Meta-analysis of the association between the monoamine oxidase-A gene and mood disorders

Good parent-child relationship protects against alcohol use in maltreated adolescent females carrying the MAOA-uVNTR susceptibility allele

Introduction

Risk-allele carriers of a Monoamine oxidase A (MAOA) gene, short-allele (MAOA-S) in males and long-allele (MAOA-L) in females, in the presence of a negative environment, are associated with alcohol misuse. Whether MAOA-S/L alleles also present susceptibility to a positive environment to mitigate the risk of alcohol misuse is unknown. Thus, we assessed the association of the three-way interaction of MAOA, maltreatment, and positive parent-child relationship with alcohol consumption among adolescents.

Methods

This prospective study included 1416 adolescents (females: 59.88%) aged 16 - 19 years from Sweden, enrolled in the "Survey of Adolescent Life in Västmanland" in 2012. Adolescents self-reported alcohol consumption, maltreatment by a family (FM) or non-family member (NFM), parent-child relationship, and left saliva for MAOA genotyping.

Results and discussion

We observed sex-dependent results. Females carrying MAOA-L with FM or NFM and a good parent-child relationship reported lower alcohol consumption than those with an average or poor parent-child relationship. In males, the interactions were not significant. Results suggest MAOA-L in females, conventionally regarded as a "risk", is a "plasticity" allele as it is differentially susceptible to negative and positive environments. Results highlight the importance of a good parent-child relationship in mitigating the risk of alcohol misuse in maltreated individuals carrying genetic risk. However, the interactions were not significant after adjusting to several environmental and behavioural covariates, especially parent's alcohol use, negative parent-child relationship, and nicotine use (smoking and/or snus), suggesting predictor and outcome intersection. Future studies and frameworks for preventive strategies should consider these covariates together with alcohol consumption. More studies with larger sample sizes are needed to replicate the findings.

Associations of Germline Genetic Variants With Depression and Fatigue Among Hematologic Cancer Patients Treated With Allogeneic Hematopoietic Cell Transplantation

OBJECTIVE

Depression and fatigue are common among cancer patients and are associated with germline genetic variation. The goal of this pilot study was to examine genetic associations with depression and fatigue in the year after allogeneic hematopoietic cell transplant (HCT).

METHODS

Blood was collected from patients and their donors before HCT. Patients completed self-report measures of depression and fatigue before HCT (T1), 90 days post-HCT (T2), and 1 year post-HCT (T3). Of the 384 genetic variants genotyped on a custom Illumina BeadChip microarray, 267 were retained for analysis based on quality control. Main effects of patient and donor variants as well as their interaction were examined using regression analyses. Significant variants were defined as those with a false discovery rate-adjusted p value of <.05.

RESULTS

The sample consisted of 59 patient-donor pairs. Mean levels of depression and fatigue did not change significantly over time ( p values of > .41). Increases in depression from T1 to T2 were associated with patient-donor interactions at rs1928040 ( p = 3.0 × 10 -4 ) and rs6311 ( p = 2.0 × 10 -4 ) in HTR2A . Increases in fatigue from T1 to T2 were associated with patient rs689021 in SORL1 ( p = 6.0 × 10 -5 ) and a patient-donor interaction at rs1885884 in HTR2A ( p < 1.0 × 10 -4 ).

CONCLUSIONS

Data suggest that variants in genes regulating the serotonergic system ( HTR2A ) and lipid metabolism ( SORL1 ) are associated with changes in depression and fatigue in allogeneic HCT patients, implicating patients' own genetic inheritance as well as that of donors. Additional studies are warranted to confirm these findings.

The relationship of maternal rank, 5-HTTLPR genotype, and MAOA-LPR genotype to temperament in infant rhesus monkeys (Macaca mulatta)

Temperament is a construct whose manifestations are quantifiable from an early age, and whose origins have been proposed as "biological." Our goal was to determine whether maternal rank and infant genotype are associated with five measures of temperament in 3- to 4-month old rhesus monkeys (Macaca mulatta), all of whom were born and reared by their mothers in large, outdoor, half-acre cages. Maternal rank was defined as the proportion of animals outranked by each female, and the two genes of interest to us were monoamine oxidase and serotonin transporter, both of which are polymorphic in their promoter regions (MAOA-LPR and 5-HTTLPR, respectively), with one allele of each gene considered a "plasticity" allele, conferring increased sensitivity to environmental events. Our large sample size (n = 2014-3140) enabled us to examine the effects of individual genotypes rather than combining genotypes as is often done. Rank was positively associated with Confident temperament, but only for animals with the 5-repeat allele for MAOA-LPR. Rank had no other effect on temperament. In contrast, genotype had many different effects, with 5-HTTLPR associated with behavioral inhibition, and MAOA-LPR associated with ratings-based measures of temperament. We also examined the joint effect of the two genotypes and found some evidence for a dose-response: animals with the plasticity alleles for both genes were more likely to be behaviorally inhibited. Our results suggest phenotypic differences between animals possessing alleles for MAOA-LPR that show functional equivalence based on in vitro tests, and our data for 5-HTTLPR revealed differences between short/short homozygotes and long/short heterozygotes, strongly suggesting that combining genotypes for statistical analysis should be avoided if possible. Our analysis also provides evidence of sex differences in temperament, and, to our knowledge, the only evidence of differences in temperament based on specific pathogen-free status. We suggest several directions for future research.

Familial coaggregation of major psychiatric disorders in first-degree relatives of individuals with autism spectrum disorder: a nationwide population-based study

BACKGROUND

Family coaggregation of attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), bipolar disorder (BD), major depressive disorder (MDD) and schizophrenia have been presented in previous studies. The shared genetic and environmental factors among psychiatric disorders remain elusive.

METHODS

This nationwide population-based study examined familial coaggregation of major psychiatric disorders in first-degree relatives (FDRs) of individuals with ASD. Taiwan's National Health Insurance Research Database was used to identify 26 667 individuals with ASD and 67 998 FDRs of individuals with ASD. The cohort was matched in 1:4 ratio to 271 992 controls. The relative risks (RRs) and 95% confidence intervals (CI) of ADHD, ASD, BD, MDD and schizophrenia were assessed among FDRs of individuals with ASD and ASD with intellectual disability (ASD-ID).

RESULTS

FDRs of individuals with ASD have higher RRs of major psychiatric disorders compared with controls: ASD 17.46 (CI 15.50-19.67), ADHD 3.94 (CI 3.72-4.17), schizophrenia 3.05 (CI 2.74-3.40), BD 2.22 (CI 1.98-2.48) and MDD 1.88 (CI 1.76-2.00). Higher RRs of schizophrenia (4.47, CI 3.95-5.06) and ASD (18.54, CI 16.18-21.23) were observed in FDRs of individuals with both ASD-ID, compared with ASD only.

CONCLUSIONS

The risk for major psychiatric disorders was consistently elevated across all types of FDRs of individuals with ASD. FDRs of individuals with ASD-ID are at further higher risk for ASD and schizophrenia. Our results provide leads for future investigation of shared etiologic pathways of ASD, ID and major psychiatric disorders and highlight the importance of mental health care delivered to at-risk families for early diagnoses and interventions.

