Gene-sex interactions in schizophrenia: focus on dopamine neurotransmission

Prefrontal allopregnanolone synergizes with D1 receptor activation to disrupt sensorimotor gating in male Sprague-Dawley rats

RATIONALE

The prepulse inhibition (PPI) of the startle reflex is the best-established index of sensorimotor gating. We documented that the neurosteroid allopregnanolone (AP) is necessary to reduce PPI in response to D₁ dopamine receptor agonists. Since Sprague-Dawley (SD) rats are poorly sensitive to the PPI-disrupting effects of these drugs, we hypothesized that AP might increase this susceptibility.

OBJECTIVES

We tested whether AP is sufficient to increase the vulnerability of SD rats to PPI deficits in response to the D₁ receptor full agonist SKF82958.

METHODS

SD rats were tested for PPI after treatment with SKF82958 (0.05-0.3 mg/kg, SC) in combination with either intraperitoneal (1-10 mg/kg) or intracerebral (0.5 μg/μl/side) AP administration into the medial prefrontal cortex (mPFC) or nucleus accumbens shell. To rule out potential confounds, we measured whether SKF82958 affected the endogenous mPFC levels of AP.

RESULTS

SD rats exhibited marked PPI deficits in response to the combination of systemic and intra-mPFC AP with SKF82958 but not with the D₂ receptor agonist quinpirole (0.3-0.6 mg/kg, SC). SKF82958 did not elevate mPFC levels of AP but enhanced the content of its precursor progesterone. The PPI deficits caused by SKF82958 in combination with AP were opposed by the AP antagonist isoallopregnanolone (10 mg/kg, IP) and the glutamate NMDA receptor positive modulator CIQ (5 mg/kg, IP).

CONCLUSION

These results suggest that AP enables the detrimental effects of D₁ receptor activation on sensorimotor gating. AP antagonism or glutamatergic modulation counters these effects and may have therapeutic potential for neuropsychiatric disorders characterized by gating deficits.

In-depth investigations of the molecular basis underlying sex differences among middle-aged and elderly schizophrenia populations

Sex can influence almost all aspects of schizophrenia. However, the molecular mechanisms underlying sex differences in schizophrenia remain poorly understood. In this project, the dataset GSE107638 containing neuronal RNA-seq data and age/sex information of individuals with or without schizophrenia were retrieved. Schizophrenia samples were divided into young male (M-1), young female (F-1), middle-aged and elderly male (M-2) and middle-aged and elderly female (F-2) groups. Next, green/yellow/turquoise modules related to the M-2 trait and turquoise module correlated with the F-2 trait were identified by weighted correlation network analysis (WGCNA) analysis (soft thresholding power: 13; min module size: 200). Crucial genes in the M-2 green, M-2 turquoise and F-2 turquoise modules were identified by WGCNA, gene significance/module membership, and protein-protein interaction (PPI) analysis. Moreover, 2067 and 934 differentially expressed genes (|log2 fold-change| ≥0.58 and P-value < 0.05) in M-2 and F-2 schizophrenia subgroups versus same-age and same-sex counterparts were identified, respectively. Additionally, 82 core genes in the M-2 turquoise module and 4 hub genes in the F-2 turquoise module were differentially expressed in M-2 and F-2 schizophrenia subgroups versus their counterparts, respectively. Among the 82 hub genes, 15 genes were found to be correlated with neuronal development by the Kyoto Encyclopedia of Genes and Genomes enrichment analysis. Also, 2 potential PPI networks related to neuronal development were identified. Taken together, multiple potential hub genes and 2 potential neurobiological networks related to schizophrenia sex differences and disease progression were identified among middle-aged and elderly schizophrenia populations.

The Translational Machine: A novel machine-learning approach to illuminate complex genetic architectures

The Translational Machine (TM) is a machine learning (ML)-based analytic pipeline that translates genotypic/variant call data into biologically contextualized features that richly characterize complex variant architectures and permit greater interpretability and biological replication. It also reduces potentially confounding effects of population substructure on outcome prediction. The TM consists of three main components. First, replicable but flexible feature engineering procedures translate genome-scale data into biologically informative features that appropriately contextualize simple variant calls/genotypes within biological and functional contexts. Second, model-free, nonparametric ML-based feature filtering procedures empirically reduce dimensionality and noise of both original genotype calls and engineered features. Third, a powerful ML algorithm for feature selection is used to differentiate risk variant contributions across variant frequency and functional prediction spectra. The TM simultaneously evaluates potential contributions of variants operative under polygenic and heterogeneous models of genetic architecture. Our TM enables integration of biological information (e.g., genomic annotations) within conceptual frameworks akin to geneset-/pathways-based and collapsing methods, but overcomes some of these methods' limitations. The full TM pipeline is executed in R. Our approach and initial findings from its application to a whole-exome schizophrenia case-control data set are presented. These TM procedures extend the findings of the primary investigation and yield novel results.

