Genetic models of schizophrenia and bipolar disorder: overlapping inheritance or discrete genotypes?

Understanding translational research in schizophrenia: A novel insight into animal models

Schizophrenia affects millions of people worldwide and is a major challenge for the scientific community. Like most psychotic diseases, it is also considered a complicated mental disorder caused by an imbalance in neurotransmitters. Due to the complexity of neuropathology, it is always a complicated disorder. The lack of proper understanding of the pathophysiology makes the disorder unmanageable in clinical settings. However, due to recent advances in animal models, we hope we can have better therapeutic approaches with more success in clinical settings. Dopamine, glutamate, GABA, and serotonin are the neurotransmitters involved in the pathophysiology of schizophrenia. Various animal models have been put forward based on these neurotransmitters, including pharmacological, neurodevelopmental, and genetic models. Polymorphism of genes such as dysbindin, DICS1, and NRG1 has also been reported in schizophrenia. Hypothesis based on dopamine, glutamate, and serotonin are considered successful models of schizophrenia on which drug therapies have been designed to date. New targets like the orexin system, muscarinic and nicotinic receptors, and cannabinoid receptors have been approached to alleviate the negative and cognitive symptoms. The non-pharmacological models like the post-weaning social isolation model (maternal deprivation), the isolation rearing model etc. have been also developed to mimic the symptoms of schizophrenia and to create and test new approaches of drug therapy which is a breakthrough at present in psychiatric disorders. Different behavioral tests have been evaluated in these specific models. This review will highlight the currently available animal models and behavioral tests in psychic disorders concerning schizophrenia.

Diagnosis stability and outcome of psychotic episodes in a Romanian group of children and adolescents

Studies on early onset schizophrenia are limited because of their low prevalence but the reported results stated that early onset is associated with a poorer outcome. The present research analyzed the stability rate of the psychotic-related disorders from childhood to adult life. The study was based on an observational, retrospective, descriptive analysis study. The subjects were selected from patients admitted to the pediatric psychiatry ward of "Alexandru Obregia" Psychiatry Hospital between 2009 and 2018 for a psychosis-related disorder, who were 18 years or older at the moment of data collection and who also had admissions into the adult's psychiatry wards of the hospital. Of the 115 subjects, 93, representing 80.87% of the total, maintained a diagnosis of psychotic spectrum disorder into adulthood. The diagnosis was maintained in 82.4% of cases with onset before 13 years old and 80.6% of cases with onset after the age of 13 years of age. Of the 42 subjects who presented affective symptoms during childhood, 71.43% also presented affective symptoms into adulthood. These findings indicate an important stability rate of psychosis from childhood and adulthood and come in accordance with the theory of overlap between psychotic and affective disorders. The results underline the importance of an accurate diagnosis of early and very early onset schizophrenia (VEOS), the need for early and multimodal intervention, but also the need for long-term management of these patients and continuing research regarding psychotic-related disorders in children and adolescents.

Distribution of 1298A > C polymorphism of methylenetetrahydrofolate reductase gene in patients with bipolar disorder and schizophrenia

We investigated the genotype frequency of methylenetetrahydrofolate reductase (MTHFR) 1298A > C polymorphism in the group of patients with bipolar disorder type I (BDI) (n = 200) and schizophrenia (n = 200) and in the control group (n = 300). Odds ratio (OR) for patients with BD and schizophrenia in 1298CC homozygous state was 3.768 (95% CI = 1.752–8.104); P = 0.0003; (P = 0.0006 after Bonferroni correction) and 2.694; (95% CI = 1.207–6.013); P = 0.0123 (P = 0.0246 after Bonferroni correction), respectively. The stratification of patients based on gender revealed significant association of 1298CC genotype with female patients only with BDI (OR = 7.293; 95% CI = 2.017–26.363; P = 0.0005).

Our results confirm association of BD and schizophrenia with the 1p36.3 MTHFR locus and with the methyl group transfer using folate-dependent one-carbon pathway.

TAAR6variation effect on clinic presentation and outcome in a sample of schizophrenic in-patients: An open label study

We recently reported an association betweenTAAR6(trace amine associated receptor 6 gene) variations and schizophrenia (SZ). We now report an association of a set ofTAAR6variations and clinical presentation and outcome in a sample of 240 SZ Korean patients. Patients were selected by a Structured Clinical Interview, DSM-IV Axis I disorders – Clinical Version (SCID-CV). Other psychiatric or neurologic disorders, as well as medical diseases, were exclusion criteria. To assess symptom severity, patients were administered the CGI scale and the PANSS at baseline and at the moment of discharge, 1 month later on average.TAAR6variations rs6903874, rs7452939, rs8192625 and rs4305745 were investigated; rs6903874, rs7452939 and rs8192625 entered the statistical investigation after LD analysis. Rs8192625 G/G homozygosis was found to be significantly associated both with a worse clinical presentation at PANSS total and positive scores and with a shorter period of illness before hospitalization. No haplotype significant findings were found. The present study stands for a role of theTAAR6in the clinical presentation of SZ. Moreover, our results show that this genetic effect may be counteracted by a correct treatment. Haplotype analysis was not informative in our sample, probably also because of the incomplete SNPs' coverage of the gene we performed. Further studies in this direction are warranted.

Diagnostic Interview for Genetic Studies (DIGS): Inter-rater and test-retest reliability and validity in a Spanish population

Objective

To test the reliability and validity of the DIGS in Spanish population.

Methods

Inter-rater and test-retest reliability of the Spanish version of DIGS was tested in 95 inpatients and outpatients. The resultant diagnoses were compared with diagnoses obtained by the LEAD (Longitudinal Expert All Data) procedure as “gold standard”. The kappa statistic was used to measure concordance between blind inter-raters and between the diagnoses obtained by LEAD procedure and through the DIGS.

Results

Overall kappa coefficient for inter-rater reliability was 0.956. The kappa value for individual diagnosis varied from major depression = 0.877 to schizophrenia = 1. Test-retest reliability was 0.926. Kappa for all individual target diagnoses ranged from 0.776 (major depression) to 1. Kappa between LEAD procedure and DIGS ranged from 0.704 (major depression) to 0.825 (bipolar I disorder).

Conclusion

Most of the DSM-IV major psychiatric disorders can be assessed with acceptable to excellent reliability with the Spanish version of the DIGS interview. The Spanish version of DIGS showed an acceptable to excellent concurrent validity. Giving the good reliability and validity of Spanish version of DIGS it should be considered to identify psychiatric phenotypes for genetics studies.

The molecular genetics of hand preference revisited

Hand preference is a prominent behavioural trait linked to human brain asymmetry. A handful of genetic variants have been reported to associate with hand preference or quantitative measures related to it. Most of these reports were on the basis of limited sample sizes, by current standards for genetic analysis of complex traits. Here we performed a genome-wide association analysis of hand preference in the large, population-based UK Biobank cohort (N = 331,037). We used gene-set enrichment analysis to investigate whether genes involved in visceral asymmetry are particularly relevant to hand preference, following one previous report. We found no evidence supporting any of the previously suggested variants or genes, nor that genes involved in visceral laterality have a role in hand preference. It remains possible that some of the previously reported genes or pathways are relevant to hand preference as assessed in other ways, or else are relevant within specific disorder populations. However, some or all of the earlier findings are likely to be false positives, and none of them appear relevant to hand preference as defined categorically in the general population. Our analysis did produce a small number of novel, significant associations, including one implicating the microtubule-associated gene MAP2 in handedness.

