An inherited duplication at the gene p21 Protein-Activated Kinase 7 (PAK7) is a risk factor for psychosis

Meta-analyses of epigenetic age acceleration and GrimAge components of schizophrenia or first-episode psychosis

Schizophrenia is a common chronic psychiatric disorder that causes age-related dysfunction. The life expectancy in patients with schizophrenia is ≥10 years shorter than that in the general population because of the higher risk of other diseases, such as cardiovascular diseases. Aging studies based on DNA methylation status have received considerable attention. Several epigenetic age accelerations and predicted values of aging-related proteins (GrimAge and GrimAge2 components) have been analyzed in multiple diseases. However, no studies have investigated up to GrimAge and GrimAge2 components between patients with schizophrenia and controls. Therefore, we aimed to conduct multiple regression analyses to investigate the association between schizophrenia and epigenetic age accelerations and GrimAge and GrimAge2 components in seven cohorts. Furthermore, we included patients with first-episode psychosis whose illness duration was often shorter than schizophrenia in our analysis. We integrated these results with meta-analyses, noting the acceleration of GrimAge, GrimAge2, and DunedinPACE, and increase in adrenomedullin, beta-2 microglobulin, cystatin C, and plasminogen activation inhibitor-1 levels, in patients with schizophrenia or first-episode psychosis. These results corroborated the finding that patients with schizophrenia had an increased risk of diabetes, cardiovascular disease, and cognitive dysfunction from a biological perspective. Patients with schizophrenia and first-episode psychosis showed differences in the results when compared with controls. Such analyses may lead to the development of novel therapeutic targets to patients with schizophrenia or relevant diseases from the perspective of aging in the future.

Schizophrenia is associated with altered DNA methylation variance

Varying combinations of genetic and environmental risk factors are thought to underpin phenotypic heterogeneity between individuals in psychiatric conditions such as schizophrenia. While epigenome-wide association studies in schizophrenia have identified extensive alteration of mean DNA methylation levels, less is known about the location and impact of DNA methylation variance, which could contribute to phenotypic and treatment response heterogeneity. To explore this question, we conducted the largest meta-analysis of blood DNA methylation variance in schizophrenia to date, leveraging three cohorts comprising 1036 individuals with schizophrenia and 954 non-psychiatric controls. Surprisingly, only a small proportion (0.1%) of the 213 variably methylated positions (VMPs) associated with schizophrenia (Benjamini-Hochberg FDR < 0.05) were shared with differentially methylated positions (DMPs; sites with mean changes between cases and controls). These blood-derived VMPs were found to be overrepresented in genes previously associated with schizophrenia and amongst brain-enriched genes, with evidence of concordant changes at VMPs in the cerebellum, hippocampus, prefrontal cortex, or striatum. Epigenetic covariance was also observed with respect to clinically significant metrics including age of onset, cognitive deficits, and symptom severity. We also uncovered a significant VMP in individuals with first-episode psychosis (n = 644) from additional cohorts and a non-psychiatric comparison group (n = 633). Collectively, these findings suggest schizophrenia is associated with significant changes in DNA methylation variance, which may contribute to individual-to-individual heterogeneity.

Genome-wide association study and polygenic risk score analysis for schizophrenia in a Korean population

Although large-scale genome-wide association studies (GWASs) have revealed the genetic architecture of schizophrenia, these studies have mainly focused on populations of European ancestry. This study aimed to identify common genetic variants associated with schizophrenia in the Korean population and evaluate the performance of polygenic risk scores (PRSs) derived from large-scale GWASs across ancestries. In the Korean psychiatric GWAS project (KPGP), seven academic institutes and their affiliated hospitals across South Korea recruited a cohort of 1670 patients with DSM-IV-defined schizophrenia and 2271 healthy controls. A total of 6690,822 SNPs were tested for association with schizophrenia. We identified one previously unreported genome-wide significant locus rs2423464 (P = 2.83 × 10-11; odds ratio = 1.65; 95 % confidence interval = 1.43-1.91, minor allele frequency = 0.126). This variant was also associated with increased lysosomal-associated membrane protein family member 5 (LAMP5) gene expression. The PRS derived from the meta-analysis results of East Asian and European GWASs explained a larger proportion of the phenotypic variance in the Korean schizophrenia sample than the PRS of an East Asian or European GWAS. (R2 = 0.073 for meta-analysis; 0.028 for East Asian GWAS; 0.037 for European GWAS). GWASs involving diverse ethnic groups will expand our understanding of the genetic architecture of schizophrenia.