The role of monoamine oxidase A in the neurobiology of aggressive, antisocial, and violent behavior: A tale of mice and men

Over the past two decades, research has revealed that genetic factors shape the propensity for aggressive, antisocial, and violent behavior. The best-documented gene implicated in aggression is MAOA (Monoamine oxidase A), which encodes the key enzyme for the degradation of serotonin and catecholamines. Congenital MAOA deficiency, as well as low-activity MAOA variants, has been associated with a higher risk for antisocial behavior (ASB) and violence, particularly in males with a history of child maltreatment. Indeed, the interplay between low MAOA genetic variants and early-life adversity is the best-documented gene × environment (G × E) interaction in the pathophysiology of aggression and ASB. Additional evidence indicates that low MAOA activity in the brain is strongly associated with a higher propensity for aggression; furthermore, MAOA inhibition may be one of the primary mechanisms whereby prenatal smoke exposure increases the risk of ASB. Complementary to these lines of evidence, mouse models of Maoa deficiency and G × E interactions exhibit striking similarities with clinical phenotypes, proving to be valuable tools to investigate the neurobiological mechanisms underlying antisocial and aggressive behavior. Here, we provide a comprehensive overview of the current state of the knowledge on the involvement of MAOA in aggression, as defined by preclinical and clinical evidence. In particular, we show how the convergence of human and animal research is proving helpful to our understanding of how MAOA influences antisocial and violent behavior and how it may assist in the development of preventative and therapeutic strategies for aggressive manifestations.

The Role of Genetic Variation of BMI, Body Composition, and Fat Distribution for Mental Traits and Disorders: A Look-Up and Mendelian Randomization Study

Anthropometric traits and mental disorders or traits are known to be associated clinically and to show genetic overlap. We aimed to identify genetic variants with relevance for mental disorders/traits and either (i) body mass index (or obesity), (ii) body composition, (and/or) (iii) body fat distribution. We performed a look-up analysis of 1,005 genome-wide significant SNPs for BMI, body composition, and body fat distribution in 15 mental disorders/traits. We identified 40 independent loci with one or more SNPs fulfilling our threshold significance criterion (P < 4.98 × 10^–5) for the mental phenotypes. The majority of loci was associated with schizophrenia, educational attainment, and/or intelligence. Fewer associations were found for bipolar disorder, neuroticism, attention deficit/hyperactivity disorder, major depressive disorder, depressive symptoms, and well-being. Unique associations with measures of body fat distribution adjusted for BMI were identified at five loci only. To investigate the potential causality between body fat distribution and schizophrenia, we performed two-sample Mendelian randomization analyses. We found no causal effect of body fat distribution on schizophrenia and vice versa. In conclusion, we identified 40 loci which may contribute to genetic overlaps between mental disorders/traits and BMI and/or shape related phenotypes. The majority of loci identified for body composition overlapped with BMI loci, thus suggesting pleiotropic effects.

Sexual hormones regulate the redox status and mitochondrial function in the brain. Pathological implications

Compared to other organs, the brain is especially exposed to oxidative stress. In general, brains from young females tend to present lower oxidative damage in comparison to their male counterparts. This has been attributed to higher antioxidant defenses and a better mitochondrial function in females, which has been linked to neuroprotection in this group. However, these differences usually disappear with aging, and the incidence of brain pathologies increases in aged females. Sexual hormones, which suffer a decrease with normal aging, have been proposed as the key factors involved in these gender differences. Here, we provide an overview of redox status and mitochondrial function regulation by sexual hormones and their influence in normal brain aging. Furthermore, we discuss how sexual hormones, as well as phytoestrogens, may play an important role in the development and progression of several brain pathologies, including neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, stroke or brain cancer.

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Sex hormones are reduced with aging, especially in females, affecting redox balance.

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Normal aging is associated to a worse redox homeostasis in the brain.

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Young females show better mitochondrial function and higher antioxidant defenses.

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Development of brain pathologies is influenced by sex hormones and phytoestrogens.

Sex-specific patterns of age-related cerebral atrophy in a nonhuman primate Microcebus murinus

Steadily aging populations result in a growing need for research regarding age-related brain alterations and neurodegenerative pathologies. By allowing a good translation of results to humans, nonhuman primates, such as the gray mouse lemur Microcebus murinus, have gained attention in this field. Our aim was to examine correlations between atrophy-induced brain alterations and age, with special focus on sex differences in mouse lemurs. For cerebral volumetric measurements, in vivo magnetic resonance imaging was performed on 59 animals (28♀♀/31♂♂) aged between 1.0 to 11.9 years. Volumes of different brain regions, cortical thicknesses, and ventricular expansions were evaluated. Analyses revealed significant brain atrophies with increasing age, particularly around the caudate nucleus, the thalamus, and frontal, parietal, and temporo-occipital regions. Especially old females showed a strong decline in cingulate cortex thickness and had higher values of ventricular expansion, whereas cortical thickness of the splenium and occipital regions decreased mainly in males. Our study, thus, provides first evidence for sex-specific, age-related brain alterations in a nonhuman primate, suggesting that mouse lemurs can help elucidating the mechanism underlying sex disparities in cerebral aging, for which there is mixed evidence in humans.

