Genetic analysis of a functional GRIN2A promoter (GT)n repeat in bipolar disorder pedigrees in humans

Normative modelling of molecular-based functional circuits captures clinical heterogeneity transdiagnostically in psychiatric patients

Advanced methods such as REACT have allowed the integration of fMRI with the brain's receptor landscape, providing novel insights transcending the multiscale organisation of the brain. Similarly, normative modelling has allowed translational neuroscience to move beyond group-average differences and characterise deviations from health at an individual level. Here, we bring these methods together for the first time. We used REACT to create functional networks enriched with the main modulatory, inhibitory, and excitatory neurotransmitter systems and generated normative models of these networks to capture functional connectivity deviations in patients with schizophrenia, bipolar disorder (BPD), and ADHD. Substantial overlap was seen in symptomatology and deviations from normality across groups, but these could be mapped into a common space linking constellations of symptoms through to underlying neurobiology transdiagnostically. This work provides impetus for developing novel biomarkers that characterise molecular- and systems-level dysfunction at the individual level, facilitating the transition towards mechanistically targeted treatments.

The role of NMDA receptors in bipolar disorder: A systematic review

OBJECTIVES

Glutamatergic transmission and N-methyl-D-aspartate receptors (NMDARs) have been implicated in the pathophysiology schizophrenic spectrum and major depressive disorders. Less is known about the role of NMDARs in bipolar disorder (BD). The present systematic review aimed to investigate the role of NMDARs in BD, along with its possible neurobiological and clinical implications.

METHODS

We performed a computerized literature research on PubMed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, using the following string: (("Bipolar Disorder"[Mesh]) OR (manic-depressive disorder[Mesh]) OR ("BD") OR ("MDD")) AND ((NMDA [Mesh]) OR (N-methyl-D-aspartate) OR (NMDAR[Mesh]) OR (N-methyl-D-aspartate receptor)).

RESULTS

Genetic studies yield conflicting results, and the most studied candidate for an association with BD is the GRIN2B gene. Postmortem expression studies (in situ hybridization and autoradiographic and immunological studies) are also contradictory but suggest a reduced activity of NMDARs in the prefrontal, superior temporal cortex, anterior cingulate cortex, and hippocampus.

CONCLUSIONS

Glutamatergic transmission and NMDARs do not appear to be primarily involved in the pathophysiology of BD, but they might be linked to the severity and chronicity of the disorder. Disease progression could be associated with a long phase of enhanced glutamatergic transmission, with ensuing excitotoxicity and neuronal damage, resulting into a reduced density of functional NMDARs.

Association of polygenic score and the involvement of cholinergic and glutamatergic pathways with lithium treatment response in patients with bipolar disorder

Lithium is regarded as the first-line treatment for bipolar disorder (BD), a severe and disabling mental health disorder that affects about 1% of the population worldwide. Nevertheless, lithium is not consistently effective, with only 30% of patients showing a favorable response to treatment. To provide personalized treatment options for bipolar patients, it is essential to identify prediction biomarkers such as polygenic scores. In this study, we developed a polygenic score for lithium treatment response (Li+PGS) in patients with BD. To gain further insights into lithium's possible molecular mechanism of action, we performed a genome-wide gene-based analysis. Using polygenic score modeling, via methods incorporating Bayesian regression and continuous shrinkage priors, Li+PGS was developed in the International Consortium of Lithium Genetics cohort (ConLi+Gen: N = 2367) and replicated in the combined PsyCourse (N = 89) and BipoLife (N = 102) studies. The associations of Li+PGS and lithium treatment response - defined in a continuous ALDA scale and a categorical outcome (good response vs. poor response) were tested using regression models, each adjusted for the covariates: age, sex, and the first four genetic principal components. Statistical significance was determined at P < 0.05. Li+PGS was positively associated with lithium treatment response in the ConLi+Gen cohort, in both the categorical (P = 9.8 × 10-12, R2 = 1.9%) and continuous (P = 6.4 × 10-9, R2 = 2.6%) outcomes. Compared to bipolar patients in the 1st decile of the risk distribution, individuals in the 10th decile had 3.47-fold (95%CI: 2.22-5.47) higher odds of responding favorably to lithium. The results were replicated in the independent cohorts for the categorical treatment outcome (P = 3.9 × 10-4, R2 = 0.9%), but not for the continuous outcome (P = 0.13). Gene-based analyses revealed 36 candidate genes that are enriched in biological pathways controlled by glutamate and acetylcholine. Li+PGS may be useful in the development of pharmacogenomic testing strategies by enabling a classification of bipolar patients according to their response to treatment.

A pilot investigation of differential hydroxymethylation levels in patient-derived neural stem cells implicates altered cortical development in bipolar disorder

Introduction

Bipolar disorder (BD) is a chronic mental illness characterized by recurrent episodes of mania and depression and associated with social and cognitive disturbances. Environmental factors, such as maternal smoking and childhood trauma, are believed to modulate risk genotypes and contribute to the pathogenesis of BD, suggesting a key role in epigenetic regulation during neurodevelopment. 5-hydroxymethylcytosine (5hmC) is an epigenetic variant of particular interest, as it is highly expressed in the brain and is implicated in neurodevelopment, and psychiatric and neurological disorders.

Methods

Induced pluripotent stem cells (iPSCs) were generated from the white blood cells of two adolescent patients with bipolar disorder and their same-sex age-matched unaffected siblings (n = 4). Further, iPSCs were differentiated into neuronal stem cells (NSCs) and characterized for purity using immuno-fluorescence. We used reduced representation hydroxymethylation profiling (RRHP) to perform genome-wide 5hmC profiling of iPSCs and NSCs, to model 5hmC changes during neuronal differentiation and assess their impact on BD risk. Functional annotation and enrichment testing of genes harboring differentiated 5hmC loci were performed with the online tool DAVID.

Results

Approximately 2 million sites were mapped and quantified, with the majority (68.8%) located in genic regions, with elevated 5hmC levels per site observed for 3' UTRs, exons, and 2-kb shorelines of CpG islands. Paired t-tests of normalized 5hmC counts between iPSC and NSC cell lines revealed global hypo-hydroxymethylation in NSCs and enrichment of differentially hydroxymethylated sites within genes associated with plasma membrane (FDR = 9.1 × 10-12) and axon guidance (FDR = 2.1 × 10-6), among other neuronal processes. The most significant difference was observed for a transcription factor binding site for the KCNK9 gene (p = 8.8 × 10-6), encoding a potassium channel protein involved in neuronal activity and migration. Protein-protein-interaction (PPI) networking showed significant connectivity (p = 3.2 × 10-10) between proteins encoded by genes harboring highly differentiated 5hmC sites, with genes involved in axon guidance and ion transmembrane transport forming distinct sub-clusters. Comparison of NSCs of BD cases and unaffected siblings revealed additional patterns of differentiation in hydroxymethylation levels, including sites in genes with functions related to synapse formation and regulation, such as CUX2 (p = 2.4 × 10-5) and DOK-7 (p = 3.6 × 10-3), as well as an enrichment of genes involved in the extracellular matrix (FDR = 1.0 × 10-8).

Discussion

Together, these preliminary results lend evidence toward a potential role for 5hmC in both early neuronal differentiation and BD risk, with validation and more comprehensive characterization to be achieved through follow-up study.

