DRD2/AKT1 interaction on D2 c-AMP independent signaling, attentional processing, and response to olanzapine treatment in schizophrenia.

The D2/AKT1/GSK-3ß signaling pathway has been involved in the downstream intracellular effects of dopamine, in the pathophysiology of cognitive deficits and related brain activity in schizophrenia, as well as in response to treatment with antipsychotics. Polymorphisms in the D2 (DRD2 rs1076560) and AKT1 (AKT1 rs1130233) genes have been associated with their respective protein expression and with higher-order cognition and brain function, including attention. Given the strong potential for their relationship, we investigated the interaction of these polymorphisms on multiple molecular and in vivo phenotypes associated with this signaling pathway. We measured AKT1 and GSK-3ß proteins and phosphorylation in human peripheral blood mononuclear cells, functional MRI cingulate response during attentional control, behavioral accuracy during sustained attention, and response to 8 wk of treatment with olanzapine in a total of 190 healthy subjects and 66 patients with schizophrenia. In healthy subjects, we found that the interaction between the T allele of DRD2 rs1076560 and the A allele of AKT1 rs1130233 was associated with reduced AKT1 protein levels and reduced phosphorylation of GSK-3ß, as well as with altered cingulate response and reduced behavioral accuracy during attentional processing. On the other hand, interaction of these two alleles was associated with greater improvement of Positive and Negative Syndrome Scale scores in patients with schizophrenia after treatment with olanzapine. The present results indicate that these functional polymorphisms are epistatically associated with multiple phenotypes of relevance to schizophrenia. Our results also lend support to further investigation of this downstream molecular pathway in the etiology and treatment of this disorder.

Nonlinear response of the anterior cingulate and prefrontal cortex in schizophrenia as a function of variable attentional control.

Previous studies have reported abnormal prefrontal and cingulate activity during attentional control processing in schizophrenia. However, it is not clear how variation in attentional control load modulates activity within these brain regions in this brain disorder. The aim of this study in schizophrenia is to investigate the impact of increasing levels of attentional control processing on prefrontal and cingulate activity. Blood oxygen level-dependent (BOLD) responses of 16 outpatients with schizophrenia were compared with those of 21 healthy subjects while performing a task eliciting increasing levels of attentional control during event-related functional magnetic resonance imaging at 3 T. Results showed reduced behavioral performance in patients at greater attentional control levels. Imaging data indicated greater prefrontal activity at intermediate attentional control levels in patients but greater prefrontal and cingulate responses at high attentional control demands in controls. The BOLD activity profile of these regions in controls increased linearly with increasing cognitive loads, whereas in patients, it was nonlinear. Correlation analysis consistently showed differential region and load-specific relationships between brain activity and behavior in the 2 groups. These results indicate that varying attentional control load is associated in schizophrenia with load- and region-specific modification of the relationship between behavior and brain activity, possibly suggesting earlier saturation of cognitive capacity.

Genetically determined interaction between the dopamine transporter and the D2 receptor on prefronto-striatal activity and volume in humans.

Dopamine modulation of neuronal activity during memory tasks identifies a nonlinear inverted-U shaped function. Both the dopamine transporter (DAT) and dopamine D(2) receptors (encoded by DRD(2)) critically regulate dopamine signaling in the striatum and in prefrontal cortex during memory. Moreover, in vitro studies have demonstrated that DAT and D(2) proteins reciprocally regulate each other presynaptically. Therefore, we have evaluated the genetic interaction between a DRD(2) polymorphism (rs1076560) causing reduced presynaptic D(2) receptor expression and the DAT 3'-VNTR variant (affecting DAT expression) in a large sample of healthy subjects undergoing blood oxygenation level-dependent (BOLD)-functional magnetic resonance imaging (MRI) during memory tasks and structural MRI. Results indicated a significant DRD(2)/DAT interaction in prefrontal cortex and striatum BOLD activity during both working memory and encoding of recognition memory. The differential effect on BOLD activity of the DAT variant was mostly manifest in the context of the DRD(2) allele associated with lower presynaptic expression. Similar results were also evident for gray matter volume in caudate. These interactions describe a nonlinear relationship between compound genotypes and brain activity or gray matter volume. Complementary data from striatal protein extracts from wild-type and D(2) knock-out animals (D2R(-/-)) indicate that DAT and D(2) proteins interact in vivo. Together, our results demonstrate that the interaction between genetic variants in DRD(2) and DAT critically modulates the nonlinear relationship between dopamine and neuronal activity during memory processing.

