The molecular genetics of schizophrenia: new findings promise new insights

Genes implicated by a methylome-wide schizophrenia study in neonatal blood show differential expression in adult brain samples

Schizophrenia is a disabling disorder involving genetic predisposition in combination with environmental influences that likely act via dynamic alterations of the epigenome and the transcriptome but its detailed pathophysiology is largely unknown. We performed cell-type specific methylome-wide association study of neonatal blood (N = 333) from individuals who later in life developed schizophrenia and controls. Suggestively significant associations (P < 1.0 × 10-6) were detected in all cell-types and in whole blood with methylome-wide significant associations in monocytes (P = 2.85 × 10-9-4.87 × 10-9), natural killer cells (P = 1.72 × 10-9-7.82 × 10-9) and B cells (P = 3.8 × 10-9). Validation of methylation findings in post-mortem brains (N = 596) from independent schizophrenia cases and controls showed significant enrichment of transcriptional differences (enrichment ratio = 1.98-3.23, P = 2.3 × 10-3-1.0 × 10-5), with specific highly significant differential expression for, for example, BDNF (t = -6.11, P = 1.90 × 10-9). In addition, expression difference in brain significantly predicted schizophrenia (multiple correlation = 0.15-0.22, P = 3.6 × 10-4-4.5 × 10-8). In summary, using a unique design combining pre-disease onset (neonatal) blood methylomic data and post-disease onset (post-mortem) brain transcriptional data, we have identified genes of likely functional relevance that are associated with schizophrenia susceptibility, rather than confounding disease associated artifacts. The identified loci may be of clinical value as a methylation-based biomarker for early detection of increased schizophrenia susceptibility.

Deep multimodal predictome for studying mental disorders

Characterizing neuropsychiatric disorders is challenging due to heterogeneity in the population. We propose combining structural and functional neuroimaging and genomic data in a multimodal classification framework to leverage their complementary information. Our objectives are two-fold (i) to improve the classification of disorders and (ii) to introspect the concepts learned to explore underlying neural and biological mechanisms linked to mental disorders. Previous multimodal studies have focused on naïve neural networks, mostly perceptron, to learn modality-wise features and often assume equal contribution from each modality. Our focus is on the development of neural networks for feature learning and implementing an adaptive control unit for the fusion phase. Our mid fusion with attention model includes a multilayer feed-forward network, an autoencoder, a bi-directional long short-term memory unit with attention as the features extractor, and a linear attention module for controlling modality-specific influence. The proposed model acquired 92% (p < .0001) accuracy in schizophrenia prediction, outperforming several other state-of-the-art models applied to unimodal or multimodal data. Post hoc feature analyses uncovered critical neural features and genes/biological pathways associated with schizophrenia. The proposed model effectively combines multimodal neuroimaging and genomics data for predicting mental disorders. Interpreting salient features identified by the model may advance our understanding of their underlying etiological mechanisms.

Genetic Influences on Cognitive Dysfunction in Schizophrenia

Schizophrenia is a severe and debilitating psychotic disorder that is highly heritable and relatively common in the population. The clinical heterogeneity associated with schizophrenia is substantial, with patients exhibiting a broad range of deficits and symptom severity. Large-scale genomic studies employing a case-control design have begun to provide some biological insight. However, this strategy combines individuals with clinically diverse symptoms and ignores the genetic risk that is carried by many clinically unaffected individuals. Consequently, the majority of the genetic architecture underlying schizophrenia remains unexplained, and the pathways by which the implicated variants contribute to the clinically observable signs and symptoms are still largely unknown. Parsing the complex, clinical phenotype of schizophrenia into biologically relevant components may have utility in research aimed at understanding the genetic basis of liability. Cognitive dysfunction is a hallmark symptom of schizophrenia that is associated with impaired quality of life and poor functional outcome. Here, we examine the value of quantitative measures of cognitive dysfunction to objectively target the underlying neurobiological pathways and identify genetic variants and gene networks contributing to schizophrenia risk. For a complex disorder, quantitative measures are also more efficient than diagnosis, allowing for the identification of associated genetic variants with fewer subjects. Such a strategy supplements traditional analyses of schizophrenia diagnosis, providing the necessary biological insight to help translate genetic findings into actionable treatment targets. Understanding the genetic basis of cognitive dysfunction in schizophrenia may thus facilitate the development of novel pharmacological and procognitive interventions to improve real-world functioning.

Further validation of the Cognitive Biases Questionnaire for psychosis

BACKGROUND

Cognitive biases are recognized as important treatment targets for reducing symptoms associated with severe mental disorders. Although cognitive biases have been linked to symptoms in most studies, few studies have looked at such biases transdiagnostically. The Cognitive Bias Questionnaire for psychosis (CBQp) is a self-reported questionnaire that assesses cognitive biases amongst individuals with a psychotic disorder, as well as individuals with other severe mental disorders. The current study aims to validate a French version of the CBQp and to explore transdiagnostic cognitive biases in individuals with psychotic disorders, individuals with depression, and in healthy controls.

METHODS

The CBQp was translated into French following a protocol based on international standards. Discriminant validity and internal consistency were determined for total score and each subscale score. Confirmatory factor analyses were performed to test construct validity. Finally, cluster analyses were conducted to investigate cognitive biases across diagnostic groups.

RESULTS

Our results were similar to those of the original authors, with the one-factor solution (assessment of a general thinking bias) being the strongest, but the two-factor solution (assessing biases within two themes relating to psychosis) and the five-factor solution (assessment of multiple distinct biases) being clinically more interesting. A six-cluster solution emerged, suggesting that individuals with similar diagnoses score differently on all cognitive biases, and that individuals with different diagnoses might have similar cognitive biases.

CONCLUSIONS

The current findings support the validity of the French translation of the CBQp. Our cluster analyses overall support the transdiagnostic presence of cognitive biases.

Analysis of Molecular Networks in the Cerebellum in Chronic Schizophrenia: Modulation by Early Postnatal Life Stressors in Murine Models

Despite the growing importance of the cerebellum as a region highly vulnerable to accumulating molecular errors in schizophrenia, limited information is available regarding altered molecular networks with potential therapeutic targets. To identify altered networks, we conducted one-shot liquid chromatography–tandem mass spectrometry in postmortem cerebellar cortex in schizophrenia and healthy individuals followed by bioinformatic analysis (PXD024937 identifier in ProteomeXchange repository). A total of 108 up-regulated proteins were enriched in stress-related proteins, half of which were also enriched in axonal cytoskeletal organization and vesicle-mediated transport. A total of 142 down-regulated proteins showed an enrichment in proteins involved in mitochondrial disease, most of which were also enriched in energy-related biological functions. Network analysis identified a mixed module of mainly axonal-related pathways for up-regulated proteins with a high number of interactions for stress-related proteins. Energy metabolism and neutrophil degranulation modules were found for down-regulated proteins. Further, two double-hit postnatal stress murine models based on maternal deprivation combined with social isolation or chronic restraint stress were used to investigate the most robust candidates of generated networks. CLASP1 from the axonal module in the model of maternal deprivation was combined with social isolation, while YWHAZ was not altered in either model. METTL7A from the degranulation pathway was reduced in both models and was identified as altered also in previous gene expression studies, while NDUFB9 from the energy network was reduced only in the model of maternal deprivation combined with social isolation. This work provides altered stress- and mitochondrial disease-related proteins involved in energy, immune and axonal networks in the cerebellum in schizophrenia as possible novel targets for therapeutic interventions and suggests that METTL7A is a possible relevant altered stress-related protein in this context.