Association of Polygenic Score and the involvement of Cholinergic and Glutamatergic Pathways with Lithium Treatment Response in Patients with Bipolar Disorder

Lithium is regarded as the first-line treatment for bipolar disorder (BD), a severe and disabling mental disorder that affects about 1% of the population worldwide. Nevertheless, lithium is not consistently effective, with only 30% of patients showing a favorable response to treatment. To provide personalized treatment options for bipolar patients, it is essential to identify prediction biomarkers such as polygenic scores. In this study, we developed a polygenic score for lithium treatment response (Li+PGS) in patients with BD. To gain further insights into lithium's possible molecular mechanism of action, we performed a genome-wide gene-based analysis. Using polygenic score modeling, via methods incorporating Bayesian regression and continuous shrinkage priors, Li+PGS was developed in the International Consortium of Lithium Genetics cohort (ConLi+Gen: N=2,367) and replicated in the combined PsyCourse (N=89) and BipoLife (N=102) studies. The associations of Li+PGS and lithium treatment response - defined in a continuous ALDA scale and a categorical outcome (good response vs. poor response) were tested using regression models, each adjusted for the covariates: age, sex, and the first four genetic principal components. Statistical significance was determined at P<����������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������.

Amygdala and anterior cingulate transcriptomes from individuals with bipolar disorder reveal downregulated neuroimmune and synaptic pathways

Recent genetic studies have identified variants associated with bipolar disorder (BD), but it remains unclear how brain gene expression is altered in BD and how genetic risk for BD may contribute to these alterations. Here, we obtained transcriptomes from subgenual anterior cingulate cortex and amygdala samples from post-mortem brains of individuals with BD and neurotypical controls, including 511 total samples from 295 unique donors. We examined differential gene expression between cases and controls and the transcriptional effects of BD-associated genetic variants. We found two coexpressed modules that were associated with transcriptional changes in BD: one enriched for immune and inflammatory genes and the other with genes related to the postsynaptic membrane. Over 50% of BD genome-wide significant loci contained significant expression quantitative trait loci (QTL) (eQTL), and these data converged on several individual genes, including SCN2A and GRIN2A. Thus, these data implicate specific genes and pathways that may contribute to the pathology of BP.

Brain Environment Interactions: Stress, Posttraumatic Stress Disorder, and the Need for a Postmortem Brain Collection

Stress, especially the extreme stress of traumatic events, can alter both neurobiology and behavior. Such extreme environmental situations provide a useful model for understanding environmental influences on human biology and behavior. This paper will review some of the evidence of brain alterations that occur with exposure to environmental stress. This will include recent studies using neuroimaging and will address the need for histological confirmation of imaging study results. We will review the current scientific approaches to understanding brain environment interactions, and then make the case for the collection and study of postmortem brain tissue for the advancement of our understanding of the effects of environment on the brain.Creating a brain tissue collection specifically for the investigation of the effects of extreme environmental stressors fills a gap in the current research; it will provide another of the important pieces to the puzzle that constitutes the scientific investigation of negative effects of environmental exposures. Such a resource will facilitate new discoveries related to the psychiatric illnesses of acute stress disorder and posttraumatic stress disorder, and can enable scientists to correlate structural and functional imaging findings with tissue abnormalities, which is essential to validate the results of recent imaging studies.

Genetic Factors That Could Affect Concussion Risk in Elite Rugby

Elite rugby league and union have some of the highest reported rates of concussion (mild traumatic brain injury) in professional sport due in part to their full-contact high-velocity collision-based nature. Currently, concussions are the most commonly reported match injury during the tackle for both the ball carrier and the tackler (8-28 concussions per 1000 player match hours) and reports exist of reduced cognitive function and long-term health consequences that can end a playing career and produce continued ill health. Concussion is a complex phenotype, influenced by environmental factors and an individual's genetic predisposition. This article reviews concussion incidence within elite rugby and addresses the biomechanics and pathophysiology of concussion and how genetic predisposition may influence incidence, severity and outcome. Associations have been reported between a variety of genetic variants and traumatic brain injury. However, little effort has been devoted to the study of genetic associations with concussion within elite rugby players. Due to a growing understanding of the molecular characteristics underpinning the pathophysiology of concussion, investigating genetic variation within elite rugby is a viable and worthy proposition. Therefore, we propose from this review that several genetic variants within or near candidate genes of interest, namely APOE, MAPT, IL6R, COMT, SLC6A4, 5-HTTLPR, DRD2, DRD4, ANKK1, BDNF and GRIN2A, warrant further study within elite rugby and other sports involving high-velocity collisions.

Association between (GT)n Promoter Polymorphism and Recovery from Concussion: A Pilot Study

Variability in recovery among concussed athletes can be attributed to several risk factors. One risk factor not definitively explored is genetic variation. Genetic variations such as variable number tandem repeats (VNTR) in the promotor region are normal in the population, and can lead to disparities in the amount of protein produced, which could be associated with neuronal recovery. Little research has been conducted to investigate promoter VNTRs within genes responsible for recovery following a concussion. The authors implemented a prospective cohort design using a standardized concussion protocol to diagnose and follow 93 athletes to full recovery at three different sites to determine the association between promotor GT(n) VNTR polymorphisms and recovery time within concussed athletes. The GT(n) VNTR within the promoter region of glutamate ionotropic receptor N-methyl-d-aspartate (NMDA) type subunit 2A (GRIN2A), potassium voltage-gated channel subfamily H member 2 (KCNH2), glutamate ionotropic receptor kainate type subunit 1 (GRIK1), and neurofilament light (NEFL) were genotyped using capillary electrophoresis. GT(n) VNTR promotor polymorphisms were dichotomized into long (L) and short (s) alleles. Using adjusted negative binomial regression models we found that athletes carrying the LL GRIN2A GT(n) VNTR within the promoter region were more likely to experience a prolonged concussion recovery, which resulted in their not being able to return to play for ∼60 days. Additionally, there was a trend toward significance, in which the ss NEFL GT(n) Caucasian athletes had prolonged concussion recovery. This could presumably be attributed to altered proteins or protein levels that disrupt neuronal recovery. This pilot study suggests that these VNTRs are associated with prolonged concussion recovery. In future studies, we plan to measure the extent to which the L or s alleles alter the level and the activity of the GluNR2a and NEFL proteins that GRIN2A and NEFL produce, respectively.

Sex-specific effects of a microsatellite polymorphism on human growth hormone receptor gene expression

Growth hormone (GH) binds to its specific receptor (GHR) at the surface of target cells activating multiple signaling pathways implicated in growth and metabolism. Dysregulation of GHRs leads to pathophysiological states that most commonly affect stature. We previously showed the association of a polymorphic (n = 15-37) GT microsatellite in the human GHR gene promoter with short stature in a sex-specific manner. In the present study we evaluated the functional relevance of this polymorphism in regulating GHR expression. Using luciferase reporter assays, we found that the GT repeat had a significant cis regulatory effect in response to HIF1α and a potential repressor role following C/EBPβ stimulation. Using a digital PCR application to measure allelic imbalance (AI), we showed a high prevalence of AI (∼76%) at the GHR locus in lymphoblastoid cell lines (LCLs), with a significantly higher degree of imbalance in LCLs derived from males. Examination of expression of GHR as well as other members of the GH-IGF1 axis in the LCLs revealed significant associations of GHR, IGF1 and BCL2 expression with GT genotype in a sex-specific manner. Our results suggest that this GT microsatellite exerts both cis and trans effects in a sex-specific context, revealing a new mechanism by which GHR gene expression is regulated.