Neurobehavioural complications of sleep deprivation: Shedding light on the emerging role of neuroactive steroids

Sleep deprivation (SD) is associated with a broad spectrum of cognitive and behavioural complications, including emotional lability and enhanced stress reactivity, as well as deficits in executive functions, decision making and impulse control. These impairments, which have profound negative consequences on the health and productivity of many individuals, reflect alterations of the prefrontal cortex (PFC) and its connectivity with subcortical regions. However, the molecular underpinnings of these alterations remain elusive. Our group and others have begun examining how the neurobehavioural outcomes of SD may be influenced by neuroactive steroids, a family of molecules deeply implicated in sleep regulation and the stress response. These studies have revealed that, similar to other stressors, acute SD leads to increased synthesis of the neurosteroid allopregnanolone in the PFC. Whereas this up-regulation is likely aimed at counterbalancing the detrimental impact of oxidative stress induced by SD, the increase in prefrontal allopregnanolone levels contributes to deficits in sensorimotor gating and impulse control, signalling a functional impairment of PFC. This scenario suggests that the synthesis of neuroactive steroids during acute SD may be enacted as a neuroprotective response in the PFC; however, such compensation may in turn set off neurobehavioural complications by interfering with the corticolimbic connections responsible for executive functions and emotional regulation.

Galphimia glauca and Natural Galphimines Block Schizophrenia-Like Symptoms Induced with Apomorphine and MK-801 in Mice

BACKGROUND

Galphimia glauca has been used for many years in Mexican Traditional Medicine to calm "insane people." Triterpenes, known as galphimines, were identified in this species. One of them, Galphimine-B (G-B), acts selectively on dopaminergic neurons by antagonizing the effect of glutamate on NMDA receptors. The objective of this study was to evaluate the effect of G. glauca methanolic extract (GgMeOH), a Galphimine-Rich Fraction (GRF), as well as the galphimines G-A, G-B, and G-E, on the acute psychosis induced by Apomorphine (APO) in mice and on schizophrenia-like symptoms induced by subchronic administration of MK-801.

METHOD

On the first day, ICR male mice were given GgMeOH, GRF, or one of the galphimines. On day two, animals were treated with APO, and on day 3, they were subjected to behavioral tests. In a second test, MK-801 was administered daily for 28 days. In this case, animals were treated daily with G. glauca products from day 9 to day 28 and then subjected to behavioral tests (passive avoidance test, open field test, forced swimming test, and social interaction test).

RESULTS

The increased number of stereotyped behaviors and grooming behaviors induced with APO were counteracted by all of the experimental treatments. MK-801 induced an increase in immobility time, which was blocked with G-B; GRF counteracted the decreased social interaction, and GgMeOH and GRF prevented the memory loss induced by MK-801.

CONCLUSION

G. glauca and their derivatives products (GRF and galphimines) were able to interact with the dopaminergic and glutamatergic drugs and to block different behaviors associated with some of the positive, negative, and cognitive symptoms of induced schizophrenia in mice. It is necessary to continue with this research, in order to identify their mechanism of action.

In the line-up: deleted genes associated with DiGeorge/22q11.2 deletion syndrome: are they all suspects?

BACKGROUND

22q11.2 deletion syndrome (22q11DS), a copy number variation (CNV) disorder, occurs in approximately 1:4000 live births due to a heterozygous microdeletion at position 11.2 (proximal) on the q arm of human chromosome 22 (hChr22) (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011). This disorder was known as DiGeorge syndrome, Velo-cardio-facial syndrome (VCFS) or conotruncal anomaly face syndrome (CTAF) based upon diagnostic cardiovascular, pharyngeal, and craniofacial anomalies (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011; Burn et al., J Med Genet 30:822-4, 1993) before this phenotypic spectrum was associated with 22q11.2 CNVs. Subsequently, 22q11.2 deletion emerged as a major genomic lesion associated with vulnerability for several clinically defined behavioral deficits common to a number of neurodevelopmental disorders (Fernandez et al., Principles of Developmental Genetics, 2015; Robin and Shprintzen, J Pediatr 147:90-6, 2005; Schneider et al., Am J Psychiatry 171:627-39, 2014).