Assessing olfactory, memory, social and circadian phenotypes associated with schizophrenia in a genetic model based on Rim

Schizophrenia shows high heritability and several of the genes associated with this disorder are involved in calcium (Ca2+) signalling and synaptic function. One of these is the Rab-3 interacting molecule-1 (RIM1), which has recently been associated with schizophrenia by Genome Wide Association Studies (GWAS). However, its contribution to the pathophysiology of this disorder remains unexplored. In this work, we use Drosophila mutants of the orthologue of RIM1, Rim, to model some aspects of the classical and non-classical symptoms of schizophrenia. Rim mutants showed several behavioural features relevant to schizophrenia including social distancing and altered olfactory processing. These defects were accompanied by reduced evoked Ca2+ influx and structural changes in the presynaptic terminals sent by the primary olfactory neurons to higher processing centres. In contrast, expression of Rim-RNAi in the mushroom bodies (MBs), the main memory centre in flies, spared learning and memory suggesting a differential role of Rim in different synapses. Circadian deficits have been reported in schizophrenia. We observed circadian locomotor activity deficits in Rim mutants, revealing a role of Rim in the pacemaker ventral lateral clock neurons (LNvs). These changes were accompanied by impaired day/night remodelling of dorsal terminal synapses from a subpopulation of LNvs and impaired day/night release of the circadian neuropeptide pigment dispersing factor (PDF) from these terminals. Lastly, treatment with the commonly used antipsychotic haloperidol rescued Rim locomotor deficits to wildtype. This work characterises the role of Rim in synaptic functions underlying behaviours disrupted in schizophrenia.

Association of DRD2 gene polymorphisms with schizophrenia in the young Bangladeshi population: A pilot study

Purpose

DRD2 gene is considered one of the most important candidate genes for the schizophrenia (SCZ) development due to its role in dopamine signaling and no genetic association study has been conducted yet on the Bangladeshi SCZ patients. The objective of the present study was to investigate the association of DRD2 genetic polymorphisms (rs4648317, rs4936270, and rs7131056) with SCZ in the Bangladeshi population.

Patients and methods

This case-control study consisted of 101 SCZ patients and 101 controls. Genotyping was performed by the polymerase chain reaction and restriction fragment length polymorphism (PCR–RFLP) method.

Results

The average ages were 22.15 and 22.09 years in patients and controls, respectively (p > 0.05). CT genotype of rs4936270 showed a significantly higher risk for the development of SCZ compared to CC genotype (OR = 2.0, p = 0.023), whereas no association was found for TT genotype. For the dominant model and T allele, rs4936270 showed a higher risk for the development of SCZ (OR = 2.01, p = 0.020; OR = 1.76, p = 0.021, respectively), while the recessive model had no association with SCZ. A statistically significant (OR = 2.70, p = 0.036) higher risk was found for the AA genotype, but no association was found for GA genotype of rs4648317 SNP compared to GG genotype. In case of dominant and recessive models, rs4648317 showed no association with SCZ. ‘A’ allele of rs4648317 SNP was found to be significantly associated with the elevated risk of SCZ (OR = 1.50, p = 0.044). No association with SCZ of rs7131056 SNP was found for AC, CC genotypes, dominant, recessive, and allele models. Furthermore, from the haplotyping analysis, we found that CAA and TAA haplotypes of rs4936270, rs7131056 and rs4648317 SNPs are associated with SCZ (χ2 = 8.26, p = 0.004; χ2 = 5.31, p = 0.021, respectively). After Bonferroni correction, the association of SCZ did not withstand with any genotype, allele and haplotype (p < 0.017) except CAA haplotype.

Conclusion

Our results suggest that DRD2 gene polymorphisms may be associated with the susceptibility of SCZ in the young Bangladeshi population.

Association Analysis Between Common Variants of the TRPM1 Gene and Three Mental Disorders in the Han Chinese Population

Objective: Our study was designed to determine if the TRPM1 gene is associated with any of three mental disorders. The project included a cross disorder meta-analysis and association analysis including 141701 cases and 175248 controls. Materials and Methods: We genotyped eight tag single nucleotide polymorphisms (SNPs) in 1248 unrelated schizophrenia (SCZ) patients, 1056 major depressive disorder patients, 1344 bipolar disorder patients, and 1248 normal controls. We then performed a meta-analysis of 10 GWASs to identify common genetic factors among these three mental disorders. Finally, we performed a meta-analysis of six GWASs to explore the role of rs10162727 in SCZ. Result: Although two haplotypes of the TRPM1 gene, rs1035706-rs10162727 and rs10162727-rs3784599, were identified in the control group, as well as all three disease groups, none of the eight tag SNP associations remained significant after correction for multiple tests. In this cross-disorder meta-analysis of the three diseases, none of the tag SNPs were confirmed to be common among the diseases. In addition, in the meta-analysis conducted for the rs10162727 locus in SCZ, there was no significant association (p-value = 0.84, odds ratio = 1.02 [95% CI = 0.87-1.19]). Conclusion: In the Han Chinese population, no significant evidence was found linking variants of the TRPM1 gene with any of the mental disorders examined.

Effects of Cannabis Use on the Protein and Lipid Profile of Olfactory Neuroepithelium Cells from Schizophrenia Patients Studied by Synchrotron-Based FTIR Spectroscopy

Schizophrenia (SCZ) is a neurodevelopmental disorder with a high genetic component, but the presence of environmental stressors can be important for its onset and progression. Cannabis use can be a major risk factor for developing SCZ. However, despite the available data on the neurobiological underpinnings of SCZ, there is an important lack of studies in human neuronal tissue and living cells addressing the effects of cannabis in SCZ patients. In this study, we analysed the most relevant bio-macromolecular constituents in olfactory neuroepithelium (ON) cells of healthy controls non-cannabis users, healthy cannabis users, SCZ patients non-cannabis users, and SCZ patients cannabis users using Synchrotron Radiation-Fourier Transform Infrared (SR-FTIR) spectrometry and microscopy. Our results revealed that SCZ patients non-cannabis users, and healthy cannabis users exhibit similar alterations in the macromolecular profile of ON cells, including disruption in lipid composition, increased lipid membrane renewal rate and lipid peroxidation, altered proteins containing more β-sheet structures, and showed an increase in DNA and histone methylation. Notably, these alterations were not observed in SCZ patients who use cannabis regularly. These data suggest a differential effect of cannabis in healthy controls and in SCZ patients in terms of the macromolecular constituents of ON cells.

Chromosomal region 1q24.1 is associated with increased risk of schizophrenia in Pakistani population

Schizophrenia is a stressful, chronic and in many cases incorrigible psychological disorder. Till now no biomarker is available for diagnosis of this condition and diagnosis is done purely on psychiatric bases. A strong genetic association of human genome region 1q24.1 is implicated with onset of schizophrenia in many studies. Present study is first from Pakistan to report effect of this locus in transmission and liaison of schizophrenia in Pakistani population. For this analysis 300 samples were genotyped of four SNPs, rs1417584, rs1954175, rs821616 and rs113012343 that were selected on basis of minor allele frequency and effects on schizophrenia. Haplotype and transmission disequilibrium analysis was also performed on data. Association of SNPs revealed a significant relation between MAF of rs1417584 and schizophrenia in given samples (χ² 5.57; p 0.02). Haplotype association led to formation of three significant blocks TCAG (OR 20.06), TTAG (OR 4.65) and CCTG (OR 26.17) for rs1417584, rs1954175, rs821616 and rs113012343 that were expected to cause schizophrenia in said combinations. rs1417584, rs1954175 and rs821616 were found to be in a linkage block based on D' value (p < 0.0001) with 22% co inheritance alongside disease onset. This block was represented by 325 kb on chromosome 1. It is concluded from this study that this 325 Kb region can be considered prognostic marker for schizophrenia development in Pakistani population.