Copy Number Variations in Neuropsychiatric Disorders

Neuropsychiatric disorders are complex conditions that represent a significant global health burden with complex and multifactorial etiologies. Technological advances in recent years have improved our understanding of the genetic architecture of the major neuropsychiatric disorders and the genetic loci involved. Previous studies mainly investigated genome-wide significant SNPs to elucidate the cross-disorder and disorder-specific genetic basis of neuropsychiatric disorders. Although copy number variations represent a major source of genetic variations, they are known risk factors in developing a variety of human disorders, including certain neuropsychiatric diseases. In this review, we demonstrate the current understanding of CNVs contributing to liability for schizophrenia, bipolar disorder, and major depressive disorder.

Evaluating the role of common risk variation in the recurrence risk of schizophrenia in multiplex schizophrenia families

Multiplex families have higher recurrence risk of schizophrenia compared to the families of sporadic cases, but the source of this increased recurrence risk is unknown. We used schizophrenia genome-wide association study data (N = 156,509) to construct polygenic risk scores (PRS) in 1005 individuals from 257 multiplex schizophrenia families, 2114 ancestry-matched sporadic cases, and 2205 population controls, to evaluate whether increased PRS can explain the higher recurrence risk of schizophrenia in multiplex families compared to ancestry-matched sporadic cases. Using mixed-effects logistic regression with family structure modeled as a random effect, we show that SCZ PRS in familial cases does not differ significantly from sporadic cases either with, or without family history (FH) of psychotic disorders (All sporadic cases p = 0.90, FH+ cases p = 0.88, FH- cases p = 0.82). These results indicate that increased burden of common schizophrenia risk variation as indexed by current SCZ PRS, is unlikely to account for the higher recurrence risk of schizophrenia in multiplex families. In the absence of elevated PRS, segregation of rare risk variation or environmental influences unique to the families may explain the increased familial recurrence risk. These findings also further validate a genetically influenced psychosis spectrum, as shown by a continuous increase of common SCZ risk variation burden from unaffected relatives to schizophrenia cases in multiplex families. Finally, these results suggest that common risk variation loading are unlikely to be predictive of schizophrenia recurrence risk in the families of index probands, and additional components of genetic risk must be identified and included in order to improve recurrence risk prediction.

MiR-145-5p modulates lipid metabolism and M2 macrophage polarization by targeting PAK7 and regulating β-catenin signaling in hyperlipidemia

The present study aims to explore the role of microRNA 145-5p (miR-145-5p) in hyperlipidemia. Using bioinformatics tools and a wide range of function and mechanism assays, we attempted to understand the specific function and potential mechanism of miR-145-5p in hyperlipidemia. A cholesterol-enriched diet induced an increase of serum cholesterol and triacylglycerol but a decrease of serum high-density lipoprotein. MiR-145-5p level was decreased in hyperlipidemia rat models. MiR-145-5p regulated lipid metabolism by antagonizing the alteration of high-density lipoprotein, cholesterol, and triacylglycerol in serum mediated by a cholesterol-enriched diet. In mechanism, miR-145-5p directly bound with p21 protein (RAC1)-activated kinase 7 (PAK7) and negatively regulated mRNA and protein levels of PAK7 in THP-1 cells. Furthermore, miR-145-5p level was negatively associated with PAK7 level in rat cardiac tissues. Finally, overexpression of PAK7 reversed the effects of miR-145-5p on β-catenin activation and M2 macrophages polarization in THP-1 cells. In conclusion, MiR-145-5p modulated lipid metabolism and M2 macrophage polarization by targeting PAK7 and regulating β-catenin signaling in hyperlipidemia, which may provide a potential biomarker for the treatment of hyperlipidemia-induced cardiovascular diseases.

Genetic control of variability in subcortical and intracranial volumes

Sensitivity to external demands is essential for adaptation to dynamic environments, but comes at the cost of increased risk of adverse outcomes when facing poor environmental conditions. Here, we apply a novel methodology to perform genome-wide association analysis of mean and variance in ten key brain features (accumbens, amygdala, caudate, hippocampus, pallidum, putamen, thalamus, intracranial volume, cortical surface area, and cortical thickness), integrating genetic and neuroanatomical data from a large lifespan sample (n = 25,575 individuals; 8-89 years, mean age 51.9 years). We identify genetic loci associated with phenotypic variability in thalamus volume and cortical thickness. The variance-controlling loci involved genes with a documented role in brain and mental health and were not associated with the mean anatomical volumes. This proof-of-principle of the hypothesis of a genetic regulation of brain volume variability contributes to establishing the genetic basis of phenotypic variance (i.e., heritability), allows identifying different degrees of brain robustness across individuals, and opens new research avenues in the search for mechanisms controlling brain and mental health.

Rare Copy Number Variants Are Associated With Poorer Cognition in Schizophrenia

BACKGROUND

Cognitive impairment in schizophrenia is a major contributor to poor outcomes, yet its causes are poorly understood. Some rare copy number variants (CNVs) are associated with schizophrenia risk and affect cognition in healthy populations, but their contribution to cognitive impairment in schizophrenia has not been investigated. We examined the effect of 12 schizophrenia CNVs on cognition in those with schizophrenia.

