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.

Objective Obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) are heritable, neurodevelopmental disorders with a partially shared genetic etiology. This study represents the first genome-wide investigation of large (>500kb), rare (<1%) copy number variants (CNVs) in OCD and the largest genome-wide CNV analysis in TS to date. Method The primary analyses utilized a cross-disorder design for 2,699 patients (1,613 ascertained for OCD, 1,086 ascertained for TS) and 1,789 controls. Parental data facilitated a de novo analysis in 348 OCD trios. Results Although no global CNV burden was detected in the cross-disorder analysis or in secondary, disease-specific analyses, there was a 3.3-fold increased burden of large deletions previously associated with other neurodevelopmental disorders (p=.09). Half of these neurodevelopmental deletions were located in a single locus, 16p13.11 (5 patient deletions: 0 control deletions, p=0.08 in current study, p=0.025 compared to published controls). Three 16p13.11 deletions were confirmed de novo, providing further support to the etiological significance of this region. The overall OCD de novo rate was 1.4%, which is intermediate between published rates in controls (0.7%) and in autism or schizophrenia (2–4%). Conclusion Several converging lines of evidence implicate 16p13.11 deletions in OCD, with weaker evidence for a role in TS. The trend toward increased overall neurodevelopmental CNV burden in TS and OCD suggests that deletions previously associated with other neurodevelopmental disorders may also contribute to these phenotypes.

Obsessive-compulsive disorder (OCD) and Tourette Syndrome (TS) are highly heritable neurodevelopmental disorders that are thought to share genetic risk factors. However, the identification of definitive susceptibility genes for these etiologically complex disorders remains elusive. Here, we report a combined genome-wide association study (GWAS) of TS and OCD in 2723 cases (1310 with OCD, 834 with TS, 579 with OCD plus TS/chronic tics (CT)), 5667 ancestry-matched controls, and 290 OCD parent-child trios. Although no individual single nucleotide polymorphisms (SNPs) achieved genome-wide significance, the GWAS signals were enriched for SNPs strongly associated with variations in brain gene expression levels, i.e. expression quantitative loci (eQTLs), suggesting the presence of true functional variants that contribute to risk of these disorders. Polygenic score analyses identified a significant polygenic component for OCD (p=2×10−4), predicting 3.2% of the phenotypic variance in an independent data set. In contrast, TS had a smaller, non-significant polygenic component, predicting only 0.6% of the phenotypic variance (p=0.06). No significant polygenic signal was detected across the two disorders, although the sample is likely underpowered to detect a modest shared signal. Furthermore, the OCD polygenic signal was significantly attenuated when cases with both OCD and TS/CT were included in the analysis (p=0.01). Previous work has shown that TS and OCD have some degree of shared genetic variation. However, the data from this study suggest that there are also distinct components to the genetic architectures of TS and OCD. Furthermore, OCD with co-occurring TS/CT may have different underlying genetic susceptibility compared to OCD alone.

Photoreceptor cell death accompanying many retinal degenerative disorders results in irreversible loss of vision in humans. However, the precise molecular pathway that executes cell death is not known. Our results from a Drosophila model of retinal degeneration corroborate previously reported findings that the developmental apoptotic pathway is not involved in photoreceptor cell demise. By undertaking a candidate gene approach, we find that players involved in the immune response against Gram-negative bacteria are involved in retinal degeneration. Here, we report that the NF-κB transcription factor Relish regulates neuronal cell death. Retinal degeneration is prevented in genetic backgrounds that block Relish activation. We also report that the N-terminal domain of Relish encodes unique toxic functions. These data uncover a unique molecular pathway of retinal degeneration in Drosophila and identify a previously unknown function of NF-κB signaling in cell death.apoptosis | retinitis pigmentosa | nuclear factor kappa B | innate immunity | norpA

Tourette Syndrome (TS) is a neurodevelopmental disorder with a complex genetic etiology. Through an international collaboration, we genotyped 42 single nucleotide polymorphisms (SNPs)(p<10−3) from the recent TS genome-wide association study (GWAS) in 609 independent cases and 610 ancestry-matched controls. Only rs2060546 on chromosome 12q22 (p=3.3×10−4) remained significant after Bonferroni correction. Meta-analysis with the original GWAS yielded the strongest association to date (p=5.8×10−7). Although its functional significance is unclear, rs2060546 lies closest to NTN4, an axon guidance molecule expressed in developing striatum. Risk score analysis significantly predicted case/control status (p=0.042), suggesting that many of these variants are true TS risk alleles.