Copy number variant syndromes are frequent in schizophrenia: Progressing towards a CNV-schizophrenia model

The genetic underpinnings of schizophrenia (SCZ) remain unclear. SCZ genetic studies thus far have only identified numerous single nucleotide polymorphisms with small effect sizes and a handful of copy number variants (CNVs). This study investigates the prevalence of well-characterized CNV syndromes and candidate CNVs within a cohort of 348 SCZ patients, and explores correlations to their phenotypic findings. There was an enrichment of syndromic CNVs in the cohort, as well as brain-related and immune pathway genes within the detected CNVs. SCZ patients with brain-related CNVs had increased CNV burden, neurodevelopmental features, and types of hallucinations. Based on these results, we propose a CNV-SCZ model wherein specific phenotypic profiles should be prioritized for CNV screening within the SCZ patient population.

Polymorphisms in Dopaminergic Genes in Schizophrenia and Their Implications in Motor Deficits and Antipsychotic Treatment

Dopaminergic system dysfunction is involved in schizophrenia (SCZ) pathogenesis and can mediate SCZ-related motor disorders. Recent studies have gradually revealed that SCZ susceptibility and the associated motor symptoms can be mediated by genetic factors, including dopaminergic genes. More importantly, polymorphisms in these genes are associated with both antipsychotic drug sensitivity and adverse effects. The study of genetic polymorphisms in the dopaminergic system may help to optimize individualized drug strategies for SCZ patients. This review summarizes the current progress about the involvement of the dopamine system in SCZ-associated motor disorders and the motor-related adverse effects after antipsychotic treatment, with a special focus on polymorphisms in dopaminergic genes. We hypothesize that the genetic profile of the dopaminergic system mediates both SCZ-associated motor deficits associated and antipsychotic drug-related adverse effects. The study of dopaminergic gene polymorphisms may help to predict drug efficacy and decrease adverse effects, thereby optimizing treatment strategies.

Endophenotypes in Schizophrenia: Digging Deeper to Identify Genetic Mechanisms

Schizophrenia (SZ) is a severe psychotic disorder that is highly heritable and common in the general population. The genetic heterogeneity of SZ is substantial, with contributions from common, rare, and de novo variants, in addition to environmental factors. Large genome-wide association studies have detected many variants that are associated with SZ, yet the pathways by which these variants influence risk remain largely unknown. SZ is also clinically heterogeneous, with patients exhibiting a broad range of deficits and symptom severity that vary over the course of illness and treatment, which has complicated efforts to identify risk variants. However, the underlying brain dysfunction forms a more stable trait marker that quantitative neurocognitive and neurophysiological endophenotypes may be able to objectively measure. These endophenotypes are less likely to be heterogeneous than the disorder and provide a neurobiological context to detect risk variants and underlying pathways among genes associated with SZ diagnosis. Furthermore, many endophenotypes are translational into animal model systems, allowing for direct evaluation of the neural circuit dysfunctions and neurobiological substrates. We review a selection of the most promising SZ endophenotypes, including prepulse inhibition, mismatch negativity, oculomotor antisaccade, letter-number sequencing, and continuous performance tests. We also highlight recent findings from large consortia that suggest the potential role of genes, particularly in the neuregulin and glutamate pathways, in several of these endophenotypes. Although endophenotypes require additional time and effort to assess, the insight into the underlying neurobiology that they provide may ultimately reveal the underlying genetic architecture for SZ and suggest novel treatment targets.

Current Knowledge on Gene-Environment Interactions in Personality Disorders: an Update

PURPOSE OF REVIEW

We review the existing literature on gene-environment interactions (G×E) and epigenetic changes primarily in borderline personality disorder (BPD) but also in antisocial, schizotypal, and avoidant personality disorders.

RECENT FINDINGS

Research supports that susceptibility genes to BPD or its underlying traits may be expressed under certain environmental conditions such as physical or childhood sexual abuse. Epigenetic modifications of neurodevelopment- and stress-related genes are suggested to underlie the relationship between early life adversary and borderline personality disorder. Only limited studies have investigated the role of gene-environment interactions and epigenetic changes in the genesis of antisocial, schizotypal, and avoidant personality disorders. Considering the lack of pharmacological treatment for most personality disorders, the emerging evidence on the critical role of G×E and epigenetic changes in the genesis of personality disorders could help develop more biologically oriented therapeutic approaches. Future studies should explore the potential of this new therapeutic dimension.

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.

Transfer of disrupted-in-schizophrenia 1 aggregates between neuronal-like cells occurs in tunnelling nanotubes and is promoted by dopamine

The disrupted-in-schizophrenia 1 (DISC1) gene was identified as a genetic risk factor for chronic mental illnesses (CMI) such as schizophrenia, bipolar disorder and severe recurrent depression. Insoluble aggregated DISC1 variants were found in the cingular cortex of sporadic, i.e. non-genetic, CMI patients. This suggests protein pathology as a novel, additional pathogenic mechanism, further corroborated in a recent transgenic rat model presenting DISC1 aggregates. Since the potential role of aggregation of DISC1 in sporadic CMI is unknown, we investigated whether DISC1 undergoes aggregation in cell culture and could spread between neuronal cells in a prion-like manner, as shown for amyloid proteins in neurodegenerative diseases. Co-culture experiments between donor cells forming DISC1 aggregates and acceptor cells showed that 4.5% of acceptor cells contained donor-derived DISC1 aggregates, thus indicating an efficient transfer in vitro. DISC1 aggregates were found inside tunnelling nanotubes (TNTs) and transfer was enhanced by increasing TNT formation and notably by dopamine treatment, which also induces DISC1 aggregation. These data indicate that DISC1 aggregates can propagate between cells similarly to prions, thus providing some molecular basis for the role of protein pathology in CMI.

Theranostic Biomarkers for Schizophrenia

Schizophrenia is a highly heritable, chronic, severe, disabling neurodevelopmental brain disorder with a heterogeneous genetic and neurobiological background, which is still poorly understood. To allow better diagnostic procedures and therapeutic strategies in schizophrenia patients, use of easy accessible biomarkers is suggested. The most frequently used biomarkers in schizophrenia are those associated with the neuroimmune and neuroendocrine system, metabolism, different neurotransmitter systems and neurotrophic factors. However, there are still no validated and reliable biomarkers in clinical use for schizophrenia. This review will address potential biomarkers in schizophrenia. It will discuss biomarkers in schizophrenia and propose the use of specific blood-based panels that will include a set of markers associated with immune processes, metabolic disorders, and neuroendocrine/neurotrophin/neurotransmitter alterations. The combination of different markers, or complex multi-marker panels, might help in the discrimination of patients with different underlying pathologies and in the better classification of the more homogenous groups. Therefore, the development of the diagnostic, prognostic and theranostic biomarkers is an urgent and an unmet need in psychiatry, with the aim of improving diagnosis, therapy monitoring, prediction of treatment outcome and focus on the personal medicine approach in order to improve the quality of life in patients with schizophrenia and decrease health costs worldwide.