METHODS

General cognitive ability was measured using the Measurement and Treatment Research to Improve Cognition in Schizophrenia composite z score in 875 patients with schizophrenia and in a replication sample of 519 patients with schizophrenia using Wechsler Adult Intelligence Scale Full Scale IQ. Using linear regression, we tested for association between cognition and schizophrenia CNV status, covarying for age and sex. In addition, we tested whether CNVs hitting genes in schizophrenia-enriched gene sets (loss-of-function intolerant and synaptic gene sets) were associated with cognitive impairment.

RESULTS

A total of 23 schizophrenia CNV carriers were identified. Schizophrenia CNV carriers had lower general cognitive ability than nonschizophrenia CNV carriers in discovery (β = -0.66, 95% confidence interval [CI] = -1.31 to -0.01) and replication samples (β = -0.91, 95% CI = -1.71 to -0.11) and after meta-analysis (β = -0.76, 95% CI = -1.26 to -0.25, p = .003). CNVs hitting loss-of-function intolerant genes were associated with lower cognition (β = -0.15, 95% CI = -0.29 to -0.001, p = .048).

CONCLUSIONS

In those with schizophrenia, cognitive ability in schizophrenia CNV carriers is 0.5-1.0 standard deviations below non-CNV carriers, which may have implications for clinical assessment and management. We also demonstrate that rare CNVs hitting genes intolerant to loss-of-function variation lead to more severe cognitive impairment, above and beyond the effect of known schizophrenia CNVs.

The Role of p21-Activated Kinases in Cancer and Beyond: Where Are We Heading?

The p21-activated kinases (PAKs), downstream effectors of Ras-related Rho GTPase Cdc42 and Rac, are serine/threonine kinases. Biologically, PAKs participate in various cellular processes, including growth, apoptosis, mitosis, immune response, motility, inflammation, and gene expression, making PAKs the nexus of several pathogenic and oncogenic signaling pathways. PAKs were proved to play critical roles in human diseases, including cancer, infectious diseases, neurological disorders, diabetes, pancreatic acinar diseases, and cardiac disorders. In this review, we systematically discuss the structure, function, alteration, and molecular mechanisms of PAKs that are involved in the pathogenic and oncogenic effects, as well as PAK inhibitors, which may be developed and deployed in cancer therapy, anti-viral infection, and other diseases. Furthermore, we highlight the critical questions of PAKs in future research, which provide an opportunity to offer input and guidance on new directions for PAKs in pathogenic, oncogenic, and drug discovery research.

Neurexins in autism and schizophrenia-a review of patient mutations, mouse models and potential future directions

Mutations in the family of neurexins (NRXN1, NRXN2 and NRXN3) have been repeatedly identified in patients with autism spectrum disorder (ASD) and schizophrenia (SCZ). However, it remains unclear how these DNA variants affect neurexin functions and thereby predispose to these neurodevelopmental disorders. Understanding both the wild-type and pathologic roles of these genes in the brain could help unveil biological mechanisms underlying mental disorders. In this regard, numerous studies have focused on generating relevant loss-of-function (LOF) mammalian models. Although this has increased our knowledge about their normal functions, the potential pathologic role(s) of these human variants remains elusive. Indeed, after reviewing the literature, it seems apparent that a traditional LOF-genetic approach based on complete LOF might not be sufficient to unveil the role of these human mutations. First, these genes present a very complex transcriptome and total-LOF of all isoforms may not be the cause of toxicity in patients, particularly given evidence that causative variants act through haploinsufficiency. Moreover, human DNA variants may not all lead to LOF but potentially to intricate transcriptome changes that could also include the generation of aberrant isoforms acting as a gain-of-function (GOF). Furthermore, their transcriptomic complexity most likely renders them prone to genetic compensation when one tries to manipulate them using traditional site-directed mutagenesis approaches, and this could act differently from model to model leading to heterogeneous and conflicting phenotypes. This review compiles the relevant literature on variants identified in human studies and on the mouse models currently deployed, and offers suggestions for future research.

DNA methylation meta-analysis reveals cellular alterations in psychosis and markers of treatment-resistant schizophrenia

We performed a systematic analysis of blood DNA methylation profiles from 4483 participants from seven independent cohorts identifying differentially methylated positions (DMPs) associated with psychosis, schizophrenia, and treatment-resistant schizophrenia. Psychosis cases were characterized by significant differences in measures of blood cell proportions and elevated smoking exposure derived from the DNA methylation data, with the largest differences seen in treatment-resistant schizophrenia patients. We implemented a stringent pipeline to meta-analyze epigenome-wide association study (EWAS) results across datasets, identifying 95 DMPs associated with psychosis and 1048 DMPs associated with schizophrenia, with evidence of colocalization to regions nominated by genetic association studies of disease. Many schizophrenia-associated DNA methylation differences were only present in patients with treatment-resistant schizophrenia, potentially reflecting exposure to the atypical antipsychotic clozapine. Our results highlight how DNA methylation data can be leveraged to identify physiological (e.g., differential cell counts) and environmental (e.g., smoking) factors associated with psychosis and molecular biomarkers of treatment-resistant schizophrenia.