Preliminary examination of microRNA expression profiling in bipolar disorder I patients during antipsychotic treatment

Although major progress has been achieved in research and development of antipsychotic medications for bipolar disorder (BPD), knowledge of the molecular mechanisms underlying this disorder and the action of atypical antipsychotics remains incomplete. The levels of microRNAs (miRNAs)-small non-coding RNA molecules that regulate gene expression, including genes involved in neuronal function and plasticity-are frequently altered in psychiatric disorders. This study aimed to examine changes in miRNA expression in bipolar mania patients after treatment with asenapine and risperidone. Using a miRNA microarray, we analyzed miRNA expression in the blood of 10 bipolar mania patients following 12 weeks of treatment with asenapine or risperidone. Selected miRNAs were validated by using real-time PCR. A total of 16 miRNAs were differentially expressed after treatment in the asenapine group, 14 of which were significantly upregulated and the other two significantly downregulated. However, all three differentially expressed miRNAs in the risperidone group were downregulated. MiRNA target gene prediction and gene ontology analysis revealed significant enrichment for pathways associated with immune system response and regulation of programmed cell death and transcription. Our results suggest that candidate miRNAs may be involved in the mechanism of action of both antipsychotics in bipolar mania. © 2016 Wiley Periodicals, Inc.

Family History in Patients with Bipolar Disorder

INTRODUCTION

In this study, we aimed to better understand the genetic transmission of bipolar disorder by examining the family history of patients.

METHODS

Sixty-three patients with bipolar disorder and their families were included. The final sample comprised 156 bipolar patients and their family members. An inclusion criterion was the presence of bipolar disorder history in the family. The diagnosis of other family members was confirmed by analyzing their files, hospital records, and by calling them to the hospital.

RESULTS

Sixty-five patients were women (41.6%) and 91 were men (58.3%) (ratio of men/women: 1.40). When analyzing the results in terms of the transition of disease from the mother's or father's side, similar results were obtained: 25 patients were from the mother's side and 25 patients were from the father's side in 63 cases.

CONCLUSION

The results of our study support the fact that a significant relationship exists between the degree of kinship and the heritability of bipolar disorder and, furthermore, that the effect of the maternal and paternal sides is similar on the transmission of genetic susceptibility.

Genetic association of LMAN2L gene in schizophrenia and bipolar disorder and its interaction with ANK3 gene polymorphism

Recent studies have shown that bipolar disorder (BPD) and schizophrenia (SZ) share some common genetic risk factors. This study aimed to examine the association between candidate single nucleotide polymorphisms (SNPs) identified from genome-wide association studies (GWAS) and risk of BPD and SZ. A total of 715 patients (244 BPD and 471 SZ) and 593 controls were genotyped using the Sequenom MassARRAY platform. We showed a positive association between LMAN2L (rs6746896) and risk of both BPD and SZ in a pooled population (P-value=0.001 and 0.009, respectively). Following stratification by ethnicity, variants of the ANK3 gene (rs1938516 and rs10994336) were found to be associated with BPD in Malays (P-value=0.001 and 0.006, respectively). Furthermore, an association exists between another variant of LMAN2L (rs2271893) and SZ in the Malay and Indian ethnic groups (P-value=0.003 and 0.002, respectively). Gene-gene interaction analysis revealed a significant interaction between the ANK3 and LMAN2L genes (empirical P=0.0107). Significant differences were shown between patients and controls for two haplotype frequencies of LMAN2L: GA (P=0.015 and P=0.010, for BPD and SZ, respectively) and GG (P=0.013 for BPD). Our study showed a significant association between LMAN2L and risk of both BPD and SZ.

Expression of the G72/G30 gene in transgenic mice induces behavioral changes

The G72/G30 gene complex is a candidate gene for schizophrenia and bipolar disorder. However, G72 and G30 mRNAs are expressed at very low levels in human brain, with only rare splicing forms observed. We report here G72/G30 expression profiles and behavioral changes in a G72/G30 transgenic mouse model. A human BAC clone containing the G72/G30 genomic region was used to establish the transgenic mouse model, on which gene expression studies, western blot and behavioral tests were performed. Relative to their minimal expression in humans, G72 and G30 mRNAs were highly expressed in the transgenic mice, and had a more complex splicing pattern. The highest G72 transcript levels were found in testis, followed by cerebral cortex, with very low or undetectable levels in other tissues. No LG72 (the long putative isoform of G72) protein was detected in the transgenic mice. Whole-genome expression profiling identified 361 genes differentially expressed in transgenic mice compared with wild-type, including genes previously implicated in neurological and psychological disorders. Relative to wild-type mice, the transgenic mice exhibited fewer stereotypic movements in the open field test, higher baseline startle responses in the course of the prepulse inhibition test, and lower hedonic responses in the sucrose preference test. The transcriptome profile changes and multiple mouse behavioral effects suggest that the G72 gene may play a role in modulating behaviors relevant to psychiatric disorders.

Association between FAT Gene and Schizophrenia in the Korean Population

OBJECTIVE

The aim of this study was to investigate the genetic association of the FAT gene with schizophrenia in the Korean population, as well as analyzing the association of FAT gene with clinical variables.

METHODS

Four variants within the FAT gene were investigated in 189 patients with schizophrenia and 119 healthy controls (rs2306987 A/C, rs2306990 T/C, rs2637777 G/T, and rs2304865 G/C).

RESULTS

Significant association at the rs273777 with schizophrenia was observed; however, rs2306987, rs2306990, and rs2304865 were not associated with schizophrenia. Haplotype analyses revealed that the haplotype A/T/T/G was associated with a significantly protective effect. Sliding window analysis (rs2637777 G/T and rs2304865 G/C) revealed the more common T/G haplotype, included in the A/T/T/G protective combination, showed a small protective effect, in particular the effect was due to the rs273777 T variant (minor allele).

CONCLUSION

The present finding suggests that FAT polymorphism may play a putative role in the susceptibility to schizophrenia in the Korean population. Further studies using a larger number of subjects should be performed to determine whether the FAT gene polymorphism may be truly involved in the development of schizophrenia.

White matter deficits in first episode schizophrenia: an activation likelihood estimation meta-analysis

BACKGROUND

Diffusion tensor imaging (DTI) has been widely used in psychiatric research and has provided evidence of white matter abnormalities in first episode schizophrenia (FES). The goal of the present meta-analysis was to identify white matter deficits by DTI in FES.

METHODS

A systematic search was conducted to collect DTI studies with voxel-wised analysis of the fractional anisotropy (FA) in FES. The coordinates of regions with FA changes were meta-analyzed using the activation likelihood estimation (ALE) method which weighs each study on the basis of its sample size.

RESULTS

A total of 8 primary studies were selected, including 271 FES patients and 297 healthy controls. Among these studies, 52 regions showed reductions in the FA in FES while 2 regions had increased FA. Consistent FA reductions in the white matter of the right deep frontal and left deep temporal lobes were identified in all FES patients relative to healthy controls. Fiber tracking showed that the main tracts involved were the cingulum bundle, the left inferior longitudinal fasciculus, the left inferior fronto-occipital fasciculus and the interhemispheric fibers running through the corpus callosum.

CONCLUSIONS

The current findings provide evidence confirming the lack of connection in the fronto-limbic circuitry at the early stages of the schizophrenia. Because the coordinates reported in the primary literature were highly variable, future investigations with large samples would be required to support the identified white matter changes in FES.

