Seizure: European Journal of Epilepsy
Volume 19, Issue 4 , Pages 237-241, May 2010

Association of alpha subunit of GABAA receptor subtype gene polymorphisms with epilepsy susceptibility and drug resistance in north Indian population

  • Ritu Kumari

      Affiliations

    • Department of Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow 226014, India
    • ,
  • Ram Lakhan

      Affiliations

    • Department of Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow 226014, India
    • ,
  • J. Kalita

      Affiliations

    • Department of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014, India
    • ,
  • U.K. Misra

      Affiliations

    • Department of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow 226014, India
    • ,
  • Balraj Mittal

      Affiliations

    • Department of Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow 226014, India
    • Corresponding Author InformationCorresponding author. Tel.: +91 522 2668700x2322; fax: +91 522 2668017.

Received 5 October 2009; received in revised form 21 February 2010; accepted 26 February 2010. published online 31 March 2010.

Article Outline

Abstract 

GABA (γ-amino butyric acid) receptors have always been an inviting target in the etiology and treatment of epilepsy because of its role as a major inhibitory neurotransmitter in the brain. The aim of our study was to find out the possible role of single nucleotide polymorphisms (SNPs) present in GABRA1 IVS11+15 A>G (rs2279020) and GABRG2 588C>T (rs211037) genes in seizure susceptibility and pharmaco-resistance in northern Indian patients with epilepsy. A total of 395 epilepsy patients and 199 control subjects were enrolled for present study. The genotyping was done by PCR-RFLP methods. The GABRA1 IVS11+15 A>G polymorphism conferred high risk for epilepsy susceptibility at genotype ‘AG’ (P=0.004, OR=1.77, 95% CI=1.20–2.63), ‘GG’ (P=0.01, OR=1.80, 95% CI=1.15–2.80) and G allele level (P=0.001, OR=1.50, 95% CI=1.16–1.92). Moreover this polymorphism was also associated with multiple drug resistance in patients with epilepsy for homozygous variant ‘GG’ genotype (P=0.031, OR=1.84, 95% CI=1.05–3.23) and G allele (P=0.020, OR=1.43, 95% CI=1.05–1.95). However GABRG2 588C>T polymorphism was not found to be associated either with epilepsy susceptibility or with drug resistance. Overall results indicate differential role of different subunits of GABAA receptor subtypes in epilepsy susceptibility and pharmacotherapy.

Keywords: GABAA receptor, Drug resistance, Epilepsy, Antiepileptic drugs, GABRA1 and GABRG2

 

Back to Article Outline

1. Introduction 

Epilepsy is most common paroxysmal and heterogeneous neurological disorder affecting an estimated 42 million people worldwide with distinct symptoms, etiology, prognosis and treatments.1 Overall prevalence of epilepsy roughly lies in the range of 5–10 per 1000 people, which is usually higher in developing countries.2, 3 Majority of epilepsy phenotypes result from interaction between genes and environmental factors. It is just over a decade since the discovery of the first human epilepsy associated ion channel gene mutation, at least 25 different genes have been described till now, although the strength of the evidences for these genes having a pathogenic role in epilepsy varies. Only 1–2% idiopathic epilepsies seem to be monogenic; whereas most of them are believed to be polygenic.4 These gene and their variants influence seizures, epileptogenesis and epilepsy at multiple levels.5 Therefore, genes encoding voltage gated Na+, K+, Ca++, Cl− and HCN,6, 7 and ligand-gated (nicotinic acetylcholine and GABA receptors) ion channels are considered to be major class of genes associated with various epilepsy phenotypes.

