele in 30% of cases.
      • Guipponi M.
      • Baldy-Moulinier M.
      • Malafosse A.
      A fok1 polymorphism in the human neuronal nicotinic acetylcholine receptor alpha 4 subunit gene.
      The genotype frequencies of yet another polymorphism, 1674+14A>G, located 14 bp into intron5, were similar in the IGE patients and controls in the earlier study.
      • Chioza B.
      • Goodwin H.
      • Blower J.
      • McCormick D.
      • Nashef L.
      • Asherson P.
      • et al.
      Failure to replicate association between the gene for the neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) and IGE.
      In our study, there were also no differences between the genotype frequencies of this polymorphism in the JME patients, and the controls. However, the genotype frequencies in the controls obtained (AA = 38%, AG = 51% and GG = 11%) were different from those originally reported by Chioza et al.
      • Chioza B.
      • Goodwin H.
      • Blower J.
      • McCormick D.
      • Nashef L.
      • Asherson P.
      • et al.
      Failure to replicate association between the gene for the neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) and IGE.
      (AA = 77%, AG = 18% and GG = 5%). These discrepancies, however, might be due to different populations studied.
      In our study, another polymorphic variant, 1674+11C>T, which was never investigated in epileptic syndromes so far, located 11 bp into intron5 of the CHRNA4 was analyzed. This polymorphism was recently detected in the patients with Alzheimer's disease, but did not have any significant association with AD.
      • Dorszewska J.
      • Florczak J.
      • Rozycka A.
      • Jaroszewska-Kolecka J.
      • Trzeciak W.H.
      • Kozubski W.
      Polymorphisms of the CHRNA4 gene encoding the alpha4 subunit of nicotinic acetylcholine receptor as related to the oxidative DNA damage and the level of apoptotic proteins in lymphocytes of the patients with Alzheimer's disease.
      On the contrary, the association between CHRNA4 1674+11C>T polymorphism and JME was evidenced. We found that the 1674+11T allele appeared with a significantly higher frequency in the patients than in the control group and the patients with the 1674+11CT+TT genotypes showed increased risk of JME, indicating the 1674+11T allele as a risk factor for this form of epilepsy. This demonstrated that the CHRNA4 might be yet another important gene connected with JME. Further investigations are required, however, to substantiate our findings.

      Acknowledgements

      Supported by grant No. 3 PO5A 115 25 from the State Committee for Scientific Research (KBN). Expert editorial assistance of Robert Meehan (M.D.) is gratefully acknowledged.