Construction and analysis of the protein-protein interaction networks for schizophrenia, bipolar disorder, and major depression

BACKGROUND

Schizophrenia, bipolar disorder, and major depression are devastating mental diseases, each with distinctive yet overlapping epidemiologic characteristics. Microarray and proteomics data have revealed genes which expressed abnormally in patients. Several single nucleotide polymorphisms (SNPs) and mutations are associated with one or more of the three diseases. Nevertheless, there are few studies on the interactions among the disease-associated genes and proteins.

RESULTS

This study, for the first time, incorporated microarray and protein-protein interaction (PPI) databases to construct the PPI network of abnormally expressed genes in postmortem brain samples of schizophrenia, bipolar disorder, and major depression patients. The samples were collected from Brodmann area (BA) 10 of the prefrontal cortex. Abnormally expressed disease genes were selected by t-tests comparing the disease and control samples. These genes were involved in housekeeping functions (e.g. translation, transcription, energy conversion, and metabolism), in brain specific functions (e.g. signal transduction, neuron cell differentiation, and cytoskeleton), or in stress responses (e.g. heat shocks and biotic stress).The diseases were interconnected through several "switchboard"-like nodes in the PPI network or shared abnormally expressed genes. A "core" functional module which consisted of a tightly knitted sub-network of clique-5 and -4s was also observed. These cliques were formed by 12 genes highly expressed in both disease and control samples.

CONCLUSIONS

Several previously unidentified disease marker genes and drug targets, such as SBNO2 (schizophrenia), SEC24C (bipolar disorder), and SRRT (major depression), were identified based on statistical and topological analyses of the PPI network. The shared or interconnecting marker genes may explain the shared symptoms of the studied diseases. Furthermore, the "switchboard" genes, such as APP, UBC, and YWHAZ, are proposed as potential targets for developing new treatments due to their functional and topological significance.

Brain cortical thickness and surface area correlates of neurocognitive performance in patients with schizophrenia, bipolar disorder, and healthy adults

Relationships between cortical brain structure and neurocognitive functioning have been reported in schizophrenia, but findings are inconclusive, and only a few studies in bipolar disorder have addressed this issue. This is the first study to directly compare relationships between cortical thickness and surface area with neurocognitive functioning in patients with schizophrenia (n = 117) and bipolar disorder (n = 121) and healthy controls (n = 192). MRI scans were obtained, and regional cortical thickness and surface area measurements were analyzed for relationships with test scores from 6 neurocognitive domains. In the combined sample, cortical thickness in the right rostral anterior cingulate was inversely related to working memory, and cortical surface area in four frontal and temporal regions were positively related to neurocognitive functioning. A positive relationship between left transverse temporal thickness and processing speed was specific to schizophrenia. A negative relationship between right temporal pole thickness and working memory was specific to bipolar disorder. In conclusion, significant cortical structure/function relationships were found in a large sample of healthy controls and patients with schizophrenia or bipolar disorder. The differences that were found between schizophrenia and bipolar may indicate differential relationship patterns in the two disorders, which may be of relevance for understanding the underlying pathophysiology.

The contribution of epidemiology to defining the most appropriate approach to genetic research on schizophrenia

Psychosis is thought to have a strong genetic component, but many efforts to discover the underlying putative schizophrenia genes have yielded disappointing results. In fact, no strong associations emerged in the first genome-wide association studies in psychiatry and weakly observed associations were not related to the candidate genes identified in previous studies. These partially successful findings may be explained by the fact that genetic research in psychiatry suffers from confounding issues related to phenotype definition, the considerable degree of phenotypic variability and diagnostic uncertainty, absence of specific neuropathological features and environmental influences. To make progress it is first necessary to deconstruct psychosis based on symptomatology, and then to correlate particular phenotypes with genetic variants. Moreover, it is time to conduct studies that define persistent aspects of the schizophrenic profile that are more likely to represent an underlying biological pathogenesis, as opposed to fluctuating symptoms that are possibly environmentally mediated. In fact, progress in understanding the etiology of schizophrenia will depend upon the availability of good measures of genetic liability as well as relevant environmental exposures during critical periods of an individual's life. If environmental and/or genetic factors are not precisely measured, it is impossible to study their independent effects or interactions.

Dissecting the many genetic faces of schizophrenia

Recent genome-wide association studies in schizophrenia have provided strongest evidence for association and this strengthened when the affected phenotype included bipolar disorder suggesting that genes may not always associate with operationalised diagnostic entities. Several further large Genome Wide Association (GWA) studies on schizophrenia are under way and identified and replicated further loci in well-powered cohorts. The last 2 years have also witnessed an explosion of interest in human Copy Number Variants (CNVs). Deletions recently identified in schizophrenia (1q21.1; 2p16.3; 15q11.2; 15q13.3) have also been most recently found in further neurodevelopmental diseases. Thus, a significant fraction of individuals with neurodevelopmental diseases including schizophrenia carry CNVs and many will be defined as “genomic disorders” in the coming years. These findings could represent a decisive step towards understanding the causes of this severe mental disorder as well as developing new potential treatments. There is new hope that these new avenues will help understanding the neurobiology of schizophrenia in more depth leading to the development of new innovative diagnostic tools and therapies as was the case after the discovery of rare APP and presenilin 1 and 2 mutations in Alzheimer's disease.

Comparisons of the tolerability and sensitivity of quetiapine-XR in the acute treatment of schizophrenia, bipolar mania, bipolar depression, major depressive disorder, and generalized anxiety disorder

Quetiapine extended-release (quetiapine-XR) has been studied in patients with schizophrenia, bipolar mania, bipolar depression, major depressive disorder (MDD), and generalized anxiety disorder (GAD). The purpose of this study was to compare the tolerability and sensitivity of quetiapine-XR among these psychiatric conditions. The discontinuation due to adverse events (DAEs) and reported somnolence in randomized, double-blind, placebo-controlled studies of quetiapine-XR in these psychiatric conditions were examined. The absolute risk reduction or increase and the number needed to treat to benefit (NNTB) or harm (NNTH) for DAEs and reported somnolence of quetiapine-XR ≥ 300 mg/d relative to placebo were estimated. Data from one study in schizophrenia (n=465), one in mania (n=316), one in bipolar depression (n=280), two in refractory MDD (n=624), two in MDD (n=669) and three in GAD (n=1109) were available. The risk for DAEs of quetiapine-XR relative to placebo was significantly increased in bipolar depression (NNTH=9), refractory MDD (NNTH=8), MDD (NNTH=9), and GAD (NNTH=5), but not in schizophrenia and mania. The risk for reported somnolence of quetiapine-XR relative to placebo was significantly increased in schizophrenia (600 mg/d NNTH=15 and 800 mg/d NNTH=11), mania (NNTH=8), bipolar depression (NNTH=4), refractory MDD (NNTH=5), MDD (NNTH=5) and GAD (NNTH=5). These results suggest that patients with GAD had the poorest tolerability during treatment with quetiapine-XR, but they had a similar sensitivity as those with bipolar depression and MDD. Patients with schizophrenia or mania had a higher tolerability and a lower sensitivity than those with bipolar depression, MDD, or GAD.