Genetic Overlap Between Alzheimer's Disease and Bipolar Disorder Implicates the MARK2 and VAC14 Genes

Background: Alzheimer's disease (AD) and bipolar disorder (BIP) are complex traits influenced by numerous common genetic variants, most of which remain to be detected. Clinical and epidemiological evidence suggest that AD and BIP are related. However, it is not established if this relation is of genetic origin. Here, we applied statistical methods based on the conditional false discovery rate (FDR) framework to detect genetic overlap between AD and BIP and utilized this overlap to increase the power to identify common genetic variants associated with either or both traits. Methods: We obtained genome wide association studies data from the International Genomics of Alzheimer's Project part 1 (17,008 AD cases and 37,154 controls) and the Psychiatric Genetic Consortium Bipolar Disorder Working Group (20,352 BIP cases and 31,358 controls). We used conditional QQ-plots to assess overlap in common genetic variants between AD and BIP. We exploited the genetic overlap to re-rank test-statistics for AD and BIP and improve detection of genetic variants using the conditional FDR framework. Results: Conditional QQ-plots demonstrated a polygenic overlap between AD and BIP. Using conditional FDR, we identified one novel genomic locus associated with AD, and nine novel loci associated with BIP. Further, we identified two novel loci jointly associated with AD and BIP implicating the MARK2 gene (lead SNP rs10792421, conjunctional FDR = 0.030, same direction of effect) and the VAC14 gene (lead SNP rs11649476, conjunctional FDR = 0.022, opposite direction of effect). Conclusion: We found polygenic overlap between AD and BIP and identified novel loci for each trait and two jointly associated loci. Further studies should examine if the shared loci implicating the MARK2 and VAC14 genes could explain parts of the shared and distinct features of AD and BIP.

Segregating polymorphism in the NMDA receptor gene GRIN2A, schizotypy, and mental rotation among healthy individuals

Common alleles associated with psychiatric disorders are often regarded as deleterious genes that influence vulnerability to disease, but they may also be considered as mediators of variation in adaptively structured cognitive phenotypes among healthy individuals. The schizophrenia-associated gene GRIN2A (glutamate ionotropic receptor NMDA type subunit 2a) codes for a protein subunit of the NMDA (N-methyl-D-aspartate) receptor that underlies central aspects of human cognition. Pharmacological NMDA blockage recapitulates the major features of schizophrenia in human subjects, and represents a key model for the neurological basis of this disorder. We genotyped two functional GRIN2A polymorphisms in a large population of healthy individuals who were scored for schizotypy and mental imagery/manipulation (the mental rotation test). Rare-allele homozygosity of the promoter microsatellite rs3219790 was associated with high total schizotypy (after adjustment for multiple comparisons) and with enhanced mental rotation ability (nominally, but not after adjustment for multiple comparisons), among males. These findings provide preliminary evidence regarding a genetic basis to previous reports of enhanced mental imagery in schizophrenia and schizotypy. The results also suggest that some schizophrenia-related alleles may be subject to cognitive tradeoffs involving both positive and negative effects on psychological phenotypes, which may help to explain the maintenance of psychiatric-disorder risk alleles in human populations.

Hemoglobins emerging roles in mental disorders. Metabolical, genetical and immunological aspects

Hemoglobin (Hb) expression in the central nervous system is recently shown. Cooccurences of mental disorders (mainly bipolar disorder (BD) and tic disorders) with β- or α-thalassemia trait or erythrocytosis were witnessed, which may be due to peripheral or central hypoxia/hyperoxia or haplotypal gene interactions. β-Globin genes reside at 11p15.5 close to tyrosine hydroxylase, dopamine receptor DRD4 and Brain Derived Neurotrophic Factor, which involve in psychiatric diseases. α-Globin genes reside at 16p13.3 which associates with BD, tic disorders, ATR-16 Syndrome and Rubinstein Taybi Syndrome (RTS). CREB-Binding Protein (CEBBP)-gene is mutated in RTS, which commonly associates with mood disorders. 16p13.3 region also contains GRIN2A gene encoding N-methyl-d-aspartate receptor-2A and SSTR5 (Somatostatin Receptor-5), again involving in mental disorders. We demonstrated a protective role of minor HbA2 against post-partum episodes in BD and association of higher minor HbF (fetal hemoglobin) levels with family history of psychosis in a BD-patient cohort. HbA2 increases in cardiac ischemia and in mountain dwellers indicating its likely protection against ischemia/hypoxia. HMGIY, a repressive transcription factor of δ-globin chain of HbA2 is increased in lymphocytes of schizophrenics. In autism, deletional mutations were found in BCL11A gene, which cause persistence of HbF at high levels in adulthood. Also, certain polymorphisms in BCL11A strongly associate with schizophrenia. Further, many drugs from anabolic steroids to antimalarial agents elevate HbF and may cause mania. We ascribe a protective role to HbA2 and a maladaptive detrimental role to HbF in psychopathology. We believe that future studies on hemoglobins may pave to discover novel pathogenesis mechanisms in mental disorders.

Genetic findings in sport-related concussions: potential for individualized medicine?

Concussion is a traumatic transient disturbance of the brain. In sport, the initial time and severity of concussion is known giving an opportunity for subsequent analysis. Variability in susceptibility and recovery between individual athletes depends, among other parameters, on genetic factors. The genes-encoding polypeptides that determine incidence, severity and prognosis for concussion are the primary candidates for genetic analysis. Genetic polymorphisms in the genes contributing to plasticity and repair (APOE), synaptic connectivity (GRIN2A), calcium influx (CACNA1E), uptake and deposit of glutamate (SLC17A7) are potential biomarkers of concussion incidence and recovery rate. With catalogued genetic variants, prospective genotyping of athletes at the beginning of their career will allow medical professionals to improve concussion management and return-to-play decisions.

Clinical and biochemical study of d-serine metabolism among schizophrenia patients

BACKGROUND

Schizophrenia is a typical N-methyl-d-aspartate receptor (NMDA-R) hypofunction disorder. Decreased d-serine (d-Ser) levels in the periphery occur in schizophrenia and may reflect decreased availability of d-Ser to activate NMDA-R in the brain.

OBJECTIVE

The objective of this study was to investigate the role of d-Ser metabolism in the pathogenesis of schizophrenia via biochemical assays and correlates, the serum level of d-Ser, d-serine racemase (SR) (responsible for its formation from l-serine [l-Ser]) and d-amino acid oxidase (DAAO) (responsible for its catabolism), among different clinical types of schizophrenia patients.

PATIENTS AND METHODS

This cross-sectional case-control study was carried out on 100 patients and 50 controls. They were recruited from the outpatients' psychiatric unit of the Neuropsychiatric Department of Assiut University Hospital, Upper Egypt. The type of schizophrenia was determined according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), while the severity of schizophrenia was determined according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Serum d-Ser levels were estimated using high-performance liquid chromatography (HPLC), while serum SR and DAAO were measured using commercially available enzyme-linked immunosorbent assay kits.

RESULTS

There were significantly lower mean serum levels of d-Ser and SR and significantly higher mean serum levels of DAAO (P-value <0.01 for each) among schizophrenia patients when compared with the control group. Paranoid schizophrenia had the highest frequency, with a significantly lower serum levels of d-Ser and SR in the residual type and significantly higher serum levels of DAAO in undifferentiated and catatonic types. Combined receiver-operating characteristic curve for serum d-Ser, SR and DAAO indicated that the best serum level cutoff points at which schizophrenia manifestations started to appear were ≤ 61.4 mg/L for d-Ser, ≤ 15.5 pg/mL for SR and >35.6 pg/mL for DAAO.

CONCLUSION

The present study confirms that disturbed d-Ser metabolism could be implicated in the pathogenesis of schizophrenia.

