A comparative study of theory of mind in taxon-like clusters of psychometric schizotypes and individuals at genetic risk for schizophrenia.

Introduction: Clinical and family studies suggest that alterations of theory of mind (ToM) represent a marker of genetic liability to schizophrenia. Findings regarding ToM in schizotypy are less consistent. The study aimed to explore whether this might be due to an insufficient account of the heterogeneity of schizotypy in prior research and/or the fact that in psychometric schizotypy ToM alterations could manifest as subtle peculiarities rather than overt errors of mentalising.Methods: Individuals without a family history of psychosis (n = 150) were assigned to low, positive, negative, and high mixed schizotypy classes based on a cluster analysis of 1322 subjects who completed the Schizotypal Personality Questionnaire. The classes were compared on their performance of faux pas tasks with 77 adult first-degree relatives of schizophrenia patients, who represent individuals at genetic risk for schizophrenia. Besides overt errors, subtle alterations in ToM were analysed using expert judgment.Results: The relatives tended to make overt errors and demonstrated specific features of intentional reasoning. None of the schizotypal classes showed similar trends.Conclusions: The results complement the literature on the subjective-objective disjunction in psychometric schizotypes and did not provide evidence that ToM anomalies are a marker of genetic liability to schizophrenia in this cohort.

Impact on the Risk and Severity of Childhood Onset Schizophrenia of Schizophrenia Risk Genetic Variants at the DRD2 and ZNF804A Loci.

The study explored whether schizophrenia risk alleles of the DRD2 rs2514218 and ZNF804A rs1344706 polymorphisms also influenced the risk and severity of childhood-onset schizophrenia (COS) and differentiated it from autism spectrum disorders (ASD). We compared 75 children with COS to 75 children with ASD, 150 patients with adult-onset schizophrenia and 150 healthy individuals. Frequency of the DRD2 T-allele, assumed to be protective against schizophrenia overall, was higher in COS compared to adult-onset schizophrenia and healthy controls. The risk allele A of ZNF804A was associated with greater severity of negative symptoms in COS. The latter result is consistent with the involvement of ZNF804A in the development of severe forms of schizophrenia. The findings regarding DRD2 suggest that the same genetic variants may play different roles in schizophrenia with childhood and adult onset. This warrants further research, since D2 receptor blockade is a general pharmacodynamic property of antipsychotics.

A Role of DNA Methylation within the CYP17A1 Gene in the Association of Genetic and Environmental Risk Factors with Stress-Related Manifestations of Schizophrenia.

As genetic and environmental influences on schizophrenia might converge on DNA methylation (DNAm) within loci which are both associated with the disease and implicated in response to environmental stress, we examined whether DNAm within CYP17A1, a hypothalamus-pituitary-adrenal axis gene which is situated within the schizophrenia risk locus 10q24.32, would mediate genetic and environmental effects on stress-related schizophrenia symptoms. DNAm within an exonic-intronic fragment of CYP17A1 was assessed in the blood of 66 schizophrenia patients and 63 controls using single-molecule real-time bisulfite sequencing. Additionally, the VNTR polymorphism of the AS3MT gene, a plausible causal variant within the 10q24.32 locus, was genotyped in extended patient and control samples (n = 700). The effects of local haplotype, VNTR and a polyenviromic risk score (PERS) on DNAm, episodic verbal memory, executive functions, depression, and suicidality of patients were assessed. Haplotype and PERS differentially influenced DNAm at four variably methylated sites identified within the fragment, with stochastic, additive, and allele-specific effects being found. An allele-specific DNAm at CpG-SNP rs3781286 mediated the relationship between the local haplotype and verbal fluency. Our findings do not confirm that the interrogated DNA fragment is a place where genetic and environmental risk factors converge to influence schizophrenia symptoms through DNAm.

The Dopamine Receptor D2 C957T Polymorphism Modulates Early Components of Event-Related Potentials in Visual Word Recognition Task.

