Activated protein C (APC) is a serine protease with potent anticoagulant properties, which is formed in blood on the endothelium from an inactive precursor. During normal haemostasis, APC limits clot formation by proteolytic inactivation of factors Va and VIIIa (ref. 2). To do this efficiently the enzyme needs a nonenzymatic cofactor, protein S (ref. 3). Recently it was found that the anticoagulant response to APC (APC resistance) was very weak in the plasma of 21% of unselected consecutive patients with thrombosis and about 50% of selected patients with a personal or family history of thrombosis; moreover, 5% of healthy individuals show APC resistance, which is associated with a sevenfold increase in the risk for deep vein thrombosis. Here we demonstrate that the phenotype of APC resistance is associated with heterozygosity or homozygosity for a single point mutation in the factor V gene (at nucleotide position 1,691, G-->A substitution) which predicts the synthesis of a factor V molecule (FV Q506, or FV Leiden) that is not properly inactivated by APC. The allelic frequency of the mutation in the Dutch population is approximately 2% and is at least tenfold higher than that of all other known genetic risk factors for thrombosis (protein C (ref. 8), protein S (ref. 9), antithrombin10 deficiency) together.

Disorders of the brain can exhibit considerable epidemiological comorbidity and often share symptoms, provoking debate about their etiologic overlap. We quantified the genetic sharing of 25 brain disorders from genome-wide association studies of 265,218 patients and 784,643 control participants and assessed their relationship to 17 phenotypes from 1,191,588 individuals. Psychiatric disorders share common variant risk, whereas neurological disorders appear more distinct from one another and from the psychiatric disorders. We also identified significant sharing between disorders and a number of brain phenotypes, including cognitive measures. Further, we conducted simulations to explore how statistical power, diagnostic misclassification, and phenotypic heterogeneity affect genetic correlations. These results highlight the importance of common genetic variation as a risk factor for brain disorders and the value of heritability-based methods in understanding their etiology.

on behalf of the Brainstorm consortium 1 7 2 4 UK 2 5

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...