GRIN2A polymorphisms and expression levels are associated with lead-induced neurotoxicity

Lead acts as an antagonist of the N-methyl-d-aspartate receptor (NMDAR). GRIN2A encodes an important subunit of NMDARs and may be a critical factor in the mechanism of lead neurotoxicity. Changes in GRIN2A expression levels or gene variants may be mechanisms of lead-induced neurotoxicity. In this study, we hypothesized that GRIN2A might contribute to lead-induced neurotoxicity. A preliminary HEK293 cell experiment was performed to analyze the association between GRIN2A expression and lead exposure. In addition, in a population-based study, serum GRIN2A levels were measured in both lead-exposed and control populations. To detect further the influence of GRIN2A gene single nucleotide polymorphisms (SNPs) in lead-induced neurotoxicity, 3 tag SNPs (rs2650429, rs6497540, and rs9302415) were genotyped in a case-control study that included 399 lead-exposed subjects and 398 controls. Lead exposure decreased GRIN2A expression levels in HEK293 cells ( p < 0.001) compared with lead-free cells. Lead-exposed individuals had lower serum GRIN2A levels compared with controls ( p < 0.001), and we found a trend of decreasing GRIN2A level with an increase in blood lead level ( p < 0.001). In addition, we found a significant association between rs2650429 CT and TT genotypes and risk of lead poisoning compared with the rs2650429 CC genotype (adjusted odds ratio = 1.42, 95% confidence interval = 1.01-2.00]. Therefore, changes in GRIN2A expression levels and variants may be important mechanisms in the development of lead-induced neurotoxicity.

Bipolar disorder and antibodies against the N-methyl-d-aspartate receptor: A gate to the involvement of autoimmunity in the pathophysiology of bipolar illness

The high prevalence of comorbidity between bipolar disorder (BD) and other medical conditions, including autoimmune diseases, supports the hypothesis of the nature of BD as a biological illness category. Hence, an immune dysregulation process may play an important role in the development of at least certain subtypes of BD. Increasing evidence also suggests that the N-methyl-d-aspartate receptor (NMDAR) may be relevant in the pathophysiology of BD. A possible key mechanism underlying the physiopathology of certain autoimmune diseases that may present with affective symptoms might be the production of anti-NMDAR auto-antibodies (auto-Abs). The best characterized autoimmune anti-NMDAR disease is the anti-NMDAR encephalitis. It has been found that 4% of these patients present isolated, mostly affective, psychiatric manifestations during their illness. An interesting suggestion emerged from this overview is that the same mechanisms that trigger affective symptoms in patients with increased anti-NMDAR auto-Abs levels could be involved in the physiopathology of at least a subgroup of BD. Future studies are needed to characterize the relationship between anti-NMDAR auto-Abs and BD.

Correlation of functional GRIN2A gene promoter polymorphisms with schizophrenia and serum D-serine levels

Schizophrenia is a severe, complex mental disorder. Abnormal glutamate neurotransmission mediated by decreased expression of N-methyl-d-aspartic acid receptors (NMDArs) and its endogenous co-agonist d-serine (d-Ser) has been proposed as one of the hypotheses of the pathogenesis of schizophrenia. GRIN2A gene promoter polymorphism causes changes in the regulation of the expression of NMDAr subunit genes. Our study is aimed at evaluating a possible association between GRIN2A promoter GT polymorphisms and schizophrenia in the Han Chinese population in Shaanxi and the relationship between serum d-Ser levels and GRIN2A (GT)n in schizophrenia. Four hundred and twenty patients with schizophrenia and 410 healthy individuals were recruited in this study and GRIN2A (GT)n repeats as well as serum d-Ser levels were measured in all of the subjects. Nineteen alleles were found in (GT)n locus. The allele frequency of (GT)21, (GT)22 and (GT)23 in schizophrenic subjects was significantly lower compared with the mentally healthy controls, while the allele (GT)26 was significantly more frequent than in normal persons. Transcriptional activity of GRIN2A promoter was gradually suppressed with the increase in the length of the (GT)n repeats. d-Ser levels in the serum of the GRIN2A (GT)21 schizophrenic patients were significantly lower than those of the GRIN2A (GT)21 healthy control. A significant correlation between serum d-Ser levels and GRIN2A (GT)21 in schizophrenia was detected. GRIN2A (GT)21 may play a significant role in the etiology of schizophrenia among the Chinese Han population of Shaanxi.

Lithium-induced neuroprotection is associated with epigenetic modification of specific BDNF gene promoter and altered expression of apoptotic-regulatory proteins

Bipolar disorder (BD), one of the most debilitating mental disorders, is associated with increased morbidity and mortality. Lithium is the first line of treatment option for BD and is often used for maintenance therapy. Recently, the neuroprotective action of lithium has gained tremendous attention, given that BD is associated with structural and functional abnormalities of the brain. However, the precise molecular mechanism by which lithium exerts its neuroprotective action is not clearly understood. In hippocampal neurons, the effects of lithium (1 and 2 mM) on neuronal viability against glutamate-induced cytotoxicity, dendritic length and number, and expression and methylation of BDNF promoter exons and expression of apoptotic regulatory genes were studied. In rat hippocampal neurons, lithium not only increased dendritic length and number, but also neuronal viability against glutamate-induced cytotoxicity. While lithium increased the expression of BDNF as well as genes associated with neuroprotection such as Bcl2 and Bcl-XL, it decreased the expression of pro-apoptotic genes Bax, Bad, and caspases 3. Interestingly, lithium activated transcription of specific exon IV to induce BDNF gene expression. This was accompanied by hypomethylation of BDNF exon IV promoter. This study delineates mechanisms by which lithium mediates its effects in protecting neurons.

The role of NMDA receptors in the pathophysiology and treatment of mood disorders

Mood disorders such as major depressive disorder and bipolar disorder are chronic and recurrent illnesses that cause significant disability and affect approximately 350 million people worldwide. Currently available biogenic amine treatments provide relief for many and yet fail to ameliorate symptoms for others, highlighting the need to diversify the search for new therapeutic strategies. Here we present recent evidence implicating the role of N-methyl-D-aspartate receptor (NMDAR) signaling in the pathophysiology of mood disorders. The possible role of NMDARs in mood disorders has been supported by evidence demonstrating that: (i) both BPD and MDD are characterized by altered levels of central excitatory neurotransmitters; (ii) NMDAR expression, distribution, and function are atypical in patients with mood disorders; (iii) NMDAR modulators show positive therapeutic effects in BPD and MDD patients; and (iv) conventional antidepressants/mood stabilizers can modulate NMDAR function. Taken together, this evidence suggests the NMDAR system holds considerable promise as a therapeutic target for developing next generation drugs that may provide more rapid onset relief of symptoms. Identifying the subcircuits involved in mood and elucidating the role of NMDARs subtypes in specific brain circuits would constitute an important step toward the development of more effective therapies with fewer side effects.

Caffeine interaction with glutamate receptor gene GRIN2A: Parkinson's disease in Swedish population

A complex interplay between genetic and environmental factors is thought to be involved in the etiology of Parkinson's disease (PD). A recent genome-wide association and interaction study (GWAIS) identified GRIN2A, which encodes an NMDA-glutamate-receptor subunit involved in brain's excitatory neurotransmission, as a PD genetic modifier in inverse association with caffeine intake. Here in, we attempted to replicate the reported association of a single nucleotide polymorphism, GRIN2A_rs4998386, and its interaction with caffeine intake with PD in patient-control study in an ethnically homogenous population in southeastern Sweden, as consistent and independent genetic association studies are the gold standard for the validation of genome-wide association studies. All the subjects (193 sporadic PD patients and 377 controls) were genotyped, and the caffeine intake data was obtained by questionnaire. We observed an association between rs4998386 and PD with odds ratio (OR) of 0.61, 95% confidence intervals (CI) of 0.39–0.96, p = 0.03, under a model excluding rare TT allele. There was also a strong significance in joint effects of gene and caffeine on PD risk (TC heavy caffeine vs. CC light caffeine: OR = 0.38, 95%CI = [0.20–0.70], p = 0.002) and gene-caffeine interaction (OR = 0.998, 95%CI = [0.991–0.999], p<0.001). Overall, our results are in support of the findings of the GWAIS and provided additional evidence indicating PD protective effects of coffee drinking/caffeine intake as well as the interaction with glutamate receptor genotypes.