Gene expression analysis of MAOA and the clock gene ARNTL in individuals with bipolar disorder compared to healthy controls

INTRODUCTION

Circadian rhythms are associated with bipolar disorder (BD). This cross-sectional study aimed at investigating ARNTL and MAOA gene expression differences (1) between individuals with BD and controls, (2) between affective episodes, and (3) the relationship between ARNTL and MAOA expression.

METHODS

ARNTL and MAOA gene expression in peripheral mononuclear blood cells were analysed from fasting blood samples (BD n =  81, controls n = 54) with quantitative real-time PCR operating on TaqMan® assays (normalised to 18S RNA expression). ANCOVAs corrected for age, sex, body mass index, and medication was used to evaluate expression differences and correlation analyses for the relation between ARNTL and MAOA expression.

RESULTS

ARNTL gene expression differed between affective episodes (F(2,78) = 3.198, p = 0.047, Partial Eta2= 0.083), but not between BD and controls (n.s.). ARNTL and MAOA expression correlated positively in BD (r = 0.704, p < 0.001) and in controls (r = 0.932, p < 0.001). MAOA expression differed neither between BD and controls nor between affective episodes (n.s.).

DISCUSSION

Clock gene expression changes were observed in different affective states of BD. More precisely, ARNTL gene expression was significantly higher in euthymia than in depression. ARNTL and MAOA gene expression correlated significantly in BD and in controls, which emphasises the strong concatenation between circadian rhythms and neurotransmitter breakdown.

Knowledge of Biobehavioral Organization Can Facilitate Better Science: A Review of the BioBehavioral Assessment Program at the California National Primate Research Center

Animals vary on intrinsic characteristics such as temperament and stress responsiveness, and this information can be useful to experimentalists for identifying more homogeneous subsets of animals that show consistency in risk for a particular research outcome. Such information can also be useful for balancing experimental groups, ensuring animals within an experiment have similar characteristics. In this review, we describe the BioBehavioral Assessment Program at the California National Primate Research Center, which, since its inception in 2001, has been providing quantitative information on intrinsic characteristics to scientists for subject selection and balancing, and to colony management staff for management purposes. We describe the program and review studies relating to asthma, autism, behavioral inhibition, etc., where the BBA Program was used to select animals. We also review our work, showing that factors such as rearing, ketamine exposure, and prenatal experience can affect biobehavioral organization in ways that some investigators might want to control for in their studies. Attention to intrinsic characteristics of subject populations is consistent with the growing interest in precision medicine and can lead to a reduction in animal numbers, savings in time and money for investigators, and reduced distress for the animals.

Therapy response prediction in major depressive disorder: current and novel genomic markers influencing pharmacokinetics and pharmacodynamics

Major depressive disorder is connected with high rates of functional disability and mortality. About a third of the patients are at risk of therapy failure. Several pharmacogenetic markers especially located in CYP450 genes such as CYP2D6 or CYP2C19 are of relevance for therapy outcome prediction in major depressive disorder but a further optimization of predictive tools is warranted. The article summarizes the current knowledge on pharmacogenetic variants, therapy effects and side effects of important antidepressive therapeutics, and sheds light on new methodological approaches for therapy response estimation based on genetic markers with relevance for pharmacokinetics, pharmacodynamics and disease pathology identified in genome-wide association study analyses, highlighting polygenic risk score analysis as a tool for further optimization of individualized therapy outcome prediction.

Association of variable number of tandem repeats (VNTR) and T941G polymorphism of monoamine oxidase (MAO-A) gene with aggression in Pakistani subjects

Background

Human behavioral traits are known to be significantly heritable. Certain individuals have a greater tendency of negative behavioral aspects including aggression. The quest to identify tunderlying genetic causes has led to identification of a number of genetic markers, one of them is the monoamine oxidase-A (MAO-A) gene.

Objective

We aimed to genotype a variable number of tandem repeats (VNTRs) in the promoter region and a functional SNP within this gene (T941G, dbSNP ID: rs6323) in the recruited cohort of 482 subjects.

Methods

After DNA isolation, genotyping was done by PCR-RFLP and the results were confirmed by sequencing.

Results

For VNTRs, the results showed, highest frequency of 3.5 repeats in males and 4 repeats in females in the promoter region. The genotype frequencies for the SNP in cases were GG=16.3%, TG=20.6% and TT=63.1%, while in controls, the frequencies were GG=12.7%, TG=6.3%, and TT=81.0%. The allele frequencies were significantly different between cases and controls (p=0.015; OR=1.51; CI=1.085–2.102).

Conclusion

The selected VNTR and SNP appeared to be significantly associated with aggression. These VNTRs and SNP have not been studied previously in the Pakistani population, hence they represent a unique ethnic group. These results, however, would have to be replicated in larger cohorts.

Association Between OLIG2 Gene SNP rs1059004 and Negative Self-Schema Constructing Trait Factors Underlying Susceptibility to Depression

Recent evidence has indicated that the disruption of oligodendrocytes may be involved in the pathogenesis of depression. Genetic factors are likely to affect trait factors, such as characteristics, rather than state factors, such as depressive symptoms. Previously, a negative self-schema had been proposed as the major characteristic of constructing trait factors underlying susceptibility to depression. Thus, the association between a negative self-schema and the functional single nucleotide polymorphism (SNP) rs1059004 in the OLIG2 gene, which influences OLIG2 gene expression, white matter integrity, and cerebral blood flow, was evaluated. A total of 546 healthy subjects were subjected to genotype and psychological evaluation using the Beck Depression Inventory-II (BDI-II) and the Brief Core Schema Scale (BCSS). The rs1059004 SNP was found to be associated with the self-schema subscales of the BCSS and scores on the BDI-II in an allele dose-dependent manner, and to have a predictive impact on depressive symptoms via a negative-self schema. The results suggest the involvement of a genetic factor regulating oligodendrocyte function in generating a negative-self schema as a trait factor underlying susceptibility to depression.

Enhancing and Complementary Mechanisms of Synergistic Action of Acori Tatarinowii Rhizoma and Codonopsis Radix for Alzheimer's Disease Based on Systems Pharmacology

Materials and Methods

In this study, a systems pharmacology-based strategy was used to elucidate the synergistic mechanism of Acori Tatarinowii Rhizoma and Codonopsis Radix for the treatment of AD. This novel systems pharmacology model consisted of component information, pharmacokinetic analysis, and pharmacological data. Additionally, the related pathways were compressed using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and the organ distributions were determined in the BioGPS bank.

Results

Sixty-eight active ingredients with suitable pharmacokinetic profiles and biological activities were selected through ADME screening in silico. Based on 62 AD-related targets, such as APP, CHRM1, and PTGS1, systematic analysis showed that these two herbs were mainly involved in the PI3K-Akt signaling pathway, MAPK signaling pathway, neuroactive ligand-receptor interaction, and fluid shear stress and atherosclerosis, indicating that they had a synergistic effect on AD. However, ATR acted on the KDR gene, while CR acted on IGF1R, MET, IL1B, and CHUK, showing that they also had complementary effects on AD. The ingredient contribution score involved 29 ingredients contributing 90.14% of the total contribution score of this formula for AD treatment, which emphasized that the effective therapeutic effects of these herbs for AD were derived from both ATR and CR, not a single herb. Organ distribution showed that the targets of the active ingredients were mainly located in the whole blood, the brain, and the muscle, which are associated with AD.