BACKGROUND: Visual word recognition is one of the central topics in cognitive psychology and cognitive neuroscience. Genetic factors are known to contribute to the visual word recognition, but no genes associated with this process have been identified so far. We studied the impact of the DRD2 C957T polymorphism on the efficiency of visual word recognition by measuring its neuronal correlates and behavioral parameters. Early (~200 ms) components of event-related potentials (ERP) were recorded during a lexical decision task. The DRD2 C957T polymorphism is thought to be associated with D2 receptor's availability and binding potential. Earlier studies have demonstrated the influence of this variation on perception and processing of verbal stimuli. The DRD2 C957T is also associated with schizophrenia, with the C allele being the risk allele. METHODS: Electroencephalogram, genetic, and behavioral data were collected from 96 healthy individuals (53.1% men). ERPs were recorded for words and pseudowords in implicit and explicit tasks. Two regions of interests in the left ventral temporal cortex, whose role in early visual word processing is well established, were selected for analysis. RESULTS: The results showed the main effect of the DRD2 C957T polymorphism on P200 amplitude. Carriers of the TT genotype had higher P200 amplitudes compared to subjects with schizophrenia risk C allele. Within-group comparisons demonstrated a better ability to adjust attention to orthographic stimuli depending on task demands and lexicality in the TT group. CONCLUSION: The results of the study suggest that the DRD2 C957T polymorphism modulates early stages of visual word recognition.

Bench Research Informed by GWAS Results.

Scientifically interesting as well as practically important phenotypes often belong to the realm of complex traits. To the extent that these traits are hereditary, they are usually 'highly polygenic'. The study of such traits presents a challenge for researchers, as the complex genetic architecture of such traits makes it nearly impossible to utilise many of the usual methods of reverse genetics, which often focus on specific genes. In recent years, thousands of genome-wide association studies (GWAS) were undertaken to explore the relationships between complex traits and a large number of genetic factors, most of which are characterised by tiny effects. In this review, we aim to familiarise 'wet biologists' with approaches for the interpretation of GWAS results, to clarify some issues that may seem counterintuitive and to assess the possibility of using GWAS results in experiments on various complex traits.

Profiling haplotype specific CpG and CpH methylation within a schizophrenia GWAS locus on chromosome 14 in schizophrenia and healthy subjects.

Interrogating DNA methylation within schizophrenia risk loci holds promise to identify mechanisms by which genes influence the disease. Based on the hypothesis that allele specific methylation (ASM) of a single CpG, or perhaps CpH, might mediate or mark the effects of genetic variants on disease risk and phenotypes, we explored haplotype specific methylation levels of individual cytosines within a genomic region harbouring the BAG5, APOPT1 and KLC1 genes in peripheral blood of schizophrenia patients and healthy controls. Three DNA fragments located in promoter, intronic and intergenic areas were studied by single-molecule real-time bisulfite sequencing enabling the analysis of long reads of DNA with base-pair resolution and the determination of haplotypes directly from sequencing data. Among 1,012 cytosines studied, we did not find any site where methylation correlated with the disease or cognitive deficits after correction for multiple testing. At the same time, we determined the methylation profile associated with the schizophrenia risk haplotype within the KLC1 fourth intron and confirmed ASM for cytosines located in the vicinity of rs67899457. These genetically associated DNA methylation variations may be related to the pathophysiological mechanism differentiating the risk and non-risk haplotypes and merit further investigation.

Effect of the C-reactive protein gene on risk and clinical characteristics of schizophrenia in winter-born individuals.

C-reactive protein (CRP) levels are elevated in a subset of schizophrenia patients and correlated with more severe symptoms, which makes CRP a potential theranostic biomarker for the disease. However, genotypes associated with higher CRP concentrations have the protective effect against schizophrenia. To resolve this discrepancy, more research on the role of CRP in schizophrenia is needed. The present study aimed to investigate the effects on schizophrenia of the CRP gene in combination with season of birth (SOB), the known risk factor for the disease. We first examined the impact of seasonality on schizophrenia risk in the Russian population, using samples of 2452 patients and 1203 controls, and then assessed the CRP rs2794521 polymorphism × SOB interaction effect on the disease risk, age-of-onset and symptoms severity in 826 patients and 476 controls. An excess of winter births in patients was not significant. At the same time, we found that winter-born patients carrying the CRP GG genotype, which is associated with low transcriptional activity, had an earlier age at onset than the other patients. The findings are in line with the protective role of high active CRP genetic variants in the development of schizophrenia and provide support for the hypothesis that this effect of CRP takes place early in life.

Emotional distress in parents of psychotic patients is modified by serotonin transporter gene (5-HTTLPR)--brain-derived neurotrophic factor gene interactions.