In the central nervous system, GABA is the major inhibitory neurotransmitter that controls neuronal excitability and network interactions in the cerebral cortex of the brain. It acts through three receptor classes: the ionotropic GABAA, GABAC receptors and the metabotropic GABAB receptors. Among the three receptors, recent findings highlight the significance of GABAA receptor heterogeneity for the concept of E/I (excitation/inhibition) balance and its relevance for epilepsy.8 Structurally GABAA receptors are pentameric chloride ion channels formed from various combinations of proteins encoded by α (α1–α6), β (β1–β3), γ (γ1–γ3); δ, ɛ, π, θ, and ρ (ρ1–ρ3) subunit gene families. The α1β2γ2 subunit combination of GABAA receptor is most abundant in almost all regions of the brain.3 Dysfunction of genes coding these subunits affects ion channel gating, expression, and trafficking of the GABA receptor to the cell surface. These genes are also believed to influence important drug targets necessary for the regulation of neuronal activity in the brain.9 Antiepileptic drugs (AEDs) such as benzodiazepines, phenobarbital, gabapentin and topiramate are important targets of GABAA receptor.10 Recently it has been reported that AED resistant rats differ from drug responsive rats in GABAA receptor subunit expression in rat model of temporal lobe epilepsy. It also suggests that alterations in GABAA receptor subunits may be involved in resistance to AEDs.11

Several SNPs in the GABAA receptor subtypes have been described so far but only few including intronic GABRA1 IVS11+15 A>G and an exonic GABRG2 588C>T gene polymorphisms are found to have functional significance in different neurological disorders. These gene variants have been attributed as one of the several susceptibility factors for febrile seizures9, 12; with the development of alcoholism and substance abuse disorders affecting neuronal channels.13, 14

Thus, genes encoding GABAA receptor subunits represent high ranking candidates for epilepsy susceptibility and targets for pharmacotherapeutic agents in epilepsy treatment. Therefore, on the basis of functional significance, previous observations and current knowledge we investigated the possible role of these genetic polymorphisms GABRA1 IVS11+15 A>G (rs2279020) and GABRG2 588C>T (rs211037) [Fig. 1(a) and (b)] in epilepsy susceptibility and antiepileptic drug (AED) response in northern Indian patients with epilepsy.

Back to Article Outline

2. Materials and methods 

2.1. Patients and controls 

Epilepsy patients were enrolled from the outpatients department (OPD) of neurology attending the clinics of Sanjay Gandhi Postgraduate Institute of Medical Sciences (SGPGIMS), Lucknow, India. The patients were diagnosed and classified by an experienced neurologist. The clinical profile of drug responsive and drug resistant epilepsy patients were based on hospital investigations. Exclusion criteria included severe adverse drug reactions; poor compliance with AEDs, unreliable record of seizure frequency, history of pseudo seizures, alcohol or drug abuse, or any other malignant diseases such as brain tumor, secondary metastasis, hepatic failure or renal failure. An informed consent was signed by each participant or responsible adult and they were personally interviewed for information on ethnicity, seizure frequency, and duration of seizure, compliance and other habits. After screening of more than 500 patients a total of 395 patients were included rest were excluded. 259 patients were diagnosed as drug responsive and 122 are nonresponsive. We found that in responders group, 123 (45.1%) patients were on monotherapy and 150 (54.9%) were on polytherapy, i.e. on more than two drugs. In case of nonresponsive epilepsy patients, all were undergoing polytherapy. It was observed that patients who respond early to treatment are less likely to become drug resistant. There appears to be no significant differences in response when compared on the basis of monotherapy and polytherapy. Fourteen patients showed only partial response and therefore excluded from the study analysis involving drug response.

A total of 199 healthy controls were recruited from staff of SGPGIMS and unrelated persons from north India visiting the hospital for minor medical or surgical problems, reported no history of epileptic seizures, and other brain abnormalities. All controls, drug resistance and drug responsive patients were of same ethnic origin. The study was approved by local ethics committee of the institute at SGPGIMS, Lucknow, India.

2.2. Definition of drug resistance and responsiveness 

The main criterion for drug resistance was the occurrence of at least four seizures over a period of one year with three appropriate antiepileptic drugs (AEDs) at maximum tolerated doses.15, 16 Patients who had under-gone surgeries for seizure control were considered refractory irrespective of their outcome after surgery. The epilepsy patients who had complete freedom from seizures for at least one year from last follow up visit were considered drug responsive.