Conclusions

In sum, our findings suggest that the systems pharmacology methods successfully revealed the synergistic and complementary mechanisms of ATR and CR for the treatment of AD.

The MAOA Gene Influences the Neural Response to Psychosocial Stress in the Human Brain

The stress response is regulated by many mechanisms. Monoamine oxidase A (MAOA) has been related to many mental illnesses. However, few studies have explored the relationship between MAOA and acute laboratory-induced psychosocial stress with functional magnetic resonance imaging (fMRI). In the current study, the Montreal Imaging Stress Task (MIST) and fMRI were used to investigate how MAOA influences the stress response. Increased cortisol concentrations were observed after the task; functional connectivity between the bilateral anterior hippocampus and other brain regions was reduced during stress. MAOA-H allele carriers showed greater deactivation of the right anterior hippocampus and greater cortisol response after stress than did MAOH-L allele carriers. Hippocampal deactivation may lead to disinhibition of the hypothalamic-pituitary-adrenal (HPA) axis and the initiation of stress hormone release under stress. Our results suggest that the MAOA gene regulates the stress response by influencing the right anterior hippocampus.

Genetics of resilience: Implications from genome-wide association studies and candidate genes of the stress response system in posttraumatic stress disorder and depression

Resilience is the ability to cope with critical situations through the use of personal and socially mediated resources. Since a lack of resilience increases the risk of developing stress-related psychiatric disorders such as posttraumatic stress disorder (PTSD) and major depressive disorder (MDD), a better understanding of the biological background is of great value to provide better prevention and treatment options. Resilience is undeniably influenced by genetic factors, but very little is known about the exact underlying mechanisms. A recently published genome-wide association study (GWAS) on resilience has identified three new susceptibility loci, DCLK2, KLHL36, and SLC15A5. Further interesting results can be found in association analyses of gene variants of the stress response system, which is closely related to resilience, and PTSD and MDD. Several promising genes, such as the COMT (catechol-O-methyltransferase) gene, the serotonin transporter gene (SLC6A4), and neuropeptide Y (NPY) suggest gene × environment interaction between genetic variants, childhood adversity, and the occurrence of PTSD and MDD, indicating an impact of these genes on resilience. GWAS on PTSD and MDD provide another approach to identifying new disease-associated loci and, although the functional significance for disease development for most of these risk genes is still unknown, they are potential candidates due to the overlap of stress-related psychiatric disorders and resilience. In the future, it will be important for genetic studies to focus more on resilience than on pathological phenotypes, to develop reasonable concepts for measuring resilience, and to establish international cooperations to generate sufficiently large samples.

Parenting Practices and Adolescent Effortful Control: MAOA T941G Gene Polymorphism as a Moderator

Effortful control (EC) plays a crucial role in psychopathology disorders. Emerging studies have paid attention to the effects of G × E interaction on EC. The present study investigated interactions between monoamine oxidase A (MAOA) T941G polymorphism with parenting practices on EC in a sample of 1,531 Chinese adolescents. The adolescents completed the Early Adolescent Temperament Questionnaire-Revised (EATQ-R) EC scale and the Parenting Style Index provided during the study to assess EC and parenting practices, respectively. MAOA T941G polymorphism exerted no effect on adolescent EC; however, results revealed that the MAOA gene interacted with parental acceptance/involvement in their associations with EC among boys. Specifically, although increased levels of parental acceptance/involvement benefited all adolescents, boys with G alleles of the MAOA gene exhibited higher sensitivity to parental acceptance/involvement, compared with T carriers; this interaction was not significant among girls. This study is the first to identify MAOA × parenting interaction on adolescent EC, further contributing to the literature in MAOA gene-EC.

MAOA-VNTR genotype affects structural and functional connectivity in distributed brain networks

Previous studies have linked the low expression variant of a variable number of tandem repeat polymorphism in the monoamine oxidase A gene (MAOA‐L) to the risk for impulsivity and aggression, brain developmental abnormalities, altered cortico‐limbic circuit function, and an exaggerated neural serotonergic tone. However, the neurobiological effects of this variant on human brain network architecture are incompletely understood. We studied healthy individuals and used multimodal neuroimaging (sample size range: 219–284 across modalities) and network‐based statistics (NBS) to probe the specificity of MAOA‐L‐related connectomic alterations to cortical‐limbic circuits and the emotion processing domain. We assessed the spatial distribution of affected links across several neuroimaging tasks and data modalities to identify potential alterations in network architecture. Our results revealed a distributed network of node links with a significantly increased connectivity in MAOA‐L carriers compared to the carriers of the high expression (H) variant. The hyperconnectivity phenotype primarily consisted of between‐lobe (“anisocoupled”) network links and showed a pronounced involvement of frontal‐temporal connections. Hyperconnectivity was observed across functional magnetic resonance imaging (fMRI) of implicit emotion processing (p_FWE = .037), resting‐state fMRI (p_FWE = .022), and diffusion tensor imaging (p_FWE = .044) data, while no effects were seen in fMRI data of another cognitive domain, that is, spatial working memory (p_FWE = .540). These observations are in line with prior research on the MAOA‐L variant and complement these existing data by novel insights into the specificity and spatial distribution of the neurogenetic effects. Our work highlights the value of multimodal network connectomic approaches for imaging genetics.

Distinct chromatin structures at the monoamine oxidase-A promoter correlate with allele-specific expression in SH-SY5Y cells

Monoamine oxidase-A (MAOA) metabolises monoamines and is implicated in the pathophysiology of psychiatric disorders. A polymorphic repetitive DNA domain, termed the uVNTR (upstream variable number tandem repeat), located at the promoter of the MAOA gene is a risk factor for many of these disorders. MAOA is on the X chromosome suggesting gender could play a role in regulation. We analysed MAOA regulation in the human female cell line, SH-SY5Y, which is polymorphic for the uVNTR. This heterozygosity allowed us to correlate allele-specific gene expression with allele-specific transcription factor binding and epigenetic marks for MAOA. Gene regulation was analysed under basal conditions and in response to the mood stabiliser sodium valproate. Both alleles were transcriptionally active under basal growth conditions; however, the alleles showed distinct transcription factor binding and epigenetic marks at their respective promoters. Exposure of the cells to sodium valproate resulted in differential allelic expression which correlated with allele-specific changes in distinct transcription factor binding and epigenetic marks at the region encompassing the uVNTR. Biochemically our model for MAOA promoter function has implications for gender differences in gene × environment responses in which the uVNTR has been implicated as a genetic risk.

[Postpartum depression: association with genetic polymorphisms of noradrenaline metabolic enzymes and the risk factors]

OBJECTIVE

To investigate the association of genetic polymorphisms of norepinephrine metabolizing enzymes with postpartum depression and analyze the risk factors for postpartum depression in women following cesarean section.