Elucidating the role of the pLG72 R30K substitution in schizophrenia susceptibility

In the human brain, pLG72 interacts with the flavoenzyme d-amino acid oxidase (hDAAO), which is involved in catabolism of d-serine, a co-agonist of N-methyl-d-aspartate receptors (NMDAR). Here, we investigated the wild-type pLG72, the R30K variant associated with schizophrenia susceptibility, and the K62E variant. The protein conformation, oligomeric state, ligand-, and hDAAO-binding properties are only slightly modified by the substitutions. All pLG72 variants inhibit hDAAO and lead to an increase in cellular (d/d+l)-serine. However, the R30K pLG72 is significantly more prone to degradation than the R30 and the K62E variants in a cell system, thus possessing a lower ability to interact/inhibit hDAAO. This links R30K pLG72 with the hyperactivity of hDAAO, the decreased d-serine level, and NMDAR hypofunction observed in schizophrenia-affected patients.

Pharmacoinformatics, Adaptive Evolution, and Elucidation of Six Novel Compounds for Schizophrenia Treatment by Targeting DAOA (G72) Isoforms

Studies on Schizophrenia so far reveal a complex picture of neurological malfunctioning reported to be strongly associated with DAOA. Detailed sequence analyses proved DAOA as a primate specific gene having conserved gene desert region on both upstream and downstream region. The analyses of 10 MB chromosomal region of primates, birds, rodents, and reptiles having DAOA evidenced the conserved part in primates and in the rest of species, while DAOA is only present in primates. DAOA has four isoforms having one interaction partner DAO. Protein-protein analyses of four DAOA isoforms with DAO were performed individually and find potential interacting residues computationally. It was observed that molecular docking of approved FDA drugs revealed efficient results but there was no common drug with effective binding to all DAOA isoforms. Library of compounds was constructed by virtual screening of 2D similarity search against recommended SZ drugs in conjunction with their physiochemical properties. Molecular docking resulted in six novel compounds exhibiting maximum binding affinity with selected four DAOA isoforms. However not the entire schizophrenic population responds to the single drug and interestingly in this study six novel compounds having promising results and same binding site to that DAOA that may be used to interact with DAO against four DAOA isoforms were observed.

Interaction of multiple gene variants and their effects on schizophrenia phenotypes

BACKGROUND

Schizophrenia is a clinically heterogeneous disorder and may be explained by its complex genetic architecture. Many schizophrenia susceptibility genes were identified but the picture remains unclear due to inconsistent or contradictory genetic association studies. This confusion may, in part, be because symptoms result from the combined interaction of many genes and these interacting genes are associated with specific sub-phenotypes of schizophrenia rather than schizophrenia as a whole. This study investigates the relationship between schizophrenia susceptibility genes and schizophrenia sub-phenotypes by identifying multiple gene variant interactions.

MATERIALS AND METHODS

Fifty SNPs from 21 genes were genotyped in 235 Australian participants with schizophrenia screened for various phenotypes. Schizophrenia participants were grouped into relevant phenotype clusters using cluster analysis and normalized phenotype cluster scores were calculated for each patient. The relationship between genotypes and normalized phenotype cluster scores were analyzed by linear regression analysis.

RESULTS

Three phenotype clusters were identified. There was some overlap in symptoms between phenotype clusters, particularly for depression. However, cluster 1 appears to be characterized by speech disorder and affective behavior symptoms, cluster 2 has predominantly hallucination symptoms and cluster 3 has mainly delusion symptoms. Interaction of five SNPs was found to have an effect on cluster 1 symptoms; ten SNPs on cluster 2 symptoms; and eight SNPs on cluster 3 symptoms.

CONCLUSION

The interaction of specific susceptibility genes is likely to lead to specific clinical sub-phenotypes of schizophrenia. Larger patient cohorts with more extensive clinical data will improve the detection of gene interactions and the resultant schizophrenia clinical phenotypes.

Nonfunctional Glial Proteins in Tripartite Synapses: A Pathophysiological Model of Schizophrenia

A model for the pathophysiology of schizophrenia is proposed that focuses on an unbalance of transmission in tripartite synapses. Synaptically associated astrocytes should be viewed as integral modulatory elements of tripartite synapses consisting of the presynapse, the postsynapse, and the glial element. Astrocytes may secrete glial binding protein into the synaptic cleft, thus binding free neurotransmitters and thereby reducing the levels of neurotransmitters available for stimulating the postsynapse. Astrocytes also have membrane-bound receptors for neurotransmitters, and when these bind neurotransmitters, the astrocytes upregulate the amount of binding protein secreted into the synapse, resulting in a negative feedback to the presynaptic terminal. The hypothesis presented here is that glia lose their negative feedback function due to loss of function mutations in the genes encoding the binding proteins and glial receptors. The mutations generate proteins that cannot be occupied by their cognate substances of the neuronal system, primarily neurotransmitters. Therefore, the glial-neuronal interaction in tripartite synapses affected becomes totally unbalanced, and the glia lose their inhibitory or boundary-setting function. As a result, neural flux is unconstrained by normal glial boundaries, also the flux of thought on the phenomenological level. Schizophrenia may be caused by the inability to delimit conceptual boundaries.

Gene Expression Profiling in Schizophrenia and Related Mental Disorders

The etiology and pathophysiology of schizophrenia and related mental disorders such as bipolar disorder and major depression remain largely unclear. Recent advances in mRNA profiling techniques made it possible to perform genome-wide gene expression analysis in a hypothesis-free manner. It was thought that this large-scale data mining approach would reveal unknown molecular cascades involved in mental disorders. Contrary to this initial expectation, however, DNA microarray results in psychiatric fields have been notoriously discordant. Here the authors review the findings of DNA microarray analysis, focusing on systematic gene expression changes in schizophrenia, as well as alterations in the expression of specific genes, that have been reported and replicated. The authors also address the probable causes for the discordance among studies, possible ways to solve the problem, and their preferred approach for data interpretation.

The basis for folinic acid treatment in neuro-psychiatric disorders

Multiple factors such as genetic and extraneous causes (drugs, toxins, adverse psychological events) contribute to neuro-psychiatric conditions. In a subgroup of these disorders, systemic folate deficiency has been associated with macrocytic anemia and neuropsychiatric phenotypes. In some of these, despite normal systemic levels, folate transport to the brain is impaired in the so-called cerebral folate deficiency (CFD) syndromes presenting as developmental and psychiatric disorders. These include infantile-onset CFD syndrome, infantile autism with or without neurologic deficits, a spastic-ataxic syndrome and intractable epilepsy in young children expanding to refractory schizophrenia in adolescents, and finally treatment-resistant major depression in adults. Folate receptor alpha (FRα) autoimmunity with low CSF N(5)-methyl-tetrahydrofolate (MTHF) underlies most CFD syndromes, whereas FRα gene abnormalities and mitochondrial gene defects are rarely found. The age at which FRα antibodies of the blocking type emerge, determines the clinical phenotype. Infantile CFD syndrome and autism with neurological deficits tend to be characterized by elevated FRα antibody titers and low CSF MTHF. In contrast, in infantile autism and intractable schizophrenia, abnormal behavioral signs and symptoms may wax and wane with fluctuating FRα antibody titers over time accompanied by cycling changes in CSF folate, tetrahydrobiopterin (BH4) and neurotransmitter metabolites ranging between low and normal levels. We propose a hypothetical model explaining the pathogenesis of schizophrenia. Based on findings from clinical, genetic, spinal fluid and MRI spectroscopic studies, we discuss the neurochemical changes associated with these disorders, metabolic and regulatory pathways, synthesis and catabolism of neurotransmitters, and the impact of oxidative stress on the pathogenesis of these conditions. A diagnostic algorithm and therapeutic regimens using high dose folinic acid, corticosteroids and milk-free diet is presented which has proven to be beneficial in providing adequate folate to the brain and decreasing the FRα autoantibody titer in those positive for the antibody.

