RESUMO
PURPOSE: Although complex idiopathic generalized epilepsies (IGEs) are recognized to have a significant genetic component, as yet there are no known common susceptibility variants. It has recently been suggested that variation in the BRD2 gene confers increased risk of juvenile myoclonic epilepsy (JME), which accounts for around a quarter of all IGE. Here we examine the association between the candidate causal SNP (the promoter variant rs3918149) and JME in five independent cohorts comprising in total 531 JME cases and 1,390 healthy controls. METHODS: The strongest candidate causal variant from the original report (rs3918149) was genotyped across all five cohorts. In an effort to identify novel candidate causal polymorphisms, previously unscreened regions of UTR were resequenced. RESULTS: We observed a significant effect in a small sample recruited in Britain (genotype p = 0.001, allele p = 0.001), a borderline significant effect in a sample recruited in Ireland and no association in larger samples of German, Australian, and Indian populations. There was no association with other common forms of epilepsy or any other clear candidate casual variants in or near the BRD2 region. CONCLUSIONS: The replication of an effect in the British cohort and suggestive evidence from that recruited in Ireland but lack of replication from the larger German, Australian, and Indian cohorts is surprising and difficult to explain. Further replication in carefully matched populations is required. Results presented here do not, however, support a strong effect for susceptibility to JME across populations of European descent.
Assuntos
Variação Genética , Epilepsia Mioclônica Juvenil/genética , Proteínas Serina-Treonina Quinases/genética , Estudos de Casos e Controles , Estudos de Coortes , Heterogeneidade Genética , Predisposição Genética para Doença , Genética Populacional , Genótipo , Humanos , Epilepsia Mioclônica Juvenil/epidemiologia , Fenótipo , Polimorfismo de Nucleotídeo Único/genética , Regiões Promotoras Genéticas/genética , Fatores de Risco , Fatores de Transcrição , Reino Unido/epidemiologia , População Branca/genética , População Branca/estatística & dados numéricosRESUMO
A trait locus for electroencephalographic photoparoxysmal response (PPR) has been mapped to the chromosomal region 6p21 near a susceptibility locus for juvenile myoclonic epilepsy (JME). Linkage disequilibrium mapping revealed strong associations between JME and polymorphisms of the gene encoding the bromodomain-containing protein 2 (BRD2). The present association study tested whether genetic variation of BRD2 confers also susceptibility to PPR. All study participants were of German descent, comprising 187 subjects exhibiting PPR (types I-IV) and 666 healthy controls. Genotypes of each study participant were assessed for seven single nucleotide polymorphisms and one dinucleotide repeat polymorphism, covering the genomic BRD2 sequence. Allelic and haplotypic associations were found between PPR and six BRD2 polymorphisms (P: 0.0075-0.035). Considering the strong neurobiological association of JME and PPR, the present results support evidence that PPR and JME share epileptogenic pathways, for which BRD2 might be an underlying susceptibility gene.
Assuntos
Predisposição Genética para Doença , Transtornos de Fotossensibilidade/genética , Polimorfismo de Nucleotídeo Único , Proteínas Serina-Treonina Quinases/genética , Mapeamento Cromossômico , Frequência do Gene , Genótipo , Humanos , Epilepsia Mioclônica Juvenil/genética , Fatores de TranscriçãoRESUMO
Succinic semialdehyde dehydrogenase (SSADH) is involved in the degradation of the inhibitory neurotransmitter GABA and about 50% of patients with SSADH deficiency suffer from seizures. The gene encoding SSADH (gene symbol: ALDH5A1) maps in proximity to susceptibility loci for juvenile myoclonic epilepsy (JME) and photosensitivity on chromosome 6p22. The present study tested whether variation of the ALDH5A1 gene confers susceptibility to common syndromes of idiopathic generalized epilepsy (IGE) and an abnormal photoparoxysmal response (PPR). Mutation screening of the ALDH5A1 coding sequence of 35IGE/PPR patients and four healthy control subjects identified 17 sequence variants, of which three resulted in an exchange of amino acids (H180Y, P182L, A237S). Association analysis was carried out for six single nucleotide polymorphisms (SNPs) and one trinucleotide repeat polymorphism (TNR, intron 1), covering the genomic ALDH5A1 sequence. The study sample comprised 566 unrelated German IGE patients, including 218 JME and 95 photosensitive IGE patients, 78 PPR probands without IGE, and 662 German population controls. None of the investigated ALDH5H1 polymorphisms showed evidence for an allelic or genotypic association with either IGE, JME, or PPR, when corrected for multiple tests. A tentative haplotypic association of the two-marker haplotype (rs1883415-TNR) covering the 5'-regulatory region in IGE patients (chi2=11.65, d.f.=3, P=0.009) warrants further replication studies. The present results do not provide evidence that any ALDH5A1 missense variant itself contributes a common and substantial susceptibility effect (RR>2) to IGE syndromes or an increased liability to visually-induced cortical synchronization.