Caregiving of a family member with psychotic disorder is considered among the most significant stressors and relatives of a sufferer experienced psychological and physical burden that may be the cause of neurotic states. There is growing evidence that sensitivity of individuals to depressogenic effects of stressful factor is moderated by genetic variants of serotonin transporter (SERT) and brain-derived neurotrophic factors (BDNF). We examined the association of the 5-HTTLPR SERT and Val66Met BDNF polymorphisms with signs of depression and anxiety measured with the Minnesota Multiphasic Personality Inventory (MMPI) in 235 unaffected parents of patients with major psychosis and 102 age-matched controls. A significant effect of the SERT-BDNF interaction on Depression and Psychasthenia scales was found in the group of parents, but not in the control group. Carriers of the Val/Val x SS variant scored higher as compared to other allelic combinations. The results obtained revealed that the SERT-BDNF interactions might moderate the level of anxiety and depression caused by caregiving status in parents of psychotic patients.

Facial affect recognition deficit as a marker of genetic vulnerability to schizophrenia.

The aim of this study was to investigate the possibility that affect recognition impairments are associated with genetic liability to schizophrenia. In a group of 55 unaffected relatives of schizophrenia patients (parents and siblings) we examined the capacity to detect facially expressed emotions and its relationship to schizotypal personality, neurocognitive functioning, and the subject's actual emotional state. The relatives were compared with 103 schizophrenia patients and 99 healthy subjects without any family history of psychoses. Emotional stimuli were nine black-and-white photos of actors, who portrayed six basic emotions as well as interest, contempt, and shame. The results evidenced the affect recognition deficit in relatives, though milder than that in patients themselves. No correlation between the deficit and schizotypal personality measured with SPQ was detected in the group of relatives. Neither cognitive functioning, including attention, verbal memory and linguistic ability, nor actual emotional states accounted for their affect recognition impairments. The results suggest that the facial affect recognition deficit in schizophrenia may be related to genetic predisposition to the disorder and may serve as an endophenotype in molecular-genetic studies.

Relationship between Alzheimer's disease-associated SNPs within the CLU gene, local DNA methylation and episodic verbal memory in healthy and schizophrenia subjects.

Genetic variation may impact on local DNA methylation patterns. Therefore, information about allele-specific DNA methylation (ASM) within disease-related loci has been proposed to be useful for the interpretation of GWAS results. To explore mechanisms that may underlie associations between Alzheimer's disease (AD) and schizophrenia risk CLU gene and verbal memory, one of the most affected cognitive domains in both conditions, we studied DNA methylation in a region between AD-associated SNPs rs9331888 and rs9331896 in 72 healthy individuals and 73 schizophrenia patients. Using single-molecule real-time bisulfite sequencing we assessed the haplotype-dependent ASM in this region. We then investigated whether its methylation could influence episodic verbal memory measured with the Rey Auditory Verbal Learning Test in these two cohorts. The region showed a complex methylation pattern, which was similar in healthy and schizophrenia individuals and unrelated to haplotypes. The pattern predicted memory scores in controls. The results suggest that epigenetic modifications within the CLU locus may play a role in memory variation, independent of ASM.

Effects of a GWAS-Supported Schizophrenia Variant in the DRD2 Locus on Disease Risk, Anhedonia, and Prefrontal Cortical Thickness.

The study aimed to confirm the association of the schizophrenia genome-wide association study (GWAS) hit rs2514218 located near the DRD2 gene with the risk of the disease and to investigate the relationships between rs2514218 and schizophrenia-related clinical and neuroimaging phenotypes. Genotypes at the rs2514218 site were determined for 2148 schizophrenia spectrum patients and 1273 control subjects from the Russian population. In subsets of subjects, we assessed symptomatic dimensions using the Positive and Negative Syndrome Scale (n = 1651) and Temporal Experience of Pleasure Scale (n = 471). At the brain level, gray matter volumes in striatal structures and cortical thickness in the lateral prefrontal cortical regions were investigated (n = 97). Genotype frequencies did not differ between patients and controls. The allelic association analysis yielded a near-threshold p value (p = 0.054), the magnitude (OR = 0.90), and direction of the minor allele (T) effect being in accord with those in the schizophrenia GWAS. Also, patients homozygous for the risk allele C had more severe consummatory anhedonia and a thinner cortex than controls and patients carrying the T allele. The largest effect size of the genotype with diagnosis interaction was seen in the right pars opercularis area. The findings support the role of rs2514218 in schizophrenia risk and presentation and suggest rs2514218 has an influence on brain morphology and negative symptoms.

Prediction of smoking by multiplex bisulfite PCR with long amplicons considering allele-specific effects on DNA methylation.