The emerging role of dopamine-glutamate interaction and of the postsynaptic density in bipolar disorder pathophysiology: Implications for treatment

Aberrant synaptic plasticity, originating from abnormalities in dopamine and/or glutamate transduction pathways, may contribute to the complex clinical manifestations of bipolar disorder (BD). Dopamine and glutamate systems cross-talk at multiple levels, such as at the postsynaptic density (PSD). The PSD is a structural and functional protein mesh implicated in dopamine and glutamate-mediated synaptic plasticity. Proteins at PSD have been demonstrated to be involved in mood disorders pathophysiology and to be modulated by antipsychotics and mood stabilizers. On the other side, post-receptor effectors such as protein kinase B (Akt), glycogen synthase kinase-3 (GSK-3) and the extracellular signal-regulated kinase (Erk), which are implicated in both molecular abnormalities and treatment of BD, may interact with PSD proteins, and participate in the interplay of the dopamine-glutamate signalling pathway. In this review, we describe emerging evidence on the molecular cross-talk between dopamine and glutamate signalling in BD pathophysiology and pharmacological treatment, mainly focusing on dysfunctions in PSD molecules. We also aim to discuss future therapeutic strategies that could selectively target the PSD-mediated signalling cascade at the crossroads of dopamine-glutamate neurotransmission.

Analysis of variations in the glutamate receptor, N-methyl D-aspartate 2A (GRIN2A) gene reveals their relative importance as genetic susceptibility factors for heroin addiction

The glutamate receptor, N-methyl D-aspartate 2A (GRIN2A) gene that encodes the 2A subunit of the N-methyl D-aspartate (NMDA) receptor was recently shown to be involved in the development of opiate addiction. Genetic polymorphisms in GRIN2A have a plausible role in modulating the risk of heroin addiction. An association of GRIN2A single-nucleotide polymorphisms (SNPs) with heroin addiction was found earlier in African Americans. To identify markers that contribute to the genetic susceptibility to heroin addiction, we examined the potential association between heroin addiction and forty polymorphisms of the GRIN2A gene using the MassARRAY system and GeneScan in this study. The frequency of the (GT)26 repeats (rs3219790) in the heroin addiction group was significantly higher than that in the control group (χ² = 5.360, P = 0.021). The allele frequencies of three polymorphisms (rs1102972, rs1650420, and rs3104703 in intron 3) were strongly associated with heroin addiction (P<0.001, 0.0002, and <0.001, after Bonferroni correction). Three additional SNPs from the same intron (rs1071502, rs6497730, and rs1070487) had nominally significant P values for association (P<0.05), but did not pass the threshold value. Haplotype analysis revealed that the G-C-T-C-C-T-A (block 6) and T-T (block 10) haplotypes of the GRIN2A gene displayed a protective effect (P = <0.001 and 0.003). These findings point to a role for GRIN2A polymorphisms in heroin addiction among the Han Chinese from Shaanxi province, and may be informative for future genetic or neurobiological studies on heroin addiction.

Brain glutamate levels measured by magnetic resonance spectroscopy in patients with bipolar disorder: a meta-analysis

OBJECTIVES

Bipolar disorder (BD) is a common and highly disabling disease characterized by substantial cognitive and functional impairment. The exact neurobiological mechanisms underlying the expression of symptoms in this condition remain unknown but there is growing evidence that glutamate might play an important role. Using proton magnetic resonance spectroscopy (¹H-MRS), a number of studies have examined brain glutamate/glutamine levels in patients with bipolar disorder, but they have produced conflicting results. The objective of this paper was to conduct a systematic review and meta-analysis of the literature on brain glutamate/glutamine in BD as measured by ¹H-MRS.

METHODS

A Medline search for the period January 1980-April 2010 was conducted to identify published studies that used ¹H-MRS to measure glutamate + glutamine (Glx), the Glx/creatine (Cr) ratio, glutamate (Glu), or the Glu/Cr ratio in any brain region in adult or child/adolescent patients with BD and healthy subjects. A meta-analysis of the pooled data was conducted.

RESULTS

BD patients were found to have increased Glx compared to healthy subjects when all brain areas were combined. This finding remained true in medicated and non-medicated patients, and in frontal brain areas in adults. There was a non-significant trend (p = 0.09) for an increase in whole-brain Glx/Cr and Glu in patients compared with healthy subjects. No significant difference was found in Glu/Cr.

CONCLUSIONS

The results of this meta-analysis suggest that brain Glx levels are elevated in BD patients and support the idea that glutamate might play an important role in the pathophysiology of BD.

Association between a polymorphism in the promoter of a glutamate receptor subunit gene (GRIN2A) and alcoholism

A variable (GT)(n) repeat in the 5'-regulatory region of N-methyl-D-aspartate GRIN2A subtype has recently been identified and associated with psychiatric disorders. In this study, we examined the association of this polymorphism with alcohol dependence. Subject-control analysis included 206 alcohol-dependent and 168 control subjects. Average observed repeat numbers and genotype distributions were significantly different (P-value = 0.001) in alcohol-dependent subjects versus control subjects. Short alleles were significantly less frequent among alcohol-dependent subjects (odds ratio = 0.58, P-value = 7 × 10(-4)). These results could be replicated in an independent sample of 116 alcohol-dependent subjects. For the first time, a significant association was identified between this polymorphism and alcoholism.

Tandem repeat sequence variation as causative cis-eQTLs for protein-coding gene expression variation: the case of CSTB

Association studies have revealed expression quantitative trait loci (eQTLs) for a large number of genes. However, the causative variants that regulate gene expression levels are generally unknown. We hypothesized that copy-number variation of sequence repeats contribute to the expression variation of some genes. Our laboratory has previously identified that the rare expansion of a repeat c.-174CGGGGCGGGGCG in the promoter region of the CSTB gene causes a silencing of the gene, resulting in progressive myoclonus epilepsy. Here, we genotyped the repeat length and quantified CSTB expression by quantitative real-time polymerase chain reaction in 173 lymphoblastoid cell lines (LCLs) and fibroblast samples from the GenCord collection. The majority of alleles contain either two or three copies of this repeat. Independent analysis revealed that the c.-174CGGGGCGGGGCG repeat length is strongly associated with CSTB expression (P = 3.14 × 10(-11)) in LCLs only. Examination of both genotyped and imputed single-nucleotide polymorphisms (SNPs) within 2 Mb of CSTB revealed that the dodecamer repeat represents the strongest cis-eQTL for CSTB in LCLs. We conclude that the common two or three copy variation is likely the causative cis-eQTL for CSTB expression variation. More broadly, we propose that polymorphic tandem repeats may represent the causative variation of a fraction of cis-eQTLs in the genome.