In order to ascertain drug compliance, antiepileptic drug levels in plasma were measured using HPLC (Perkin Elmer) in 20% of patients to confirm compliance and all patients enrolled in the study showed drug compliance. Mean carbamazepine, phenytoin and valproate levels were 8.26±5.25μg/ml, 11.27±8.12μg/ml and 68.0±36.22μg/ml respectively in epileptic patients; and were in therapeutic range. The maximum tolerated doses were different for different individuals in our epilepsy patients. These were 20mg/kg/day for carbamazepine, 20mg/kg for phenytoin and 10mg/kg for valproate.

2.3. Laboratory protocols 

2.3.1. Genotyping of GABRA1 (rs2279020) and GABRG2 (rs211037) 

The genomic DNA was extracted from peripheral blood leucocytes pellet using the standard salting out method with slight modifications.17 The plasma was separated and stored at −20°C for drug level assay. We genotyped total 395 epilepsy patients and 199 healthy controls. Genotyping was performed using PCR-RFLP method as reported previously (Table 1). Twenty percent of samples from patients including samples of each genotype were re-genotyped by different laboratory personnel and results were concordant with no discrepancy noticed in genotyping. PCR reaction was carried out in final volume of 20μl containing 50–100ng genomic DNA. PCR conditions were as follows: a denaturing step at 95°C for 5min, then 30 cycles at 94°C for 30s, annealing temperature 60°C for GABRA1 IVS11+15 and 57°C for GABRG2 588C>T for 30s, 72°C for 30s, and a final extension at 72°C for 7min. After amplification, PCR products of 165bp and 122bp observed respectively; which were digested using specific restriction endonuclease. The AvaII (Fermentas Inc., USA) RFLP assay in GABRA1 IVS11+15 A>G polymorphism was used to distinguish the A/G substitution at nucleotide 15 of the last intron and the products were separated by using 15% poly-acryl amide gel electrophoresis and genotyping patterns were recorded. For GABRA1 IVS11+15 polymorphism genotypes were classified as ‘AA’ homozygote 165bp, ‘AG’ heterozygote 165bp and 141bp, and ‘GG’ homozygote 141bp (Fig. 2). The GABRG2 588C>T polymorphism containing PCR product of 122bp was digested with ApoI restriction enzyme (NEB Inc., USA) at 57°C in total volume of 10μl. After restriction digestion with ApoI; the T allele produced two fragments of 102bp and 20bp and stained with ethidium bromide (Fig. 3). Gel documentation was done using Alpha imager™ 1220, Alpha Innotech Corporation, and San Leandro, CA.

Table 1. List of primers used.
SNPPrimer sequenceRestriction enzymeReference
GABRA1 IVS11+15 A>G (rs2279020)F 5′-GCT ATG GAT TGG TTT ATT GCC GTG TG-3′AvaII14
R 5′-ATA ATA TTG ATG TAC TAC AGG GAC-3′

GABRG2 588C>T (rs211037)F 5′-AATCACCTTTTATTCTAATGGTC-3′ApoI9
R 5′-CAGTGAAGGCAACTTACTAAGA-3′
  • View full-size image.
  • Fig. 2. 

    Representative gel picture for GABRA1 IVS11+15 A>G (rs2279020) genotyping; lane 1, 50bp DNA ladder; lane 2, homozygous AA genotype; lane 3, heterozygous AG genotype; lane 4, homozygous GG genotype.

  • View full-size image.
  • Fig. 3. 

    Representative gel picture for GABRG2 588C>T (rs211037) genotyping. Lane 1, undigested; lane 2, DNA ladder; lane 3, homozygous CC genotype; lane 4, heterozygous CT genotype; lane 5, homozygous TT genotype.

2.4. Statistical analysis 

The relationship between various genotypes and responsiveness was examined using binary logistic regression. Association was expressed as odds ratios (OR) or risk estimates with 95% confidence intervals (CI). The significant association was considered when P-value was <0.05. All analyses were performed using the SPSS statistical analysis software, version 15.0 (SPSS, Chicago, IL, USA). The sample size was calculated using the QUANTO 1.1 program (http://hydra.usc.edu/gxe). Desired power of study was set 80%. Relative risks for power calculation were set at 2.