Functional variation of the dopamine D2 receptor gene is associated with emotional control as well as brain activity and connectivity during emotion processing in humans.

Personality traits related to emotion processing are, at least in part, heritable and genetically determined. Dopamine D(2) receptor signaling is involved in modulation of emotional behavior and activity of associated brain regions such as the amygdala and the prefrontal cortex. An intronic single nucleotide polymorphism within the D(2) receptor gene (DRD2) (rs1076560, guanine > thymine or G > T) shifts splicing of the two protein isoforms (D(2) short, mainly presynaptic, and D(2) long) and has been associated with modulation of memory performance and brain activity. Here, our aim was to investigate the association of DRD2 rs1076560 genotype with personality traits of emotional stability and with brain physiology during processing of emotionally relevant stimuli. DRD2 genotype and Big Five Questionnaire scores were evaluated in 134 healthy subjects demonstrating that GG subjects have reduced "emotion control" compared with GT subjects. Functional magnetic resonance imaging in a sample of 24 individuals indicated greater amygdala activity during implicit processing and greater dorsolateral prefrontal cortex (DLPFC) response during explicit processing of facial emotional stimuli in GG subjects compared with GT. Other results also demonstrate an interaction between DRD2 genotype and facial emotional expression on functional connectivity of both amygdala and dorsolateral prefrontal regions with overlapping medial prefrontal areas. Moreover, rs1076560 genotype is associated with differential relationships between amygdala/DLPFC functional connectivity and emotion control scores. These results suggest that genetically determined D(2) signaling may explain part of personality traits related to emotion processing and individual variability in specific brain responses to emotionally relevant inputs.

Functional variants of the dopamine receptor D2 gene modulate prefronto-striatal phenotypes in schizophrenia.

Dopamine D2 receptor signalling is strongly implicated in the aetiology of schizophrenia. We have recently characterized the function of three DRD2 SNPs: rs12364283 in the promoter affecting total D2 mRNA expression; rs2283265 and rs1076560, respectively in introns 5 and 6, shifting mRNA splicing to two functionally distinct isoforms, the short form of D2 (D2S) and the long form (D2L). These two isoforms differentially contribute to dopamine signalling in prefrontal cortex and in striatum. We performed a case-control study to determine association of these variants and of their main haplotypes with several schizophrenia-related phenotypes. We demonstrate that the minor allele in the intronic variants is associated with reduced expression of %D2S of total mRNA in post-mortem prefrontal cortex, and with impaired working memory behavioural performance, both in patients and controls. However, the fMRI results show opposite effects in patients compared with controls: enhanced engagement of prefronto-striatal pathways in controls and reduced activity in patients. Moreover, the promoter variant is also associated with working memory activity in prefrontal cortex and striatum of patients, and less robustly with negative symptoms scores. Main haplotypes formed by the three DRD2 variants showed significant associations with these phenotypes consistent with those of the individual SNPs. Our results indicate that the three functional DRD2 variants modulate schizophrenia phenotypes possibly by modifying D2S/D2L ratios in the context of different total D2 density.

Multivariate classification of schizophrenia and its familial risk based on load-dependent attentional control brain functional connectivity.

Patients with schizophrenia (SCZ), as well as their unaffected siblings (SIB), show functional connectivity (FC) alterations during performance of tasks involving attention. As compared with SCZ, these alterations are present in SIB to a lesser extent and are more pronounced during high cognitive demand, thus possibly representing one of the pathways in which familial risk is translated into the SCZ phenotype. Our aim is to measure the separability of SCZ and SIB from healthy controls (HC) using attentional control-dependent FC patterns, and to test to which extent these patterns span a continuum of neurofunctional alterations between HC and SCZ. 65 SCZ with 65 age and gender-matched HC and 39 SIB with 39 matched HC underwent the Variable Attentional Control (VAC) task. Load-dependent connectivity matrices were generated according to correct responses in each VAC load. Classification performances of high, intermediate and low VAC load FC on HC-SCZ and HC-SIB cohorts were tested through machine learning techniques within a repeated nested cross-validation framework. HC-SCZ classification models were applied to the HC-SIB cohort, and vice-versa. A high load-related decreased FC pattern discriminated between HC and SCZ with 66.9% accuracy and with 57.7% accuracy between HC and SIB. A high load-related increased FC network separated SIB from HC (69.6% accuracy), but not SCZ from HC (48.5% accuracy). Our findings revealed signatures of attentional FC abnormalities shared by SCZ and SIB individuals. We also found evidence for potential, SIB-specific FC signature, which may point to compensatory neurofunctional mechanisms in persons at familial risk for schizophrenia.