RESULTS

The mechanistic relationships between heterozygously deleted 22q11.2 genes and 22q11DS phenotypes are still unknown. We assembled a comprehensive "line-up" of the 36 protein coding loci in the 1.5 Mb minimal critical deleted region on hChr22q11.2, plus 20 protein coding loci in the distal 1.5 Mb that defines the 3 Mb typical 22q11DS deletion. We categorized candidates based upon apparent primary cell biological functions. We analyzed 41 of these genes that encode known proteins to determine whether haploinsufficiency of any single 22q11.2 gene-a one gene to one phenotype correspondence due to heterozygous deletion restricted to that locus-versus complex multigenic interactions can account for single or multiple 22q11DS phenotypes.

CONCLUSIONS

Our 22q11.2 functional genomic assessment does not support current theories of single gene haploinsufficiency for one or all 22q11DS phenotypes. Shared molecular functions, convergence on fundamental cell biological processes, and related consequences of individual 22q11.2 genes point to a matrix of multigenic interactions due to diminished 22q11.2 gene dosage. These interactions target fundamental cellular mechanisms essential for development, maturation, or homeostasis at subsets of 22q11DS phenotypic sites.

Associations of schizophrenia risk genes ZNF804A and CACNA1C with schizotypy and modulation of attention in healthy subjects

Schizotypy is a multidimensional risk phenotype distributed in the general population, constituting of subclinical, psychotic-like symptoms. It is associated with psychosis proneness, and several risk genes for psychosis are associated with schizotypy in non-clinical populations. Schizotypy might also modulate cognitive abilities as it is associated with attentional deficits in healthy subjects. In this study, we tested the hypothesis that established genetic risk variants ZNF804A rs1344706 and CACNA1C rs1006737 are associated with psychometric schizotypy and that schizotypy mediates their effect on attention or vice versa. In 615 healthy subjects from the FOR2107 cohort study, we analysed the genetic risk variants ZNF804A rs1344706 and CACNA1C rs1006737, psychometric schizotypy (schizotypal personality questionnaire-brief SPQB), and a neuropsychological measure of sustained and selective attention (d2 test). ZNF804A rs1344706 C (non-risk) alleles were significantly associated with higher SPQ-B Cognitive-Perceptual subscores in women and with attention deficits in both sexes. This schizotypy dimension also mediated the effect of ZNF804A on attention in women, but not in men. CACNA1C rs1006737-A showed a significant sex-modulated negative association with Interpersonal schizotypy only in men, and no effect on attention. Our multivariate model demonstrates differential genetic contributions of two psychosis risk genes to dimensions of schizotypy and, partly, to attention. This supports a model of shared genetic influence between schizotypy and cognitive functions impaired in schizophrenia.

Men and women respond differently to antipsychotic drugs

BACKGROUND

Because women are often perceived as having better outcomes than men in psychotic illnesses such as schizophrenia - women are less often in hospital, have a lower suicide rate, are less often involved with the law, enjoy better relationships with family and friends - the question arises as to whether or not this apparent advantage is attributable to a gender difference in antipsychotic response.

OBJECTIVE

The aim of this paper is to critically review the quantitative and qualitative literature on gender difference in antipsychotic response sourced mainly from medical databases of the last ten years.

FINDINGS

There are theoretical reasons why women's effective doses of antipsychotics might need to be lower than guidelines recommend for men, especially as regards olanzapine and clozapine, but, because there are so many variables that impinge on antipsychotic response, it is difficult to provide definitive guidance. What is evident is that some antipsychotic side effects, weight gain for instance, are more worrisome for women than for men. It is also evident that, after menopause, women need an increase in their antipsychotic dose; other reproductive stages in women's lives require special prescribing considerations as well.

CONCLUSION

There is a science, and an art, to prescribing antipsychotics, which needs to take gender into account. This article is part of the issue entitled 'Special Issue on Antipsychotics'.

A New T. gondii Mouse Model of Gene-Environment Interaction Relevant to Psychiatric Disease

Infection with the protozoan parasite, Toxoplasma gondii (T. gondii), was linked to several psychiatric disorders. The exact mechanisms of a hypothesized contribution of T. gondii infection are poorly understood, and it appears that only a subset of seropositive individuals go on to develop a mental illness, suggesting genetic vulnerability. In order to stimulate mechanistic studies of how exposure to T. gondii could interact with genetic predisposition to psychiatric disorders, we have generated and characterized a mouse model of chronic T. gondii infection in BALB/c mice with inducible forebrain neuronal expression of a C-terminus truncated dominant-negative form of disrupted-in-schizophrenia 1 (DN-DISC1). In this gene-environment interaction (GxE) model, exposing control and DN-DISC1 male and female mice to T. gondii produced sex-dependent abnormalities in locomotor activity and prepulse inhibition of the acoustic startle. No genotype- or sex-dependent effects were found on levels of anti-Toxoplasma IgG antibodies or anti-NMDAR or C1q antibodies. Our work demonstrates that a psychiatric genetic risk factor, DN-DISC1, modulates the neurobehavioral effects of chronic T. gondii infection in a sex-dependent manner. The present T. gondii model of GxE provides a valuable experimental system for future mechanistic studies and evaluation of new treatments.