Lack of association between MAGEL2 and schizophrenia and mood disorders in the Japanese population

Several investigations have reported that abnormalities in circadian rhythms might be related with the pathophysiology of psychiatric disorders, since many psychiatric patients have insomnia and sleep-awake disturbance. A recent animal study reported that Magel2, which encodes a member of the MAGE/necdin family of proteins, might be associated in the pathophysiology of psychiatric disorders. Magel2 gene knockout mice showed altered concentrations of both dopamine and serotonin in several parts of the brain compared with controls. In addition, the authors of that study detected a bilateral reduction in cortical volume in distinct regions of the Magel2 gene knockout mice brain, including focused regions in the parieto-temporal lobe of the cerebral cortex, the amygdala, the hippocampus, and the nucleus accumbens. These mice were also found to have hypoactivity and abnormalities in circadian rhythms. From this evidence, we considered Magel2 gene (MAGEL2) to be a good candidate gene for the pathophysiology of schizophrenia and mood disorder, and we conducted a case-control study among Japanese (731 schizophrenia patients, 465 MDD patients, 156 BP patients and 758 controls) using three tagging SNPs in MAGEL2 (rs850815, rs8920 and rs4480754), selected using the HapMap database. We did not find any association between MAGEL2 and schizophrenia, BP or MDD in allele/genotype-wise analysis or haplotype-wise analysis. Our results suggest that MAGEL2 may not play a role in the pathophysiology of schizophrenia and mood disorders in the Japanese population. A replication study using larger samples may be required for conclusive results, since our sample size was small and our study analyzed only three SNPs in MAGEL2.

Strong genetic evidence for a selective influence of GABAA receptors on a component of the bipolar disorder phenotype

Despite compelling evidence for a major genetic contribution to risk of bipolar mood disorder, conclusive evidence implicating specific genes or pathophysiological systems has proved elusive. In part this is likely to be related to the unknown validity of current phenotype definitions and consequent aetiological heterogeneity of samples. In the recent Wellcome Trust Case Control Consortium genome-wide association analysis of bipolar disorder (1868 cases, 2938 controls) one of the most strongly associated polymorphisms lay within the gene encoding the GABA(A) receptor beta1 subunit, GABRB1. Aiming to increase biological homogeneity, we sought the diagnostic subset that showed the strongest signal at this polymorphism and used this to test for independent evidence of association with other members of the GABA(A) receptor gene family. The index signal was significantly enriched in the 279 cases meeting Research Diagnostic Criteria for schizoaffective disorder, bipolar type (P=3.8 x 10(-6)). Independently, these cases showed strong evidence that variation in GABA(A) receptor genes influences risk for this phenotype (independent system-wide P=6.6 x 10(-5)) with association signals also at GABRA4, GABRB3, GABRA5 and GABRR3. [corrected] Our findings have the potential to inform understanding of presentation, pathogenesis and nosology of bipolar disorders. Our method of phenotype refinement may be useful in studies of other complex psychiatric and non-psychiatric disorders.

Psychiatric family history and schizophrenia risk in Denmark: which mental disorders are relevant?

BACKGROUND

A family history of schizophrenia is the strongest single indicator of individual schizophrenia risk. Bipolar affective disorder and schizo-affective disorders have been documented to occur more frequently in parents and siblings of schizophrenia patients, but the familial occurrence of the broader range of mental illnesses and their role as confounders have not been studied in large population-based samples.

METHOD

All people born in Denmark between 1955 and 1991 (1.74 million) were followed for the development of schizophrenia (9324 cases) during 28 million person-years at risk. Information of schizophrenia in cohort members and psychiatric history in parents and siblings was established through linkage with the Danish Psychiatric Central Register. Data were analysed using log-linear Poisson regression.

RESULTS

Schizophrenia was, as expected, strongly associated with schizophrenia and related disorders among first-degree relatives. However, almost any other psychiatric disorder among first-degree relatives increased the individual's risk of schizophrenia. The population attributable risk associated with psychiatric family history in general was 27.1% whereas family histories including schizophrenia only accounted for 6.0%. The general psychiatric family history was a confounder of the association between schizophrenia and urbanization of place of birth.

CONCLUSIONS

Clinically diagnosed schizophrenia is associated with a much broader range of mental disorders in first-degree relatives than previously reported. This may suggest risk haplotypes shared across many disorders and/or shared environmental factors clustering in families. Failure to take the broad range of psychiatric family history into account may bias results of all risk-factor studies of schizophrenia.

Genetic association studies of glutamate, GABA and related genes in schizophrenia and bipolar disorder: a decade of advance

Schizophrenia (SZ) and bipolar disorder (BD) are debilitating neurobehavioural disorders likely influenced by genetic and non-genetic factors and which can be seen as complex disorders of synaptic neurotransmission. The glutamatergic and GABAergic neurotransmission systems have been implicated in both diseases and we have reviewed extensive literature over a decade for evidence to support the association of glutamate and GABA genes in SZ and BD. Candidate-gene based population and family association studies have implicated some ionotrophic glutamate receptor genes (GRIN1, GRIN2A, GRIN2B and GRIK3), metabotropic glutamate receptor genes (such as GRM3), the G72/G30 locus and GABAergic genes (e.g. GAD1 and GABRB2) in both illnesses to varying degrees, but further replication studies are needed to validate these results. There is at present no consensus on specific single nucleotide polymorphisms or haplotypes associated with the particular candidate gene loci in these illnesses. The genetic architecture of glutamate systems in bipolar disorder need to be better studied in view of recent data suggesting an overlap in the genetic aetiology of SZ and BD. There is a pressing need to integrate research platforms in genomics, epistatic models, proteomics, metabolomics, neuroimaging technology and translational studies in order to allow a more integrated understanding of glutamate and GABAergic signalling processes and aberrations in SZ and BD as well as their relationships with clinical presentations and treatment progress over time.

The effect of the COMT val(158)met polymorphism on neural correlates of semantic verbal fluency

Variation in the val(158)met polymorphism of the COMT gene has been found to be associated with cognitive performance. In functional neuroimaging studies, this dysfunction has been linked to signal changes in prefrontal areas. Given the complex modulation and functional heterogeneity of frontal lobe systems, further specification of COMT gene-related phenotypes differing in prefrontally mediated cognitive performance are of major interest. Eighty healthy individuals (54 men, 26 women; mean age 23.3 years) performed an overt semantic verbal fluency task while brain activation was measured with functional magnetic resonance imaging (fMRI). COMT val(158)met genotype was determined and correlated with brain activation measured with fMRI during the task. Although there were no differences in performance, brain activation in the left inferior frontal gyrus [Brodmann area 10] was positively correlated with the number of val alleles in the COMT gene. COMT val(158)met status modulates brain activation during the language production on a semantic level in an area related to executive functions.

Common and rare variants of DAOA in bipolar disorder

The D-amino acid oxidase activator (DAOA, previously known as G72) gene, mapped on 13q33, has been reported to be genetically associated with bipolar disorder (BP) in several populations. The consistency of associated variants is unclear and rare variants in exons of the DAOA gene have not been investigated in psychiatric diseases. We employed a conditional linkage method-STatistical Explanation for Positional Cloning (STEPC) to evaluate whether any associated single nucleotide polymorphisms (SNPs) account for the evidence of linkage in a pedigree series that previously has been linked to marker D13S779 at 13q33. We also performed an association study in a sample of 376 Caucasian BP parent-proband trios by genotyping 38 common SNPs in the gene region. Besides, we resequenced coding regions and flanking intronic sequences of DAOA in 555 Caucasian unrelated BP patients and 564 mentally healthy controls, to identify putative functional rare variants that may contribute to disease. One SNP rs1935058 could "explain" the linkage signal in the family sample set (P = 0.055) using STEPC analysis. No significant allelic association was detected in an association study by genotyping 38 common SNPs in 376 Caucasian BP trios. Resequencing identified 53 SNPs, of which 46 were novel SNPs. There was no significant excess of rare variants in cases relative to controls. Our results suggest that DAOA does not have a major effect on BP susceptibility. However, DAOA may contribute to bipolar susceptibility in some specific families as evidenced by the STEPC analysis.