METHODS

A total of 591 Chinese woman of Han Nationality undergoing caesarean section were enrolled in this study. The diagnosis of postpartum depression was established for an Edinburgh Postnatal Depression Scale (EPDS) score ≥9. For all the women without antepartum depression, the genotypes of catechol-O-methyltransferase (COMT; at 5 sites including rs2020917 and rs737865) and monoamine oxidase A (rs6323) were determined using Sequenom^? Mass Array single nucleotide polymorphism (SNP) analysis. We analyzed the contribution of the genetic factors (SNPs, linkage disequilibrium and haplotype) to postpartum depression and performed logistic regression analysis to identify all the potential risk factors for postpartum depression and define the interactions between the genetic and environmental factors.

RESULTS

The incidence of postpartum depression was 18.1% in this cohort. Univariate analysis suggested that COMT polymorphism at rs2020917 (TT genotype) and rs737865 (GG genotype) were significantly correlated with the occurrence of postpartum depression (P &lt; 0.05). Logistic regression analysis showed that COMT polymorphism at rs2020917 (TT genotype) and rs737865 (GG genotype), severe stress during pregnancy, and domestic violence were the risk factors for postpartum depression (P &lt; 0.05); no obvious interaction was found between the genetic polymorphisms and the environmental factors in the occurrence of postpartum depression.

CONCLUSIONS

The rs2020917TT and rs737865GG genotypes of COMT, stress in pregnancy, and domestic violence are the risk factors for postpartum depression.

Dysmorphic contribution of neurotransmitter and neuroendocrine system polymorphisms to subtherapeutic mood states

OBJECTIVE

From an evolutionary perspective, emotions emerged as rapid adaptive reactions that increase survival rates. Current psychobiology includes the consideration that genetic changes affecting neuroendocrine and neurotransmission pathways may also be affecting mood states. Following this hypothesis, abnormal levels of any of the aminergic neurotransmitters would be of considerable importance in the development of a pathophysiological state.

MATERIALS AND METHODS

A total of 668 students from the School of Medicine of the University of Malaga (Average = 22.41 ± 3; 41% men) provided self-report measures of mood states using POMS and GHQ-28 questionnaires and buccal cells for genotyping 19 polymorphisms from 14 selected neurotransmitter pathways genes (HTR1A; HTR2A; HTR2C; HTR3B; TPH1; SLC18A1; SLC18A2; COMT; MAOA; MAOB) and neuroendocrine system (AVPR1B; OPRM1; BDNF; OXTR).

RESULTS

MAOA rs3788862 genotype correlates with decreasing levels of Tension among females (beta = -0.168, p-value = 0.003) but it is neutral among males in this subscale. On the contrary, it correlates with lower GHQ-28 depression scores among males (beta = -0.196, p-value = 0.008). Equivalently, SLC18A1 and HTR2A variants correlated with anger and vigor scores, only among males. From the neuroendocrine system, OPRM1 rs1799971 correlated increasing levels of female's Anxiety, depression and Social Dysfunction scores.

CONCLUSION

Our findings suggest that these polymorphisms contribute to define general population mood levels, although exhibiting a clear sexual dimorphism.

Type A monoamine oxidase and serotonin are coordinately involved in depressive disorders: from neurotransmitter imbalance to impaired neurogenesis

Type A monoamine oxidase (MAOA) catabolizes monoamine transmitters, serotonin, norepinephrine and dopamine, and plays a major role in the onset, progression and therapy of neuropsychiatric disorders. In depressive disorders, increase in MAOA expression and decrease in brain levels of serotonin and norepinephrine are proposed as the major pathogenic factors. The functional polymorphism of MAOA gene and genes in serotonin signal pathway are associated with depression. This review presents recent advance in studies on the role of MAOA in major depressive disorder and related emotional disorders. MAOA and serotonin regulate the prenatal development and postnatal maintenance of brain architecture and neurocircuit, as shown by MAOA-deficient humans and MAO knockout animal models. Impaired neurogenesis in the mature hippocampus has been proposed as "adult neurogenesis" hypothesis of depression. MAOA modulates the sensitivity to stress in the stages of brain development and maturation, and the interaction of gene-environmental factors in the early stage regulates the onset of depressive behaviors in adulthood. Vice versa environmental factors affect MAOA expression by epigenetic regulation. MAO inhibitors not only restore compromised neurotransmitters, but also protect neurons from cell death in depression through induction of anti-apoptotic Bcl-2 and prosurvival neurotrophic factors, especially brain-derived neurotrophic factor, the deficiency of which is detected in depression. This review discusses novel role of MAOA and serotonin in the pathogenesis and therapy of depressive disorders.

The interactive effect of the MAOA-VNTR genotype and childhood abuse on aggressive behaviors in Chinese male adolescents

OBJECTIVE

Gene-environment interactions that moderate aggressive behavior have been identified in association with the MAOA (monoamine oxidase A) gene. The present study examined the moderating effect of MAOA-VNTR (variable number of tandem repeats) on aggression behavior relating to child abuse among Chinese adolescents.

MATERIALS AND METHODS

A sample of 507 healthy Chinese male adolescents completed the Child Trauma Questionnaire-Short Form (CTQ-SF) and Youth Self-report of the Child Behavior Checklist. The participants' buccal cells were sampled and subjected to DNA analysis. The effects of childhood abuse (CTQ-SF scores), MAOA-VNTR [high-activity allele (H) versus low-activity allele (L)], and their interaction in aggressive behaviors were analyzed by linear regression.

RESULTS

Child maltreatment was found to be a significant independent factor in the manifestation of aggressive behavior, whereas MAOA activity was not. There was a significant interaction between MAOA-VNTR and childhood maltreatment in the exhibition of aggressive behaviors. In the context of physical or emotional abuse, boys in the MAOA-L group showed a greater tendency toward aggression than those in the MAOA-H group.

CONCLUSION

Aggressive behavior arising from childhood maltreatment is moderated by MAOA-VNTR, which may be differentially sensitive to the subtype of childhood maltreatment experienced, among Chinese adolescents.

Regulation of emotional response in juvenile monkeys treated with fluoxetine: MAOA interactions

Juvenile male rhesus macaques received therapeutic doses of fluoxetine daily from one to three years of age and were compared to vehicle-treated controls (N=16/group). Genotyping for monoamine oxidase A (MAOA) polymorphisms was used to form subgroups (N=8) with high and low expression of the gene. Behavioral responses were scored during 30-second exposures to pictures differing in affective content. As expected from its therapeutic effect, fluoxetine decreased the behavioral response to emotionally evocative pictures. A 44% reduction in number of expressive behaviors was seen, but only in subjects with low expression MAOA polymorphisms. In general, this effect occurred for pictures of varying affective content and was not due to altered occurrence of one specific behavior or type of behavior. The drug*genotype interaction was seen after one and two years of treatment and did not reverse one year after discontinuation of dosing. Two potential translational implications are suggested: (1) MAOA genetic polymorphisms may be the source of some of the variability in response to fluoxetine treatment in children; (2) extended fluoxetine treatment during juvenile brain development may result in persistent effects on emotional regulation.

