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The hippocampus in mammalian brain varies in size across individuals. Here, Hibar and colleagues perform a genome-wide association meta-analysis to find six genetic loci with significant association to hippocampus volume.

In a GWAS study of 32,438 adults, the authors discovered five novel loci for intracranial volume and confirmed two known signals. Variants for intracranial volume were also related to childhood and adult cognitive function and to Parkinson's disease, and enriched near genes involved in growth pathways, including PI3K-AKT signaling.

Genome-wide analysis identifies variants associated with the volume of seven different subcortical brain regions defined by magnetic resonance imaging. Implicated genes are involved in neurodevelopmental and synaptic signaling pathways.

Autism spectrum disorders (ASDs) are neurodevelopmental disorders characterized by impairments in social and communication skills. Accumulating evidence suggests a genetic component to ASDs, and here a two-stage, genome-wide approach is used to identify candidate genomic loci enriched in ASD cases. The majority of these loci are found to be involved in neuronal adhesion and ubiquitin degradation, suggesting novel susceptibility mechanisms.

Although structural variation has been previously associated with autism spectrum disorders, this study reports a genome-wide significant association of common variants with susceptibility to this disorder group. The results implicate neuronal cell-adhesion molecules in the pathogenesis of this group of neurodevelopmental and neuropsychiatric disorders.

The authors defined a roadmap for investigating the genetic covariance between structural or functional brain phenotypes and risk for psychiatric disorders. Their proof-of-concept study using the largest available common variant data sets for schizophrenia and volumes of several (mainly subcortical) brain structures did not find evidence of genetic overlap.

Better analytical methods are needed to extract biological meaning from genome-wide association studies (GWAS) of psychiatric disorders. Here the authors take GWAS data from over 60,000 subjects, including patients with schizophrenia, bipolar disorder and major depression, and identify common etiological pathways shared amongst them.

Genome-wide association studies are used to identify common genetic variants that affect the structure of selected subcortical regions of the human brain; their identification provides insight into the causes of variability in brain development and may help to determine mechanisms of neuropsychiatric dysfunction.

The autistic spectrum disorders (ASDs) are highly heritable, yet the underlying genetic determinants remain largely unknown. Here, a genome-wide analysis of rare copy number variants (CNVs) has been carried out, revealing that ASD sufferers carry a higher load of rare, genic CNVs than do controls. Many of these CNVs are de novo and inherited. The results implicate several novel genes in ASDs, and point to the importance of cellular proliferation, projection and motility, as well as specific signalling pathways, in these disorders.

Naomi Wray and colleagues report an analysis of genome-wide association data sets from the Psychiatric Genomics Consortium for five psychiatric disorders. They find that common variation explains 17–29% of the variance in liability and provide further support for a shared genetic etiology for these related psychiatric disorders.

Elise Robinson and colleagues present the polygenic transmission disequilibrium test (pTDT) for evaluating transmission of polygenic risk in family-based study designs. The authors apply pTDT to a cohort of autism spectrum disorder (ASD) families and find that common polygenic variation acts additively with de novo variants to contribute to ASD risk.

Autism is a highly heritable neurodevelopmental disorder, and yet few specific susceptibility genes have been identified to date. A linkage and association mapping study using half a million genome-wide single nucleotide polymorphisms is now described in a common set of 1,031 multiplex autism families. The linkage regions identified provide targets for rare variation screening whereas the discovery of a single novel association, SEMA5A, demonstrates the action of common variants.