Development of DSM-V and ICD-11: tendencies and potential of new classifications in psychiatry at the current state of knowledge

A reason for the necessity to revise ICD-10 and DSM-IV is the increase of knowledge in the past 20 years, especially neurobiological knowledge. But is this increase of knowledge, for example in the field of neurogenetics, of such magnitude that a revision of the psychiatric classification is necessary and promises to be fruitful? The current plans for DSM-V or ICD-11, respectively, focus on different improvements. In this context also the introduction of a purely syndromatic/dimensional approach without including etiopathogenetic hypotheses, is discussed. A switch to such a dimensional approach, which was discussed among others in the DSM-V task force Deconstructing Psychosis, would be the most radical development. It could avoid many theoretical pre-assumptions about causal hypotheses, which are still associated with ICD-10 and DSM-IV. This would indeed increase the validity of psychiatric classification, but it would also reduce the information as compared to traditional diagnostic categories with all the current implications concerning etiopathogenesis, therapy and prognosis. Such a dimensional approach would also mean that the syndromes would have to be assessed in a standardized way for each person seeking help from the psychiatric service system or for each person undergoing psychiatric research. This would have to be a multi-dimensional assessment covering all syndromes existing within different psychiatric disorders. Based on the different aspects that must be considered in this context, a careful revision seems more advisable than a radical change of classification.

Effect of the G72 (DAOA) putative risk haplotype on cognitive functions in healthy subjects

BACKGROUND

In the last years, several susceptibility genes for psychiatric disorders have been identified, among others G72 (also named D-amino acid oxidase activator, DAOA). Typically, the high-risk variant of a vulnerability gene is associated with decreased cognitive functions already in healthy individuals. In a recent study however, a positive effect of the high-risk variant of G72 on verbal working memory was reported. In the present study, we therefore examined the relationship between G72 genotype status and a broad range of cognitive functions in 423 healthy individuals.

METHODS

The G72 carrier status was assessed by the two single nucleotide polymorphisms (SNPs) M23 and M24. Subjects were divided into three risk groups (low, intermediate and high risk).

RESULTS

G72 status influenced a number of cognitive functions, such as verbal working memory, attention, and, at a trend level, spatial working memory and executive functions. Interestingly, the high-risk allele carriers scored better than one or even both other groups.

CONCLUSION

Our data show that the putative high-risk haplotype (i.e. homozygote C/C-allele carriers in SNP M23 and homozygote T/T-allele carriers in SNP M24) is in healthy individuals not necessarily associated with worse performance in cognitive functions, but even with better performance in some domains. Further work is required to identify the mechanisms of G72 on brain functions.

Association study of clock gene (CLOCK) and schizophrenia and mood disorders in the Japanese population

Recently the clock genes have been reported to play some roles in neural transmitter systems, including the dopamine system, as well as to regulate circadian rhythms. Abnormalities in both of these mechanisms are thought to be involved in the pathophysiology of major mental illness such as schizophrenia and mood disorders including bipolar disorder (BP) and major depressive disorder (MDD). Recent genetic studies have reported that CLOCK, one of the clock genes, is associated with these psychiatric disorders. Therefore, we investigated the association between the six tagging SNPs in CLOCK and the risk of these psychiatric disorders in Japanese patients diagnosed with schizophrenia (733 patients), BP (149) and MDD (324), plus 795 Japanese controls. Only one association, with schizophrenia in females, was detected in the haplotype analysis (P = 0.0362). However, this significance did not remain after Bonferroni correction (P = 0.0724). No significant association was found with BP and MDD. In conclusion, we suggest that CLOCK may not play a major role in the pathophysiology of Japanese schizophrenia, BP and MDD patients. However, it will be important to replicate and confirm these findings in other independent studies using large samples.

Molecular genetic case-control women investigation from the first Brazilian high-risk study on functional psychosis

OBJECTIVE

Data from epidemiological studies have demonstrated that genetics is an important risk factor for psychosis. The present study is part of a larger project, pioneer in Brazil, which has been conducted by other researchers who intend to follow a high-risk population (children) for the development of schizophrenia and bipolar disorder. In this first phase of the project, the objective was to investigate the distribution of four candidate genetic polymorphisms for functional psychosis (Ser9Gly DRD3, 5HTTLPR, the VNTR 3'-UTR SLC6A3 and Val66Met BDNF) in a case-control sample.

METHOD

A total of 105 women (58 with schizophrenia and 47 with bipolar disorder) and 62 gender-matched controls were investigated.

RESULTS

Allele and genotype distributions of all identified functional polymorphisms did not differ statistically between cases and controls.

CONCLUSIONS

These results suggest that the investigated polymorphisms were not related to susceptibility to functional psychoses in our Brazilian sample. These findings need to be validated in larger and independent studies.

Elevated cerebrospinal fluid lactate concentrations in patients with bipolar disorder and schizophrenia: implications for the mitochondrial dysfunction hypothesis

BACKGROUND

Evidence is accumulating that mitochondrial dysfunction is involved in the pathophysiology of bipolar disorder and schizophrenia. Cerebrospinal fluid (CSF) concentration of lactate, a product of extra-mitochondrial glucose metabolism, is commonly elevated in individuals with mitochondrial disorders, especially those with neuropsychiatric symptoms. We tested the hypothesis that patients with bipolar disorder and schizophrenia would, on average, have elevated CSF lactate concentrations compared with healthy control subjects.

METHODS

The CSF lactate and CSF and plasma glucose concentrations were measured with a YSI (YSI, Yellow Springs, Ohio) 2300 STAT Plus Glucose & Lactate Analyzer in 15 samples from each of three groups of subjects: bipolar I disorder patients, schizophrenic patients, and healthy control subjects.

RESULTS

Mean CSF lactate concentrations were significantly higher in bipolar (1.76 +/- .38) and schizophrenic subjects (1.61 +/- .31) compared with control subjects (1.31 +/- .21 mmol/L). These differences persisted after adjusting means for CSF glucose concentration, which correlated positively with CSF lactate concentration.

CONCLUSIONS

This is the first report of increased CSF lactate concentrations in patients with bipolar disorder and schizophrenia. Elevated CSF lactate indicates increased extra-mitochondrial and anaerobic glucose metabolism and is consistent with impaired mitochondrial metabolism. Measuring CSF lactate concentration might help identify bipolar and schizophrenic patients with mitochondrial dysfunction who might benefit from research to elucidate and ultimately rectify possible mitochondrial pathology underlying these disorders.

A putative high risk diplotype of the G72 gene is in healthy individuals associated with better performance in working memory functions and altered brain activity in the medial temporal lobe

G72 is a vulnerability gene for schizophrenia and affective psychosis, disorders that are characterized by deficits in working memory. In the present study we investigated whether the G72 genotype influences verbal and spatial working memory functions in healthy individuals. Working memory was assessed at the behavioural level in 423 subjects using the spatial span of the Wechsler Memory Scale (spatial working memory) and the letter-number-span test (verbal working memory). In a sub-sample of 83 subjects, we assessed working memory functions also at the neural level using functional magnetic resonance imaging during a classical letter variant of the n-back task. Unexpectedly the high risk allele carriers performed better in the verbal working memory task than the other subjects. These behavioural differences were accompanied by brain activation differences in the right parahippocampus, a brain region that plays a major role in schizophrenia and affective disorders. The high risk variant of a vulnerability gene therefore does not necessarily have to negatively affect cognitive abilities per se, but may even have beneficial effects on cognitive functions in the non-affected population.