Kinase Interaction Network Expands Functional and Disease Roles of Human Kinases

Protein kinases are essential for signal transduction and control of most cellular processes, including metabolism, membrane transport, motility, and cell cycle. Despite the critical role of kinases in cells and their strong association with diseases, good coverage of their interactions is available for only a fraction of the 535 human kinases. Here, we present a comprehensive mass-spectrometry-based analysis of a human kinase interaction network covering more than 300 kinases. The interaction dataset is a high-quality resource with more than 5,000 previously unreported interactions. We extensively characterized the obtained network and were able to identify previously described, as well as predict new, kinase functional associations, including those of the less well-studied kinases PIM3 and protein O-mannose kinase (POMK). Importantly, the presented interaction map is a valuable resource for assisting biomedical studies. We uncover dozens of kinase-disease associations spanning from genetic disorders to complex diseases, including cancer.

Association of Copy Number Variation of the 15q11.2 BP1-BP2 Region With Cortical and Subcortical Morphology and Cognition

Importance

Recurrent microdeletions and duplications in the genomic region 15q11.2 between breakpoints 1 (BP1) and 2 (BP2) are associated with neurodevelopmental disorders. These structural variants are present in 0.5% to 1.0% of the population, making 15q11.2 BP1-BP2 the site of the most prevalent known pathogenic copy number variation (CNV). It is unknown to what extent this CNV influences brain structure and affects cognitive abilities.

Objective

To determine the association of the 15q11.2 BP1-BP2 deletion and duplication CNVs with cortical and subcortical brain morphology and cognitive task performance.

Design, Setting, and Participants

In this genetic association study, T1-weighted brain magnetic resonance imaging were combined with genetic data from the ENIGMA-CNV consortium and the UK Biobank, with a replication cohort from Iceland. In total, 203 deletion carriers, 45 247 noncarriers, and 306 duplication carriers were included. Data were collected from August 2015 to April 2019, and data were analyzed from September 2018 to September 2019.

Main Outcomes and Measures

The associations of the CNV with global and regional measures of surface area and cortical thickness as well as subcortical volumes were investigated, correcting for age, age2, sex, scanner, and intracranial volume. Additionally, measures of cognitive ability were analyzed in the full UK Biobank cohort.

Results

Of 45 756 included individuals, the mean (SD) age was 55.8 (18.3) years, and 23 754 (51.9%) were female. Compared with noncarriers, deletion carriers had a lower surface area (Cohen d = -0.41; SE, 0.08; P = 4.9 × 10-8), thicker cortex (Cohen d = 0.36; SE, 0.07; P = 1.3 × 10-7), and a smaller nucleus accumbens (Cohen d = -0.27; SE, 0.07; P = 7.3 × 10-5). There was also a significant negative dose response on cortical thickness (β = -0.24; SE, 0.05; P = 6.8 × 10-7). Regional cortical analyses showed a localization of the effects to the frontal, cingulate, and parietal lobes. Further, cognitive ability was lower for deletion carriers compared with noncarriers on 5 of 7 tasks.

Conclusions and Relevance

These findings, from the largest CNV neuroimaging study to date, provide evidence that 15q11.2 BP1-BP2 structural variation is associated with brain morphology and cognition, with deletion carriers being particularly affected. The pattern of results fits with known molecular functions of genes in the 15q11.2 BP1-BP2 region and suggests involvement of these genes in neuronal plasticity. These neurobiological effects likely contribute to the association of this CNV with neurodevelopmental disorders.

A Link between Genetic Disorders and Cellular Impairment, Using Human Induced Pluripotent Stem Cells to Reveal the Functional Consequences of Copy Number Variations in the Central Nervous System-A Close Look at Chromosome 15

Recent cutting-edge human genetics technology has allowed us to identify copy number variations (CNVs) and has provided new insights for understanding causative mechanisms of human diseases. A growing number of studies show that CNVs could be associated with physiological mechanisms linked to evolutionary trigger, as well as to the pathogenesis of various diseases, including cancer, autoimmune disease and mental disorders such as autism spectrum disorders, schizophrenia, intellectual disabilities or attention-deficit/hyperactivity disorder. Their incomplete penetrance and variable expressivity make diagnosis difficult and hinder comprehension of the mechanistic bases of these disorders. Additional elements such as co-presence of other CNVs, genomic background and environmental factors are involved in determining the final phenotype associated with a CNV. Genetically engineered animal models are helpful tools for understanding the behavioral consequences of CNVs. However, the genetic background and the biology of these animal model systems have sometimes led to confusing results. New cellular models obtained through somatic cellular reprogramming technology that produce induced pluripotent stem cells (iPSCs) from human subjects are being used to explore the mechanisms involved in the pathogenic consequences of CNVs. Considering the vast quantity of CNVs found in the human genome, we intend to focus on reviewing the current literature on the use of iPSCs carrying CNVs on chromosome 15, highlighting advantages and limits of this system with respect to mouse model systems.

