We identified 15q13.3 microdeletions encompassing the CHRNA7 gene in 12 of 1,223 individuals with idiopathic generalized epilepsy (IGE), which were not detected in 3,699 controls (joint P = 5.32 × 10 −8 ). Most deletion carriers showed common IGE syndromes without other features previously associated with 15q13.3 microdeletions, such as intellectual disability, autism or schizophrenia. Our results indicate that 15q13.3 microdeletions constitute the most prevalent risk factor for common epilepsies identified to date.Idiopathic generalized epilepsies (IGE) are common seizure disorders accounting for up to one-third of all epilepsies 1 . The vast majority of individuals with IGE have a complex genetic etiology2, for which the underlying genetic alterations remain largely unknown. Recently, a 15q13.3 microdeletion syndrome has been identified in 0.2-0.3% of individuals Correspondence should be addressed to T.S. (sandert@uni-koeln.de). Note: Supplementary information is available on the Nature Genetics website. AUTHOR CONTRIBUTIONST.S. and E.E.E. initiated and designed the study; I.H., H.M., S.v.S., I.S., A.A.K.-L., V.G., B.S., K.M.K., P.S.R., F.R., Y.W., H.L., F.Z., L.U., K.F., M. Feucht, F.V., G.-J.d.H., R.S.M., H.H., D. Luciano, C.R., D. Lindhout, C.E.E., U.S. and T.S. recruited and phenotyped the EPICURE sample; H.C.M., A.J.S., M.G., M. Fichera, C.B., P.G., P.T., A.M. and E.E.E. recruited and phenotyped the mixed IGE sample; A.F., M.W., M.N. and S.S. recruited and phenotyped the PopGen control sample; I.H., A.F., C.L., K.L.K., I.S., M.W., M.N., P.N. and T.S. performed the CNV analysis on SNP arrays; H.C.M., A.J.S., M. Fichera, C.B. and D. Luciano performed the qPCR screening; H.C.M., M. Fichera, C.B. and D. Luciano performed the screening using Illumina Genotyping BeadChips; H.C.M., A.J.S. and C.B. performed the confirmation using NimbleGen arrays; C.d.K., B.P.C.K. and D. Lindhout performed the confirmation using Illumina CNV BeadChips; I.H., H.C.M., A.J.S., M.G., M. Fichera, A.F., C.d.K., K.L.K., C.R., B.P.C.K., D. Lindhout, E.E.E. and T.S. coordinated the work and prepared the manuscript. Susceptibility loci for common idiopathic epilepsies, comprising benign epilepsy of childhood with centrotemporal spikes7 and common IGE syndromes8 ,9 , have also been mapped to the 15q13-q14 region. To test whether the 15q13.3 deletion increases risk of common epilepsies, we screened for structural variants within the 15q13.3 region in two independent samples of individuals with IGE and ancestrally matched controls. The first sample comprised 647 unrelated IGE cases of Western European ancestry (EPICURE sample) and 1,202 German controls (PopGen) genotyped using the Affymetrix GenomeWide Human SNP array 6.0. We identified the 15q13.3 microdeletion in 7 of 647 IGE cases ( Supplementary Fig. 1 online) with different IGE syndromes ( Supplementary Fig. 2 online). Thus, our results suggest that the 15q13.3 deletion only, and not the reciprocal duplication, represents a major risk factor for IGE. NIH Public AccessIn our stu...

Alcohol misuse is the leading cause of cirrhosis and the second most common indication for liver transplantation in the Western world. We performed a genome-wide association study for alcohol-related cirrhosis in individuals of European descent (712 cases and 1,426 controls) with subsequent validation in two independent European cohorts (1,148 cases and 922 controls). We identified variants in the MBOAT7 (P = 1.03 × 10(-9)) and TM6SF2 (P = 7.89 × 10(-10)) genes as new risk loci and confirmed rs738409 in PNPLA3 as an important risk locus for alcohol-related cirrhosis (P = 1.54 × 10(-48)) at a genome-wide level of significance. These three loci have a role in lipid processing, suggesting that lipid turnover is important in the pathogenesis of alcohol-related cirrhosis.

Inflammatory bowel disease (IBD) typically manifests as either ulcerative colitis (UC) or Crohn's disease (CD). Systematic identification of susceptibility genes for IBD has thus far focused mainly on CD, and little is known about the genetic architecture of UC. Here we report a genome-wide association study with 440,794 SNPs genotyped in 1,167 individuals with UC and 777 healthy controls. Twenty of the most significantly associated SNPs were tested for replication in three independent European case-control panels comprising a total of 1,855 individuals with UC and 3,091 controls. Among the four consistently replicated markers, SNP rs3024505 immediately flanking the IL10 (interleukin 10) gene on chromosome 1q32.1 showed the most significant association in the combined verification samples (P = 1.35 x 10(-12); OR = 1.46 (1.31-1.62)). The other markers were located in ARPC2 and in the HLA-BTNL2 region. Association between rs3024505 and CD (1,848 cases, 1,804 controls) was weak (P = 0.013; OR = 1.17 (1.01-1.34)). IL10 is an immunosuppressive cytokine that has long been proposed to influence IBD pathophysiology. Our findings strongly suggest that defective IL10 function is central to the pathogenesis of the UC subtype of IBD.

