Genome-wide association study of temperament in bipolar disorder reveals significant associations with three novel Loci

Synthesising 30 years of clinical experience and scientific insight on affective temperaments in psychiatric disorders: State of the art

The concept of affective temperament has been extensively discussed throughout the history of psychopathology and represents a cornerstone in the study of mood disorders. This review aims to trace the evolution of the concept of affective temperaments (ATs) from Kraepelin's seminal work to the present day. In the 1980s, Akiskal redefined Kraepelin's concept of affective temperaments (ATs) by integrating the five recognized ATs into the broader framework of the soft bipolar spectrum. This conceptualization viewed ATs as non-pathological predispositions underlying psychiatric disorders, particularly mood disorders. Epidemiological and clinical studies have validated the existence of the five ATs. Furthermore, evidence suggests that ATs may serve as precursors to various psychiatric disorders and influence clinical dimensions such as disease course, psychopathology, and treatment adherence. Additionally, ATs appear to play a significant role in moderating phenomena such as suicide risk and stress coping. Incorporating an evaluation of temperamental bases of disorders into the multidimensional psychiatric diagnostic process could enhance treatment optimization and prognosis estimation.

The Expression of Affective Temperaments in Cystic Fibrosis Patients: Psychopathological Associations and Possible Neurobiological Mechanisms

The aim of this study was to investigate the association between Cystic Fibrosis (CF) and affective temperaments, considering the relevance of ionic balances in neural excitability, as a possible neurobiological basis for temperamental expression. A cross-sectional study involving 55 adult CF patients was conducted. Sociodemographic, clinical and therapeutic characteristics, temperamental and personality dispositions and depressive and anxiety symptoms were evaluated through standardized semi-structured and structured interviews. The majority of the enrolled CF patients were receiving Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) therapy (72.7%), and most of them had hyperthymic temperament predominance (29.1%). Different TEMPS-A (Temperament Evaluation of Memphis, Pisa, Paris, and San Diego Autoquestionnaire) dimensions were not associated with the type of CF phenotype-related mutation or with the use of CFTR-modulator therapy. However, a tendency towards irritability was noted in patients not undergoing CFTR modulator therapy (6.7 ± 4.72 vs. 4.7 ± 4.33; p = 0.13). In light of the limitations imposed by the cross-sectional nature of the study, a hyperthymic temperament was found to be protective against current or lifetime psychopathologic events, whereas the other temperaments were associated with positive psychopathological anamnesis. Based on the measurement of temperament profiles and the study of their associations with clinically relevant variables, we argue that subjecting CF patients to such a temperament assessment could prove beneficial in the transition towards integrated and personalized care.

A genome-wide association study of tinnitus reveals shared genetic links to neuropsychiatric disorders

Tinnitus, a phantom perception of sound in the absence of any external sound source, is a prevalent health condition often accompanied by psychiatric comorbidities. Recent genome-wide association studies (GWAS) highlighted a polygenic nature of tinnitus susceptibility. A shared genetic component between tinnitus and psychiatric conditions remains elusive. Here we present a GWAS using the UK Biobank to investigate the genetic processes linked to tinnitus and tinnitus-related distress, followed by gene-set enrichment analyses. The UK Biobank sample comprised 132,438 individuals with tinnitus and genotype data. Among the study sample, 38,525 individuals reported tinnitus, and 26,889 participants mentioned they experienced tinnitus-related distress in daily living. The genome-wide association analyses were conducted on tinnitus and tinnitus-related distress. We conducted enrichment analyses using FUMA to further understand the genetic processes linked to tinnitus and tinnitus-related distress. A genome-wide significant locus (lead SNP: rs71595470) for tinnitus was obtained in the vicinity of GPM6A. Nineteen independent loci reached suggestive association with tinnitus. Fifteen independent loci reached suggestive association with tinnitus-related distress. The enrichment analysis revealed a shared genetic component between tinnitus and psychiatric traits, such as bipolar disorder, feeling worried, cognitive ability, fast beta electroencephalogram, and sensation seeking. Metabolic, cardiovascular, hematological, and pharmacological gene sets revealed a significant association with tinnitus. Anxiety and stress-related gene sets revealed a significant association with tinnitus-related distress. The GWAS signals for tinnitus were enriched in the hippocampus and cortex, and for tinnitus-related distress were enriched in the brain and spinal cord. This study provides novel insights into genetic processes associated with tinnitus and tinnitus-related distress and demonstrates a shared genetic component underlying tinnitus and psychiatric conditions. Further collaborative attempts are necessary to identify genetic components underlying the phenotypic heterogeneity in tinnitus and provide biological insight into the etiology.

CRISPR/Cas-Based Approaches to Study Schizophrenia and Other Neurodevelopmental Disorders

The study of diseases of the central nervous system (CNS) at the molecular level is challenging because of the complexity of neural circuits and the huge number of specialized cell types. Moreover, genomic association studies have revealed the complex genetic architecture of schizophrenia and other genetically determined mental disorders. Investigating such complex genetic architecture to decipher the molecular basis of CNS pathologies requires the use of high-throughput models such as cells and their derivatives. The time is coming for high-throughput genetic technologies based on CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat)/Cas systems to manipulate multiple genomic targets. CRISPR/Cas systems provide the desired complexity, versatility, and flexibility to create novel genetic tools capable of both altering the DNA sequence and affecting its function at higher levels of genetic information flow. CRISPR/Cas tools make it possible to find and investigate the intricate relationship between the genotype and phenotype of neuronal cells. The purpose of this review is to discuss innovative CRISPR-based approaches for studying the molecular mechanisms of CNS pathologies using cellular models.