High-resolution chromosome ideogram representation of recognized genes for bipolar disorder

Bipolar disorder (BPD) is genetically heterogeneous with a growing list of BPD associated genes reported in recent years resulting from increased genetic testing using advanced genetic technology, expanded genomic databases, and better awareness of the disorder. We compiled a master list of recognized susceptibility and genes associated with BPD identified from peer-reviewed medical literature sources using PubMed and by searching online databases, such as OMIM. Searched keywords were related to bipolar disorder and genetics. Our compiled list consisted of 290 genes with gene names arranged in alphabetical order in tabular form with source documents and their chromosome location and gene symbols plotted on high-resolution human chromosome ideograms. The identified genes impacted a broad range of biological pathways and processes including cellular signaling pathways particularly cAMP and calcium (e.g., CACNA1C, CAMK2A, CAMK2D, ADCY1, ADCY2); glutamatergic (e.g., GRIK1, GRM3, GRM7), dopaminergic (e.g., DRD2, DRD4, COMT, MAOA) and serotonergic (e.g., HTR1A, HTR2A, HTR3B) neurotransmission; molecular transporters (e.g., SLC39A3, SLC6A3, SLC8A1); and neuronal growth (e.g., BDNF, IGFBP1, NRG1, NRG3). The increasing prevalence of BPD calls for better understanding of the genetic etiology of this disorder and associations between the observed BPD phenotype and genes. Visual representation of genes for bipolar disorder becomes a tool enabling clinical and laboratory geneticists, genetic counselors, and other health care providers and researchers easy access to the location and distribution of currently recognized BPD associated genes. Our study may also help inform diagnosis and advance treatment developments for those affected with this disorder and improve genetic counseling for families.

Biological mechanisms underlying evolutionary origins of psychotic and mood disorders

Psychotic and mood disorders are brain dysfunctions that are caused by gene environment interactions. Although these disorders are disadvantageous and involve behavioral phenotypes that decrease the reproductive success of afflicted individuals in the modern human society, the prevalence of these disorders have remained constant in the population. Here, we propose several biological mechanisms by which the genes associated with psychotic and mood disorders could be selected for in specific environmental conditions that provide evolutionary bases for explanations of when, why, and where these disorders emerged and have been maintained in humans. We discuss the evolutionary origins of psychotic and mood disorders with specific focuses on the roles of dopamine and serotonin in the conditions of social competitiveness/hierarchy and maternal care and other potential mechanisms, such as social network homophily and symbiosis.

A review of genetic alterations in the serotonin pathway and their correlation with psychotic diseases and response to atypical antipsychotics

Serotonin is a neurotransmitter that plays a predominant role in mood regulation. The importance of the serotonin pathway in controlling behavior and mental status is well recognized. All the serotonin elements - serotonin receptors, serotonin transporter, tryptophan hydroxylase and monoamine oxidase proteins - can show alterations in terms of mRNA or protein levels and protein sequence, in schizophrenia and bipolar disorder. Additionally, when examining the genes sequences of all serotonin elements, several single nucleotide polymorphisms (SNPs) have been found to be more prevalent in schizophrenic or bipolar patients than in healthy individuals. Several of these alterations have been associated either with different phenotypes between patients and healthy individuals or with the response of psychiatric patients to the treatment with atypical antipsychotics. The complex pattern of genetic diversity within the serotonin pathway hampers efforts to identify the key variations contributing to an individual's susceptibility to the disease. In this review article, we summarize all genetic alterations found across the serotonin pathway, we provide information on whether and how they affect schizophrenia or bipolar disorder phenotypes, and, on the contribution of familial relationships on their detection frequencies. Furthermore, we provide evidence on whether and how specific gene polymorphisms affect the outcome of schizophrenic or bipolar patients of different ethnic groups, in response to treatment with atypical antipsychotics. All data are discussed thoroughly, providing prospective for future studies.

MAOA Variants and Genetic Susceptibility to Major Psychiatric Disorders

Monoamine oxidase A (MAOA) is a mitochondrial enzyme involved in the metabolism of several biological amines such as dopamine, norepinephrine, and serotonin, which are important neurochemicals in the pathogenesis of major psychiatric illnesses. MAOA is regarded as a functional plausible susceptibility gene for psychiatric disorders, whereas previous hypothesis-driven association studies obtained controversial results, a reflection of small sample size, genetic heterogeneity, or true negative associations. In addition, MAOA is not analyzed in most of genome-wide association studies (GWAS) on psychiatric disorders, since it is located on Chromosome Xp11.3. Therefore, the effects of MAOA variants on genetic predisposition to psychiatric disorders remain obscure. To fill this gap, we collected psychiatric phenotypic (schizophrenia, bipolar disorder, and major depressive disorder) and genetic data in up to 18,824 individuals from diverse ethnic groups. We employed classical fixed (or random) effects inverse variance weighted methods to calculate summary odds ratios (OR) and 95 % confidence intervals (CI). We identified a synonymous SNP rs1137070 showing significant associations with major depressive disorder (p = 0.00067, OR = 1.263 for T allele) and schizophrenia (p = 0.0039, OR = 1.225 for T allele) as well as a broad spectrum of psychiatric phenotype (p = 0.000066, OR = 1.218 for T allele) in both males and females. The effect size was similar between different ethnic populations and different gender groups. Collectively, we confirmed that MAOA is a risk gene for psychiatric disorders, and our results provide useful information toward a better understanding of genetic mechanism involving MAOA underlying risk of complex psychiatric disorders.

Molecular mechanism of monoamine oxidase A gene regulation under inflammation and ischemia-like conditions: key roles of the transcription factors GATA2, Sp1 and TBP

Monoamine oxidase A (MAOA) plays important roles in the pathogenesis of several neurological and cardiovascular disorders. The mechanism of transcriptional regulation of MAOA under basal and pathological conditions, however, remains incompletely understood. Here, we report systematic identification and characterization of cis elements and transcription factors that govern the expression of MAOA gene. Extensive computational analysis of MAOA promoter, followed by 5'-promoter deletion/reporter assays, revealed that the -71/-40 bp domain was sufficient for its basal transcription. Gel-shift and chromatin immunoprecipitation assays provided evidence of interactions of the transcription factors GATA-binding protein 2 (GATA2), Sp1 and TATA-binding protein (TBP) with this proximal promoter region. Consistently, over-expression of GATA2, Sp1 and TBP augmented MAOA promoter activity in a coordinated manner. In corroboration, siRNA-mediated down-regulation of GATA2/Sp1/TBP repressed the endogenous MAOA expression as well as transfected MAOA promoter activity. Tumor necrosis factor-α and forskolin activated MAOA transcription that was reversed by Sp1 siRNA; in support, tumor necrosis factor-α- and forskolin-induced activities were enhanced by ectopic over-expression of Sp1. On the other hand, MAOA transcription was diminished upon exposure of neuroblasts or cardiac myoblasts to ischemia-like conditions because of reduced binding of GATA2/Sp1/TBP with MAOA promoter. In conclusion, this study revealed previously unknown roles of GATA2, Sp1 and TBP in modulating MAOA expression under basal as well as pathophysiological conditions such as inflammation and ischemia, thus providing new insights into the molecular basis of aberrant MAOA expression in neuronal/cardiovascular disease states. Dysregulation of monoamine oxidase A (MAOA) have been implicated in several behavioral and neuronal disease states. Here, we identified three crucial transcription factors (GATA2, Sp1 and TBP) that regulate MAOA gene expression in a coordinated manner. Aberrant MAOA expression under pathophysiological conditions including inflammation and ischemia is mediated by altered binding of GATA2/Sp1/TBP with MAOA proximal promoter. Thus, these findings provide new insights into pathogenesis of several common diseases. GATA2, GATA-binding protein 2; Sp1, specificity protein 1; TBP, TATA-binding protein.