Genetic insights and neurobiological implications from NRXN1 in neuropsychiatric disorders

Many neuropsychiatric and neurodevelopmental disorders commonly share genetic risk factors. To date, the mechanisms driving the pathogenesis of these disorders, particularly how genetic variations affect the function of risk genes and contribute to disease symptoms, remain largely unknown. Neurexins are a family of synaptic adhesion molecules, which play important roles in the formation and establishment of synaptic structure, as well as maintenance of synaptic function. Accumulating genomic findings reveal that genetic variations within genes encoding neurexins are associated with a variety of psychiatric conditions such as schizophrenia, autism spectrum disorder, and some developmental abnormalities. In this review, we focus on NRXN1, one of the most compelling psychiatric risk genes of the neurexin family. We performed a comprehensive survey and analysis of current genetic and molecular data including both common and rare alleles within NRXN1 associated with psychiatric illnesses, thus providing insights into the genetic risk conferred by NRXN1. We also summarized the neurobiological evidences, supporting the function of NRXN1 and its protein products in synaptic formation, organization, transmission and plasticity, as well as disease-relevant behaviors, and assessed the mechanistic link between the mutations of NRXN1 and synaptic and behavioral pathology in neuropsychiatric disorders.

Dendritic structural plasticity and neuropsychiatric disease

The structure of neuronal circuits that subserve cognitive functions in the brain is shaped and refined throughout development and into adulthood. Evidence from human and animal studies suggests that the cellular and synaptic substrates of these circuits are atypical in neuropsychiatric disorders, indicating that altered structural plasticity may be an important part of the disease biology. Advances in genetics have redefined our understanding of neuropsychiatric disorders and have revealed a spectrum of risk factors that impact pathways known to influence structural plasticity. In this Review, we discuss the importance of recent genetic findings on the different mechanisms of structural plasticity and propose that these converge on shared pathways that can be targeted with novel therapeutics.

Oxytocin pathway gene networks in the human brain

Oxytocin is a neuropeptide involved in animal and human reproductive and social behavior. Three oxytocin signaling genes have been frequently implicated in human social behavior: OXT (structural gene for oxytocin), OXTR (oxytocin receptor), and CD38 (oxytocin secretion). Here, we characterized the distribution of OXT, OXTR, and CD38 mRNA across the human brain by creating voxel-by-voxel volumetric expression maps, and identified putative gene pathway interactions by comparing gene expression patterns across 20,737 genes. Expression of the three selected oxytocin pathway genes was enriched in subcortical and olfactory regions and there was high co-expression with several dopaminergic and muscarinic acetylcholine genes, reflecting an anatomical basis for critical gene pathway interactions. fMRI meta-analysis revealed that the oxytocin pathway gene maps correspond with the processing of anticipatory, appetitive, and aversive cognitive states. The oxytocin signaling system may interact with dopaminergic and muscarinic acetylcholine signaling to modulate cognitive state processes involved in complex human behaviors.

Attenuation of replication by a 29 nucleotide deletion in SARS-coronavirus acquired during the early stages of human-to-human transmission

A 29 nucleotide deletion in open reading frame 8 (ORF8) is the most obvious genetic change in severe acute respiratory syndrome coronavirus (SARS-CoV) during its emergence in humans. In spite of intense study, it remains unclear whether the deletion actually reflects adaptation to humans. Here we engineered full, partially deleted (-29 nt), and fully deleted ORF8 into a SARS-CoV infectious cDNA clone, strain Frankfurt-1. Replication of the resulting viruses was compared in primate cell cultures as well as Rhinolophus bat cells made permissive for SARS-CoV replication by lentiviral transduction of the human angiotensin-converting enzyme 2 receptor. Cells from cotton rat, goat, and sheep provided control scenarios that represent host systems in which SARS-CoV is neither endemic nor epidemic. Independent of the cell system, the truncation of ORF8 (29 nt deletion) decreased replication up to 23-fold. The effect was independent of the type I interferon response. The 29 nt deletion in SARS-CoV is a deleterious mutation acquired along the initial human-to-human transmission chain. The resulting loss of fitness may be due to a founder effect, which has rarely been documented in processes of viral emergence. These results have important implications for the retrospective assessment of the threat posed by SARS.