The genome-wide associated candidate gene ZNF804A and psychosis-proneness: Evidence of sex-modulated association

BACKGROUND

The Zinc finger protein 804A (ZNF804A) is a promising candidate gene for schizophrenia and the broader psychosis phenotype that emerged from genome-wide association studies. It is related to neurodevelopment and associated to severe symptoms of schizophrenia and alterations in brain structure, as well as positive schizotypal personality traits in non-clinical samples. Moreover, a female-specific association has been observed between ZNF804A and schizophrenia.

AIM

The present study examined the association of two ZNF804A polymorphisms (rs1344706 and rs7597593) with the positive dimension of schizotypy and psychotic-like experiences in a sample of 808 non-clinical subjects. Additionally, we wanted to explore whether the sexual differences reported in schizophrenia are also present in psychosis-proneness.

RESULTS

Our results showed an association between rs7597593 and both schizotypy and psychotic-like experiences. These associations were driven by females, such those carrying the C allele had higher scores in the positive dimension of both variables compared to TT allele homozygotes.

CONCLUSION

The findings of the present study support the inclusion of ZNF804 variability in studies of the vulnerability for the development of psychopathology in non-clinical samples and consideration of sex as a moderator of this association.

Genetics of Aggression in Alzheimer's Disease (AD)

Alzheimer’s disease (AD) is a terminal, age-related neurological syndrome exhibiting progressive cognitive and memory decline, however AD patients in addition exhibit ancillary neuropsychiatric symptoms (NPSs) and these include aggression. In this communication we provide recent evidence for the mis-regulation of a small family of genes expressed in the human hippocampus that appear to be significantly involved in expression patterns common to both AD and aggression. DNA array- and mRNA transcriptome-based gene expression analysis and candidate gene association and/or genome-wide association studies (CGAS, GWAS) of aggressive attributes in humans have revealed a surprisingly small subset of six brain genes that are also strongly associated with altered gene expression patterns in AD. These genes encoded on five different chromosomes (chr) include the androgen receptor (AR; chrXq12), brain-derived neurotrophic factor (BDNF; chr11p14.1), catechol-O-methyl transferase (COMT; chr22q11.21), neuronal specific nitric oxide synthase (NOS1; chr12q24.22), dopamine beta-hydroxylase (DBH chr9q34.2) and tryptophan hydroxylase (TPH1, chr11p15.1 and TPH2, chr12q21.1). Interestingly, (i) the expression of three of these six genes (COMT, DBH, NOS1) are highly variable; (ii) three of these six genes (COMT, DBH, TPH1) are involved in DA or serotonin metabolism, biosynthesis and/or neurotransmission; and (iii) five of these six genes (AR, BDNF, COMT, DBH, NOS1) have been implicated in the development, onset and/or propagation of schizophrenia. The magnitude of the expression of genes implicated in aggressive behavior appears to be more pronounced in the later stages of AD when compared to MCI. These recent genetic data further indicate that the extent of cognitive impairment may have some bearing on the degree of aggression which accompanies the AD phenotype.

Manic symptom severity correlates with COMT activity in the striatum: A post-mortem study

OBJECTIVES

The enzyme catechol-O-methyltransferase (COMT), which catalyses the degradation of dopamine and norepinephrine, is posited to participate in the pathophysiology of bipolar disorder (BD) and schizophrenia. In support of this notion, rich evidence has documented that the severity of various BD and schizophrenia symptoms is moderated by rs4680, a single nucleotide polymorphism of the COMT gene featuring a valine (Val)-to-methionine (Met) substitution that results in lower catalytic activity. Nevertheless, the specific relevance of COMT enzymatic activity in the pathophysiology of BD and schizophrenia dimensions remains elusive.

METHODS

We measured COMT catalytic activity in post-mortem prefrontal cortices, striata and cerebella of schizophrenia and BD patients, as well as non-affected controls. These values were then correlated with rs4680 genotypes and psychopathology scores in the last week of life.

RESULTS

No direct correlation between COMT activity and rs4680 genotypes was found; however, the severity of manic symptoms was highly correlated with COMT activity in the striatum, irrespective of the diagnostic group.

CONCLUSIONS

These results suggest that COMT striatal activity, but not rs4680 genotype, may serve as a biomarker for manic symptoms. Future studies are warranted to confirm these findings and assess the neurobiological links between COMT striatal activity and manic symptoms.

Influence of COMT Val158Met polymorphism on emotional decision-making: A sex-dependent relationship?