BACKGROUND: Methylation of DNA is associated with a variety of biological processes. With whole-genome studies of DNA methylation, it became possible to determine a set of genomic sites where DNA methylation is associated with a specific phenotype. A method is needed that allows detailed follow-up studies of the sites, including taking into account genetic information. Bisulfite PCR is a natural choice for this kind of task, but multiplexing is one of the most important problems impeding its implementation. To address this task, we took advantage of a recently published method based on Pacbio sequencing of long bisulfite PCR products (single-molecule real-time bisulfite sequencing, SMRT-BS) and tested the validity of the improved methodology with a smoking phenotype. RESULTS: Herein, we describe the "panhandle" modification of the method, which permits a more robust PCR with multiple targets. We applied this technique to determine smoking by DNA methylation in 71 healthy people and 83 schizophrenia patients (n = 50 smokers and n = 104 non-smokers, Russians of the Moscow region). We used five targets known to be influenced by smoking (regions of genes AHRR, ALPPL2, IER3, GNG12, and GFI1). We discovered significant allele-specific methylation effects in the AHRR and IER3 regions and assessed how this information could be exploited to improve the prediction of smoking based on the collected DNA methylation data. We found no significant difference in the methylation profiles of selected targets in relation to schizophrenia suggesting that smoking affects methylation at the studied genomic sites in healthy people and schizophrenia patients in a similar way. CONCLUSIONS: We determined that SMRT-BS with "panhandle" modification performs well in the described setting. Additional information regarding methylation and allele-specific effects could improve the predictive accuracy of DNA methylation-based models, which could be valuable for both basic research and clinical applications.

Correction to: Prediction of smoking by multiplex bisulfite PCR with long amplicons considering allele-specific effects on DNA methylation.

Upon publication of the original article [1], it was noticed that the Figure captions of Figs. 2 and 3 were incorrectly given. The correct Figure captions are given below.

A Potential Role of the 5-HTTLPR Polymorphism in Self-Reported Executive Functioning.

Intense effort is directed toward searching for associations between genes and neuropsychological measures of executive functions. In contrast, the impact of genetic polymorphisms on self-rating of everyday executive functioning has not been investigated so far. This study was designed to test associations of self-reported executive functioning, measured with the Behavior Rating Inventory of Executive Function (BRIEF-A), with dopaminergic and serotoninergic genes in non-clinical population and to assess impact of neuropsychological and personality characteristics on these associations. One hundred healthy adults completed the BRIEF-A, personality inventories SPQ-74, STAI, MMPI, and neuropsychological tests for executive functions. Polymorphisms in the DRD4, COMT, DRD2, HTR2A, and SLC6A4 genes were genotyped. We revealed a significant main effect of the SLC6A4's 5-HTTLPR polymorphism on BRIEF-A scores (F = 2.21, P = .018, η2 = .24). Among the BRIEF-A measures, the genotype effect was significant for the Plan/Organize (F = 7.34, P = .008, η2 = .07) and Task Monitor scales (F = 4.33, P = .04, η2 = .04), and the Metacognition index (F = 4.21, P = .043, η2 = .04). Carriers of the short allele reported fewer problems than homozygotes for the long allele. Correlations of the BRIEF-A measures with neuropsychological variables were weak, while those with personality characteristics were strong, with trait anxiety being the most powerful predictor of the BRIEF-A scores. However, the relationship between the 5-HTTLPR and BRIEF-A scores remained significant when trait anxiety was controlled for. The results suggest a potential role of the 5-HTTLPR in self-reported everyday task planning and monitoring.

Interaction Effects of Season of Birth and Cytokine Genes on Schizotypal Traits in the General Population.

Literature suggests that the effect of winter birth on vulnerability to schizophrenia might be mediated by increased expression of proinflammatory cytokines due to prenatal infection and its inadequate regulation by anti-inflammatory factors. As the response of the immune system depends on genotype, this study assessed the interaction effects of cytokine genes and season of birth (SOB) on schizotypy measured with the Schizotypal Personality Questionnaire (SPQ-74). We searched for associations of IL1B rs16944, IL4 rs2243250, and IL-1RN VNTR polymorphisms, SOB, and their interactions with the SPQ-74 total score in a sample of 278 healthy individuals. A significant effect of the IL4 X SOB interaction was found, p = 0.007 and η2 = 0.028. We confirmed this effect using an extended sample of 373 individuals. Homozygotes CC born in winter showed the highest SPQ total score and differed significantly from winter-born T allele carriers, p = 0.049. This difference was demonstrated for cognitive-perceptual and disorganized but not interpersonal dimensions. The findings are consistent with the hypothesis that the cytokine genes by SOB interaction can influence variability of schizotypal traits in the general population. The IL4 T allele appeared to have a protective effect against the development of positive and disorganized schizotypal traits in winter-born individuals.