Bipolar disorder and neurophysiologic mechanisms

Recent studies have suggested that some variants of bipolar disorder (BD) may be due to hyperconnectivity between orbitofrontal (OFC) and temporal pole (TP) structures in the dominant hemisphere. Some initial MRI studies noticed that there were corpus callosum abnormalities within specific regional areas and it was hypothesized that developmentally this could result in functional or effective connectivity changes within the orbitofrontal-basal ganglia-thalamocortical circuits. Recent diffusion tensor imaging (DTI) white matter fiber tractography studies may well be superior to region of interest (ROI) DTI in understanding BD. A "ventral semantic stream" has been discovered connecting the TP and OFC through the uncinate and inferior longitudinal fasciculi and the elusive TP is known to be involved in theory of mind and complex narrative understanding tasks. The OFC is involved in abstract valuation in goal and sub-goal structures and the TP may be critical in binding semantic memory with person-emotion linkages associated with narrative. BD patients have relative attenuation of performance on visuoconstructional praxis consistent with an atypical localization of cognitive functions. Multiple lines of evidence suggest that some BD alleles are being selected for which could explain the enhanced creativity in higher-ability probands. Associations between ROI's that are not normally connected could explain the higher incidence of artistic aptitude, writing ability, and scientific achievements among some mood disorder subjects.

Polymorphism of dopamine D2 receptor (TaqIA, TaqIB, and-141C Ins/Del) and dopamine degradation enzyme (COMT G158A, A-278G) genes and extrapyramidal symptoms in patients with schizophrenia and bipolar disorders

The relationship is examined of the dopamine D2 receptor (DRD2) polymorphism (TaqIA, TaqIB, -141 C Ins/Del) and the catechol-O-methyltransferase (COMT) polymorphism (A-278G, G158A) to the risk of antipsychotic-induced extrapyramidal symptoms (EPS) in schizophrenia and bipolar disorders. Participants comprised 80 cases presenting with EPS (Simpson-Angus Scale score >3) and 188 controls presenting without EPS (Simpson-Angus Scale score <or=3) participated in this study. The COMT(L) allele conferred a reduction of EPS risk of 60% to heterozygotes, but the finding did not survive correction for multiple comparisons. In the bipolar subgroup, with a COMT(L) allele protection of 70%, the reduction remained significant after Bonferroni correction. The analysis of the COMT haplotypes revealed an association of the A-G haplotype with EPS risk in the overall group and the bipolar disorder subgroup, and an association of the A-A haplotype with EPS protection in the bipolar subgroup. No significant associations were found for DRD2 or COMT A-278G polymorphisms. This is the first report of an association between the COMT polymorphism and EPS susceptibility. These results are of interest in view of the increased use of antipsychotic drugs in bipolar patients in both the acute manic and the depressive phase.

Review of the literature regarding early intervention for children and adolescents aged 0-15 experiencing a first-episode psychiatric disturbance

AIM

The purpose of this review is to report on existing literature regarding children and adolescents younger than 16 years of age experiencing a first-episode psychiatric disturbance. Rather than providing a comprehensive list of service implications, this paper identifies some of the gaps in knowledge and practice to encourage ongoing analysis regarding better practices for early intervention for children and adolescents experiencing a first-episode psychiatric disturbance.

METHODS

A search was conducted to identify key evidence-based literature published from 1985 to 2007 discussing various aspects of child and youth mental health in Canada, the USA, the UK, Australia and New Zealand. The review also included 'grey' literature. Categories of information include diagnoses, pharmacological and non-pharmacological treatment, prevalence, environmental and other risk factors, and demographic variables.

RESULTS

Understanding first-episode psychiatric disturbance for patients under the age of 16 years is limited because of a scarcity of controlled studies focusing on this population. Programme evaluations are sparse, perhaps because of the small number of specialized units servicing this population. It may be helpful to enlist early intervention psychosis programmes that have been successful in assisting young people aged 16-24 in the development of better practices and care outcomes for younger age groups.

CONCLUSIONS

The authors highlight information that has the potential to assist in optimizing care for those youth younger than 16 years experiencing or exhibiting signs of a first-episode psychiatric disturbance.

BanI polymorphism of cytosolic phospholipase A2 gene is associated with age at onset in male patients with schizophrenia and schizoaffective disorder

The enzymes phospholipases A2 are believed to be involved in the pathology of schizophrenia. We investigated allelic and genotype frequencies of PLA2G4A BanI polymorphism and the rs4375 in PLA2G6A in Croatian schizophrenic patients (n=81) and controls (n=182), using PCR/RFLP. Genotype and allelic frequencies of both loci, alone or in combination did not show significant difference (chi2-test). Allele-wise and genotype-wise meta-analyses of BanI polymorphism in case-control and family-based studies also revealed no significant association with schizophrenia. Multiple logistic regression analyses revealed statistically significant association between several items from PANSS general psychopathology scale and BanI polymorphism in PLA2G4A. BanI polymorphism further showed a significant impact on mean age of the onset of disease in males (betaA1=0.351, P=0.021; Spearman's rA1=0.391, P=0.010) indicating lower mean age at admission in homozygous A2A2 males.

Systematic of psychiatric disorders between categorical and dimensional approaches: Kraepelin's dichotomy and beyond

This paper describes basic principles of systematics for psychiatric disorders such as the categorical and dimensional approach. It summarises validity aspects of the traditional psychiatric nosology and syndromatology. The importance and limitations of the dichotomy of schizophrenia and affective disorders, first suggested by Kraepelin, is reviewed in the light of results from modern research in the field of classification, follow-up and neurobiological studies, especially neurochemical, neurogenetic and neuroimaging studies. Current developments towards DSM-V and ICD-11 are critically reflected. The conclusion is reached that there might be insufficient data to establish a new systematics of psychoses. Therefore it might be premature to leave the Kraepelinian dichotomy totally although it has to be modified in the light of new research.

Meta-analysis of 12 genomic studies in bipolar disorder

Multiple genome-wide expression studies of bipolar disorder have been published. However, a unified picture of the genomic basis for the disease has not yet emerged. Genes identified in one study often fail to be identified in other studies, prompting the question of whether microarray studies in the brain are inherently unreliable. To answer this question, we performed a meta-analysis of 12 microarray studies of bipolar disorder. These studies included >500 individual array samples, on a range of microarray platforms and brain regions. Although we confirmed that individual studies showed some differences in results, clear and striking regulation patterns emerged across the studies. These patterns were found at the individual gene level, at the functional level, and at the broader pathway level. The patterns were generally found to be reproducible across platform and region, and were highly statistically significant. We show that the seeming discordance between the studies was primarily a result of the following factors, which are also typical for other brain array studies: (1) Sample sizes were, in retrospect, too small; (2) criteria were at once too restrictive (generally focusing on fold changes >1.5) and too broad (generally using p < 0.05 or p < 0.01 as criteria for significance); and (3) statistical adjustments were not consistently applied for confounders. In addition to these general conclusions, we also summarize the primary biological findings of the meta-analysis, focusing on areas that confirm previous research and also on novel findings.