Back to Article Outline

3. Results 

The mean age±SD of patients with epilepsy was 24.25±11.65. Among all the patients with epilepsy, 72.2% (285/395) were male and 27.8% (110/395) were female. Patients were also categorized on the basis of their drug response status. The mean age of the drug resistant patients was 23.84±11.94 years versus drug responsive patients was 24.72±11.24 years. Epilepsy was classified as symptomatic, idiopathic, or cryptogenic. Seizures were classified as generalized or partial; 57.5% (227/395) had generalized seizures, whereas 42.5% (168/395) had partial seizures. Mean age of onset for seizures in epilepsy patients was 16.39±10.71 years. We were not able to correlate drug levels in patients with genotypes because sample size was very small for the given drugs and particular genotypes.

Among responders 116 (44.8%) were found to have symptomatic and 143 (55.2%) idiopathic epilepsy. Similarly among drug resistant group 58 (47.5%) were having symptomatic epilepsy and 64 (52.5%) exhibited idiopathic epilepsy.

3.1. Association of GABRA1 A>G and GABRG2 588C>T gene polymorphisms and susceptibility to epilepsy 

We analyzed the genotype and allelic frequencies in 395 sporadic epilepsy patients and 199 control subjects by PCR-RFLP assay (Table 2, Table 3). Genotype and allelic frequencies of GABRA1 IVS11+15 A>G and GABRG2 588C>T polymorphisms studied were consistent with Hardy–Weinberg equilibrium (P=0.730) in our control population. Frequencies of AG and GG genotypes of GABRA1 IVS11+15 A>G were found to be significantly higher in epilepsy patients versus control subjects for AG (P=0.004, OR=1.77, 95% CI=1.20–2.63), GG (P=0.010, OR=1.80, 95% CI=1.15–2.80) genotype as well as for variant G allele (P=0.001, OR=1.50, 95%, CI=1.16–1.92) (Table 2). However, for GABRG2 588C>T gene polymorphism we did not observe any significant differences in genotype or allelic frequencies between the epilepsy and control subjects (Table 3).

Table 2. Distribution of GABRA1 (rs2279020) polymorphism in epilepsy patients versus healthy controls and drug responsive versus drug resistant epilepsy.
Genotypes/alleleControl subjects (N=199)Epilepsy patients (N=395)P-ValueOR (95% CI)Drug responsive (N=259)Drug resistant (N=122)P-ValueOdds ratio (95% CI)
AA94 (47.23%)132(33.41%)ReferenceReference92(35.52%)34 (27.86%)ReferenceReference
AG63(31.65%)157(39.74%)0.0041.77(1.20–2.63)107(41.31%)47 (38.52%)0.5171.18(0.70–2.00)
GG42(21.10%)106(26.83%)0.0101.80(1.15–2.80)60(23.16%)41(33.60%)0.0311.84(1.05–3.23)
A*251 (63.06%)421 (53.29%)ReferenceReference291(56.18%)115(47.13%)ReferenceReference
G*147 (36.93%)369 (46.71%)0.0011.50(1.16–1.92)227(43.82%)129(52.87%)0.0201.43(1.05–1.95)
Table 3. Distribution of GABRG2 (rs211037) polymorphism in epilepsy patients versus healthy controls and responsive versus refractory epilepsy.
Genotypes/alleleHealthy controls (N=199)Epilepsy patients (N=395)P-ValueOdds ratio (95% CI)Drug responsive (N=259)Drug resistant (N=122)P-ValueOdds ratio (95% CI)
CC117(58.79%)211(53.41%)ReferenceReference137(52.89%)66 (54.09%)ReferenceReference
CT73(36.68%)168(42.53%)0.1791.28 (0.89–1.82)109(42.08%)53 (43.44%)0.9671.01(0.65–1.57)
TT9(4.52%)16(4.05%)0.9740.99 (0.42–2.30)13(5.01%)3(2.45%)0.2630.48(0.13–1.74)
C*307 (77.13%)591(74.68%)ReferenceReference383(73.94%)185(75.81%)ReferenceReference
T*91 (22.86%)199(25.31%)0.3791.14 (0.85–1.51)135(26.06%)59(24.18%)0.5780.91(0.64–1.29)