Association study of COMT gene Val158Met polymorphism with auditory P300 and performance on neurocognitive tests in patients with schizophrenia and their relatives.

A number of studies have reported an association between catechol-O-methyltransferase (COMT) gene Val158Met polymorphism and neuropsychological traits in patients with schizophrenia, their relatives and healthy controls, with the Met allele carriers performing better on neurocognitive tasks than those with the Val allele. But the association was not confirmed in all studies. The present paper was aimed at further investigation of the COMT gene relationship with some neurocognitive traits, assessing mainly working and verbal memory, and to P300 event-related potentials (auditory oddball). A total sample of 319 individuals, including schizophrenic patients, their relatives and controls, was studied. No significant differences in performance of neurocognitive tasks were found by Val158Met genotypes. An association was observed between the Met/Met genotype and higher amplitude in centro-parietal area in relatives. Factors that could explain the non-replication of previous studies on the COMT gene polymorphism and neurocognitive traits are discussed. We suggest here that (1) Val158Met polymorphism rather exerts a modifying influence on brain activation in general than impacts directly on performance of the particular neurocognitive test, and (2) P300 amplitude seems to be a correlate of this activation reflecting, along with information processing, the subject's affective and personality features.

Arginine vasopressin 1a receptor RS3 promoter microsatellites in schizophrenia: a study of the effect of the "risk" allele on clinical symptoms and facial affect recognition.

We studied AVPR1A RS3 polymorphism in schizophrenic patients and controls. AVPR1A RS3 was not associated with schizophrenia. The allele 327bp implicated in autism and social behavior was associated with negative symptoms and tended to be linked to patient facial affect recognition suggesting its impact on schizophrenia social phenotypes.

Serotonin transporter gene polymorphism and schizoid personality traits in the patients with psychosis and psychiatrically well subjects.

BACKGROUND AND OBJECTIVES: serotonin transporter (5-HTT) gene allelic variants were shown to be associated with Neuroticism and Harm Avoidance but the results were not replicated in other studies. The current investigation was undertaken in a further attempt to study the relationship between 5-HTT polymorphism and personality traits. SUBJECTS AND METHODS: to evaluate a spectrum of personality traits, MMPI was administered to a sample including patients with affective disorders (n=114), patients with schizophrenia spectrum illnesses (n=110) and psychiatrically well controls (n=124). All groups were genotyped for VNTR-17 and functional insertion-deletion (5-HTTLPR) polymorphisms. RESULTS: an association was found between 5-HTTLPR polymorphism and scores on three MMPI scales: Psychopathic deviance, Paranoia and Schizophrenia in patients with affective disorders and S chizophrenia in normal subjects. Both affected and control individuals with 'ss' genotype exhibited lower scores on these scales. CONCLUSION: we demonstrated that functional deletion/insertion allelic variation associated with decreased expression of serotonin transporter ('s' allele or 'ss' genotype) may restrict expression of schizoid traits in normal subjects and patients with affective disorders.

Cognitive peculiarities in relatives of schizophrenic and schizoaffective patients: heritability and resting EEG-correlates.

The role of genetic factors in liability to schizophrenia is well established. It is supposed that different susceptibility genes produce distinct neurobiological and behavioural phenotypes that may each increase the risk for developing schizophrenia. The aim of the study was to search for genetically and pathophysiologically independent domains of mild cognitive disturbances that might be the components of liability to schizophrenia. One hundred and twenty-seven adult relatives of schizophrenic and schizoaffective patients were tested with a battery of cognitive tasks. Results were subjected to a principal component analysis, and factors obtained were further investigated with behavioural genetic methods in 56 families of schizophrenics. Resting EEGs were recorded from a subsample of 66 relatives. Correlations of the cognitive factors with absolute power values of seven frequency bands at 16 derivations were assessed using regression analysis. The study revealed four components of cognitive deficits in relatives of schizophrenics in domains of verbal short-term memory, thinking, communication and attention/working memory, all with substantive heritability except the last. The four components had a partial overlapping, but still distinct patterns of resting EEG correlates. The findings are in line with the assumption that cognitive deficit in high-risk individuals may be decomposed to relatively independent dimensions, each with its specific genetic and pathophysiological background.