Gene polymorphisms and their role in epilepsy treatment and prognosis

Prognostic factors for employment outcomes in patients with a history of childhood-onset drug-resistant epilepsy

Objective

The employment outcomes of childhood-onset drug-resistant epilepsy (DRE) has not been studied enough. The aim of this retrospective cohort study is to investigate the employment outcomes of childhood-onset DRE in June 2022 and identify the risk factors associated with non-employment.

Materials and methods

The sample consisted of 65 participants ≥18 years of age with a history of childhood-onset DRE. Fifty participants (77%) were salaried employees and 15 participants (23%) were non-employed. Clinical and psychosocial information were evaluated for calculating the relative risk (RR) of non-employment.

Results

Regarding medical factors, lower IQ [RR, 0.645; 95% confidence interval (CI), 0.443-0.938; p = 0.022] was positively associated with employment. In contrast, age at follow-up (RR, 1.046; 95% CI, 1.009-1.085; p = 0.014); number of ASMs at follow-up (RR, 1.517; 95% CI, 1.081-2.129; p = 0.016); use of medications such as phenobarbital (RR, 3.111; 95% CI, 1.383-6.997; p = 0.006), levetiracetam (RR, 2.471; 95% CI, 1.056-5.782; p = 0.037), and topiramate (RR, 3.576; 95% CI, 1.644-7.780; p = 0.001) were negatively associated with employment. Regarding psychosocial factor, initial workplace at employment support facilities (RR, 0.241; 95% CI, 0.113-0.513; p < 0.001) was positively associated with employment. In contrast, complication of psychiatric disorder symptoms (RR, 6.833; 95% CI, 2.141-21.810; p = 0.001) was negatively associated with employment. Regarding educational factor, graduating schools of special needs education (RR, 0.148; 95% CI, 0.061-0.360; p < 0.001) was positively associated with employment.

Conclusions

Specific medical, psychosocial, and educational factors may influence the employment outcomes of childhood-onset DRE. Paying attention to ASMs' side effects, adequately preventing the complications of psychiatric disorder symptoms, and providing an environment suitable for each patient condition would promote a fine working status for people with childhood-onset DRE.

VARIANTS OF THE FORMATION AND COURSE OF DRUG-RESISTANT EPILEPSY IN CHILDREN WITH GENETIC POLYMORPHISMS OF CYP2C9, CYP2C19, CYP3A4

OBJECTIVE

The aim: To clarify the frequency with which various variants of the formation and course of drug-resistant epilepsy occur in children with genetic polymor¬phisms of cytochromes CYP2C9, CYP2C19, CYP3A4.

PATIENTS AND METHODS

Materials and methods: The genotyping of CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP3A4*1B by the allele-specific polymerase chain reaction was performed in 116 children with drug-resistant epilepsy aged from 2 to 17 years. Thirty cases (boys-15; girls-15) with a follow-up period of more than 5 years were analyzed in detail.

RESULTS

Results: Of 30 cases analyzed, polymorphisms were not detected in 8 (26.67%) children, and 22 (73.33%) had polymorphisms of the CYP2C9, CYP2C19 and CYP3A4 genes associated with a slow metabolism of AED. In children with polymorphisms of the CYP450 genes, the wave-like course of the disease with the periods of remission and its failures was characteristic, while for children with a presumably normal metabolism there was the initial resistance to the treatment with AED.

CONCLUSION

Conclusions: Individual changes in the AED metabolism affect the course of drug-resistant epilepsies. For patients with a slow metabolism of AED the wave-like course of the disease and the "slipping off" phenomenon were more characteristic.

Genetic variations associated with pharmacoresistant epilepsy (Review)

Epilepsy is a common, serious neurological disorder worldwide. Although this disease can be successfully treated in most cases, not all patients respond favorably to medical treatments, which can lead to pharmacoresistant epilepsy. Drug-resistant epilepsy can be caused by a number of mechanisms that may involve environmental and genetic factors, as well as disease- and drug-related factors. In recent years, numerous studies have demonstrated that genetic variation is involved in the drug resistance of epilepsy, especially genetic variations found in drug resistance-related genes, including the voltage-dependent sodium and potassium channels genes, and the metabolizer of endogenous and xenobiotic substances genes. The present review aimed to highlight the genetic variants that are involved in the regulation of drug resistance in epilepsy; a comprehensive understanding of the role of genetic variation in drug resistance will help us develop improved strategies to regulate drug resistance efficiently and determine the pathophysiological processes that underlie this common human neurological disease.