After Bonferroni correction for multiple testing, reference P-value became 0.01 where it was 0.001 (Table 2 for ‘G’ allele); and for AG genotype for which P-value became 0.04, in both cases it is less than 0.05 (reference P-value) and statistically significant while in case of GG genotype significance disappeared after Bonferroni correction.

3.2. GABRA1 (rs2279020) and GABRG2 (rs211037) polymorphism in drug resistance epilepsy 

We also observed significant difference at genotype as well as allele frequencies of GABRA1 A>G polymorphism in drug resistant versus drug responsive epilepsy patients for homozygous variant GG genotype (P=0.031, OR=1.84, 95% CI=1.05–3.23) and G allele (P=0.020, OR=1.43 95% CI=1.05–1.95, Table 2). However, in GABRG2 588C>T we did not observe any significant differences in drug resistant versus drug responsive epilepsy patients either at genotype or allele levels (Table 3). It suggests GABRA1 IVS11+15 A>G polymorphism modulates drug response as well as susceptibility for epilepsy in north Indian epilepsy patients.

Back to Article Outline

4. Discussion 

In the present study, we found the involvement of GABRA1 IVS11+15 A>G polymorphism in increasing risk for developing epilepsy as well as in modulating drug response in pharmacotherapy, while GABRG2 588C>T was not found to be associated either with epilepsy susceptibility or with drug resistance in north Indian epilepsy subjects.

Upon comparing allele and genotype frequencies of variant of GABRA1 IVS11+15 A>G in our control subjects with that reported for Chinese and Japanese population in Hapmap project data; similar patterns were observed. Moreover, allele frequency of this polymorphism was also similar to that reported in an Indian population of Gujarati individuals (a state in western India) living in Houston, TX (http://www.hapmap.org/cgi-perl/gbrowse/hapmap3B36/). However, allele and genotype frequencies of GABRG2 588C>T polymorphism show wide variation across different world populations9, 18 suggesting role of ethnic differences in distribution of genetic variants. We minimized the influence of genetic heterogeneity by inclusion of subjects from north India and distribution of genotypes in our control population for both the polymorphisms were consistent with Hardy–Weinberg equilibrium (HWE).

To the best of our knowledge, this is the first report in which an association of GABRA1 IVS11+15 A>G polymorphism was observed with epilepsy susceptibility and drug resistance. This is an intronic polymorphism which does not lead to any amino acid change but it is possible that it alters the conformation of mature protein by influencing alternative splicing. Several mutations in this gene have also been reported to be involved in epilepsy causation that result in loss of function of GABAA receptors via a reduction in GABA expression and, accelerated deactivation.19

Another most widely studied single nucleotide polymorphisms (SNPs) in the human GABAA receptor is GABRG2 588C>T gene polymorphism present at position 588 of exon 5. It results in synonymous or silent change asn196asn that does not affect the sequence of the encoded protein, suggesting that this SNP exists in linkage disequilibrium with other disease causing variants. An earlier study has reported association of this synonymous variant with febrile seizures in a cohort of 104 Taiwanese children [P=0.017, OR=2.56, 95% CI=1.01–6.50].9 However, we did not find association of this polymorphism either with epilepsy susceptibility or drug resistance. In our study, the number of patient with febrile seizures was limited in our study subjects and etiology of other sporadic epilepsies is different from febrile seizure. Similarly studies in Caucasian and other populations also failed to replicate its association in epilepsy patients (Table 4) except in Taiwanese population.9, 20 It suggests that association of this polymorphism is population specific.