Interleukin-1 beta gene polymorphism and its interactions with neuregulin-1 gene polymorphism are associated with schizophrenia

Interleukin-1beta (IL-1beta) and neuregulin-1 (NRG-1) have an important role in development of the central nervous system. Several recent studies suggest that their genetic polymorphisms are associated with schizophrenia. We studied the effects of the IL-1beta gene (IL-1B) -511 and NRG-1 SNP8NRG221533 polymorphisms and their interactions on the risk and age of onset of schizophrenia in 113 Finnish schizophrenic patients and 393 healthy controls. The allele and genotype frequencies of IL-1B and NRG-1 did not differ between schizophrenic patients and healthy controls, but the risk of schizophrenia was more than 10 times higher (odds ratio 10.20, 95% CI 2.53-41.09, p = 0.001) among subjects with the IL-1B 2.2, NRG-1 CC genotypes compared to subjects with the IL-1B 2.2, NRG-1 T-allele carriage. There was also a trend for an association between the interaction between IL-1B and NRG-1 polymorphisms and the age at onset of schizophrenia (chi(2) = 2.80; df = 1; p = 0.09, log rank test). IL-1B-511 allele 1 homozygotes had a significantly higher age of onset than allele 2 carriers (mean age of onset 25.9 +/- 7.7 and 22.7 +/- 5.4 years, t-test: t = 2.46; p = 0.032). Our results suggest that there is an interaction between the IL-1B and NRG-1 genes in schizophrenia. In addition, the IL-1B-511 polymorphism seems to be associated with the age at onset of schizophrenia.

Allelic association of G72/G30 with schizophrenia and bipolar disorder: a comprehensive meta-analysis

The G72/G30 gene complex (G72 also known as D-amino acid oxidase activator, DAOA) and its chromosomal region 13q32-34 have been linked and associated with both schizophrenia (SCZ) and bipolar disorder (BP) in multiple studies, including our initial association report on BP. However, the inconsistency of associated variants across studies is obvious. Previous meta-analyses had small data sets. The present meta-analysis combined 18 association articles published before April of 2007. There were 19 independent studies of SCZ, with 4304 cases, 5423 controls, and 1384 families, and four independent studies of BP with 1145 cases, 1829 controls, and 174 families. Of 15 single nucleotide polymorphisms (SNPs) analyzed in the 95-kb G72/G30 gene region, M18/rs947267 and M22/rs778293 showed association with SCZ in Asians, and M24/rs1421292 with SCZ in Europeans. The associations of C allele at M18 and A allele at M22 with SCZ in Asians survived conservative Bonferroni correction for multiple testing for 15 markers and subgroup analysis (adjusted P=0.0000253 for M18; adjusted P=0.009 for M22). No single maker showed evidence of overall association with BP. These results suggest that G72/G30 may influence susceptibility to schizophrenia with weak effects.

Association of the trace amine associated receptor 6 (TAAR6) gene with schizophrenia and bipolar disorder in a Korean case control sample

Trace amines and their receptors may be implicated in the pathogenesis of psychiatric disorders. Previous studies have reported association of the trace amine associated receptor 6 (TAAR6) gene with susceptibility to schizophrenia and bipolar disorder but results have not been consistent. The purpose of this study was to examine these associations in Korean patients and also to test for association of TAAR6 with susceptibility to major depressive disorder (MDD). A case control sample consisting of 281 patients with schizophrenia, 190 patients with bipolar disorder, 187 patients with MDD and 288 psychiatrically healthy control subjects, was examined. Patients with schizoaffective disorder were not included in any of the psychiatric samples. Five single nucleotide polymorphisms (SNPs: rs4305745; rs8192625; rs7452939; rs6903874 and rs6937506) were genotyped in the TAAR6 gene and in the 3' regulatory region, using pyrosequencing. SNP rs6903874 was significantly associated with schizophrenia (p = 0.012) and bipolar disorder (p = 0.004). A three SNP haplotype consisting of alleles GCT from SNPs rs7452939, rs6903874 and rs6937506, respectively, was significantly over-represented in patients with schizophrenia (p = 0.0003) and bipolar disorder (p = 0.00002). A second three SNP haplotype (GTT) derived from the same SNPs was significantly under-represented in patients with bipolar disorder (p = 0.001). The GTT haplotype associations withstand the most rigorous corrections for multiple testing. These findings strongly support association of the TAAR6 gene with susceptibility to both schizophrenia and bipolar disorder in Korean patients. Further studies are needed to confirm these findings in this and other populations and to identify functional variants in TAAR6 that may be implicated in pathogenesis.

Susceptibility of schizophrenia and affective disorder not associated with loci on chromosome 6q in Han Chinese population

Background

Several linkage studies across multiple population groups provide convergent support for susceptibility loci for schizophrenia – and, more recently, for affective disorder – on chromosome 6q. We explore whether schizophrenia and affective disorder have common susceptibility gene on 6q in Han Chinese population.

Methods

In the present study, we genotyped 45 family trios from Han Chinese population with mixed family history of schizophrenia and affective disorder. Twelve short tandem repeat (STRs) markers were selected, which covered 102.19 cM on chromosome 6q with average spacing 9.29 cM and heterozygosity 0.78. The transmission disequilibrium test (TDT) was performed to search for susceptibility loci to schizophrenia and affective disorder.

Results

The results showed STRs D6S257, D6S460, D6S1021, D6S292 and D6S1581 were associated with susceptibility to psychotic disorders. When families were grouped into schizophrenia and affective disorder group, D6S257, D6S460 and D6S1021, which map closely to the centromere of chromosome 6q, were associated with susceptibility to schizophrenia. Meanwhile, D6S1581, which maps closely to the telomere, was associated with susceptibility to affective disorder. But after correction of multiple test, all above association were changed into no significance (P > 0.05).

Conclusion

These results suggest that susceptibility of schizophrenia and affective disorder not associated with loci on chromosome 6q in Han Chinese population.

[Immunology in schizophrenic disorders]

This manuscript deals with whether immune-mediated mechanisms of inflammation contribute to the pathogenesis of schizophrenia. A model is presented which integrates psychoneuroimmunologic findings and actual results from pharmacological, neurochemical, and genetic studies in schizophrenia. A pivotal role in the neurobiology of schizophrenia is played by dopaminergic neurotransmission, which is modulated by influences of the glutamatergic system. The decreased function of the glutamate system described in schizophrenia seems primarily mediated by N-methyl-D-aspartate (NMDA) receptor antagonism. Kynurenine acid is the only known endogenous NMDA receptor antagonist. In higher concentrations it blocks the NMDA receptor, but in lower concentrations it blocks the nicotinergic acetylcholin receptor, which has a prominent role in cognitive functions. Therefore, higher levels of kynurenine acid may explain psychotic symptoms and cognitive dysfunction. Several findings point out that prenatal infection, associated with an early sensitisation of the immune system, may result in an imbalance of the immune response (type 1 vs type 2) in schizophrenia. This immune constellation leads to inhibition of the enzyme indoleamin dioxigenase (IDO). It and tryptophane 2,3-dioxygenase (TDO) both catalyse the degradation from tryptophan to kynurenine. Due to the inhibition of IDO, tryptophan is metabolised to kynurenine primarily by TDO. In the CNS, TDO is located only in astrocytes, which are in particular activated in schizophrenia and in which kynurenine acid is the final product and can not be further metabolised. Therefore kynurenine acid accumulates in the CNS of schizophrenics and - due to its NMDA-antagonistic properties - leads to cognitive dysfunction and psychotic symptoms. This model describes the pathway of immune-mediated glutamatergic-dopaminergic dysregulation, which may lead to the clinical symptoms of schizophrenia. Therapeutic consequences (e.g. cyclo-oxygenase-2 inhibitors) are discussed.