Replication of ketamine's antidepressant efficacy in bipolar depression: a randomized controlled add-on trial

BACKGROUND

Currently, no pharmacological treatments for bipolar depression exist that exert rapid (within hours) antidepressant or antisuicidal effects. We previously reported that intravenous administration of the N-methyl-D-aspartate antagonist ketamine produced rapid antidepressant effects in patients with treatment-resistant bipolar depression. The present study sought to replicate this finding in an independent sample.

METHODS

In this double-blind, randomized, crossover, placebo-controlled study, 15 subjects with DSM-IV bipolar I or II depression maintained on therapeutic levels of lithium or valproate received a single intravenous infusion of either ketamine hydrochloride (.5 mg/kg) or placebo on 2 test days 2 weeks apart. The primary outcome measure was the Montgomery-Asberg Depression Rating Scale, which was used to rate overall depressive symptoms at baseline; at 40, 80, 110, and 230 minutes postinfusion; and on days 1, 2, 3, 7, 10, and 14 postinfusion.

RESULTS

Within 40 minutes, depressive symptoms, as well as suicidal ideation, significantly improved in subjects receiving ketamine compared with placebo (d = .89, 95% confidence interval = .61-1.16, and .98, 95% confidence interval = .64-1.33, respectively); this improvement remained significant through day 3. Seventy-nine percent of subjects responded to ketamine and 0% responded to placebo at some point during the trial. The most common side effect was dissociative symptoms, which occurred only at the 40-minute time point.

CONCLUSIONS

This study replicated our previous finding that patients with bipolar depression who received a single ketamine infusion experienced a rapid and robust antidepressant response. In addition, we found that ketamine rapidly improved suicidal ideation in these patients.

Expression profiling in neuropsychiatric disorders: emphasis on glutamate receptors in bipolar disorder

Functional genomics and proteomics approaches are being employed to evaluate gene and encoded protein expression changes with the tacit goal to find novel targets for drug discovery. Genome-wide association studies (GWAS) have attempted to identify valid candidate genes through single nucleotide polymorphism (SNP) analysis. Furthermore, microarray analysis of gene expression in brain regions and discrete cell populations has enabled the simultaneous quantitative assessment of relevant genes. The ability to associate gene expression changes with neuropsychiatric disorders, including bipolar disorder (BP), and their response to therapeutic drugs provides a novel means for pharmacotherapeutic interventions. This review summarizes gene and pathway targets that have been identified in GWAS studies and expression profiling of human postmortem brain in BP, with an emphasis on glutamate receptors (GluRs). Although functional genomic assessment of BP is in its infancy, results to date point towards a dysregulation of GluRs that bear some similarity to schizophrenia (SZ), although the pattern is complex, and likely to be more complementary than overlapping. The importance of single population expression profiling of specific neurons and intrinsic circuits is emphasized, as this approach provides informative gene expression profile data that may be underappreciated in regional studies with admixed neuronal and non-neuronal cell types.

Novel glutamatergic agents for major depressive disorder and bipolar disorder

Mood disorders such as major depressive disorder (MDD) and bipolar disorder (BPD) are common, chronic, recurrent mental illnesses that affect the lives and functioning of millions of individuals worldwide. Growing evidence suggests that the glutamatergic system is central to the neurobiology and treatment of these disorders. Here, we review data supporting the involvement of the glutamatergic system in the pathophysiology of mood disorders as well as the efficacy of glutamatergic agents as novel therapeutics.

Glutamatergic modulators: the future of treating mood disorders?

Mood disorders such as bipolar disorder and major depressive disorder are common, chronic, and recurrent conditions affecting millions of individuals worldwide. Existing antidepressants and mood stabilizers used to treat these disorders are insufficient for many. Patients continue to have low remission rates, delayed onset of action, residual subsyndromal symptoms, and relapses. New therapeutic agents able to exert faster and sustained antidepressant or mood-stabilizing effects are urgently needed to treat these disorders. In this context, the glutamatergic system has been implicated in the pathophysiology of mood disorders in unique clinical and neurobiological ways. In addition to evidence confirming the role of the glutamatergic modulators riluzole and ketamine as proof-of-concept agents in this system, trials with diverse glutamatergic modulators are under way. Overall, this system holds considerable promise for developing the next generation of novel therapeutics for the treatment of bipolar disorder and major depressive disorder.

Increased excitotoxicity and neuroinflammatory markers in postmortem frontal cortex from bipolar disorder patients

Reports of cognitive decline, symptom worsening and brain atrophy in bipolar disorder (BD) suggest that the disease progresses over time. The worsening neuropathology may involve excitotoxicity and neuroinflammation. We determined protein and mRNA levels of excitotoxicity and neuroinflammatory markers in postmortem frontal cortex from 10 BD patients and 10 age-matched controls. The brain tissue was matched for age, postmortem interval and pH. The results indicated statistically significant lower protein and mRNA levels of the N-methyl-D-aspartate receptors, NR-1 and NR-3A, but significantly higher protein and mRNA levels of interleukin (IL)-1beta, the IL-1 receptor (IL-1R), myeloid differentiation factor 88, nuclear factor-kappa B subunits, and astroglial and microglial markers (glial fibrillary acidic protein, inducible nitric oxide synthase, c-fos and CD11b) in postmortem frontal cortex from BD compared with control subjects. There was no significant difference in mRNA levels of tumor necrosis factor alpha or neuronal nitric oxide synthase in the same region. These data show the presence of excitotoxicity and neuroinflammation in BD frontal cortex, with particular activation of the IL-R cascade. The changes may account for reported evidence of disease progression in BD and be a target for future therapy.

The association study of three FYN polymorphisms with prophylactic lithium response in bipolar patients

FYN belongs to the protein kinase family that phosphorylates NMDA receptor subunits, participating in the regulation of ion transmission and BDNF/TrkB signal transduction pathway. Lithium inhibits glutamatergic transmission via NMDA receptors, exerting neuroprotective effect against excitotoxicity. The aim of this study was to find possible association of three polymorphisms of FYN gene with prophylactic lithium response in the group of bipolar patients. We analyzed 101 bipolar patients treated with lithium carbonate for 5-27 years (mean 15 years). Twenty-four patients were identified as excellent lithium responders (ER), 51 patients as partial responders (PRs), and 26 patients were non-responders. Genotypes of the three analyzed polymorphisms were established by PCR-RFLP. Statistical analysis was done with Statistica. No significant differences in genotype distribution and allele frequencies were observed between T/G and A/G FYN polymorphisms and lithium response. We observed a trend toward association of TT genotype and T allele of T/C polymorphism with worse lithium response. The results of the study demonstrated only marginal association between FYN polymorphisms and prophylactic lithium response in bipolar patients. The results are discussed in light of our previous studies on FYN gene in bipolar illness and BDNF gene in lithium response.

The role of the tripartite glutamatergic synapse in the pathophysiology and therapeutics of mood disorders

Bipolar disorder and major depressive disorder are common, chronic, and recurrent mood disorders that affect the lives of millions of individuals worldwide. Growing evidence suggests that glutamatergic system dysfunction is directly involved in mood disorders. This article describes the role of the "tripartite glutamatergic synapse," comprising presynaptic and postsynaptic neurons and glial cells, in the pathophysiology and therapeutics of mood disorders. Glutamatergic neurons and glia directly control synaptic and extrasynaptic glutamate levels/ release through integrative effects that target glutamate excitatory amino acid transporters, postsynaptic density proteins, ionotropic receptors (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid [AMPA], N-methyl-D-aspartate [NMDA], and kainate), and metabotropic receptors. This article also explores the glutamatergic modulators riluzole and ketamine, which are considered valuable proof-of-concept agents for developing the next generation of antidepressants and mood stabilizers. In therapeutically relevant paradigms, ketamine preferentially targets postsynaptic AMPA/NMDA receptors, and riluzole preferentially targets presynaptic voltage-operated channels and glia.