Table 4. GABRG2 588 C>T (rs211037); association studies in seizure disorder.
PhenotypesNo. casesNo. controlsCountry of originP-ValueReference
Febrile convulsions74118USA0.823
Generalized7783Taiwan0.0029
All epilepsy1361656UK and Ireland>0.1124
Generalized99364UK0.61
Generalized121284Ireland0.95
Febrile convulsion10483Taiwan0.00920
Febrile Convulsions94106Japan0.525
Generalized135154Germany0.518
Generalized5858China0.0726
Febrile Convulsion107384UK0.227
Generalized96384UK0.6
All epilepsy395199India0.37Present study
Generalized227199India0.519

It is now well established that various AEDs mediate their action through GABA binding.21 It is also hypothesized that target receptor sites are somehow altered in the epileptic brain so that they are much less sensitive to administered AEDs. Therefore, it is possible that the association of GABRA1 IVS11+15 A>G polymorphism with refractory phenotype in our study may occur due to changes in the structure and function of inhibitory GABAA receptors. Excessive glutamate excitation and activation of drug resistance genes may also contribute to changes in GABA receptor conformation and loss of drug efficacy.

Overall, results from our study suggest differential behavior of subunits of GABAA receptor gene polymorphisms in epilepsy susceptibility and its therapy. However, in addition to genetic factors, there are multiple causes of drug resistance in epilepsy that include past treatment history22 and other clinical factors such as type of epilepsy, duration of seizure, and number of seizures prior to initiation of drug therapy.

Thus, our findings are supportive of the fact that different subunits of GABAA receptor subtypes play differential roles in epilepsy at multiple levels and may affect inter-individual variation in drug response for AEDs used in the treatment of epilepsy. Till now very few studies have explored role of these genetic variants in epilepsy and multiple drug resistance; it would be desirable to study them at functional level and also to replicate them in larger cohorts.

Back to Article Outline

Acknowledgments 

The study was supported by a grant received from the Department of Biotechnology, Government of India, and fellowships provided by CSIR and DST (New Delhi), India. We thankfully acknowledge support from Dr. NJ Gogtay, KEM Hospital Mumbai, for drug level assay.