Genetic Evaluation of Schizophrenia Using the Illumina HumanExome Chip

INTRODUCTION

Schizophrenia is a genetically heterogeneous disorder that is associated with several common and rare genetic variants. As technology involved, cost advantages of chip based genotyping was combined with information about rare variants, resulting in the Infinium HumanExome Beadchip. Using this chip, a sample of 493 patients with schizophrenia or schizoaffective disorder and 484 healthy controls was genotyped.

RESULTS

From the initial 242901 SNVs, 88306 had at least one minor allele and passed quality control. No variant reached genomewide-significant results (p<10(-8)). The SNP with the lowest p-value was rs1230345 in WISP3 (p = 3.05*10(-6)), followed by rs9311525 in CACNA2D3 (p = 1.03*10(-5)) and rs1558557 (p = 3.85*10(-05)) on chromosome 7. At the gene level, 3 genes were of interest: WISP3, on chromosome 6q21, a signally protein from the extracellular matrix. A second candidate gene is CACNA2D3, a regulator of the intracerebral calcium pathway. A third gene is TNFSF10, associated with p53 mediated apoptosis.

Genetic assessment of additional endophenotypes from the Consortium on the Genetics of Schizophrenia Family Study

The Consortium on the Genetics of Schizophrenia Family Study (COGS-1) has previously reported our efforts to characterize the genetic architecture of 12 primary endophenotypes for schizophrenia. We now report the characterization of 13 additional measures derived from the same endophenotype test paradigms in the COGS-1 families. Nine of the measures were found to discriminate between schizophrenia patients and controls, were significantly heritable (31 to 62%), and were sufficiently independent of previously assessed endophenotypes, demonstrating utility as additional endophenotypes. Genotyping via a custom array of 1536 SNPs from 94 candidate genes identified associations for CTNNA2, ERBB4, GRID1, GRID2, GRIK3, GRIK4, GRIN2B, NOS1AP, NRG1, and RELN across multiple endophenotypes. An experiment-wide p value of 0.003 suggested that the associations across all SNPs and endophenotypes collectively exceeded chance. Linkage analyses performed using a genome-wide SNP array further identified significant or suggestive linkage for six of the candidate endophenotypes, with several genes of interest located beneath the linkage peaks (e.g., CSMD1, DISC1, DLGAP2, GRIK2, GRIN3A, and SLC6A3). While the partial convergence of the association and linkage likely reflects differences in density of gene coverage provided by the distinct genotyping platforms, it is also likely an indication of the differential contribution of rare and common variants for some genes and methodological differences in detection ability. Still, many of the genes implicated by COGS through endophenotypes have been identified by independent studies of common, rare, and de novo variation in schizophrenia, all converging on a functional genetic network related to glutamatergic neurotransmission that warrants further investigation.

Common mechanisms of excitatory and inhibitory imbalance in schizophrenia and autism spectrum disorders

Autism Spectrum Disorders (ASD) and Schizophrenia (SCZ) are cognitive disorders with complex genetic architectures but overlapping behavioral phenotypes, which suggests common pathway perturbations. Multiple lines of evidence implicate imbalances in excitatory and inhibitory activity (E/I imbalance) as a shared pathophysiological mechanism. Thus, understanding the molecular underpinnings of E/I imbalance may provide essential insight into the etiology of these disorders and may uncover novel targets for future drug discovery. Here, we review key genetic, physiological, neuropathological, functional, and pathway studies that suggest alterations to excitatory/inhibitory circuits are keys to ASD and SCZ pathogenesis.

Adaptive evolution and elucidating the potential inhibitor against schizophrenia to target DAOA (G72) isoforms

Schizophrenia (SZ), a chronic mental and heritable disorder characterized by neurophysiological impairment and neuropsychological abnormalities, is strongly associated with D-amino acid oxidase activator (DAOA, G72). Research studies emphasized that overexpression of DAOA may be responsible for improper functioning of neurotransmitters, resulting in neurological disorders like SZ. In the present study, a hybrid approach of comparative modeling and molecular docking followed by inhibitor identification and structure modeling was employed. Screening was performed by two-dimensional similarity search against selected inhibitor, keeping in view the physiochemical properties of the inhibitor. Here, we report an inhibitor compound which showed maximum binding affinity against four selected isoforms of DAOA. Docking studies revealed that Glu-53, Thr-54, Lys-58, Val-85, Ser-86, Tyr-87, Leu-88, Glu-90, Leu-95, Val-98, Ser-100, Glu-112, Tyr-116, Lys-120, Asp-121, and Arg-122 are critical residues for receptor–ligand interaction. The C-terminal of selected isoforms is conserved, and binding was observed on the conserved region of isoforms. We propose that selected inhibitor might be more potent on the basis of binding energy values. Further analysis of this inhibitor through site-directed mutagenesis could be helpful for exploring the details of ligand-binding pockets. Overall, the findings of this study may be helpful in designing novel therapeutic targets to cure SZ.

Contingent negative variation in patients with deficit schizophrenia or bipolar I disorder with psychotic features: measurement and correlation with clinical characteristics

BACKGROUND

Schizophrenia is a highly heterogeneous disease. Event-related potentials have been regarded to establish intermediate phenotypes of schizophrenia. Our previous study found that patients with deficit schizophrenia (DS) are relatively homogeneous and show a significantly longer onset latency of contingent negative variation (CNV) expectancy wave.

AIMS

To further examine CNV in patients with first-episode and drug-naïve DS or bipolar I disorder (BP I) with psychotic features, and also investigate correlations between CNV and clinical characteristics in DS and BP I.

METHOD

We elicited a CNV using an alarm (S1)-imperative (S2) paradigm in 30 DS patients or 33 BP I with psychotic features as well as 40 healthy controls.

RESULTS

CNV amplitude was significantly smaller and reaction time significantly longer in the DS and BP I groups than in healthy controls. Post-imperative negative variation (PINV) interval was significantly shorter in the DS group than in healthy controls. The onset latency of CNV expectancy wave was significantly longer and PINV area significantly smaller in the DS group than in the other groups. In the DS group, CNV amplitude and PINV interval correlated negatively with the subscale of negative symptoms on the Positive and Negative Syndrome Scale (PANSS); CNV amplitude also correlated negatively with disease duration. In the BP I group, CNV amplitude and reaction time showed no correlation with clinical features.

CONCLUSIONS

CNV amplitude is a common trait marker for psychosis. The onset latency of CNV expectancy wave appears to be a specific trait marker and may be used to identify candidate genes for DS.

Folinic acid treatment for schizophrenia associated with folate receptor autoantibodies

BACKGROUND

Auto-antibodies against folate receptor alpha (FRα) at the choroid plexus that block N(5)-methyltetrahydrofolate (MTHF) transfer to the brain were identified in catatonic schizophrenia. Acoustic hallucinations disappeared following folinic acid treatment. Folate transport to the CNS prevents homocysteine accumulation and delivers one-carbon units for methyl-transfer reactions and synthesis of purines. The guanosine derivative tetrahydrobiopterin acts as common co-factor for the enzymes producing dopamine, serotonin and nitric oxide.

