The Pex3–Inp1 complex tethers yeast peroxisomes to the plasma membrane

A subset of peroxisomes is retained at the mother cell cortex by the Pex3–Inp1 complex. We identify Inp1 as the first known plasma membrane–peroxisome (PM-PER) tether by demonstrating that Inp1 meets the predefined criteria that a contact site tether protein must adhere to. We show that Inp1 is present in the correct subcellular location to interact with both the plasma membrane and peroxisomal membrane and has the structural and functional capacity to be a PM-PER tether. Additionally, expression of artificial PM-PER tethers is sufficient to restore retention in inp1Δ cells. We show that Inp1 mediates peroxisome retention via an N-terminal domain that binds PI(4,5)P2 and a C-terminal Pex3-binding domain, forming a bridge between the peroxisomal membrane and the plasma membrane. We provide the first molecular characterization of the PM-PER tether and show it anchors peroxisomes at the mother cell cortex, suggesting a new model for peroxisome retention

Intra-ER sorting of the peroxisomal membrane protein Pex3 relies on its luminal domain.

Pex3 is an evolutionarily conserved type III peroxisomal membrane protein required for peroxisome formation. It is inserted into the ER membrane and sorted via an ER subdomain (the peroxisomal ER, or pER) to peroxisomes. By constructing chimeras between Pex3 and the type III ER membrane protein Sec66, we have been able to separate the signals that mediate insertion of Pex3 into the ER from those that mediate sorting within the ER to the pER subdomain. The N-terminal 17-amino acid segment of Pex3 contains two signals that are each sufficient for sorting to the pER: a chimeric protein containing the N-terminal domain of Pex3 fused to the transmembrane and cytoplasmic segments of Sec66 sorts to the pER in wild type cells, and does not colocalise with peroxisomes. Subsequent transport to existing peroxisomes requires the Pex3 transmembrane segment. When expressed in Drosophila S2R+ cells, ScPex3 targeting to peroxisomes is dependent on the intra-ER sorting signals in the N-terminal segment. The N-terminal segments of both human and Drosophila Pex3 contain intra-ER sorting information and can replace that of ScPex3. Our analysis has uncovered the signals within Pex3 required for the various steps of its transport to peroxisomes. Our generation of versions of Pex3 that are blocked at each stage along its transport pathway provides a tool to dissect the mechanism, as well as the molecular machinery required at each step of the pathway

Meta-analysis of genome-wide association studies of anxiety disorders.

Anxiety disorders (ADs), namely generalized AD, panic disorder and phobias, are common, etiologically complex conditions with a partially genetic basis. Despite differing on diagnostic definitions based on clinical presentation, ADs likely represent various expressions of an underlying common diathesis of abnormal regulation of basic threat-response systems. We conducted genome-wide association analyses in nine samples of European ancestry from seven large, independent studies. To identify genetic variants contributing to genetic susceptibility shared across interview-generated DSM-based ADs, we applied two phenotypic approaches: (1) comparisons between categorical AD cases and supernormal controls, and (2) quantitative phenotypic factor scores (FS) derived from a multivariate analysis combining information across the clinical phenotypes. We used logistic and linear regression, respectively, to analyze the association between these phenotypes and genome-wide single nucleotide polymorphisms. Meta-analysis for each phenotype combined results across the nine samples for over 18 000 unrelated individuals. Each meta-analysis identified a different genome-wide significant region, with the following markers showing the strongest association: for case-control contrasts, rs1709393 located in an uncharacterized non-coding RNA locus on chromosomal band 3q12.3 (P=1.65 × 10(-8)); for FS, rs1067327 within CAMKMT encoding the calmodulin-lysine N-methyltransferase on chromosomal band 2p21 (P=2.86 × 10(-9)). Independent replication and further exploration of these findings are needed to more fully understand the role of these variants in risk and expression of ADs.Molecular Psychiatry advance online publication, 12 January 2016; doi:10.1038/mp.2015.197

Meta-analysis of Genome-Wide Association Studies for Extraversion: Findings from the Genetics of Personality Consortium

Extraversion is a relatively stable and heritable personality trait associated with numerous psychosocial, lifestyle and health outcomes. Despite its substantial heritability, no genetic variants have been detected in previous genome-wide association (GWA) studies, which may be due to relatively small sample sizes of those studies. Here, we report on a large meta-analysis of GWA studies for extraversion in 63,030 subjects in 29 cohorts. Extraversion item data from multiple personality inventories were harmonized across inventories and cohorts. No genome-wide significant associations were found at the single nucleotide polymorphism (SNP) level but there was one significant hit at the gene level for a long non-coding RNA site (LOC101928162). Genome-wide complex trait analysis in two large cohorts showed that the additive variance explained by common SNPs was not significantly different from zero, but polygenic risk scores, weighted using linkage information, significantly predicted extraversion scores in an independent cohort. These results show that extraversion is a highly polygenic personality trait, with an architecture possibly different from other complex human traits, including other personality traits. Future studies are required to further determine which genetic variants, by what modes of gene action, constitute the heritable nature of extraversion

Resting-State Directional Connectivity and Anxiety and Depression Symptoms in Adult Cannabis Users