A Pattern of Cognitive Deficits Stratified for Genetic and Environmental Risk Reliably Classifies Patients With Schizophrenia From Healthy Control Subjects.

BACKGROUND: Schizophrenia risk is associated with both genetic and environmental risk factors. Furthermore, cognitive abnormalities are established core characteristics of schizophrenia. We aim to assess whether a classification approach encompassing risk factors, cognition, and their associations can discriminate patients with schizophrenia (SCZs) from healthy control subjects (HCs). We hypothesized that cognition would demonstrate greater HC-SCZ classification accuracy and that combined gene-environment stratification would improve the discrimination performance of cognition. METHODS: Genome-wide association study-based genetic, environmental, and neurocognitive classifiers were trained to separate 337 HCs from 103 SCZs using support vector classification and repeated nested cross-validation. We validated classifiers on independent datasets using within-diagnostic (SCZ) and cross-diagnostic (clinically isolated syndrome for multiple sclerosis, another condition with cognitive abnormalities) approaches. Then, we tested whether gene-environment multivariate stratification modulated the discrimination performance of the cognitive classifier in iterative subsamples. RESULTS: The cognitive classifier discriminated SCZs from HCs with a balanced accuracy (BAC) of 88.7%, followed by environmental (BAC = 65.1%) and genetic (BAC = 55.5%) classifiers. Similar classification performance was measured in the within-diagnosis validation sample (HC-SCZ BACs, cognition = 70.5%; environment = 65.8%; genetics = 49.9%). The cognitive classifier was relatively specific to schizophrenia (HC-clinically isolated syndrome for multiple sclerosis BAC = 56.7%). Combined gene-environment stratification allowed cognitive features to classify HCs from SCZs with 89.4% BAC. CONCLUSIONS: Consistent with cognitive deficits being core features of the phenotype of SCZs, our results suggest that cognitive features alone bear the greatest amount of information for classification of SCZs. Consistent with genes and environment being risk factors, gene-environment stratification modulates HC-SCZ classification performance of cognition, perhaps providing another target for refining early identification and intervention strategies.

Changes in prefrontal and amygdala activity during olanzapine treatment in schizophrenia.

Earlier imaging studies in schizophrenia have reported abnormal amygdala and prefrontal cortex activity during emotion processing. We investigated with functional magnetic resonance imaging (fMRI) during emotion processing changes in activity of the amygdala and of prefrontal cortex in patients with schizophrenia during 8 weeks of olanzapine treatment. Twelve previously drug-free/naive patients with schizophrenia were treated with olanzapine for 8 weeks and underwent two fMRI scans after 4 and 8 weeks of treatment during implicit and explicit emotional processing. Twelve healthy subjects were also scanned twice to control for potential repetition effects. Results showed a diagnosis by time interaction in left amygdala and a diagnosis by time by task interaction in right ventrolateral prefrontal cortex. In particular, activity in left amygdala was greater in patients than in controls at the first scan during both explicit and implicit processing, while it was lower in patients at the second relative to the first scan. Furthermore, during implicit processing, right ventrolateral prefrontal cortex activity was lower in patients than controls at the first scan, while it was greater in patients at the second relative to the first scan. These results suggest that longitudinal treatment with olanzapine may be associated with specific changes in activity of the amygdala and prefrontal cortex during emotional processing in schizophrenia.

Association of the SerCys DISC1 polymorphism with human hippocampal formation gray matter and function during memory encoding.