Understanding the genetic structure of the European population is important, not only from a historical perspective, but also for the appropriate design and interpretation of genetic epidemiological studies. Previous population genetic analyses with autosomal markers in Europe either had a wide geographic but narrow genomic coverage [1, 2], or vice versa [3-6]. We therefore investigated Affymetrix GeneChip 500K genotype data from 2,514 individuals belonging to 23 different subpopulations, widely spread over Europe. Although we found only a low level of genetic differentiation between subpopulations, the existing differences were characterized by a strong continent-wide correlation between geographic and genetic distance. Furthermore, mean heterozygosity was larger, and mean linkage disequilibrium smaller, in southern as compared to northern Europe. Both parameters clearly showed a clinal distribution that provided evidence for a spatial continuity of genetic diversity in Europe. Our comprehensive genetic data are thus compatible with expectations based upon European population history, including the hypotheses of a south-north expansion and/or a larger effective population size in southern than in northern Europe. By including the widely used CEPH from Utah (CEU) samples into our analysis, we could show that these individuals represent northern and western Europeans reasonably well, thereby confirming their assumed regional ancestry.

Idiopathic focal epilepsy (IFE) with rolandic spikes is the most common childhood epilepsy, comprising a phenotypic spectrum from rolandic epilepsy (also benign epilepsy with centrotemporal spikes, BECTS) to atypical benign partial epilepsy (ABPE), Landau-Kleffner syndrome (LKS) and epileptic encephalopathy with continuous spike and waves during slow-wave sleep (CSWS). The genetic basis is largely unknown. We detected new heterozygous mutations in GRIN2A in 27 of 359 affected individuals from 2 independent cohorts with IFE (7.5%; P = 4.83 × 10(-18), Fisher's exact test). Mutations occurred significantly more frequently in the more severe phenotypes, with mutation detection rates ranging from 12/245 (4.9%) in individuals with BECTS to 9/51 (17.6%) in individuals with CSWS (P = 0.009, Cochran-Armitage test for trend). In addition, exon-disrupting microdeletions were found in 3 of 286 individuals (1.0%; P = 0.004, Fisher's exact test). These results establish alterations of the gene encoding the NMDA receptor NR2A subunit as a major genetic risk factor for IFE.

Epileptic encephalopathies are a phenotypically and genetically heterogeneous group of severe epilepsies accompanied by intellectual disability and other neurodevelopmental features1-6. Using next generation sequencing, we identified four different de novo mutations in KCNA2, encoding the potassium channel KV1.2, in six patients with epileptic encephalopathy (one mutation recurred three times independently). Four individuals presented with febrile and multiple afebrile, often focal seizure types, multifocal epileptiform discharges strongly activated by sleep, mild-moderate intellectual disability, delayed speech development and sometimes ataxia. Functional studies of the two mutations associated with this phenotype revealed an almost complete loss-of-function with a dominant-negative effect. Two further individuals presented with a different and more severe epileptic encephalopathy phenotype. They carried mutations inducing a drastic gain-of-function effect leading to permanently open channels. These results establish KCNA2 as a novel gene involved in human neurodevelopmental disorders by two different mechanisms, predicting either hyperexcitability or electrical silencing of KV1.2-expressing neurons.

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The purpose of this work is to quantify the effects that errors in genotyping have on power and the sample size necessary to maintain constant asymptotic Type I and Type II error rates (SSN) for case-control genetic association studies between a disease phenotype and a di-allelic marker locus, for example a single nucleotide polymorphism (SNP) locus. We consider the effects of three published models of genotyping errors on the chi-square test for independence in the 2 × 3 table. After specifying genotype frequencies for the marker locus conditional on disease status and error model in both a genetic model-based and a genetic model-free framework, we compute the asymptotic power to detect association through specification of the test’s non-centrality parameter. This parameter determines the functional dependence of SSN on the genotyping error rates. Additionally, we study the dependence of SSN on linkage disequilibrium (LD), marker allele frequencies, and genotyping error rates for a dominant disease model. Increased genotyping error rate requires a larger SSN. Every 1% increase in sum of genotyping error rates requires that both case and control SSN be increased by 2–8%, with the extent of increase dependent upon the error model. For the dominant disease model, SSN is a nonlinear function of LD and genotyping error rate, with greater SSN for lower LD and higher genotyping error rate. The combination of lower LD and higher genotyping error rates requires a larger SSN than the sum of the SSN for the lower LD and for the higher genotyping error rate.