Genetic susceptibility in Juvenile Myoclonic Epilepsy: Systematic review of genetic association studies

BACKGROUND

Several genetic association investigations have been performed over the last three decades to identify variants underlying Juvenile Myoclonic Epilepsy (JME). Here, we evaluate the accumulating findings and provide an updated perspective of these studies.

METHODOLOGY

A systematic literature search was conducted using the PubMed, Embase, Scopus, Lilacs, epiGAD, Google Scholar and Sigle up to February 12, 2016. The quality of the included studies was assessed by a score and classified as low and high quality. Beyond outcome measures, information was extracted on the setting for each study, characteristics of population samples and polymorphisms.

RESULTS

Fifty studies met eligibility criteria and were used for data extraction. With a single exception, all studies used a candidate gene approach, providing data on 229 polymorphisms in or near 55 different genes. Of variants investigating in independent data sets, only rs2029461 SNP in GRM4, rs3743123 in CX36 and rs3918149 in BRD2 showed a significant association with JME in at least two different background populations. The lack of consistent associations might be due to variations in experimental design and/or limitations of the approach.

CONCLUSIONS

Thus, despite intense research evidence established, specific genetic variants in JME susceptibility remain inconclusive. We discussed several issues that may compromise the quality of the results, including methodological bias, endophenotype and potential involvement of epigenetic factors.

PROSPERO REGISTRATION NUMBER

CRD42016036063.

Association study between polymorphisms in the CACNA1A, CACNA1C, and CACNA1H genes and drug-resistant epilepsy in the Chinese Han population

PURPOSE

As important ion channels of the central nervous system, calcium channels not only take part in epileptogenesis but also act as the targets of commonly used antiepileptic drugs (AEDs). Thus, this study aimed to provide the first investigation of the association between CACNA1A, CACNA1C, and CACNA1H single nucleotide polymorphisms (SNPs) and AED resistance in the Chinese Han population.

METHODS

We performed genotyping of tagging single nucleotide polymorphisms (tagSNPs) of CACNA1A, 1C and 1H in 480 Chinese epilepsy patients (288 drug-responsive and 192 drug-resistant patients). The Illumina GoldenGate BeadArray assay was used to detect the genotypes of all of the patients. A total of 15 SNPs were selected based on the HapMap database. The genotype distributions in drug-responsive and drug-resistant patients were compared, and the haplotype frequencies of each gene were calculated.

RESULTS

None of the 15 tagSNPs alleles were found to be associated with drug-resistant epilepsy. However, the frequency of the TAGAA haplotype in CACNA1A was significantly higher in drug-resistant patients than in drug-responsive patients after the correction of multiple comparisons with Bonferroni's method (TAGAA 13.3% vs. 7.1%, OR=2.129 [1.373-3.299], P=0.00059<0.05/10).

CONCLUSIONS

This study revealed no association between the 15 tagSNPs of CACNA1A, 1C, and 1H and drug efficacy in the Chinese Han population. The TAGAA haplotype of CACNA1A may be a risk factor for AED resistance.

The effect of genetic polymorphisms of cytochrome P450 CYP2C9, CYP2C19, and CYP2D6 on drug-resistant epilepsy in Turkish children

BACKGROUND AND OBJECTIVE

Despite the availability of several antiepileptic drugs, drug resistance remains one of the major challenges in epilepsy therapy. Genetic factors are known to play a significant role in the prognosis and treatment of epilepsy. The aim of this study was to determine the frequencies of alleles for CYP2C9, CYP2C19, and CYP2D6 genes in Turkish children with epilepsy, and to investigate the relationship between the genetic polymorphism of these genes with multiple drug resistance in epilepsy patients.

METHODS

We genotyped 132 epileptic patients (60 drug resistant and 72 drug responsive) and 55 healthy controls for six single nucleotide polymorphisms (SNPs) in CYP2C9, CYP2C19, and CYP2D6. Genotype, allele, and haplotype frequencies were compared between groups.