A common nonsynonymous single nucleotide polymorphism leading to a serine-to-cysteine substitution at amino acid 704 (Ser(704)Cys) in the DISC1 protein sequence has been recently associated with schizophrenia and with specific hippocampal abnormalities. Here, we used multimodal neuroimaging to investigate in a large sample of healthy subjects the putative association of the Ser(704)Cys DISC1 polymorphism with in vivo brain phenotypes including hippocampal formation (HF) gray matter volume and function (as assessed with functional MRI) as well as HF functional coupling with the neural network engaged during encoding of recognition memory. Individuals homozygous for DISC1 Ser allele relative to carriers of the Cys allele showed greater gray matter volume in the HF. Further, Ser/Ser subjects exhibited greater engagement of the HF together with greater HF-dorsolateral prefrontal cortex functional coupling during memory encoding, in spite of similar behavioral performance. These findings consistently support the notion that Ser(704)Cys DISC1 polymorphism is physiologically relevant. Moreover, they support the hypothesis that genetic variation in DISC1 may affect the risk for schizophrenia by modifying hippocampal gray matter and function.

Additive effects of genetic variation in dopamine regulating genes on working memory cortical activity in human brain.

Functional polymorphisms in the catechol-O-methyltransferase (COMT) and the dopamine transporter (DAT) genes modulate dopamine inactivation, which is crucial for determining neuronal signal-to-noise ratios in prefrontal cortex during working memory. We show that the COMT Met158 allele and the DAT 3' variable number of tandem repeat 10-repeat allele are independently associated in healthy humans with more focused neuronal activity (as measured with blood oxygen level-dependent functional magnetic resonance imaging) in the working memory cortical network, including the prefrontal cortex. Moreover, subjects homozygous for the COMT Met allele and the DAT 10-repeat allele have the most focused response, whereas the COMT Val and the DAT 9-repeat alleles have the least. These results demonstrate additive genetic effects of genes regulating dopamine signaling on specific neuronal networks subserving working memory.

Activity in medial prefrontal cortex during cognitive evaluation of threatening stimuli as a function of personality style.

Cognitive evaluation of emotional stimuli involves a network of brain regions including the medial prefrontal cortex (mPFC). However, threatening stimuli may be perceived with differential salience in different individuals. The goal of our study was to evaluate how different personality styles are associated with differential modulation of brain activity during explicit recognition of fearful and angry facial expressions. Twenty-eight healthy subjects underwent fMRI. Based on a cognitivist model, subjects were categorized according to how they attribute salience to emotional stimuli and how they regulate their emotional activation. We compared 14 phobic prone (PP) subjects, whose identity is more centered on the inner experience ("inward") and around control of environmental threat, and 14 eating disorders prone (EDP) subjects, whose identity is more centered on external referential contexts ("outward") and much less around control of threatening stimuli. During fMRI subjects either matched the identity of one of two angry and fearful faces to that of a simultaneously presented target face or identified the expression of a target face by choosing one of two simultaneously presented linguistic labels. The fMRI results indicated that PP subjects had greater mPFC activation when compared with EDP subjects during cognitive labeling of threatening stimuli. Activity in the mPFC also correlated with personality style scores. These results demonstrate that PP subjects recruit greater neuronal resources in mPFC whose activity is associated with cognitive aspects that are closely intertwined with emotional processing. These findings are consistent with the contention that cognitive evaluation and salience of emotional stimuli are associated with different personality styles.

Grey matter volume patterns in thalamic nuclei are associated with familial risk for schizophrenia.

Previous evidence suggests reduced thalamic grey matter volume (GMV) in patients with schizophrenia (SCZ). However, it is not considered an intermediate phenotype for schizophrenia, possibly because previous studies did not assess the contribution of individual thalamic nuclei and employed univariate statistics. Here, we hypothesized that multivariate statistics would reveal an association of GMV in different thalamic nuclei with familial risk for schizophrenia. We also hypothesized that accounting for the heterogeneity of thalamic GMV in healthy controls would improve the detection of subjects at familial risk for the disorder. We acquired MRI scans for 96 clinically stable SCZ, 55 non-affected siblings of patients with schizophrenia (SIB), and 249 HC. The thalamus was parceled into seven regions of interest (ROIs). After a canonical univariate analysis, we used GMV estimates of thalamic ROIs, together with total thalamic GMV and premorbid intelligence, as features in Random Forests to classify HC, SIB, and SCZ. Then, we computed a Misclassification Index for each individual and tested the improvement in SIB detection after excluding a subsample of HC misclassified as patients. Random Forests discriminated SCZ from HC (accuracy=81%) and SIB from HC (accuracy=75%). Left anteromedial thalamic volumes were significantly associated with both multivariate classifications (p<0.05). Excluding HC misclassified as SCZ improved greatly HC vs. SIB classification (Cohen's d=1.39). These findings suggest that multivariate statistics identify a familial background associated with thalamic GMV reduction in SCZ. They also suggest the relevance of inter-individual variability of GMV patterns for the discrimination of individuals at familial risk for the disorder.