Copy Number Variations in Adult-onset Neuropsychiatric Diseases

Adult-onset neuropsychiatric diseases are one of the most challenging areas of medicine. While symptomatic treatments are available, for most of these diseases the exact pathomechanism is not known, thus, disease-modifying therapies are difficult to conceptualize and find. The two most common and best studied neuropsychiatric diseases affecting higher cortical functions in humans are schizophrenia and Alzheimer's disease; both diseases have high heritability, however, the genetic architecture is not fully elucidated. Robust Single Nucleotide Variant (SNV) studies have identified several loci with modest effect sizes. While Copy Number Variants (CNV) make an important contribution to genetic variation, CNV GWAS suffer from dependence on mainly SNP arrays with underperforming genotyping accuracy. We evaluated dynamic range of the assays for three types of CNV loci, including biallelic deletion, high copy gain, and fusion gene, to assess the depth of exploration of the contribution of CNVs to disease susceptibility. Despite the suboptimal genotyping, novel mechanisms are emerging and further large-scale studies with genotyping assays optimized for CNV detection are needed. Furthermore, the CHRFAM7A human-specific fusion gene association warrants large scale locus specific association studies in AD, schizophrenia, bipolar disorder and ADHD.

Brain, blood, cerebrospinal fluid, and serum biomarkers in schizophrenia

Over the last decade, finding a reliable biomarker for the early detection of schizophrenia (Scz) has been a topic of interest. The main goal of the current review is to provide a comprehensive view of the brain, blood, cerebrospinal fluid (CSF), and serum biomarkers of Scz disease. Imaging studies have demonstrated that the volumes of the corpus callosum, thalamus, hippocampal formation, subiculum, parahippocampal gyrus, superior temporal gyrus, prefrontal and orbitofrontal cortices, and amygdala-hippocampal complex were reduced in patients diagnosed with Scz. It has been revealed that the levels of interleukin 1β (IL-1β), IL-6, IL-8, and TNF-α were increased in patients with Scz. Decreased mRNA levels of brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB), neurotrophin-3 (NT-3), nerve growth factor (NGF), and vascular endothelial growth factor (VEGF) genes have also been reported in Scz patients. Genes with known strong relationships with this disease include BDNF, catechol-O-methyltransferase (COMT), regulator of G-protein signaling 4 (RGS4), dystrobrevin-binding protein 1 (DTNBP1), neuregulin 1 (NRG1), Reelin (RELN), Selenium-binding protein 1 (SELENBP1), glutamic acid decarboxylase 67 (GAD 67), and disrupted in schizophrenia 1 (DISC1). The levels of dopamine, tyrosine hydroxylase (TH), serotonin or 5-hydroxytryptamine (5-HT) receptor 1A and B (5-HTR1A and 5-HTR1B), and 5-HT1B were significantly increased in Scz patients, while the levels of gamma-aminobutyric acid (GABA), 5-HT transporter (5-HTT), and 5-HT receptor 2A (5-HTR2A) were decreased. The increased levels of SELENBP1 and Glycogen synthase kinase 3 subunit α (GSK3α) genes in contrast with reduced levels of B-cell translocation gene 1 (BTG1), human leukocyte antigen DRB1 (HLA-DRB1), heterogeneous nuclear ribonucleoprotein A3 (HNRPA3), and serine/arginine-rich splicing factor 1 (SFRS1) genes have also been reported. This review covers various dysregulation of neurotransmitters and also highlights the strengths and weaknesses of studies attempting to identify candidate biomarkers.

Genetics of Schizophrenia: Ready to Translate?

PURPOSE OF REVIEW

This is an era where we have significantly advanced the understanding of the genetic architecture of schizophrenia. In this review, we consider how this knowledge may translate into advances that will improve patient care.

RECENT FINDINGS

Large-scale genome-wide association studies (GWAS) have identified more than a hundred loci each making a small contribution to illness risk. Meta-analysis of copy number variants (CNVs) in the Psychiatric Genomics Consortium (PGC) dataset has confirmed that some variants have a moderate or large impact on risk, although these are rare in the population. Genome sequencing advances allow a much more comprehensive evaluation of genomic variation. We describe the key findings from whole exome studies to date. These studies are happening against a backdrop of growing understanding of the regulation and expression of genes and better functional tools to investigate molecular mechanisms in model systems. We provide an overview of how recent approaches in schizophrenia genetics are converging and consider how they could impact on diagnostics, the development of personalized medicine, and drug discovery.