      References

        • Berkovic S.F.
        • Howell R.A.
        • Hay D.A.
        • Hopper J.L.
        Epilepsies in twins: genetics of the major epilepsy syndromes.
        Ann Neurol. 1998; 43: 435-445
        • Cossette P.
        • Liu L.
        • Brisebois K.
        • Dong H.
        • Lortie A.
        • Vanasse M.
        • et al.
        Mutation of GABRA1 in an autosomal dominant form of juvenile myoclonic epilepsy.
        Nat Genet. 2002; 31: 184-189
        • Engel J.
        A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology.
        Epilepsia. 2001; 42: 796-803
        • Haug K.
        • Warnstedt M.
        • Alekov A.K.
        • Sander T.
        • Ramírez A.
        • Poser B.
        • et al.
        Mutations in CLCN2 encoding a voltage-gated chloride channel are associated with idiopathic generalized epilepsies.
        Nat Genet. 2003; 33: 527-532
        • Marini C.
        • Scheffer I.E.
        • Crossland K.M.
        • Grinton B.E.
        • Phillips F.L.
        • McMahon J.M.
        • et al.
        Genetic architecture of idiopathic generalized epilepsy: clinical genetic analysis of 55 multiplex families.
        Epilepsia. 2004; 45: 467-478
        • Elmslie F.V.
        • Rees M.
        • Williamson M.P.
        • Kerr M.
        • Kjeldsen M.J.
        • Pang K.A.
        • et al.
        Genetic mapping of a major susceptibility locus for juvenile myoclonic epilepsy on chromosome 15q.
        Hum Mol Genet. 1997; 6: 1329-1334
        • Taske N.L.
        • Williamson M.P.
        • Makoff A.
        • Bate L.
        • Curtis D.
        • Kerr M.
        • et al.
        Evaluation of the positional candidate gene CHRNA7 at the juvenile myoclonic epilepsy locus (EJM2) on chromosome 15q13-14.
        Epilepsy Res. 2002; 49: 157-172
        • Steinlein O.
        • Sander T.
        • Stoodt J.
        • Kretz R.
        • Janz D.
        • Propping P.
        Possible association of a silent polymorphism in the neuronal nicotinic acetylcholine receptor subunit alpha4 with common idiopathic generalized epilepsies.
        Am J Med Genet. 1997; 74: 445-449
        • Lee C.C.
        • Chou I.C.
        • Tsai C.H.
        • Wan L.
        • Shu Y.A.
        • Tsai Y.
        • et al.
        Association of idiopathic generalized epilepsy with polymorphisms in the neuronal nicotinic acetylcholine receptor subunits.
        J Clin Lab Anal. 2007; 21: 67-70
        • Chioza B.
        • Goodwin H.
        • Blower J.
        • McCormick D.
        • Nashef L.
        • Asherson P.
        • et al.
        Failure to replicate association between the gene for the neuronal nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4) and IGE.
        Am J Med Genet. 2000; 96: 814-816
        • Haider M.Z.
        • Habeeb Y.
        • Al-Nakkas E.
        • Al-Anzi H.
        • Zaki M.
        • Al-Tawari A.
        • et al.
        Lack of an association between candidate gene loci and idiopathic generalized epilepsy in Kuwaiti Arab children.
        J Biomed Sci. 2005; 12: 815-818
        • Dorszewska J.
        • Florczak J.
        • Rozycka A.
        • Jaroszewska-Kolecka J.
        • Trzeciak W.H.
        • Kozubski W.
        Polymorphisms of the CHRNA4 gene encoding the alpha4 subunit of nicotinic acetylcholine receptor as related to the oxidative DNA damage and the level of apoptotic proteins in lymphocytes of the patients with Alzheimer's disease.
        DNA Cell Biol. 2005; 24: 786-794
        • Sander T.
        • Schulz H.
        • Vieira-Saeker A.M.
        • Bianchi A.
        • Sailer U.
        • Bauer G.
        • et al.
        Evaluation of a putative major susceptibility locus for juvenile myoclonic epilepsy on chromosome 15q14.
        Am J Med Genet. 1999; 88: 182-187
        • Darner M.
        • Shinnar S.
        • Resor S.R.
        • Moshe S.L.
        • Rosenbaum D.
        • Cohen J.
        • et al.
        No evidence for a major susceptibility locus for juvenile myoclonic epilepsy on chromosome 15q.
        Am J Med Genet. 2000; 96: 49-52
        • Picard F.
        • Bruel D.
        • Servent D.
        • Saba W.
        • Fruchart-Gaillard C.
        • Schöllhorn-Peyronneau M.A.
        • et al.
        Alteration of the in vivo nicotinic receptor density in ADNFLE patients: a PET study.
        Brain. 2006; 129: 2047-2060
        • Rozycka A.
        • Skorupska E.
        • Kostyrko A.
        • Trzeciak W.H.
        Evidence for S284L mutation of the CHRNA4 in a white family with autosomal dominant nocturnal frontal lobe epilepsy.
        Epilepsia. 2003; 44: 1113-1117
        • Guipponi M.
        • Baldy-Moulinier M.
        • Malafosse A.
        A fok1 polymorphism in the human neuronal nicotinic acetylcholine receptor alpha 4 subunit gene.
        Clin Genet. 1997; 51: 78-79