Genomic imprinting in the development and evolution of psychotic spectrum conditions

I review and evaluate genetic and genomic evidence salient to the hypothesis that the development and evolution of psychotic spectrum conditions have been mediated in part by alterations of imprinted genes expressed in the brain. Evidence from the genetics and genomics of schizophrenia, bipolar disorder, major depression, Prader-Willi syndrome, Klinefelter syndrome, and other neurogenetic conditions support the hypothesis that the etiologies of psychotic spectrum conditions commonly involve genetic and epigenetic imbalances in the effects of imprinted genes, with a bias towards increased relative effects from imprinted genes with maternal expression or other genes favouring maternal interests. By contrast, autistic spectrum conditions, including Kanner autism, Asperger syndrome, Rett syndrome, Turner syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome, commonly engender increased relative effects from paternally expressed imprinted genes, or reduced effects from genes favouring maternal interests. Imprinted-gene effects on the etiologies of autistic and psychotic spectrum conditions parallel the diametric effects of imprinted genes in placental and foetal development, in that psychotic spectrum conditions tend to be associated with undergrowth and relatively-slow brain development, whereas some autistic spectrum conditions involve brain and body overgrowth, especially in foetal development and early childhood. An important role for imprinted genes in the etiologies of psychotic and autistic spectrum conditions is consistent with neurodevelopmental models of these disorders, and with predictions from the conflict theory of genomic imprinting.

Replication of linkage with bipolar disorder on chromosome 16p in the Eastern Quebec population

In a previous study [Maziade et al. (2005); Mol Psychiatry 10:486-499], we provided evidence for linkage (parametric lod score of 4.05) on chromosome 16p for bipolar affective disorder (BP) in 21 kindreds from Eastern Quebec, a population characterized by a founder effect. Using a stringent design, we performed a replication study in a second sample of 27 kindreds (sample 2) collected from the same population and assessed with the same methodologies as in our original sample (sample 1), that is with the same diagnostic procedure and using a common set of 23 markers studied with model-based (parametric) and model-free (nonparametric) linkage analyses. We replicated our initial finding with P values <0.001. Indeed, maximum NPL(all) scores of 3.7 and 3.52 were found at marker D16S3060 in sample 2 for the narrow and broad BP phenotype definition, respectively. For the latter definition, the nonparametric score reached 3.87 in the combined sample, a value that exceeded the maximum NPL score obtained in each individual sample (NPL(all) = 2.32 in sample 1; NPL(all) = 3.52 in sample 2). Moreover, a refined phenotype restricted to BP associated with psychosis yielded significant evidence for linkage in each individual sample (NPL(all) = 2.38 in sample 1; NPL(all) = 2.72) while yielding the best result (NPL(all) score = 3.90) in the combined sample (samples 1 and 2), despite an important reduction in the number of affected individuals. It is also noteworthy that the use of the refined phenotype provided a location of the maximum linkage peak shared by both samples, that is, at marker D16S668 in 16p13.12, suggesting consistency across samples. Our study provided one of the strongest pieces of evidence for linkage with BP in 16p and illustrated the heuristic potential of a replication study in a second sample ascertained from the same population and using homogeneous methodologies.

The genetics of bipolar disorder: genome 'hot regions,' genes, new potential candidates and future directions

Bipolar disorder (BP) is a complex disorder caused by a number of liability genes interacting with the environment. In recent years, a large number of linkage and association studies have been conducted producing an extremely large number of findings often not replicated or partially replicated. Further, results from linkage and association studies are not always easily comparable. Unfortunately, at present a comprehensive coverage of available evidence is still lacking. In the present paper, we summarized results obtained from both linkage and association studies in BP. Further, we indicated new potential interesting genes, located in genome 'hot regions' for BP and being expressed in the brain. We reviewed published studies on the subject till December 2007. We precisely localized regions where positive linkage has been found, by the NCBI Map viewer (http://www.ncbi.nlm.nih.gov/mapview/); further, we identified genes located in interesting areas and expressed in the brain, by the Entrez gene, Unigene databases (http://www.ncbi.nlm.nih.gov/entrez/) and Human Protein Reference Database (http://www.hprd.org); these genes could be of interest in future investigations. The review of association studies gave interesting results, as a number of genes seem to be definitively involved in BP, such as SLC6A4, TPH2, DRD4, SLC6A3, DAOA, DTNBP1, NRG1, DISC1 and BDNF. A number of promising genes, which received independent confirmations, and genes that have to be further investigated in BP, have been also systematically listed. In conclusion, the combination of linkage and association approaches provided a number of liability genes. Nevertheless, other approaches are required to disentangle conflicting findings, such as gene interaction analyses, interaction with psychosocial and environmental factors and, finally, endophenotype investigations.

Chronic carbamazepine administration reduces N-methyl-D-aspartate receptor-initiated signaling via arachidonic acid in rat brain

BACKGROUND

Lithium and carbamazepine (CBZ) are used to treat mania in bipolar disorder. When given chronically to rats, both agents reduce arachidonic acid (AA) turnover in brain phospholipids and downstream AA metabolism. Lithium in rats also attenuates brain N-methyl-D-aspartic acid receptor (NMDAR) signaling via AA. We hypothesized that, like chronic lithium, chronic CBZ administration to rats would reduce NMDAR-mediated signaling via AA.

METHODS

We used our fatty acid method with quantitative autoradiography to image the regional brain incorporation coefficient k* of AA, a marker of AA signaling, in unanesthetized rats that had been given 25 mg/kg/day I.P. CBZ or vehicle for 30 days, then injected with NMDA (25 mg/kg I.P.) or saline. We also measured brain concentrations of two AA metabolites, prostaglandin E(2) (PGE(2)) and thromboxane B(2) (TXB(2)).

RESULTS

In chronic vehicle-treated rats, NMDA compared with saline increased k* significantly in 69 of 82 brain regions examined, but did not change k* significantly in any region in CBZ-treated rats. In vehicle- but not CBZ-treated rats, NMDA also increased brain concentrations of PGE(2) and TXB(2).

CONCLUSIONS

Chronic CBZ administration to rats blocks increments in the AA signal k*, and in PGE(2) and TXB(2) concentrations that are produced by NMDA in vehicle-treated rats. The clinical action of antimanic drugs might involve inhibition of brain NMDAR-mediated signaling involving AA and its metabolites.

Genetic susceptibility and development of chronic non-malignant back pain

Previous data indicate that persistent pain states often involve sensitization within the central nervous system (CNS). Many recently described human genetic variants may affect these central processes. Genetic variability influences both synthesis and function of proteins affecting the plasticity of the CNS. Hence, individual genetic variability may be important to understand the development of many persistent pain conditions including chronic nonmalignant back pain. In this review we argue that genotyping of each patient may be a valuable complement to diagnosis of back disorders. This may be important for future prescription of medicine to individuals predisposed for persistent pain. Increased understanding of genetic variability may also improve multidisciplinary and cognitive-behavioral approaches to management of persistent pain. Translation of this information from the laboratory into clinical application will be important for future prevention as well as treatment of long-lasting non-malignant pain conditions.