Polymorphisms in dopamine receptor DRD1 and DRD2 genes and psychopathological and extrapyramidal symptoms in patients on long-term antipsychotic treatment

DRD(1) and DRD(2) receptor gene variants have been associated with clinical aspects of schizophrenia; however only specific features were analyzed in different samples. To assess the complex interaction between genetic and clinical factors, we studied the possible cross-interactions between DRD1 and DRD2 dopamine receptor gene polymorphisms, symptomatology of schizophrenia and schizoaffective disorders, and the occurrence of treatment induced side effects taking into consideration possible clinical confounding variables. One hundred thirty one outpatients in stable remission meeting the DSMIV criteria for schizophrenia spectrum disorders and receiving long-term maintenance therapy with haloperidol, fluphenazine, zuclopenthixole, or risperidone were genotyped for DRD1 A-48G, DRD2 Ins-141CDel, and DRD2 Ser311Cys polymorphisms. Psychopathological symptoms were assessed with the positive and negative syndrome scale for schizophrenia (PANSS). Extrapyramidal side effects were assessed with the Simpson-Angus extrapyramidal side effects scale (EPS), the Barnes Akathisia scale (BARS), and the abnormal involuntary movement scale (AIMS). Drug dosage was included as covariant because it was associated with the severity of symptomatology, akathisia, and parkinsonism. No association was observed for DRD1 and DRD2 polymorphisms and extrapyramidal side effects, or with the other clinical variables considered. Our study suggests that DRD1 and DRD2 variants are not liability factors for tardive dyskinesia.

No evidence for association between 19 cholinergic genes and bipolar disorder

Cholinergic dysfunction has been proposed for the pathogenesis of bipolar disorder (BD), and we have therefore performed a systematic association study of cholinergic system genes in BD (including schizoaffective disorder bipolar type). We genotyped 93 single nucleotide polymorphisms (SNPs) in 19 genes (CHAT, CHRM1-5, CHRNA1-7, CHRNA9, CHRNA10, and CHRNB1-4) in two series of samples: the National Institute of Mental Health (NIMH) Genetics Initiative pedigrees with 474 samples from 152 families, and the Clinical Neurogenetics (CNG) pedigrees with 83 samples from 22 multiplex families. Sib-transmission/disequilibrium test (sib_TDT) analysis showed nominally significant transmission bias for four SNPs (CHRNA2: rs7017417, P = 0.024; CHRNA5: rs514743, P = 0.031; CHRNB1: rs2302762, P = 0.049; CHRNB4: rs1948, P = 0.031). Haploview analyses showed nominally significant transmission bias of several haplotypes in CHRNA2, CHRNA7, CHRNB1, and CHRNB4, respectively. However, none of these associations reached gene-wide significance after correction by permutation. Alcohol dependence (including alcohol abuse) was not a significant covariate in the present genetic association analysis. Thus, it is unlikely that these 19 cholinergic genes play a major role in the pre-disposition to BD in these pedigrees.

MTHFD 1958G>A and MTR 2756A>G polymorphisms are associated with bipolar disorder and schizophrenia

BACKGROUND

The etiology of bipolar disorder (BD) and schizophrenia is very complex. Polymorphic variants of genes encoding enzymes of the monoaminergic may be involved in development of BD and schizophrenia. Therefore, we examined the prevalence of 1958G>A polymorphism of MTHFD1 gene, encoding trifunctional folate enzyme 5,10-methylenetetrahydrofolate dehydrogenase, 5,10-methenyltetrahydrofolate cyclohydrolase and 10-formyltetrahydrofolate synthetase (MTHFD1), and 2756A>G variant of methionine synthase (MTR) gene in patients with BD (n=200), schizophrenia (n=200) and in controls (n=300).

OBJECTIVE

We investigated the genotypic and allelic frequencies of MTHFD1 1958G>A (R653Q) and MTR 2756A>G (D919G) gene polymorphisms in a group of bipolar (n=200) and schizophrenic patients (n=200), as well as in controls (n=300).

METHODS

The distributon of genotypes in all groups was tested for deviation from Hardy-Weinberg equilibrium (HWE). The Pearson's chi-square (chi) test and Fisher's exact test were applied to assess differences in the genotypic and allelic (respectively) distribution between groups of patients and controls.

MAIN RESULTS

We found that MTHFD1 1958AA or 1958AG genotypes constitute risk factors for development of bipolar disorder type I (BDI) or schizophrenia with odds ratios (OR)=1.743 (95% CI=1.211-2.508; P=0.0027; P (corr)=0.0054) and 2.667 (95% CI=1.845-3.854; P=0.0001; P (corr)=0.0002), respectively. In the same groups, the MTR 2756GG or 2756AG genotypes also constitute significant risk factors in occurrence of BDI and schizophrenia with OR=1.621 (95% CI=1.130-2.326; P=0.0086; P (corr)=0.0172) and 1.556 (95% CI=1.085-2.232; P=0.0160; P (corr)=0.032), respectively. Gender classification of patients indicated significant association only of MTHFD1 1958A allele with BDI and schizophrenia in the male patients OR=1.838 (95% CI=1.114-3.031; P=0.0166; P (corr)=0.0332) and OR=3.964 (95% CI=2.358-6.663; P=0.0001 P (corr)=0.0002), respectively.

CONCLUSION

Since MTHFD and MTR genes are located in 14q24 and 1q43 loci, our findings support the significance of chromosomes 14q and 1q in etiopathogenesis of bipolar disorder and schizophrenia.

Which perspectives can endophenotypes and biological markers offer in the early recognition of schizophrenia?

The early recognition of schizophrenia seems crucial; various studies relate a longer duration-of-untreated-psychosis to a worse prognosis. We give an overview over common psychopathological early recognition instruments (BSABS, CAARMS, SIPS, IRAOS, ERIraos). However, many clinical symptoms of prodromal schizophrenia stages are not sufficiently specific. Thus we review recent contributions of neuroimaging and electrophysiological as well as genetic studies: which new diagnostic perspectives offer endophenotypes (such as P300, P50 sensory gating, MMN, smooth pursuit eye movements; indicating a specific genetic vulnerability) together with a better understanding of schizophrenic pathophysiology (state-dependent biological markers, e.g. aggravated motor neurological soft signs during psychosis) in prodromal schizophrenia when still ambiguous clinical symptoms are present. Several examples (e.g. from COMT polymorphisms to working memory deficits) illustrate more specific underlying neuronal mechanisms behind behavioural symptoms. This way, a characteristic pattern of disturbed cerebral maturation might be distinguished in order to complement clinical instruments of early schizophrenia detection.

Dysbindin gene variants are associated with bipolar I disorder in a Korean population

The dysbindin gene (DTNBP1) has been associated with schizophrenia in several populations. Because the clinical characteristics of schizophrenia and bipolar disorder overlap in many respects and findings from genetic studies have suggested common genes between them, we conducted a case control association study of bipolar disorder in Korea to investigate the genetic association between DTNBP1 and bipolar disorder. In total, 163 patients with bipolar disorder and 350 controls were evaluated. We genotyped three single nucleotide polymorphisms of DTNBP1 (SNP A, P1763, and P1320) and analyzed the allele, genotype, and haplotype associations with bipolar disorder. We found significant genotypic associations with P1763 and P1320, but no association with SNP A in the bipolar I group. When we included bipolar II and schizoaffective disorder in the affected phenotype, the significance decreased. A positive association was observed between the SNP A-P1763 haplotype and the bipolar I phenotype. This haplotype association was lost when we either broadened our phenotype or included P1320 in a haplotype. The positive results of the present study lost significance after a Bonferroni correction for multiple testing. These findings are consistent with previous findings that showed a positive association of DTNBP1 with bipolar disorders. Moreover, our results suggest that DTNBP1 may contribute more to bipolar I disorder than bipolar II disorder or schizoaffective disorder. Further comprehensive studies will be required to clarify these association, however, it seems likely that DTNBP1 is a susceptibility gene for bipolar disorder.