The biological underpinnings of sex-related differences in decision-making are still under-explored. The COMT gene is related to sexual dimorphism and with different choices made under uncertainty, albeit no study has specifically investigated a moderation effect of sex on the association between the COMT gene and the performance on decision-making paradigms. In this study, we investigated the influence of the COMT Val¹⁵⁸Met polymorphism on Iowa Gambling Task (IGT) performance depending on sex in a healthy adult sample. Participants were 192 healthy adults (84 men and 108 women). The first 40 choices in the IGT were considered decisions under ambiguity and the last 60 choices decisions under risk. To test our moderation hypothesis we used a separate regressions approach. The results revealed a sex-dependent effect of COMT Va l¹⁵⁸Met polymorphism on decision-making as measured by the IGT. Val/Val women showed the best performance in the last trials of the IGT. Therefore, the COMT Val¹⁵⁸Met polymorphism may be considered a genetic marker underlying sex differences in decision-making.

Childhood trauma, BDNF Val66Met and subclinical psychotic experiences. Attempt at replication in two independent samples

Childhood trauma exposure is a robust environmental risk factor for psychosis. However, not all exposed individuals develop psychotic symptoms later in life. The Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (rs6265) has been suggested to moderate the psychosis-inducing effects of childhood trauma in clinical and nonclinical samples. Our study aimed to explore the interaction effect between childhood trauma and the BDNF Val66Met polymorphism on subclinical psychotic experiences (PEs). This was explored in two nonclinical independent samples: an undergraduate and technical-training school student sample (n = 808, sample 1) and a female twin sample (n = 621, sample 2). Results showed that childhood trauma was strongly associated with positive and negative PEs in nonclinical individuals. A BDNF Val66Met x childhood trauma effect on positive PEs was observed in both samples. These results were discordant in terms of risk allele: while in sample 1 Val allele carriers, especially males, were more vulnerable to the effects of childhood trauma regarding PEs, in sample 2 Met carriers presented higher PEs scores when exposed to childhood trauma, compared with Val carriers. Moreover, in sample 2, a significant interaction was also found in relation to negative PEs. Our study partially replicates previous findings and suggests that some individuals are more prone to develop PEs following childhood trauma because of a complex combination of multiple factors. Further studies including genetic, environmental and epigenetic factors may provide insights in this field.

COMT val158met polymorphism and molecular alterations in the human dorsolateral prefrontal cortex: Differences in controls and in schizophrenia

The single nucleotide val158met polymorphism in catechol o-methyltransferase (COMT) influences prefrontal cortex function. Working memory, dependent on the dorsolateral prefrontal cortex (DLPFC), has been repeatedly shown to be influenced by this COMT polymorphism. The high activity COMT val isoform is associated with lower synaptic dopamine levels. Altered synaptic dopamine levels are expected to lead to molecular adaptations within the synapse and within DLPFC neural circuitry. In this human post mortem study using high quality DLPFC tissue, we first examined the influence of the COMT val158met polymorphism on markers of dopamine neurotransmission, N-methyl-d-aspartate (NMDA) receptor subunits and glutamatic acid decarboxylase 67 (GAD67), all known to be critical to DLPFC circuitry and function. Next, we compared target gene expression profiles in a cohort of control and schizophrenia cases, each characterized by COMT genotype. We find that the COMT val allele in control subjects is associated with significant upregulation of GluN2A and GAD67 mRNA levels compared to met carriers. Comparisons between control and schizophrenia groups reveal that GluN2A, GAD67 and DRD2 are differentially regulated between diagnostic groups in a genotype specific manner. Chronic antipsychotic treatment in rodents did not explain these differences. These data demonstrate an association between COMTval158met genotype and gene expression profile in the DLPFC of controls, possibly adaptations to maintain DLPFC function. In schizophrenia val homozygotes, these adaptations are not seen and could reflect pathophysiologic mechanisms related to the known poorer performance of these subjects on DLPFC-dependent tasks.

Dopamine-prolactin pathway potentially contributes to the schizophrenia and type 2 diabetes comorbidity

Schizophrenia (SCZ) and type 2 diabetes (T2D) are clinically associated, and common knowledge attributes this association to side effects of antipsychotic treatment. However, even drug-naive patients with SCZ are at increased risk for T2D. Dopamine dysfunction has a central role in SCZ. It is well-known that dopamine constitutively inhibits prolactin (PRL) secretion via the dopamine receptor 2 (DR2D). If dopamine is increased or if dopamine receptors hyperfunction, PRL may be reduced. During the first SCZ episode, low PRL levels are associated with worse symptoms. PRL is essential in human and social bonding, as well as it is implicated in glucose homeostasis. Dopamine dysfunction, beyond contributing to SCZ symptoms, may lead to altered appetite and T2D. To our knowledge, there are no studies of the genetics of the SCZ-T2D comorbidity focusing jointly on the dopamine and PRL pathway in the attempt to capture molecular heterogeneity correlated to possible disease manifestation heterogeneity. In this dopamine-PRL pathway-focused-hypothesis-driven review on the association of SCZ with T2D, we report a specific revision of what it is known about PRL and dopamine in relation to what we theorize is one of the missing links between the two disorders. We suggest that new studies are necessary to establish the genetic role of PRL and dopamine pathway in SCZ-T2D comorbidity.