Rare and common variants at 16p11.2 are associated with schizophrenia

Recent studies suggest that both common and rare variants are involved in the genetic risk of schizophrenia. Using a Cochran-Mantel-Haenszel (CMH) adjusted meta-analysis in 36,676 schizophrenia patients and 48,331 healthy controls from 24 independent samples, we identify the microduplications at 16p11.2 locus (29.6-30.2Mb, hg19) to be strongly associated with the illness (P value<2.2×10^-16, CHM-adjusted OR=10.79). The frequency of this microduplication is significantly higher in schizophrenia patients (0.267%) comparing to healthy controls (0.025%). Further, using the largest published genome-wide association study (GWAS) data (36,989 cases and 113,075 controls), we show that common variants at the 16p11.2 locus are also significantly associated with schizophrenia (e.g., rs12691307, P value=4.55×10^-11, OR=1.073). These results confirm the link between 16p11.2 genomic region and genetic risk of schizophrenia.

Structure, biochemistry, and biology of PAK kinases

PAKs, p21-activated kinases, play central roles and act as converging junctions for discrete signals elicited on the cell surface and for a number of intracellular signaling cascades. PAKs phosphorylate a vast number of substrates and act by remodeling cytoskeleton, employing scaffolding, and relocating to distinct subcellular compartments. PAKs affect wide range of processes that are crucial to the cell from regulation of cell motility, survival, redox, metabolism, cell cycle, proliferation, transformation, stress, inflammation, to gene expression. Understandably, their dysregulation disrupts cellular homeostasis and severely impacts key cell functions, and many of those are implicated in a number of human diseases including cancers, neurological disorders, and cardiac disorders. Here we provide an overview of the members of the PAK family and their current status. We give special emphasis to PAK1 and PAK4, the prototypes of groups I and II, for their profound roles in cancer, the nervous system, and the heart. We also highlight other family members. We provide our perspective on the current advancements, their growing importance as strategic therapeutic targets, and our vision on the future of PAKs.

Replication analyses of four chromosomal deletions with schizophrenia via independent large-scale meta-analyses

Recent studies suggest that copy number variations (CNVs) are also involved in the genetic risk of schizophrenia. Using a Cochran-Mantel-Haenszel (CMH) adjusted meta-analysis in 18,497 schizophrenia patients and 25,522 healthy controls from 14 independent samples, we conducted replication analyses of four chromosomal deletions at 1q21.1, 15q11.2, 15q13.3, and 22q11.2 Loci for their associations with schizophrenia. Only CNVs larger than 100 kb that had >50% reciprocal overlap with the canonical deletion chromosomal regions were considered. We successfully replicate the significant associations at 1q21.1 (P value = 3.101 × 10^-7 , odds ratio (OR) = 6.91), 15q13.3 (P value = 4.771 × 10^-4 , OR = 7.83), and 22q11.2 (P value = 1.725 × 10^-5 , OR = 9.21) deletions, although the effect sizes are relatively smaller than the original studies, which is not unexpected and adds further support for the involvement of these genetic lesions in the risk of schizophrenia. The 15q11.2 deletion, which shows higher frequency in healthy populations than the other three CNV loci, though is not significant in the present meta-analysis (P value = 0.1545, OR = 1.42), it shows the same direction of effects with previous studies. These results further confirm the genetic connections between rare CNVs and schizophrenia, and suggest the importance of adequate sample size in replication analyses for such risk loci with low frequency in general populations. © 2016 Wiley Periodicals, Inc.

Molecular substrates of schizophrenia: homeostatic signaling to connectivity

Schizophrenia (SZ) is a devastating psychiatric condition affecting numerous brain systems. Recent studies have identified genetic factors that confer an increased risk of SZ and participate in the disease etiopathogenesis. In parallel to such bottom-up approaches, other studies have extensively reported biological changes in patients by brain imaging, neurochemical and pharmacological approaches. This review highlights the molecular substrates identified through studies with SZ patients, namely those using top-down approaches, while also referring to the fruitful outcomes of recent genetic studies. We have subclassified the molecular substrates by system, focusing on elements of neurotransmission, targets in white matter-associated connectivity, immune/inflammatory and oxidative stress-related substrates, and molecules in endocrine and metabolic cascades. We further touch on cross-talk among these systems and comment on the utility of animal models in charting the developmental progression and interaction of these substrates. Based on this comprehensive information, we propose a framework for SZ research based on the hypothesis of an imbalance in homeostatic signaling from immune/inflammatory, oxidative stress, endocrine and metabolic cascades that, at least in part, underlies deficits in neural connectivity relevant to SZ. Thus, this review aims to provide information that is translationally useful and complementary to pathogenic hypotheses that have emerged from genetic studies. Based on such advances in SZ research, it is highly expected that we will discover biomarkers that may help in the early intervention, diagnosis or treatment of SZ.