Back to Article Outline

References 

  1. Depondt C. The potential of pharmacogenetics in the treatment of epilepsy. Eur J Paediatr Neurol. 2006;10:57–65
  2. Helbig I, Scheffer IE, Mulley JC, Berkovic SF. Navigating the channels and beyond: unravelling the genetics of the epilepsies. Lancet Neurol. 2008;7:231–245
  3. Reid CA, Berkovic SF, Petrou S. Mechanisms of human inherited epilepsies. Prog Neurobiol. 2009;87:41–57
  4. Weber YG, Lerche H. Genetic mechanisms in idiopathic epilepsies. Dev Med Child Neurol. 2008;50:648–654
  5. Sisodiya SM. Genetics of drug resistance in epilepsy. Curr Neurol Neurosci Rep. 2005;5:307–311
  6. Lakhan R, Kumari R, Misra UK, Kalita J, Pradhan S, Mittal B. Differential role of sodium channels SCN1A and SCN2A gene polymorphisms with epilepsy and multiple drug resistance in north Indian population. Br J Clin Pharmacol. 2009;68:214–220
  7. Lu Y, Wang X. Genes associated with idiopathic epilepsies: a current overview. Neurol Res. 2009;31:135–143
  8. Fritschy JM. Epilepsy, E/I balance and GABA(A) receptor plasticity. Front Mol Neurosci. 2008;1:5
  9. Chou IC, Lee CC, Tsai CH, Tsai Y, Wan L, Hsu YA, et al. Association of GABRG2 polymorphisms with idiopathic generalized epilepsy. Pediatr Neurol. 2007;36:40–44
  10. Moshe SL. Mechanisms of action of anticonvulsant agents. Neurology. 2000;55:S32–S40discussion S54–38
  11. Bethmann K, Fritschy JM, Brandt C, Loscher W. Antiepileptic drug resistant rats differ from drug responsive rats in GABA A receptor subunit expression in a model of temporal lobe epilepsy. Neurobiol Dis. 2008;31:169–187
  12. Kang JQ, Macdonald RL. Making sense of nonsense GABA(A) receptor mutations associated with genetic epilepsies. Trends Mol Med. 2009;15:430–438
  13. Czuczwar SJ. GABA-ergic system and antiepileptic drugs. Neurol Neurochir Pol. 2000;34(Suppl. 1):13–20
  14. Park CS, Park SY, Lee CS, Sohn JW, Hahn GH, Kim BJ. Association between alcoholism and the genetic polymorphisms of the GABAA receptor genes on chromosome 5q33–34 in Korean population. J Korean Med Sci. 2006;21:533–538
  15. Siddiqui A, Kerb R, Weale ME, Brinkmann U, Smith A, Goldstein DB, et al. Association of multidrug resistance in epilepsy with a polymorphism in the drug-transporter gene ABCB1. N Engl J Med. 2003;348:1442–1448
  16. Lakhan R, Misra UK, Kalita J, Pradhan S, Gogtay NJ, Singh MK, et al. No association of ABCB1 polymorphisms with drug-refractory epilepsy in a north Indian population. Epilepsy Behav. 2009;14:78–82
  17. Miller SA, Dykes DD, Polesky HF. A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic Acids Res. 1988;16:1215
  18. Kananura C, Haug K, Sander T, Runge U, Gu W, Hallmann K, et al. A splice-site mutation in GABRG2 associated with childhood absence epilepsy and febrile convulsions. Arch Neurol. 2002;59:1137–1141
  19. Krampfl K, Maljevic S, Cossette P, Ziegler E, Rouleau GA, Lerche H, et al. Molecular analysis of the A322D mutation in the GABA receptor alpha-subunit causing juvenile myoclonic epilepsy. Eur J Neurosci. 2005;22:10–20
  20. Chou IC, Peng CT, Huang CC, Tsai JJ, Tsai FJ, Tsai CH. Association analysis of gamma 2 subunit of gamma-aminobutyric acid type A receptor polymorphisms with febrile seizures. Pediatr Res. 2003;54:26–29
  21. Benarroch EE. GABAA receptor heterogeneity, function, and implications for epilepsy. Neurology. 2007;68:612–614
  22. Schiller Y, Najjar Y. Quantifying the response to antiepileptic drugs: effect of past treatment history. Neurology. 2008;70:54–65
  23. Ma S, Abou-Khalil B, Blair MA, Sutcliffe JS, Haines JL, Hedera P. Mutations in GABRA1, GABRA5, GABRG2 and GABRD receptor genes are not a major factor in the pathogenesis of familial focal epilepsy preceded by febrile seizures. Neurosci Lett. 2006;394:74–78
  24. Kinirons P, Cavalleri GL, Shahwan A, Wood NW, Goldstein DB, Sisodiya SM, et al. Examining the role of common genetic variation in the [gamma]2 subunit of the GABAA receptor in epilepsy using tagging SNPs. Epilepsy Res. 2006;70:229–238
  25. Nakayama J, Hamano K, Noguchi E, Horiuchi Y, Iwasaki N, Ohta M, et al. Failure to find causal mutations in the GABA(A)-receptor gamma2 subunit (GABRG2) gene in Japanese febrile seizure patients. Neurosci Lett. 2003;343:117–120
  26. Lu J, Chen Y, Zhang Y, Pan H, Wu H, Xu K, et al. Mutation screen of the GABA(A) receptor gamma 2 subunit gene in Chinese patients with childhood absence epilepsy. Neurosci Lett. 2002;332:75–78
  27. Cavalleri GL, Lynch JM, Depondt C, Burley MW, Wood NW, Sisodiya SM, et al. Failure to replicate previously reported genetic associations with sporadic temporal lobe epilepsy: where to from here?. Brain. 2005;128:1832–1840

PII: S1059-1311(10)00052-X

doi:10.1016/j.seizure.2010.02.009

Seizure: European Journal of Epilepsy
Volume 19, Issue 4 , Pages 237-241, May 2010

Article Tools

* Image Usage & Resolution