RESULTS

The frequencies of CYP2C9*3/*3 genotype and CYP2C9*3 allele, and the haplotype CCGG (CYP2C9*2 C>T, CYP2C9*3 A>C, and CYP2C19*2 G>A, CYP2C19* G>A) were significantly higher in drug-resistant versus -responsive patients.

CONCLUSION

Our results demonstrated the important role of the CYP2C9*3 allelic variant in preventing epilepsy patients from developing drug resistance. These data suggest that CYP2C9, CYP2C19, and CYP2D6 SNPs and haplotypes may affect the response to antiepileptic drugs.

Susceptibility to seizure-induced excitotoxic cell death is regulated by an epistatic interaction between Chr 18 (Sicd1) and Chr 15 (Sicd2) loci in mice

Seizure-induced cell death is believed to be regulated by multiple genetic components in addition to numerous external factors. We previously defined quantitative trait loci that control susceptibility to seizure-induced cell death in FVB/NJ (susceptible) and C57BL/6J (resistant) mice. Two of these quantitative trait loci assigned to chromosomes 18 (Sicd1) and 15 (Sicd2), control seizure-induced cell death resistance. In this study, through the use of a series of novel congenic strains containing the Sicd1 and Sicd2 congenic strains and different combinations of the Sicd1 or Sicd2 sub region(s), respectively, we defined these genetic interactions. We generated a double congenic strain, which contains the two C57BL/6J differential segments from chromosome 18 and 15, to determine how these two segments interact with one another. Phenotypic comparison between FVB-like littermates and the double congenic FVB.B6-Sicd1/Sicd2 strain identified an additive effect with respect to resistance to seizure-induced excitotoxic cell death. It thus appears that C57BL/6J alleles located on chromosomes 18 and 15 interact epistatically in an additive manner to control the extent of seizure-induced excitotoxic cell death. Three interval-specific congenic lines were developed, in which either segments of C57BL/6J Chr 18 or C57BL/6J Chr 15 were introduced in the FVB/NJ genetic background, and progeny were treated with kainate and examined for the extent of seizure-induced cell death. All of the interval-specific congenic lines exhibited reduced cell death in both area CA3 and the dentate hilus, associated with the C57BL/6J phenotype. These experiments demonstrate functional interactions between Sicd1 and Sicd2 that improve resistance to seizure-induced excitotoxic cell death, validating the critical role played by gene-gene interactions in excitotoxic cell death.

Genetic variants of synaptic vesicle and presynaptic plasma membrane proteins in idiopathic generalized epilepsy

BACKGROUND

The aim of this study was to analyze the role of the genetic variants of two synaptic vesicle proteins (VAMP2 and Synaptotagmin XI) and two presynaptic plasma membrane proteins (Syntaxin 1A and SNAP-25) in patients with idiopathic generalized epilepsy (IGE).

METHOD

Eighty-five patients with IGE and 93 healthy subjects were included in the study. We analyzed the functional polymorphisms of VAMP2, Synaptotagmin XI, Syntaxin 1A and SNAP-25 genes with polymerase chain reaction and restriction fragment length polymorphism methods.

RESULTS

In the patients with IGE, significant differences alleles and genotypes of 26 bp Ins/Del polymorphism of the VAMP2 gene and the 33-bp promoter region of Synaptotagmin XI were observed, however no associaton was found regarding Intron 7 rs1569061 of Syntaxin 1A gene, MnlI rs3746544 and DdeI rs1051312 polymorphisms of SNAP-25 gene compared with healthy subjects. Carriers of the C allele of Synaptotagmin XI had worse measures compared with the T allele of Synaptotagmin XI. In the haplotype analysis, the frequency of the T alleles of rs1569061 and of the C alleles of the 33-bp promoter region of Synaptotagmin XI was found to be significantly higher in patients with IGE as compared with the healthy subjects.

CONCLUSION

The genetic variations of VAMP2, Synaptotagmin XI might be indication of the relationship between these genes and IGE.