METHODS

Our study selected patients with schizophrenia unresponsive to conventional treatment. Serum from these patients with normal plasma homocysteine, folate and vitamin B12 was tested for FR autoantibodies of the blocking type on serial samples each week. Spinal fluid was analyzed for MTHF and the metabolites of pterins, dopamine and serotonin. The clinical response to folinic acid treatment was evaluated.

RESULTS

Fifteen of 18 patients (83.3%) had positive serum FR auto-antibodies compared to only 1 in 30 controls (3.3%) (χ(2)=21.6; p<0.0001). FRα antibody titers in patients fluctuated over time varying between negative and high titers, modulating folate flux to the CNS, which explained low CSF folate values in 6 and normal values in 7 patients. The mean±SD for CSF MTHF was diminished compared to previously established controls (t-test: 3.90; p=0.0002). A positive linear correlation existed between CSF MTHF and biopterin levels. CSF dopamine and serotonin metabolites were low or in the lower normal range. Administration of folinic acid (0.3-1mg/kg/day) to 7 participating patients during at least six months resulted in clinical improvement.

CONCLUSION

Assessment of FR auto-antibodies in serum is recommended for schizophrenic patients. Clinical negative or positive symptoms are speculated to be influenced by the level and evolution of FRα antibody titers which determine folate flux to the brain with up- or down-regulation of brain folate intermediates linked to metabolic processes affecting homocysteine levels, synthesis of tetrahydrobiopterin and neurotransmitters. Folinic acid intervention appears to stabilize the disease process.

The genomics of schizophrenia: update and implications

Schizophrenia is strongly familial yet rarely (if ever) exhibits classical Mendelian inheritance patterns. The advent of large-scale genotyping and sequencing projects has yielded large data sets with higher statistical power in an effort to uncover new associations with schizophrenia. Here, we review the challenges in dissecting the genetics of schizophrenia and provide an update of the current understanding of the underlying genomics. We discuss the breadth of susceptibility alleles, including those that may occur with low frequency and high disease risk, such as the 22q11.2 hemideletion, as well as alleles that may occur with greater frequency but convey a lower risk of schizophrenia, such as variants in genes encoding subunits of the voltage-gated L-type calcium channel. Finally, we provide an overview of the clinical implications for the diagnosis and treatment of schizophrenia based on progress in understanding the underlying genetic basis.

Epigenetics and psychiatry

Psychiatric disorders including major depressive disorder, drug addiction, and schizophrenia are debilitating illnesses with a multitude of complex symptoms underlying each of these disorders. In recent years, it has become appreciated that the onset and development of these disorders goes beyond the one gene-one disease approach. Rather, the involvement of many genes is likely linked to these illnesses, and regulating the activation or silencing of gene function may play a crucial role in contributing to their pathophysiology. Epigenetic modifications such as histone acetylation and deacetylation, as well as DNA methylation can induce lasting and stable changes in gene expression, and have therefore been implicated in promoting the adaptive behavioral and neuronal changes that accompany each of these illnesses. In this review we will discuss some of the latest work implicating a potential role for epigenetics in psychiatric disorders, namely, depression, addiction, and schizophrenia as well as a possible role in treatment.

Genome-wide association analysis with gray matter volume as a quantitative phenotype in first-episode treatment-naïve patients with schizophrenia

Reduced Gray matter (GM) volume is a core feature of schizophrenia. Mapping genes that is associated with the heritable disease-related phenotypes may be conducive to elucidate the pathogenesis of schizophrenia. This study aims to identify the common genetic variants that underlie the deficits of GM volume in schizophrenia. High-resolution T1 images and whole genome genotyping data were obtained from 74 first-episode treatment-naïve patients with schizophrenia and 51 healthy controls in the Mental Health Centre of the West China Hospital, Sichuan University. All participants were scanned using a 3T MR imaging system and were genotyped using the HumanHap660 Bead Array. Reduced GM volumes in three brain areas including left hOC3v in the collateral sulcus of visual cortex (hOC3vL), left cerebellar vermis lobule 10 (vermisL10) and right cerebellar vermis lobule 10 (vermisR10) were found in patients with schizophrenia. There was a group by genotype interaction when genotypes from genome-wide scan were subsequently considered in the case-control analyses. SNPs from three genes or chromosomal regions (TBXAS1, PIK3C2G and HS3ST5) were identified to predict the changes of GM volume in hOC3vL, vermisL10 and vermisR10. These results also highlighted the usefulness of endophenotype in exploring the pathogenesis of neuropsychiatric diseases such as schizophrenia although further independent replication studies are needed in the future.

Combination of neonatal PolyI:C and adolescent phencyclidine treatments is required to induce behavioral abnormalities with overexpression of GLAST in adult mice

Cumulative incidences of multiple risk factors are related to pathology of psychiatric disorders. The present study was designed to examine combinative effects of a neonatal immune challenge with adolescent abused substance treatment on the psychological behaviors and molecular expressions in the adult. C57BL/6J mice were neonatally treated, with polyriboinosinic-polyribocytidylic acid (PolyI:C: 5mg/kg) during postnatal days (PD) 2-6, then with phencyclidine (PCP: 10mg/kg) during adolescence (PD35-41). Locomotor activity was analyzed to evaluate sensitivity to PCP on PD35 and PD41. Emotional and cognitive tests were carried out on PD42-48. Neonatal PolyI:C treatment markedly enhanced sensitivity to PCP- and methamphetamine-induced hyperactivity in the adolescent. Mice treated with both neonatal PolyI:C and adolescent PCP (PolyI:C/PCP) showed social deficit and object recognition memory impairment. The expression of glutamate/aspartate transporter (GLAST) in the prefrontal cortex (PFC) was significantly increased in the (PolyI:C/PCP)-treated mice. Infusion of glutamate transporter inhibitor (DL-TBOA: 1 nmol/bilaterally) into the PFC reversed the object recognition impairment in the (PolyI:C/PCP)-treated mice. These results indicate that the combined treatment of neonatal PolyI:C with adolescent PCP leads to behavioral abnormalities, which were associated with increase of GLAST expression in the adult PFC.

The DAO gene is associated with schizophrenia and interacts with other genes in the Taiwan Han Chinese population

BACKGROUND

Schizophrenia is a highly heritable disease with a polygenic mode of inheritance. Many studies have contributed to our understanding of the genetic underpinnings of schizophrenia, but little is known about how interactions among genes affect the risk of schizophrenia. This study aimed to assess the associations and interactions among genes that confer vulnerability to schizophrenia and to examine the moderating effect of neuropsychological impairment.

METHODS

We analyzed 99 SNPs from 10 candidate genes in 1,512 subject samples. The permutation-based single-locus, multi-locus association tests, and a gene-based multifactorial dimension reduction procedure were used to examine genetic associations and interactions to schizophrenia.