Evidence revealing deregulation of the KLF11-MAO A pathway in association with chronic stress and depressive disorders

The biochemical pathways underlying major depressive disorder (MDD) and chronic stress are not well understood. However, it has been reported that monoamine oxidase A (MAO A, a major neurotransmitter-degrading enzyme) is significantly increased in the brains of human subjects affected with MDD and rats exposed to chronic social defeat (CSD) stress, which is used to model depression. In the current study, we compared the protein levels of a MAO A-transcriptional activator, Kruppel-like factor 11 (KLF11 , also recognized as transforming growth factor-beta-inducible early gene 2) between the brains of 18 human subjects with MDD and 18 control subjects. We found that, indeed, the expression of KLF11 is increased by 36% (p<0.02) in the postmortem prefrontal cortex of human subjects with MDD compared with controls. We also observed a positive correlation between KLF11 levels and those of its target gene, MAO A, both in association with MDD. KLF11 protein expression was also increased by 44% (p<0.02) in the frontal cortex of KLF11 wild-type mice (Klf11(+/+)) vs Klf11(-/-) when both exposed to CSD stress. In contrast, locomotor activities, central box duration and sucrose preference were significantly reduced in the stressed Klf11(+/+) mice, suggesting that Klf11(+/+) mice are more severely affected by the stress model compared with Klf11(-/-) mice. These results serve to assign an important role of KLF11 in upregulating MAO A in MDD and chronic social stress, suggesting that inhibition of the pathways regulated by this transcription factor may aid in the therapeutics of neuropsychiatric illnesses. Thus, the new knowledge derived from the current study extends our understanding of transcriptional mechanisms that are operational in the pathophysiology of common human diseases and thus bears significant biomedical relevance.

Hypersomnia in Mood Disorders: a Rapidly Changing Landscape

Hypersomnia is commonly comorbid with depressive illness and is associated with treatment resistance, symptomatic relapse, and functional impairment. This review highlights recent changes in nosological classifications of hypersomnia. In addition, emergent findings regarding the neurobiologic underpinnings, assessment, and treatment of hypersomnia in mood disorders are reviewed, as well as the effects of hypersomnolence on illness course. Future strategies for research are proposed that may elucidate the causes of hypersomnia in mood disorders and lead to the development of improved diagnostic and therapeutic strategies.

Biomarker approaches in major depressive disorder evaluated in the context of current hypotheses

Major depressive disorder is a heterogeneous disorder, mostly diagnosed on the basis of symptomatic criteria alone. It would be of great help when specific biomarkers for various subtypes and symptom clusters of depression become available to assist in diagnosis and subtyping of depression, and to enable monitoring and prognosis of treatment response. However, currently known biomarkers do not reach sufficient sensitivity and specificity, and often the relation to underlying pathophysiology is unclear. In this review, we evaluate various biomarker approaches in terms of scientific merit and clinical applicability. Finally, we discuss how combined biomarker approaches in both preclinical and clinical studies can help to make the connection between the clinical manifestations of depression and the underlying pathophysiology.

Monoamine oxidase a gene polymorphisms and bipolar disorder in Iranian population

BACKGROUND

Bipolar disorder (BPD) is a common and severe mood disorder. Although genetic factors have important rolesin the etiology of bipolar disorder, no specific gene has been identified in relation to this disorder. Monoamine oxidase gene is suggested to be associated with bipolar disorder in many studies.

OBJECTIVES

This study aimed to investigatethe role of MAOA gene polymorphisms in the etiology of bipolar disorder in Iranian population.

PATIENTS AND METHODS

This study is a case-control study, with convenient sampling. Three common polymorphisms, a CA microsatellite, a VNTR, and a RFLP were typed in 156 bipolar patients and 173 healthy controls. Patients were chosen from Imam Hossein General Hospital, Psychiatry Ward (Tehran/Iran). Controlsamples for this study consisted of 173 healthy individuals recruitedby convenient sampling. Allelic distributions of these polymorphisms were analyzed in bipolar and control groups to investigate any association with MAOA gene.

RESULTS

Significant associations were observed regarding MAOA-CA (P = 0.016) and MAOA-VNTR (P = 0.004) polymorphisms in the bipolar females. There was no association between MAOA-RFLP and bipolar disorder.

CONCLUSIONS

The obtained results confirm some previous studies regardinga gender specific association of MAOA gene with the bipolar disorder.

Specific and common genes implicated across major mental disorders: a review of meta-analysis studies

Major efforts have been directed at family-based association and case-control studies to identify the involvement of candidate genes in the major disorders of mental health. What remains unknown is whether candidate genes are associated with multiple disorders via pleiotropic mechanisms, and/or if other genes are specific to susceptibility for individual disorders. Here we undertook a review of genes that have been identified in prior meta-analyses examining specific genes and specific mental disorders that have core disruptions to emotional and cognitive function and contribute most to burden of illness- major depressive disorder (MDD), anxiety disorders (AD, including panic disorder and obsessive compulsive disorder), schizophrenia (SZ) and bipolar disorder (BD) and attention deficit hyperactivity disorder (ADHD). A literature review was conducted up to end-March 2013 which included a total of 1519 meta-analyses across 157 studies reporting multiple genes implicated in one or more of the five disorders studied. A total of 134 genes (206 variants) were identified as significantly associated risk variants for MDD, AD, ADHD, SZ or BD. Null genetic effects were also reported for 195 genes (426 variants). 13 genetic variants were shared in common between two or more disorders (APOE e4, ACE Ins/Del, BDNF Val66Met, COMT Val158Met, DAOA G72/G30 rs3918342, DAT1 40-bp, DRD4 48-bp, SLC6A4 5-HTTLPR, HTR1A C1019G, MTHR C677T, MTHR A1298C, SLC6A4 VNTR and TPH1 218A/C) demonstrating evidence for pleiotrophy. Another 12 meta-analyses of GWAS studies of the same disorders were identified, with no overlap in genetic variants reported. This review highlights the progress that is being made in identifying shared and unique genetic mechanisms that contribute to the risk of developing several major psychiatric disorders, and identifies further steps for progress.

Androgen receptor and monoamine oxidase polymorphism in wild bonobos

Androgen receptor gene (AR), monoamine oxidase A gene (MAOA) and monoamine oxidase B gene (MAOB) have been found to have associations with behavioral traits, such as aggressiveness, and disorders in humans. However, the extent to which similar genetic effects might influence the behavior of wild apes is unclear. We examined the loci AR glutamine repeat (ARQ), AR glycine repeat (ARG), MAOA intron 2 dinucleotide repeat (MAin2) and MAOB intron 2 dinucleotide repeat (MBin2) in 32 wild bonobos, Pan paniscus, and compared them with those of chimpanzees, Pan troglodytes, and humans. We found that bonobos were polymorphic on the four loci examined. Both loci MAin2 and MBin2 in bonobos showed a higher diversity than in chimpanzees. Because monoamine oxidase influences aggressiveness, the differences between the polymorphisms of MAin2 and MBin2 in bonobos and chimpanzees may be associated with the differences in aggression between the two species. In order to understand the evolution of these loci and AR, MAOA and MAOB in humans and non-human primates, it would be useful to conduct future studies focusing on the potential association between aggressiveness, and other personality traits, and polymorphisms documented in bonobos.