RLIP76 Gene Variants are not Associated with Drug Response in Turkish Epilepsy Patients

Approximately 30% of epileptic patients remain untreated, in spite of trials with maximum tolerable doses of more than one drug. The RalA binding protein 1 (RALBP1/RLIP76), a multifunctional, anti-apoptot-ic, multidrug transporter protein, has been proposed as being responsible for the drug resistance mechanism in epilepsy. We have investigated polymorphic differences in the coding regions and exonintron boundaries of the RLIP76 gene, between 146 refractory and 155 non refractory epileptic patients in Turkey, using denaturing high performance liquid chromatography (HPLC) and sequencing analysis techniques. We have detected the following sequence variants: c.160-4G>A, c.187C>G, c.1562-38G>A, c.1670+107G>A, c.1670+93G>A, c.1670+96G>A, c.1670+100C>T, c.1670+130C>T, c.1670+131G>C, c.1670+140 G>C, and found no statistically significant correlation between allele frequencies and drug response status. We conclude that sequence variants of this gene are not involved in drug resistance in epilepsy.

ABCC2 polymorphisms and haplotype are associated with drug resistance in Chinese epileptic patients

AIMS

Some study found that ATP-binding cassette (ABC) efflux transporters play an important role in antiepileptic drug resistance, especially ABCB1 and ABCC2. The aims of this study were to evaluate the relationship between the genetic polymorphisms of ABCC2 and ABCB1 and the therapeutic efficacy of antiepileptic drugs (AEDs) in Chinese epileptic patients.

METHODS

ABCB1 rs1045642 (3435C>T) and ABCC2 rs717620 (-24C>T), rs3740066 (3972C>T), and rs2273697 (1249G>A) polymorphisms loci in 537 Chinese epilepsy patients (217 drug resistant patients and 320 drug responders) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

ABCC2 rs717620 -24TT genotype was significantly associated with drug resistant epilepsy (odds ratio [OR]= 4.06 [1.79-9.20], P= 0.001). The OR values of ABCC2 rs717620 -24 CT+TT genotypes and ABCC2 rs3740066 (3972C>T) CT+TT genotypes were markedly higher in drug resistant patients (OR = 1.57 [1.08-2.29], P= 0.018; OR = 1.49 [1.02-2.18], P= 0.038, respectively) compared with responsive patients. ABCC2 rs2273697 (1249G>A) and ABCB1 rs1045642 (3435C>T) polymorphisms were not associated with drug resistant epilepsy. Linkage disequilibrium (LD) test showed that the ABCC2 rs717620 were in strong LD with rs2273697 (D'= 0.694) and rs3740066 (D'= 0.699). The frequencies of haplotypes TGT (ABCC2 -24C>T/ABCC2 1249G>A/ABCC2 3972C>T) in resistant patients was significantly higher than those in responsive patients (21.0% vs. 14.2%, P < 0.05).

CONCLUSION

ABCC2-24C>T, 3972C>T polymorphisms and one ABCC2 haplotype is associated with AED resistance; ABCC2 1249G>A and ABCB1 3435C>T polymorphisms are not associated with AED resistance in our study. These data suggest that ABCC2 polymorphisms and haplotype may affect the response of antiepileptic drugs.

The relevance of individual genetic background and its role in animal models of epilepsy

Growing evidence has indicated that genetic factors contribute to the etiology of seizure disorders. Most epilepsies are multifactorial, involving a combination of additive and epistatic genetic variables. However, the genetic factors underlying epilepsy have remained unclear, partially due to epilepsy being a clinically and genetically heterogeneous syndrome. Similar to the human situation, genetic background also plays an important role in modulating both seizure susceptibility and its neuropathological consequences in animal models of epilepsy, which has too often been ignored or not been paid enough attention to in published studies. Genetic homogeneity within inbred strains and their general amenability to genetic manipulation have made them an ideal resource for dissecting the physiological function(s) of individual genes. However, the inbreeding that makes inbred mice so useful also results in genetic divergence between them. This genetic divergence is often unaccounted for but may be a confounding factor when comparing studies that have utilized distinct inbred strains. The purpose of this review is to discuss the effects of genetic background strain on epilepsy phenotypes of mice, to remind researchers that the background genetics of a knockout strain can have a profound influence on any observed phenotype, and outline the means by which to overcome potential genetic background effects in experimental models of epilepsy.