Linked gene ontology categories are novel and differ from associated gene ontology categories for the bipolar disorders

Family, and twin genetic studies strongly indicate gene variants as predisposing to the bipolar disorders. Now, about 3000 genes are genetically linked and about 44 genes are genetically associated. Rank differences, however, exist between the linked gene Genetic ontology categories and the associated gene Genetic ontology categories. For the linked gene Genetic ontology categories, the activation of NF-kappaB-inducing kinase category is over-represented; in contrast, the associated genes show the Synaptic transmission category as over-represented. Association studies report selecting positional candidate genes from previous linkage studies, or, selecting genes on the basis of pathophysiologic hypotheses. Only a few of the pathophysiologic hypotheses genes, however, had been previously linked to the bipolar disorders. In particular, only a couple of the Synaptic transmission genes had been previously linked to bipolar disorders.

Integrating Synapse Proteomics with Transcriptional Regulation

The mammalian postsynaptic proteome (PSP) comprises a highly interconnected set of approximately 1,000 proteins. The PSP is organized into macromolecular complexes that have a modular architecture defined by protein interactions and function. Signals initiated by neurotransmitter receptors are integrated by these complexes and their constituent enzymes to orchestrate multiple downstream cellular changes, including transcriptional regulation of genes at the nucleus. Genome wide transcriptome studies are beginning to map the sets of genes regulated by the synapse proteome. Conversely, understanding the transcriptional regulation of genes encoding the synapse proteome will shed light on synapse formation. Mutations that disrupt synapse signalling complexes result in cognitive impairments in mice and humans, and recent evidence indicates that these mutation change gene expression profiles. We discuss the need for global approaches combining genetics, transcriptomics and proteomics in order to understand cognitive function and disruption in diseases.

Chronic lithium chloride administration attenuates brain NMDA receptor-initiated signaling via arachidonic acid in unanesthetized rats

It has been proposed that lithium is effective in bipolar disorder (BD) by inhibiting glutamatergic neurotransmission, particularly via N-methyl-D-aspartate receptors (NMDARs). To test this hypothesis and to see if the neurotransmission could involve the NMDAR-mediated activation of phospholipase A2 (PLA2), to release arachidonic acid (AA) from membrane phospholipid, we administered subconvulsant doses of NMDA to unanesthetized rats fed a chronic control or LiCl diet. We used quantitative autoradiography following the intravenous injection of radiolabeled AA to measure regional brain incorporation coefficients k* for AA, which reflect receptor-mediated activation of PLA2. In control diet rats, NMDA (25 and 50 mg/kg i.p.) compared with i.p. saline increased k* significantly in 49 and 67 regions, respectively, of the 83 brain regions examined. The regions affected were those with reported NMDARs, including the neocortex, hippocampus, caudate-putamen, thalamus, substantia nigra, and nucleus accumbens. The increases could be blocked by pretreatment with the specific noncompetitive NMDA antagonist MK-801 ((5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate) (0.3 mg/kg i.p.), as well by a 6-week LiCl diet sufficient to produce plasma and brain lithium concentrations known to be effective in BD. MK-801 alone reduced baseline values for k* in many brain regions. The results show that it is possible to image NMDA signaling via PLA2 activation and AA release in vivo, and that chronic lithium blocks this signaling, consistent with its suggested mechanism of action in BD.

Regulation of murine TGFbeta2 by Pax3 during early embryonic development

Previously our laboratory identified TGFbeta2 as a potential downstream target of Pax3 by utilizing microarray analysis and promoter data base mining (Mayanil, C. S. K., George, D., Freilich, L., Miljan, E. J., Mania-Farnell, B. J., McLone, D. G., and Bremer, E. G. (2001) J. Biol. Chem. 276, 49299-49309). Here we report that Pax3 directly regulates TGFbeta2 transcription by binding to cis-regulatory elements within its promoter. Chromatin immunoprecipitation revealed that Pax3 bound to the cis-regulatory elements on the TGFbeta2 promoter (GenBanktrade mark accession number AF118263). Both TGFbeta2 promoter-luciferase activity measurements in transient cotransfection experiments and electromobility shift assays supported the idea that Pax3 regulates TGFbeta2 by directly binding to its cis-regulatory regions. Additionally, by using a combination of co-immunoprecipitation and chromatin immunoprecipitation, we show that the TGFbeta2 cis-regulatory elements between bp 741-940 and bp 1012-1212 bind acetylated Pax3 and are associated with p300/CBP and histone deacetylases. The cis-regulatory elements between bp 741 and 940 in addition to associating with acetylated Pax3 and HDAC1 also associated with SIRT1. Whole mount in situ hybridization and quantitative real time reverse transcription-PCR showed diminished levels of TGFbeta2 transcripts in Pax3(-/-) mouse embryos (whose phenotype is characterized by neural tube defects) as compared with Pax3(+/+) littermates (embryonic day 10.0; 30 somite stage), suggesting that Pax3 regulation of TGFbeta2 may play a pivotal role during early embryonic development.

Molecular genetics of bipolar disorder

Bipolar disorder (BPD) is an often devastating illness characterized by extreme mood dysregulation. Although family, twin and adoption studies consistently indicate a strong genetic component, specific genes that contribute to the illness remain unclear. This study gives an overview of linkage studies of BPD, concluding that the regions with the best evidence for linkage include areas on chromosomes 2p, 4p, 4q, 6q, 8q, 11p, 12q, 13q, 16p, 16q, 18p, 18q, 21q, 22q and Xq. Association studies are summarized, which support a possible role for numerous candidate genes in BPD including COMT, DAT, HTR4, DRD4, DRD2, HTR2A, 5-HTT, the G72/G30 complex, DISC1, P2RX7, MAOA and BDNF. Animal models related to bipolar illness are also reviewed, with special attention paid to those with clear genetic implications. We conclude with suggestions for strategies that may help clarify the genetic bases of this complex illness.

Genetic tests of biologic systems in affective disorders

To liberate candidate gene analyses from criticisms of inexhaustiveness of examination of specific candidate genes, or incompleteness in the choice of candidate genes to study for specific neurobiological pathways, study of sizeable sets of genes pertinent to each putative pathophysiological pathway is required. For many years, genes have been tested in a 'one by one' manner for association with major affective disorders, primarily bipolar illness. However, it is conceivable that not individual genes but abnormalities in several genes within a system or in several neuronal, neural, or hormonal systems are implicated in the functional hypotheses for etiology of affective disorders. Compilation of candidate genes for entire pathways is a challenge, but can reasonably be carried out for the major affective disorders as discussed here. We present here five groupings of genes implicated by neuropharmacological and other evidence, which suggest 252 candidate genes worth examining. Inexhaustiveness of gene interrogation would apply to many studies in which only one polymorphism per gene is analyzed. In contrast to whole-genome association studies, a study of a limited number of candidate genes can readily exploit information on genomic sequence variations obtained from databases and/or resequencing, and has an advantage of not having the complication of an extremely stringent statistical criterion for association.

Extended analyses support the association of a functional (GT)n polymorphism in the GRIN2A promoter with Japanese schizophrenia

Dysfunction of the N-methyl-D-aspartate (NMDA) type glutamate receptor has been proposed as a mechanism in the etiology of schizophrenia. Recently, we identified a variable (GT)n repeat in the promoter region of the NMDA NR2A subunit gene (GRIN2A), and showed its association with schizophrenia in a case-control study, together with a correlation between the length of the repeat and severity of chronic outcome. In this study, we extended our analyses, by increasing the number of case-control samples to a total of 672 schizophrenics and 686 controls, and excluded potential sample stratification effects. We confirmed the significant allelic association between the repeat polymorphism and disease (P = 0.011), and as in the previous study, we observed an over-representation of longer alleles in schizophrenia. These results suggest a probable genetic effect for the GRIN2A promoter (GT)n variation on the predisposition to schizophrenia in Japanese cohorts.