Monoamine polygenic liability in health and cocaine dependence: imaging genetics study of aversive processing and associations with depression symptomatology

BACKGROUND

Gene polymorphisms that affect serotonin signaling modulate reactivity to salient stimuli and risk for emotional disturbances. Here, we hypothesized that these serotonin genes, which have been primarily explored in depressive disorders, could also have important implications for drug addiction, with the potential to reveal important insights into drug symptomatology, severity, and/or possible sequelae such as dysphoria.

METHODS

Using an imaging genetics approach, the current study tested in 62 cocaine abusers and 57 healthy controls the separate and combined effects of variations in the serotonin transporter (5-HTTLPR) and monoamine oxidase A (MAOA) genes on processing of aversive information. Reactivity to standardized unpleasant images was indexed by a psychophysiological marker of stimulus salience (i.e., the late positive potential (LPP) component of the event-related potential) during passive picture viewing. Depressive symptomatology was assessed with the Beck Depression Inventory (BDI).

RESULTS

Results showed that, independent of diagnosis, the highest unpleasant LPPs emerged in individuals with MAOA-Low and at least one 'Short' allele of 5-HTTLPR. Uniquely in the cocaine participants with these two risk variants, higher unpleasant LPPs correlated with higher BDI scores.

CONCLUSIONS

Taken together, these results suggest that a multilocus genetic composite of monoamine signaling relates to depression symptomatology through brain function associated with the experience of negative emotions. This research lays the groundwork for future studies that can investigate clinical outcomes and/or pharmacogenetic therapies in drug addiction and potentially other psychopathologies of emotion dysregulation.

Testing for association of the monoamine oxidase A promoter polymorphism with brain structure volumes in both autism and the fragile X syndrome

BACKGROUND

Autism and the fragile X syndrome (FXS) are related to each other genetically and symptomatically. A cardinal biological feature of both disorders is abnormalities of cerebral cortical brain volumes. We have previously shown that the monoamine oxidase A (MAOA) promoter polymorphism is associated with cerebral cortical volumes in children with autism, and we now sought to determine whether the association was also present in children with FXS.

METHODS

Participants included 47 2-year-old Caucasian boys with FXS, some of whom also had autism, as well as 34 2-year-old boys with idiopathic autism analyzed in a previous study. The MAOA promoter polymorphism was genotyped and tested for relationships with gray and white matter volumes of the cerebral cortical lobes and cerebro-spinal fluid volume of the lateral ventricles.

RESULTS

MAOA genotype effects in FXS children were the same as those previously observed in idiopathic autism: the low activity MAOA promoter polymorphism allele was associated with increased gray and white matter volumes in all cerebral lobes. The effect was most pronounced in frontal lobe gray matter and all three white matter regions: frontal gray, F = 4.39, P = 0.04; frontal white, F = 5.71, P = 0.02; temporal white, F = 4.73, P = 0.04; parieto-occipital white, F = 5.00, P = 0.03. Analysis of combined FXS and idiopathic autism samples produced P values for these regions <0.01 and effect sizes of approximately 0.10.

CONCLUSIONS

The MAOA promoter polymorphism is similarly associated with brain structure volumes in both idiopathic autism and FXS. These data illuminate a number of important aspects of autism and FXS heritability: a genetic effect on a core biological trait of illness, the specificity/generalizability of the genetic effect, and the utility of examining individual genetic effects on the background of a single gene disorder such as FXS.

Investigation of association of serotonin transporter and monoamine oxidase-A genes with Alzheimer's disease and depression in the VITA study cohort: a 90-month longitudinal study

Alzheimer's disease (AD) and depression (DE) are common psychiatric disorders strongly intertwined with one another. Nevertheless, etiology and early diagnosis of the disorders are still elusive. Several genetic variations have been suggested to associate with AD and DE, particularly in genes involved in the serotonergic system such as the serotonin transporter (SERT/SLC6A4), responsible for the removal from the synaptic cleft, and the monoamine-oxidase-A (MAOA), responsible for the presynaptic degradation of serotonin. Here, we attempt to characterize this pleiotropic effect for the triallelic SERT gene-linked polymorphic region (5HTTLPR) and for the MAOA-uVNTR, in participants in the Vienna-Transdanube-Aging (VITA)-study. The VITA-study is a community-based longitudinal study following a birth cohort (75 years old at baseline examination, n = 606) from Vienna for a period of 90 months with a regular follow-up interval of 30 months. Our main finding, confirming previous reports, is that the 5HTTLPR S-allele is a risk allele for DE (OR = 1.55 CI 95% 1.03-2.32) and its carriers had a steeper increase in SGDS sum score. No association to AD was found. MAOA-uVNTR did not associate with either AD or DE. However, in AD MAOA-uVNTR S-allele carriers a steeper increase of HAMD and STAI1 sum scores (P < 0.05) was observed. Although the VITA-study cohort is rather small with low power to detect gene alterations, the uniqueness of this very thoroughly investigated and homogenous cohort strengthens the results through exceptional data collection. Still, reinvestigation in a larger cohort similar to this, as well as a meta-analysis, is important to confirm these results.

Nonparametric tests of associations with disease based on U-statistics

In case-control studies, association analysis was designed to test whether genetic variants were associated with human diseases. To evaluate the association, analysing one genetic marker at a time suffered from weak power, because of the correction for multiple testing and possibly small genetic effects. An alternative strategy was to test simultaneous effects of multiple markers, which was believed to be more powerful. However, when the number of markers under investigation was large, they would be subjected to weak power as well, because of the greater degrees of freedom. To conquer these limitations in case-control studies, we proposed a novel method that could test joint association of several loci (i.e. haplotype), with only a single degree of freedom. In this research, we developed a nonparametric approach, which was based on U-statistics. We also introduced a new kernel for U-statistic, which could combine the haplotype structure information, and was expected to enhance the power. Simulations indicated that our proposed approach offered merits in identifying the associations between diseases and haplotypes. Application of our method to a study of candidate genes for internalising disorder illustrated its virtue in utility and interpretation, and provided an excellent result in detecting the associations.

A neuroscientific update on monoamine oxidase and its inhibitors

The goal of this brief review is to explain the role of monoamine oxidase enzymes in the neurobiology, etiology, and presentation of psychiatric illnesses, primarily major depressive disorder. This article will initially focus on the basic science and function of the monoamine oxidase system and some proposed neuropsychiatric symptoms that may arise if this enzyme system is altered by genetic predisposition. These findings and theories will next be translationally discussed in regard to clinical application pertaining to enzyme inhibition and the treatment of major depressive and other psychiatric disorders.