Targeting neurosteroid synthesis as a therapy for schizophrenia-related alterations induced by early psychosocial stress

BACKGROUND

Cogent evidence has shown that schizophrenia vulnerability is enhanced by psychosocial stress in adolescence, yet the underpinnings of this phenomenon remain elusive. One of the animal models that best capture the relationship between juvenile stress and schizophrenia is isolation rearing (IR). This manipulation, which consists in subjecting rats to social isolation from weaning through adulthood, results in neurobehavioral alterations akin to those observed in schizophrenia patients. In particular, IR-subjected rats display a marked reduction of the prepulse inhibition (PPI) of the startle reflex, which are posited to reflect imbalances in dopamine neurotransmission in the nucleus accumbens (NAcc). We recently documented that the key neurosteroidogenic enzyme 5α-reductase (5αR) plays an important role in the dopaminergic regulation of PPI; given that IR leads to a marked down-regulation of this enzyme in the NAcc, the present study was designed to further elucidate the functional role of 5αR in the regulation of PPI of IR-subjected rats.

METHODS

We studied the impact of the prototypical 5αR inhibitor finasteride (FIN) on the PPI deficits and NAcc steroid profile of IR-subjected male rats, in comparison with socially reared (SR) controls.

RESULTS

FIN (25-100 mg/kg, i.p.) dose-dependently countered IR-induced PPI reduction, without affecting gating integrity in SR rats. The NAcc and striatum of IR-subjected rats displayed several changes in neuroactive steroid profile, including a reduction in pregnenolone in both SR and IR-subjected groups, as well as a decrease in allopregnanolone content in the latter group; both effects were significantly opposed by FIN.

CONCLUSIONS

These results show that 5αR inhibition counters the PPI deficits induced by IR, possibly through limbic changes in pregnenolone and/or allopregnanolone concentrations.

Animal models of gene-environment interaction in schizophrenia: A dimensional perspective

Schizophrenia has long been considered as a disorder with multifactorial origins. Recent discoveries have advanced our understanding of the genetic architecture of the disease. However, even with the increase of identified risk variants, heritability estimates suggest an important contribution of non-genetic factors. Various environmental risk factors have been proposed to play a role in the etiopathogenesis of schizophrenia. These include season of birth, maternal infections, obstetric complications, adverse events at early childhood, and drug abuse. Despite the progress in identification of genetic and environmental risk factors, we still have a limited understanding of the mechanisms whereby gene-environment interactions (G × E) operate in schizophrenia and psychoses at large. In this review we provide a critical analysis of current animal models of G × E relevant to psychotic disorders and propose that dimensional perspective will advance our understanding of the complex mechanisms of these disorders.

Transient psychosis in women on clomiphene, bromocriptine, domperidone and related endocrine drugs

BACKGROUND

There have been reports of transient psychosis in women medicated for gynecologic conditions.

OBJECTIVE

The aim of this paper was to explore this literature.

METHOD

The PubMed and Google Scholar databases were searched for relevant case reports Results: The following reports were found: psychosis induced by gonadotropin-releasing hormone in the treatment of endometriosis, by clomiphene treatment for infertility, by bromocriptine treatment for milk suppression and by the withdrawal of domperidone prescribed as a galactologue as well as by the withdrawal of estrogen replacement therapy.

CONCLUSION

In susceptible women, psychotic symptoms can result from treatments that reduce estrogen levels, such as leuprolide acetate or clomiphene, or treatments that increase dopamine levels (bromocriptine). Psychosis can also be caused indirectly when estrogen treatment is discontinued or dopamine antagonism (e.g. domperidone) withdrawn. Estrogen-reducing and dopamine-increasing treatments used in gynecology need to be carefully monitored.

Sex differences and stress across the lifespan

Sex differences in stress responses can be found at all stages of life and are related to both the organizational and activational effects of gonadal hormones and to genes on the sex chromosomes. As stress dysregulation is the most common feature across neuropsychiatric diseases, sex differences in how these pathways develop and mature may predict sex-specific periods of vulnerability to disruption and increased disease risk or resilience across the lifespan. The aging brain is also at risk to the effects of stress, where the rapid decline of gonadal hormones in women combined with cellular aging processes promote sex biases in stress dysregulation. In this Review, we discuss potential underlying mechanisms driving sex differences in stress responses and their relevance to disease. Although stress is involved in a much broader range of diseases than neuropsychiatric ones, we highlight here this area and its examples across the lifespan.