Disrupted in schizophrenia 1 (DISC1) L100P mutants have impaired activity-dependent plasticity in vivo and in vitro

Major neuropsychiatric disorders are genetically complex but share overlapping etiology. Mice mutant for rare, highly penetrant risk variants can be useful in dissecting the molecular mechanisms involved. The gene disrupted in schizophrenia 1 (DISC1) has been associated with increased risk for neuropsychiatric conditions. Mice mutant for Disc1 display morphological, functional and behavioral deficits that are consistent with impairments observed across these disorders. Here we report that Disc1 L100P mutants are less able to reorganize cortical circuitry in response to stimulation in vivo. Molecular analysis reveals that the mutants have a reduced expression of PSD95 and pCREB in visual cortex and fail to adjust expression of such markers in response to altered stimulation. In vitro analysis shows that mutants have impaired functional reorganization of cortical neurons in response to selected forms of neuronal stimulation, but there is no altered basal expression of synaptic markers. These findings suggest that DISC1 has a critical role in the reorganization of cortical plasticity and that this phenotype becomes evident only under challenge, even at early postnatal stages. This result may represent an important etiological mechanism in the emergence of neuropsychiatric disorders.

Dendritic spine alterations in schizophrenia

Schizophrenia is a chronic illness affecting approximately 0.5-1% of the world's population. The etiology of schizophrenia is complex, including multiple genes, and contributing environmental effects that adversely impact neurodevelopment. Nevertheless, a final common result, present in many subjects with schizophrenia, is impairment of pyramidal neuron dendritic morphology in multiple regions of the cerebral cortex. In this review, we summarize the evidence of reduced dendritic spine density and other dendritic abnormalities in schizophrenia, evaluate current data that informs the neurodevelopment timing of these impairments, and discuss what is known about possible upstream sources of dendritic spine loss in this illness.

A rare duplication on chromosome 16p11.2 is identified in patients with psychosis in Alzheimer's disease

Epidemiological and genetic studies suggest that schizophrenia and autism may share genetic links. Besides common single nucleotide polymorphisms, recent data suggest that some rare copy number variants (CNVs) are risk factors for both disorders. Because we have previously found that schizophrenia and psychosis in Alzheimer's disease (AD+P) share some genetic risk, we investigated whether CNVs reported in schizophrenia and autism are also linked to AD+P. We searched for CNVs associated with AD+P in 7 recurrent CNV regions that have been previously identified across autism and schizophrenia, using the Illumina HumanOmni1-Quad BeadChip. A chromosome 16p11.2 duplication CNV (chr16: 29,554,843-30,105,652) was identified in 2 of 440 AD+P subjects, but not in 136 AD subjects without psychosis, or in 593 AD subjects with intermediate psychosis status, or in 855 non-AD individuals. The frequency of this duplication CNV in AD+P (0.46%) was similar to that reported previously in schizophrenia (0.46%). This duplication CNV was further validated using the NanoString nCounter CNV Custom CodeSets. The 16p11.2 duplication has been associated with developmental delay, intellectual disability, behavioral problems, autism, schizophrenia (SCZ), and bipolar disorder. These two AD+P patients had no personal of, nor any identified family history of, SCZ, bipolar disorder and autism. To the best of our knowledge, our case report is the first suggestion that 16p11.2 duplication is also linked to AD+P. Although rare, this CNV may have an important role in the development of psychosis.

The phenotypic manifestations of rare CNVs in schizophrenia

There is compelling evidence for the role of copy number variants (CNVs) in schizophrenia susceptibility, and it has been estimated that up to 2-3% of schizophrenia cases may carry rare CNVs. Despite evidence that these events are associated with an increased risk across categorical neurodevelopmental disorders, there is limited understanding of the impact of CNVs on the core features of disorders like schizophrenia. Our objective was to evaluate associations between rare CNVs in differentially brain expressed (BE) genes and the core features and clinical correlates of schizophrenia. The sample included 386 cases of Irish ancestry with a diagnosis of schizophrenia, at least one rare CNV impacting any gene, and a core set of phenotypic measures. Statistically significant associations between deletions in differentially BE genes were found for family history of mental illness (decreased prevalence of all CNVs and deletions, unadjusted and adjusted) and for paternal age (increase in deletions only, unadjusted, among those with later ages at birth of patient). The strong effect of a lack of a family history on BE genes suggests that CNVs may comprise one pathway to schizophrenia, whereas a positive family history could index other genetic mechanisms that increase schizophrenia vulnerability. To our knowledge, this is the first investigation of the association between genome-wide CNVs and risk factors and sub-phenotypic features of schizophrenia beyond cognitive function.

Unlocking the treasure trove: from genes to schizophrenia biology

Significant progress is being made in defining the genetic etiology of schizophrenia. As the list of implicated genes grows, parallel developments in gene editing technology provide new methods to investigate gene function in model systems. The confluence of these two research fields--gene discovery and functional biology--may offer novel insights into schizophrenia etiology. We review recent advances in these fields, consider the likely obstacles to progress, and consider strategies as to how these can be overcome.