Personal resources and depression in schizophrenia: The role of self-esteem, resilience and internalized stigma.

Depression in schizophrenia represents a challenge from a diagnostic, psychopathological and therapeutic perspective. The objective of this study is to test the hypothesis that resilience and self-stigma affect depression severity and to evaluate the strength of their relations in 921 patients with schizophrenia. A structural equation model was tested where depression is hypothesized as affected by resilience, internalized stigma, gender and negative symptoms, with the latter two variables used as exogenous covariates and the former two as mediators. The analysis reveals that low resilience, high negative symptoms, female gender were directly associated with depression severity, and internalized stigma acted only as a mediator between avolition and resilience, with similar magnitude. The cross-sectional study design and the variable selection limit the generalizability of the study results. The model supports a complex interaction between personal resources and negative symptoms in predicting depression in schizophrenia. The clinical implication of these findings is that personal resources could be a significant target of psychosocial treatments.

Prefrontal-hippocampal coupling during memory processing is modulated by COMT val158met genotype.

BACKGROUND: Studies in humans and in animals have demonstrated that a network of brain regions is involved in performance of declarative and recognition memory tasks. This network includes the hippocampal formation (HF) as well as the ventrolateral prefrontal cortex (VLPFC). Studies in animals have suggested that the relationship between these brain regions is strongly modulated by dopamine. METHODS: Using fMRI in healthy humans matched for a series of demographic and genetic variables, we studied the effect of the COMT val158met polymorphism on function of HF and VLPFC as well as on their functional coupling during recognition memory. RESULTS: The COMT Val allele was associated with: relatively poorer performance at retrieval; reduced recruitment of neuronal resources in HF and increased recruitment in VLPFC during both encoding and retrieval; and unfavorable functional coupling between these two regions at retrieval. Moreover, functional coupling during retrieval was predictive of behavioral accuracy. CONCLUSIONS: These results shed new light on individual differences in responsivity and connectivity between HF and VLPFC related to genetic modulation of dopamine, a mechanism accounting at least in part for individual differences in recognition memory performance.

Prefrontal dysfunction in schizophrenia controlling for COMT Val158Met genotype and working memory performance.

Earlier studies with functional imaging in schizophrenia have demonstrated dysfunction of the dorsolateral prefrontal cortex during working memory. Controlling for behavioral performance and for catechol-O-methyltransferase (COMT) Val158Met genotype, we here demonstrate in a functional magnetic resonance imaging paradigm that patients recruit greater neuronal resources in prefrontal cortex during working memory, suggesting that this phenotype is a core functional trait of the disease. We also replicated earlier findings that the Val allele of the COMT polymorphism is associated with greater engagement of the prefrontal cortex.

Association of familial risk for schizophrenia with thalamic and medial prefrontal functional connectivity during attentional control.

Anomalies in behavioral correlates of attentional processing and related brain activity are crucial correlates of schizophrenia and associated with familial risk for this brain disorder. However, it is not clear how brain functional connectivity during attentional processes is key for schizophrenia and linked with trait vs. state related variables. To address this issue, we investigated patterns of functional connections during attentional control in healthy siblings of patients with schizophrenia, who share with probands genetic features but not variables related to the state of the disorder. 356 controls, 55 patients with schizophrenia on stable treatment with antipsychotics and 40 healthy siblings of patients with this brain disorder underwent the Variable Attentional Control (VAC) task during fMRI. Independent Component Analysis (ICA) is allowed to identify independent components (IC) of BOLD signal recorded during task performance. Results indicated reduced connectivity strength in patients with schizophrenia as well as in their healthy siblings in left thalamus within an attentional control component and greater connectivity in right medial prefrontal cortex (PFC) within the so-called Default Mode Network (DMN) compared to healthy individuals. These results suggest a relationship between familial risk for schizophrenia and brain functional networks during attentional control, such that this biological phenotype may be considered a useful intermediate phenotype in order to link genes effects to aspects of the pathophysiology of this brain disorder.