Gene environment interaction studies in depression and suicidal behavior: An update

Increasing evidence supports the involvement of both heritable and environmental risk factors in major depression (MD) and suicidal behavior (SB). Studies investigating gene-environment interaction (G × E) may be useful for elucidating the role of biological mechanisms in the risk for mental disorders. In the present paper, we review the literature regarding the interaction between genes modulating brain functions and stressful life events in the etiology of MD and SB and discuss their potential added benefit compared to genetic studies only. Within the context of G × E investigation, thus far, only a few reliable results have been obtained, although some genes have consistently shown interactive effects with environmental risk in MD and, to a lesser extent, in SB. Further investigation is required to disentangle the direct and mediated effects that are common or specific to MD and SB. Since traditional G × E studies overall suffer from important methodological limitations, further effort is required to develop novel methodological strategies with an interdisciplinary approach.

Towards translational rodent models of depression

Rodent models of depression have been developed in an effort to identify novel antidepressant compounds and to further our understanding of the pathophysiology of depression. Various rodent models of depression and antidepressant-like behaviour are currently used but, clearly, none of these current models fully recapitulate all features of depression. Moreover, these models have not resulted in the development of novel non-monoaminergic-based antidepressants with clinical efficacy. Thus, a refinement of the current models of depression is required. The present review outlines the most commonly used models of depression and antidepressant drug-like activity and suggests several factors that should be considered when refining these models.

FMR1, circadian genes and depression: suggestive associations or false discovery?

Background

There are several indications that malfunctions of the circadian clock contribute to depression. To search for particular circadian gene polymorphisms associated with depression, diverse polymorphisms were genotyped in two samples covering a range of depressed volunteers and participants with normal mood.

Methods

Depression mood self-ratings and DNA were collected independently from a sample of patients presenting to a sleep disorders center (1086 of European origin) and from a separate sample consisting of 399 participants claiming delayed sleep phase symptoms and 406 partly-matched controls. A custom Illumina Golden Gate array of 768 selected single nucleotide polymorphisms (SNPs) was assayed in both samples, supplemented by additional SNPlex and Taqman assays, including assay of 41 ancestry-associated markers (AIMs) to control stratification.

Results

In the Sleep Clinic sample, these assays yielded Bonferroni-significant association with depressed mood in three linked SNPs of the gene FMR1: rs25702 (nominal P=1.77E-05), rs25714 (P=1.83E-05), and rs28900 (P=5.24E-05). This FMR1 association was supported by 8 SNPs with nominal significance and a nominally-significant gene-wise set test. There was no association of depressed mood with FMR1 in the delayed sleep phase case–control sample or in downloaded GWAS data from the GenRED 2 sample contrasting an early-onset recurrent depression sample with controls. No replication was located in other GWAS studies of depression. Our data did weakly replicate a previously-reported association of depression with PPARGC1B rs7732671 (P=0.0235). Suggestive associations not meeting strict criteria for multiple testing and replication were found with GSK3B, NPAS2, RORA, PER3, CRY1, MTNR1A and NR1D1. Notably, 16 SNPs nominally associated with depressed mood (14 in GSK3B) were also nominally associated with delayed sleep phase syndrome (P=3E10^-6).

Conclusions

Considering the inconsistencies between samples and the likelihood that the significant three FMR1 SNPs might be linked to complex polymorphisms more functionally related to depression, large gene resequencing studies may be needed to clarify the import for depression of these circadian genes.

Psychopathology and the human connectome: toward a transdiagnostic model of risk for mental illness

The panoply of cognitive, affective, motivational, and social functions that underpin everyday human experience requires precisely choreographed patterns of interaction between networked brain regions. Perhaps not surprisingly, diverse forms of psychopathology are characterized by breakdowns in these interregional relationships. Here, we discuss how functional brain imaging has provided insights into the nature of brain dysconnectivity in mental illness. Synthesizing work to date, we propose that genetic and environmental risk factors impinge upon systems-level circuits for several core dimensions of cognition, producing transdiagnostic symptoms. We argue that risk-associated disruption of these circuits mediates susceptibility to broad domains of psychopathology rather than discrete disorders.

Novel therapeutic targets in depression: minocycline as a candidate treatment

Mood disorders are marked by high rates of non-recovery, recurrence, and chronicity, which are insufficiently addressed by current therapies. Several patho-etiological models have been proposed that are not mutually exclusive and include but are not limited to the monoamine, inflammatory, neurotrophic, gliotrophic, excitatory, and oxidative stress systems. A derivative of these observations is that treatment(s) which target one or more of these mechanistic steps may be capable of mitigating, or preventing, disparate psychopathological features. Minocycline is an agent with pleiotropic properties that targets multiple proteins and cellular processes implicated in the patho-etiology of mood disorders. Moreover, preclinical and preliminary clinical evidence suggests that minocycline possesses antidepressant properties. Herein, we provide the rationale for conducting a randomized, controlled trial to test the antidepressant properties of minocycline.

Major depressive disorder: new clinical, neurobiological, and treatment perspectives

In this Seminar we discuss developments from the past 5 years in the diagnosis, neurobiology, and treatment of major depressive disorder. For diagnosis, psychiatric and medical comorbidity have been emphasised as important factors in improving the appropriate assessment and management of depression. Advances in neurobiology have also increased, and we aim to indicate genetic, molecular, and neuroimaging studies that are relevant for assessment and treatment selection of this disorder. Further studies of depression-specific psychotherapies, the continued application of antidepressants, the development of new treatment compounds, and the status of new somatic treatments are also discussed. We address two treatment-related issues: suicide risk with selective serotonin reuptake inhibitors, and the safety of antidepressants in pregnancy. Although clear advances have been made, no fully satisfactory treatments for major depression are available.

Association of DRD2 gene polymorphisms with mood disorders: a meta-analysis

BACKGROUND

In the past few decades, a number of studies have investigated the association of dopamine D2 receptor (DRD2) gene polymorphisms with mood disorders, but the findings are not always consistent. The aim of our study was to assess the association between DRD2 gene polymorphisms and mood disorders by using a meta-analysis.

METHODS

Data were collected from the following electronic databases: PubMed, Elsevier Science Direct, Cochrane Library, Chinese Biomedical Literature Database, China National Knowledge Infrastructure, and Wanfang, with the last report up to June 2010. Meta-analysis was performed in a fixed/random effect model by using the software Review Manager 4.2.

RESULTS

We identified 19 separate studies using search, but only 14 separate studies (2157 cases and 3272 controls) were included in the current study. Meta-analysis was performed for three DRD2 gene polymorphisms (-141Cins/del, Ser311/Cys311, and TaqI A1). We performed meta-analysis in overall, Caucasian, and Asian populations. We also performed disease-specific meta-analysis in unipolar disorder and bipolar disorder. We found no association between DRD2 gene -141Cins/del polymorphism and mood disorders in overall and Caucasian populations (P>0.05). We also found no association between DRD2 gene Ser311/Cys311 polymorphism and mood disorders in overall, Caucasian, and Asian populations (P>0.05). An association of DRD2 gene TaqI A1 polymorphism with mood disorders was found in overall population, and the individuals with A1A1 genotype were more susceptible to mood disorders in comparison to those with A2A1 and A2A2 genotypes (OR=1.84, 95% CI=1.07-3.17, P=0.03).

LIMITATION

Meta-analysis is retrospective research that is subject to the methodological deficiencies of the included studies.

CONCLUSION

This meta-analysis suggests that mood disorders may be associated with DRD2 gene TaqI A1 polymorphism, but not -141Cins/del and Ser311/Cys311.