The enzymatic activities of brain catechol-O-methyltransferase (COMT) and methionine sulphoxide reductase are correlated in a COMT Val/Met allele-dependent fashion

AIMS

The enzyme catechol-O-methyltransferase (COMT) plays a primary role in the metabolism of catecholamine neurotransmitters and is implicated in the modulation of cognitive and emotional responses. The best characterized single nucleotide polymorphism (SNP) of the COMT gene consists of a valine (Val)-to-methionine (Met) substitution at codon 108/158. The Met-containing variant confers a marked reduction in COMT catalytic activity. We recently showed that the activity of recombinant COMT is positively regulated by the enzyme Met sulphoxide reductase (MSR), which counters the oxidation of Met residues of proteins. The current study was designed to assess whether brain COMT activity may be correlated to MSR in an allele-dependent fashion.

METHODS

COMT and MSR activities were measured from post-mortem samples of prefrontal cortices, striata and cerebella of 32 subjects by using catechol and dabsyl-Met sulphoxide as substrates, respectively. Allelic discrimination of COMT Val(108/185) Met SNP was performed using the Taqman 5'nuclease assay.

RESULTS

Our studies revealed that, in homozygous carriers of Met, but not Val alleles, the activity of COMT and MSR was significantly correlated throughout all tested brain regions.

CONCLUSION

These results suggest that the reduced enzymatic activity of Met-containing COMT may be secondary to Met sulphoxidation and point to MSR as a key molecular determinant for the modulation of COMT activity.

COMT-by-sex interaction effect on psychosis proneness

Schizotypy phenotypes in the general population share etiopathogenic mechanisms and risk factors with schizophrenia, supporting the notion of psychosis as a continuum ranging from nonclinical to clinical deviance. Catechol-O-methyltransferase (COMT) is a candidate susceptibility gene for schizophrenia that is involved in the regulation of dopamine in the prefrontal cortex. Several recent studies have reported a sex difference in the impact of COMT genotype on psychiatric and cognitive phenotypes and personality traits. The present study investigated the association of COMT Val158Met (rs4680) with psychometric positive and negative schizotypy and psychotic experiences in a sample of 808 nonclinical young adults. The main finding was that sex moderates the association of COMT genotype with the negative dimension of both schizotypy and psychotic experiences. Male subjects carrying the Val allele tended to score higher on the negative dimension of both trait and symptom-like measures. The results from the present study are consistent with recent work suggesting an association between negative schizotypy and diminished prefrontal dopamine availability. They support the idea that a biological differentiation underlies the positive and negative schizotypy dimensions. Additionally, these findings contribute to the growing literature on sex-specific effects of COMT on the predisposition to psychiatric disorders and personality traits.

Changes in the adolescent brain and the pathophysiology of psychotic disorders

Adolescence is a time of extensive neuroanatomical, functional, and chemical reorganisation of the brain which parallels substantial maturational changes in cognition and affect regulation. This period is characterised by stabilisation of synapses to diminish redundancy and increase efficiency of neural function, fine-tuning of excitatory and inhibitory neurotransmitter systems, beginning of integration between late maturing and early maturing brain structures, and development of effective connections. In effect, these so-called moving parts create a state of dynamic change that might underlie adolescent behaviours. Imbalances or changes in timing of these developmental processes clearly increase the risk for psychiatric disorders. Genetic, environmental, and epigenetic factors that shape brain development and hormonal changes that affect stress reactivity could be reasons why some, but not all, adolescents are at a heightened risk of developing a psychopathological disorder. In this Series paper, we assess the neurobiology of the changing adolescent brain, implications of this knowledge, and future research in major psychiatric disorders, particularly for psychotic disorders.

MB-COMT promoter DNA methylation is associated with working-memory processing in schizophrenia patients and healthy controls

Many genetic studies report mixed results both for the associations between COMT polymorphisms and schizophrenia and for the effects of COMT variants on common intermediate phenotypes of the disorder. Reasons for this may include small genetic effect sizes and the modulation of environmental influences. To improve our understanding of the role of COMT in the disease etiology, we investigated the effect of DNA methylation in the MB-COMT promoter on neural activity in the dorsolateral prefrontal cortex during working memory processing as measured by fMRI - an intermediate phenotype for schizophrenia. Imaging and epigenetic data were measured in 102 healthy controls and 82 schizophrenia patients of the Mind Clinical Imaging Consortium (MCIC) study of schizophrenia. Neural activity during the Sternberg Item Recognition Paradigm was acquired with either a 3T Siemens Trio or 1.5T Siemens Sonata and analyzed using the FMRIB Software Library (FSL). DNA methylation measurements were derived from cryo-conserved blood samples. We found a positive association between MB-COMT promoter methylation and neural activity in the left dorsolateral prefrontal cortex in a model using a region-of-interest approach and could confirm this finding in a whole-brain model. This effect was independent of disease status. Analyzing the effect of MB-COMT promoter DNA methylation on a neuroimaging phenotype can provide further evidence for the importance of COMT and epigenetic risk mechanisms in schizophrenia. The latter may represent trans-regulatory or environmental risk factors that can be measured using brain-based intermediate phenotypes.