Background Anxiety and depression symptoms are common among cannabis users and could be a risk factor for cannabis use (CU) disorder. Thus, it is critical to understand the neuronal circuits underlying the associations between CU and these symptoms. Alterations in resting-state functional connectivity within and/or between the default mode network and salience network have been reported in CU, anxiety, and depressive disorders and thus could be a mechanism underlying the associations between CU disorder and anxiety/depression symptoms. Methods Using resting-state functional magnetic resonance imaging, effective connectivities (ECs) among 9 major nodes from the default mode network and salience network were measured using dynamic causal modeling in 2 datasets: the Human Connectome Project (28 CU participants and 28 matched non–drug-using control participants) and a local CU study (21 CU participants and 21 matched non–drug-using control participants) in separate and parallel analyses. Results Relative to the control participants, right amygdala to left amygdala, anterior cingulate cortex to left amygdala, and medial prefrontal cortex to right insula ECs were greater, and left insula to left amygdala EC was smaller in the CU group. Each of these ECs showed a reliable linear relationship with at least one of the anxiety/depression measures. Most findings on the right amygdala to left amygdala EC were common to both datasets. Conclusions Right amygdala to left amygdala and anterior cingulate cortex to left amygdala ECs may be related to the close associations between CU and anxiety/depression symptoms. The findings on the medial prefrontal cortex to right insula and left insula to left amygdala ECs may reflect a compensatory mechanism

Assessment and characterization of phenotypic heterogeneity of anxiety disorders across five large cohorts.

To achieve sample sizes necessary for effectively conducting genome-wide association studies (GWASs), researchers often combine data from samples possessing multiple potential sources of heterogeneity. This is particularly relevant for psychiatric disorders, where symptom self-report, differing assessment instruments, and diagnostic comorbidity complicates the phenotypes and contribute to difficulties with detecting and replicating genetic association signals. We investigated sources of heterogeneity of anxiety disorders (ADs) across five large cohorts used in a GWAS meta-analysis project using a dimensional structural modeling approach including confirmatory factor analyses (CFAs) and measurement invariance (MI) testing. CFA indicated a single-factor model provided the best fit in each sample with the same pattern of factor loadings. MI testing indicated degrees of failure of metric and scalar invariance which depended on the inclusion of the effects of sex and age in the model. This is the first study to examine the phenotypic structure of psychiatric disorder phenotypes simultaneously across multiple, large cohorts used for GWAS. The analyses provide evidence for higher order invariance but possible break-down at more detailed levels that can be subtly influenced by included covariates, suggesting caution when combining such data. These methods have significance for large-scale collaborative studies that draw on multiple, potentially heterogeneous datasets. Copyright © 2016 John Wiley & Sons, Ltd

Meta-analyses of genome-wide linkage scans of anxiety-related phenotypes

Genetic factors underlying trait neuroticism, reflecting a tendency towards negative affective states, may overlap genetic susceptibility for anxiety disorders and help explain the extensive comorbidity amongst internalizing disorders. Genome-wide linkage (GWL) data from several studies of neuroticism and anxiety disorders have been published, providing an opportunity to test such hypotheses and identify genomic regions that harbor genes common to these phenotypes. In all, 11 independent GWL studies of either neuroticism (n8) or anxiety disorders (n3) were collected, which comprised of 5341 families with 15 529 individuals. The rank-based genome scan meta-analysis (GSMA) approach was used to analyze each trait separately and combined, and global correlations between results were examined. False discovery rate (FDR) analysis was performed to test for enrichment of significant effects. Using 10 cM intervals, bins nominally significant for both GSMA statistics, P SR and P OR, were found on chromosomes 9, 11, 12, and 14 for neuroticism and on chromosomes 1, 5, 15, and 16 for anxiety disorders. Genome-wide, the results for the two phenotypes were significantly correlated, and a combined analysis identified additional nominally significant bins. Although none reached genome-wide significance, an excess of significant P SR P-values were observed, with 12 bins falling under a FDR threshold of 0.50. As demonstrated by our identification of multiple, consistent signals across the genome, meta-analytically combining existing GWL data is a valuable approach to narrowing down regions relevant for anxiety-related phenotypes. This may prove useful for prioritizing emerging genome-wide association data for anxiety disorders

Peroxisome Biogenesis Occurs in an Unsynchronized Manner in Close Association with the Endoplasmic Reticulum in Temperature-sensitive Yarrowia lipolytica Pex3p Mutants

Pex3p is a peroxisomal integral membrane protein required early in peroxisome biogenesis, and Pex3p-deficient cells lack identifiable peroxisomes. Two temperature-sensitive pex3 mutant strains of the yeast Yarrowia lipolytica were made to investigate the role of Pex3p in the early stages of peroxisome biogenesis. In glucose medium at 16°C, these mutants underwent de novo peroxisome biogenesis and exhibited early matrix protein sequestration into peroxisome-like structures found at the endoplasmic reticulum-rich periphery of cells or sometimes associated with nuclei. The de novo peroxisome biogenesis seemed unsynchronized, with peroxisomes occurring at different stages of development both within cells and between cells. Cells with peripheral nascent peroxisomes and cells with structures morphologically distinct from peroxisomes, such as semi/circular tubular structures that immunostained with antibodies to peroxisomal matrix proteins and to the endoplasmic reticulum-resident protein Kar2p, and that surrounded lipid droplets, were observed during up-regulation of peroxisome biogenesis in cells incubated in oleic acid medium at 16°C. These structures were not detected in wild-type or Pex3p-deficient cells. Their role in peroxisome biogenesis remains unclear. Targeting of peroxisomal matrix proteins to these structures suggests that Pex3p directly or indirectly sequesters components of the peroxisome biogenesis machinery. Such a role is consistent with Pex3p overexpression producing cells with fewer, larger, and clustered peroxisomes