BDNF rs6265 methylation and genotype interact on risk for schizophrenia.

Epigenetic mechanisms can mediate gene-environment interactions relevant for complex disorders. The BDNF gene is crucial for development and brain plasticity, is sensitive to environmental stressors, such as hypoxia, and harbors the functional SNP rs6265 (Val(66)Met), which creates or abolishes a CpG dinucleotide for DNA methylation. We found that methylation at the BDNF rs6265 Val allele in peripheral blood of healthy subjects is associated with hypoxia-related early life events (hOCs) and intermediate phenotypes for schizophrenia in a distinctive manner, depending on rs6265 genotype: in ValVal individuals increased methylation is associated with exposure to hOCs and impaired working memory (WM) accuracy, while the opposite is true for ValMet subjects. Also, rs6265 methylation and hOCs interact in modulating WM-related prefrontal activity, another intermediate phenotype for schizophrenia, with an analogous opposite direction in the 2 genotypes. Consistently, rs6265 methylation has a different association with schizophrenia risk in ValVals and ValMets. The relationships of methylation with BDNF levels and of genotype with BHLHB2 binding likely contribute to these opposite effects of methylation. We conclude that BDNF rs6265 methylation interacts with genotype to bridge early environmental exposures to adult phenotypes, relevant for schizophrenia. The study of epigenetic changes in regions containing genetic variation relevant for human diseases may have beneficial implications for the understanding of how genes are actually translated into phenotypes.

Variation of human amygdala response during threatening stimuli as a function of 5'HTTLPR genotype and personality style.

BACKGROUND: In the brain, processing of fearful stimuli engages the amygdala, and the variability of its activity is associated with genetic factors as well as with emotional salience. The objective of this study was to explore the relevance of personality style for variability of amygdala response. METHODS: We studied two groups (n=14 in each group) of healthy subjects categorized by contrasting cognitive styles with which they attribute salience to fearful stimuli: so-called phobic prone subjects who exaggerate potential environmental threat versus so-called eating disorders prone subjects who tend to be much less centered around fear. The two groups underwent functional magnetic resonance imaging (fMRI) at 3T during performance of a perceptual task of threatening stimuli and they were also matched for the genotype of the 5' variable number tandem repeat (VNTR) polymorphism in the serotonin transporter. RESULTS: The fMRI results indicated that phobic prone subjects selectively recruit the amygdala to a larger extent than eating disorders prone subjects. Activity in the amygdala was also independently predicted by personality style and genotype of the serotonin transporter. Moreover, brain activity during a working memory task did not differentiate the two groups. CONCLUSIONS: The results of the present study suggest that aspects of personality style are rooted in biological responses of the fear circuitry associated with processing of environmental information.

Aversive emotional interference impacts behavior and prefronto-striatal activity during increasing attentional control.

Earlier studies have demonstrated that emotional stimulation modulates attentional processing during goal-directed behavior and related activity of a brain network including the inferior frontal gyrus (IFG) and the caudate nucleus. However, it is not clear how emotional interference modulates behavior and brain physiology during variation in attentional control, a relevant question for everyday life situations in which both emotional stimuli and cognitive load vary. The aim of this study was to investigate the impact of negative emotions on behavior and activity in IFG and caudate nucleus during increasing levels of attentional control. Twenty two healthy subjects underwent event-related functional magnetic resonance imaging while performing a task in which neutral or fearful facial expressions were displayed before stimuli eliciting increasing levels of attentional control processing. Results indicated slower reaction time (RT) and greater right IFG activity when fearful compared with neutral facial expressions preceded the low level of attentional control. On the other hand, fearful facial expressions preceding the intermediate level of attentional control elicited faster behavioral responses and greater activity in the right and left sides of the caudate. Finally, correlation analysis indicated a relationship between behavioral correlates of attentional control after emotional interference and right IFG activity. All together, these results suggest that the impact of negative emotions on attentional processing is differentially elicited at the behavioral and physiological levels as a function of cognitive load.