RESULTS

We found that no single SNP was significantly associated with schizophrenia. However, a risk haplotype, namely A-T-C of the SNP triplet rsDAO7-rsDAO8-rsDAO13 of the DAO gene, was strongly associated with schizophrenia. Interaction analyses identified multiple between-gene and within-gene interactions. Between-gene interactions including DAO*DISC1 , DAO*NRG1 and DAO*RASD2 and a within-gene interaction for CACNG2 were found among schizophrenia subjects with severe sustained attention deficits, suggesting a modifying effect of impaired neuropsychological functioning. Other interactions such as the within-gene interaction of DAO and the between-gene interaction of DAO and PTK2B were consistently identified regardless of stratification by neuropsychological dysfunction. Importantly, except for the within-gene interaction of CACNG2, all of the identified risk haplotypes and interactions involved SNPs from DAO.

CONCLUSIONS

These results suggest that DAO, which is involved in the N-methyl-d-aspartate receptor regulation, signaling and glutamate metabolism, is the master gene of the genetic associations and interactions underlying schizophrenia. Besides, the interaction between DAO and RASD2 has provided an insight in integrating the glutamate and dopamine hypotheses of schizophrenia.

A combined study of genetic association and brain imaging on the DAOA gene in schizophrenia

While there has been no objective biomarker available for both diagnosis and prognosis of schizophrenia, compelling evidence suggests that the glutamatergic system may influence susceptibility to schizophrenia. To test genetic association of the glutamatergic system with schizophrenia and abnormal brain activities in resting-state patients with schizophrenia, a two-stage association study was performed in 454 patients and 480 controls, followed by regional homogeneity (ReHo) analysis of resting-state functional magnetic resonance imaging in 48 first-episode medication-free patients and 43 well-matched controls. The differences in ReHo between genotypes of interest were initially tested by the Student's t-test and the 2 × 2 (genotypes × disease status) ANOVA was then performed to identify the main effects of genotypes, disease status and their interactions in schizophrenia. The stage-1 study showed association of the DAOA and PSEN2 genes with schizophrenia in a small sample; the stage-2 study with an expanded sample confirmed the disease association for 2-SNP and 3-SNP haplotypes, and the cis-phase interactions between rs2391191 and some other SNPs in the DAOA gene. Four clusters with altered ReHo in the bilateral culmen, left putamen and left cuneus were associated with rs2391191. Main effects of rs2391191 genotypes were found in the left putamen. The left cuneus showed a genotype × disease status interaction. In conclusion, the DAOA gene may confer genetic risk of schizophrenia and associate with the altered ReHo in schizophrenia; genotype effect and its interaction with disease status may contribute to the altered ReHo, leading to specific ReHo in schizophrenic brain due to glutamatergic modulation.

Implication of a rare deletion at distal 16p11.2 in schizophrenia

CONTEXT

Large genomic copy number variations have been implicated as strong risk factors for schizophrenia. However, the rarity of these events has created challenges for the identification of further pathogenic loci, and extremely large samples are required to provide convincing replication.

OBJECTIVE

To detect novel copy number variations that increase the susceptibility to schizophrenia by using 2 ethnically homogeneous discovery cohorts and replication in large samples.

DESIGN

Genetic association study of microarray data.

SETTING

Samples of DNA were collected at 9 sites from different countries.

PARTICIPANTS

Two discovery cohorts consisted of 790 cases with schizophrenia and schizoaffective disorder and 1347 controls of Ashkenazi Jewish descent and 662 parent-offspring trios from Bulgaria, of which the offspring had schizophrenia or schizoaffective disorder. Replication data sets consisted of 12,398 cases and 17,945 controls.

MAIN OUTCOME MEASURES

Statistically increased rate of specific copy number variations in cases vs controls.

RESULTS

One novel locus was implicated: a deletion at distal 16p11.2, which does not overlap the proximal 16p11.2 locus previously reported in schizophrenia and autism. Deletions at this locus were found in 13 of 13,850 cases (0.094%) and 3 of 19,954 controls (0.015%) (odds ratio, 6.25 [95% CI, 1.78-21.93]; P = .001, Fisher exact test).

CONCLUSIONS

Deletions at distal 16p11.2 have been previously implicated in developmental delay and obesity. The region contains 9 genes, several of which are implicated in neurological diseases, regulation of body weight, and glucose homeostasis. A telomeric extension of the deletion, observed in about half the cases but no controls, potentially implicates an additional 8 genes. Our findings add a new locus to the list of copy number variations that increase the risk for development of schizophrenia.

Catechol-O-methyltransferase (COMT) genotype biases neural correlates of empathy and perceived personal distress in schizophrenia

BACKGROUND

The catechol-O-methyltransferase (COMT) Val(108/158)Met polymorphism (rs4680) influences enzyme activity with valine (Val) allele associated with higher enzymatic activity. Several studies suggest that factors influencing dopaminergic transmission could control response to stressful situations. Empathy is an essential element of human behavior, requires the ability to adopt another person's perspective, and has been found to be dysfunctional in schizophrenia.

METHODS

Twenty-eight schizophrenic patients underwent functional magnetic resonance imaging performing an empathy task. Perceived empathy has been evaluated with the Interpersonal Reactivity Index.

RESULTS

An effect of COMT on perceived distress subscale has been shown, with methionine (Met)/Met subjects reporting lower rates of stress compared with Val/Val. Moreover, imaging results showed an effect of genotype on empathy processing in the anterior cingulate with Val/Val subjects showing the lowest activation.

DISCUSSION

This is the first study of the effect of rs4680 on interpersonal distress and neural correlates of empathy in schizophrenia. We found a decrease in neural responses in areas that ensure a cognitive control of emotion that is paralleled by perceived distress in interpersonal situation; this functional pattern seems to be influenced by rs4680 COMT polymorphism.

Whole-genome-wide association study in the Bulgarian population reveals HHAT as schizophrenia susceptibility gene

OBJECTIVE

Schizophrenia, the most common major psychiatric disorder (or group of disorders), entails severe decline of higher functions, principally with alterations in cognitive functioning and reality perception. Both genetic and environmental factors are involved in its pathogenesis; however, its genetic background still needs to be clarified. The objective of the study was to reveal genetic markers associated with schizophrenia in the Bulgarian population.

METHODS

We have conducted a genome-wide association study using 554 496 single nucleotide polymorphisms (SNPs) in 188 affected and 376 unaffected Bulgarian individuals. Subsequently, the 100 candidate SNPs that revealed the smallest P-values were further evaluated in an additional set of 99 case and 328 control samples.

RESULTS

We found a significant association between schizophrenia and the intronic SNP rs7527939 in the HHAT gene (P-value of 6.49×10 with an odds ratio of 2.63, 95% confidence interval of 1.89-3.66). We also genotyped additional SNPs within a 58-kb linkage disequilibrium block surrounding the landmark SNP.

CONCLUSION

We suggest rs7527939 to be the strongest indicator of susceptibility to schizophrenia in the Bulgarian population within the HHAT locus.

Exploring the relationships between tobacco smoking and schizophrenia in first-degree relatives

Up to 90% of individuals with schizophrenia suffer from nicotine dependence. Both schizophrenia and nicotine consumption have strong genetic components, which may overlap. The relationship between schizophrenia and nicotine dependence remains unclear, due in part to confounding factors. Studies of the relationship between nicotine consumption and milder schizophrenia-related phenotypes, such as schizotypy, in first-degree relatives of individuals with schizophrenia could help to better understand the relationship between smoking and schizophrenia while avoiding such confounders. We assessed the proportion of smokers, their level of nicotine dependence and their level of schizotypy in a sample of 98 first-degree relatives of schizophrenic subjects and 110 healthy controls. Partial correlation analysis was used to assess the relationship between schizotypal dimensions and smoking dependence. The prevalence of smoking and nicotine dependence levels were higher in the relatives than in the healthy control group. We found no relationship between nicotine dependence and the magnitude of schizotypal features in either group. Our results support the hypothesis that the relationship between schizophrenia and smoking is largely mediated by common familial factors, which may be genetic.

An environmental analysis of genes associated with schizophrenia: hypoxia and vascular factors as interacting elements in the neurodevelopmental model

Investigating and understanding gene-environment interaction (G × E) in a neurodevelopmentally and biologically plausible manner is a major challenge for schizophrenia research. Hypoxia during neurodevelopment is one of several environmental factors related to the risk of schizophrenia, and links between schizophrenia candidate genes and hypoxia regulation or vascular expression have been proposed. Given the availability of a wealth of complex genetic information on schizophrenia in the literature without knowledge on the connections to environmental factors, we now systematically collected genes from candidate studies (using SzGene), genome-wide association studies (GWAS) and copy number variation (CNV) analyses, and then applied four criteria to test for a (theoretical) link to ischemia-hypoxia and/or vascular factors. In all, 55% of the schizophrenia candidate genes (n=42 genes) met the criteria for a link to ischemia-hypoxia and/or vascular factors. Genes associated with schizophrenia showed a significant, threefold enrichment among genes that were derived from microarray studies of the ischemia-hypoxia response (IHR) in the brain. Thus, the finding of a considerable match between genes associated with the risk of schizophrenia and IHR and/or vascular factors is reproducible. An additional survey of genes identified by GWAS and CNV analyses suggested novel genes that match the criteria. Findings for interactions between specific variants of genes proposed to be IHR and/or vascular factors with obstetric complications in patients with schizophrenia have been reported in the literature. Therefore, the extended gene set defined here may form a reasonable and evidence-based starting point for hypothesis-based testing of G × E interactions in clinical genetic and translational neuroscience studies.

Dopamine receptor interacting proteins: targeting neuronal calcium sensor-1/D2 dopamine receptor interaction for antipsychotic drug development

D2 dopamine receptors (D2Rs) represent an important class of receptors in the pharmacological development of novel therapeutic drugs for the treatment of schizophrenia. Recent research into D2R signaling suggests that receptor properties are dependent on interaction with a cohort of dopamine receptor interacting proteins (DRIPs) within a macromolecular structure termed the signalplex. One component of this signalplex is neuronal calcium sensor 1 (NCS-1) a protein found to regulate the phosphorylation, trafficking, and signaling profile of the D2R in neurons. It has also been found that NCS-1 can contribute to the pathology of schizophrenia and may play a role in the efficacy of antipsychotic drug medication in the brain. In this review we discuss how the selective targeting of a DRIP, such as NCS-1, can be utilized as a novel strategy of drug design for the creation of new therapeutics for a disease such as schizophrenia. Using a fluorescence polarization assay we explore how the ability to detect changes in D2R/NCS-1 interaction can be exploited as an effective screening tool in the isolation and development of lead compounds for antipsychotic drug development. This line of work explores a novel direction in targeting D2Rs via their signalplex components and supports the notion that receptor interacting proteins represent an emerging new class of molecular targets for pharmacological drug development.

Patterns of Tobacco Consumption among Indian Men with Schizophrenia Compared to Their Male Siblings

OBJECTIVE

Tobacco consumption among patients with schizophrenia has been investigated extensively in western countries, but there is a dearth of studies in India, where socio-economic and cultural variables are different. This study aims to investigate the patterns of tobacco consumption among schizophrenia patients compared with their non-psychotic siblings.

METHODS

Consenting, successive male outpatients diagnosed with schizophrenia (n=100, DSM-IV criteria), and their non-psychotic brothers (n=100) were compared. Following a structured diagnostic interview, detailed information about tobacco consumption (including smokeless tobacco) was obtained using the Fagerstrom Test for Nicotine Dependence for smoked tobacco, and FTND-smokeless tobacco. The University of Pennsylvania Computerized Neurocognitive battery (CNB) was administered to a sub-group of patients (n=48).

RESULTS

Schizophrenia patients initiated tobacco use at a significantly earlier age than their brothers, but there was no significant difference with regard to type, quantity or frequency of tobacco use (smoke or smokeless varieties). Patients who consumed tobacco had significantly higher positive symptom scores compared with non-users (p=0.043). There were no significant differences between nicotine dependent and non-dependent patients with regard to CNB domains except attention.

CONCLUSION

Patterns of tobacco consumption were similar among schizophrenia patients and their non-psychotic brothers. Tobacco use was associated with increased positive symptom scores, but there were no significant differences in cognitive measures among nicotine dependent and non-dependent patients.

Is neuregulin 1 involved in determining cerebral volumes in schizophrenia? Preliminary results showing a decrease in superior temporal gyrus volume

BACKGROUND/AIMS

Reduced left superior temporal gyrus (STG) volume is one of the most replicated imaging findings in schizophrenia. However, it remains unclear whether genes play any role in our understanding of such structural alteration. It has been proposed that Neuregulin 1 (NRG1) might be a promising gene involved in schizophrenia, because of its role in neurodevelopment and neuroplasticity. In this study, the association between NRG1 and STG anatomy in patients with schizophrenia was explored for the first time.

METHODS

We investigated a 1-year treated prevalence cohort of patients with schizophrenia in contact with the South Verona Community-Based Mental Health Service. A blood sample was collected for DNA extraction and brain structure was assessed with an MRI scan. A total of 27 subjects with schizophrenia underwent both assessments and were included in the study.

RESULTS

We investigated the association between the polymorphism SNP8NRG222662 (rs4623364) of NRG1 and volume of the STG. We found that patients homozygous for the C allele had reduced left STG gray and white matter volumes in comparison to those homozygous for the G allele (p < 0.01 and p < 0.001, respectively).

CONCLUSIONS

This exploratory study suggests that NRG1 may be involved in determining STG size in schizophrenia, and may play a role in the neurogenetic basis of the language disturbances seen in this disorder. However, due to our small sample size, the results should be regarded as preliminary and replicated in a larger sample.

Cancer in parents of persons with schizophrenia: is there a genetic protection?

A reduced risk for cancer has been noted among persons with schizophrenia as well as their first degree relatives. One explanation for these findings suggests that genes associated with schizophrenia confer reduced cancer susceptibility. Given the well documented genetic factor in schizophrenia it could thus be expected that cancer incidence rates should be lower in persons with schizophrenia with a known family history of schizophrenia compared to persons with sporadic schizophrenia, as well as their first degree relatives. This study investigated the risk for cancer among the biological parents of persons with schizophrenia accounting for the familial aggregation. Linkage was conducted between national population, psychiatric and cancer databases. Standardized incidence rates for all cancer sites were calculated by comparing the parents' rates with those of the general population. In addition, the association between familial aggregation of schizophrenia and risk for cancer was calculated among the parents. A reduced cancer risk was found among the parents compared to the general population (SIR 0.8, 95% CI 0.8-0.9). However, no evidence of decreased risk was associated with familial schizophrenia. Thus, no association between familial aggregation and cancer incidents was found with regard to most cancer sites. Moreover, a small, but not statistically significant increased risk of colon cancer was associated with familial aggregation scores among the parents (OR 1.2, 95% CI 1.0-1.5). These findings undermine the support to the genetic explanation for the reduced risk for cancer in schizophrenia among patients and their biological parents.