Childhood Experiences and Mental Health of Sexual Minority Adults: Examining Three Models

Three models of recalled childhood gender nonconformity (GNC) and maltreatment are proposed to explain disparities in current psychological distress and lifetime suicidality among sexual minority individuals, using a United States probability sample of cisgender lesbian/gay (n = 701), bisexual (n = 606), and other (e.g., queer, n = 182) adults. Indirect effects indicated that lesbian/gay individuals were more likely than bisexual individuals to experience maltreatment and suicidal ideation as childhood GNC increased. Other indirect effects found that bisexual individuals reported more psychological distress and greater likelihood of lifetime suicidal ideation and attempts than lesbian/gay individuals as maltreatment increased. The direct effects of sexual orientation were stronger than the indirect effects via maltreatment or GNC, with bisexual individuals reporting more maltreatment, distress, and suicidality than lesbian/gay individuals. Significant findings for individuals with other identities were similar to those of bisexual individuals. Adjusted findings were comparable for women and men. The findings indicated that sexual minority individuals reported experiences consistent with sexual minority stress during early developmental periods, before being aware of their sexual orientation. It is necessary to understand the early lived experiences of sexual minority individuals, differences between lesbian/gay and bisexual individuals in those experiences, and their implications for adaptation.

Association analyses of rare variants identify two genes associated with refractive error

PURPOSE

Genetic variants identified through population-based genome-wide studies are generally of high frequency, exerting their action in the central part of the refractive error spectrum. However, the power to identify associations with variants of lower minor allele frequency is greatly reduced, requiring considerable sample sizes. Here we aim to assess the impact of rare variants on genetic variation of refractive errors in a very large general population cohort.

METHODS

Genetic association analyses of non-cyclopaedic autorefraction calculated as mean spherical equivalent (SPHE) used whole-exome sequence genotypic information from 50,893 unrelated participants in the UK Biobank of European ancestry. Gene-based analyses tested for association with SPHE using an optimised SNP-set kernel association test (SKAT-O) restricted to rare variants (minor allele frequency < 1%) within protein-coding regions of the genome. All models were adjusted for age, sex and common lead variants within the same locus reported by previous genome-wide association studies. Potentially causal markers driving association at significant loci were elucidated using sensitivity analyses by sequentially dropping the most associated variants from gene-based analyses.

RESULTS

We found strong statistical evidence for association of SPHE with the SIX6 (p-value = 2.15 x 10-10, or Bonferroni-Corrected p = 4.41x10-06) and the CRX gene (p-value = 6.65 x 10-08, or Bonferroni-Corrected p = 0.001). The SIX6 gene codes for a transcription factor believed to be critical to the eye, retina and optic disc development and morphology, while CRX regulates photoreceptor specification and expression of over 700 genes in the retina. These novel associations suggest an important role of genes involved in eye morphogenesis in refractive error.

CONCLUSION

The results of our study support previous research highlighting the importance of rare variants to the genetic risk of refractive error. We explain some of the origins of the genetic signals seen in GWAS but also report for the first time a completely novel association with the CRX gene.

Multivariate alterations in insula - Medial prefrontal cortex linked to genetics in 12q24 in schizophrenia

The direct effect of genetic variations on clinical phenotypes within schizophrenia (SZ) remains elusive. We examined the previously identified association of reduced gray matter concentration in the insula - medial prefrontal cortex and a quantitative trait locus located in 12q24 in a SZ dataset. The main analysis was performed on 1461 SNPs and 830 participants. The highest contributing SNPs were localized in five genes including TMEM119, which encodes a microglial marker, that is associated with neuroinflammation and Alzheimer's disease. The gene set in 12q4 may partially explain brain alterations in SZ, but they may also relate to other psychiatric and developmental disorders.

Neuronal membrane glycoprotein (nmgp-1) gene deficiency affects chemosensation-related behaviors, dauer exit and egg-laying in Caenorhabditis elegans

The nervous system monitors the environment to maintain homeostasis, which can be affected by stressful conditions. Using mammalian models of chronic stress, we previously observed altered brain levels of GPM6A, a protein involved in neuronal morphology. However, GPM6A's role in systemic stress responses remains unresolved. The nematode Caenorhabditis elegans expresses a GPM6A ortholog, the neuronal membrane glycoprotein 1 (NMGP-1). Because of the shared features between nematode and mammalian nervous systems and the vast genetic tools available in C. elegans, we used the worm to elucidate the role of GPM6A in the stress response. We first identified nmgp-1 expression in different amphid and phasmid neurons. To understand the nmgp-1 role, we characterized the behavior of nmgp-1(RNAi) animals and two nmgp-1 mutant alleles. Compared to control animals, mutant and RNAi-treated worms exhibited increased recovery time from the stress-resistant dauer stage, altered SDS chemosensation and reduced egg-laying rate resulting in egg retention (bag-of-worms phenotype). Silencing of nmgp-1 expression induced morphological abnormalities in the ASJ sensory neurons, partly responsible for dauer exit. These results indicate that nmgp-1 is required for neuronal morphology and for behaviors associated with chemosensation. Finally, we propose nmgp-1 mutants as a tool to screen drugs for human nervous system pathologies.

Affective temperaments and depressive symptoms: The mediating role of attachment

BACKGROUND

Studies showed that affective temperaments and attachment are associated with depressive symptoms, and that they bi-directionally influence each-other. The aim of this study is to explore mechanisms underlying the relationship between the affective temperaments (i.e., depressive, cyclothymic, irritable, hyperthymic and anxious), interview-based attachment, and depressive symptoms.

METHODS

A sample of 61 adolescents and young adults outpatients were asked to complete the Temperament Evaluation of Memphis, Pisa, and San Diego Autoquestionnaire (TEMPS-A) and the Hamilton Rating Scale for Depression (HAM-D). Attachment was assessed through the Adult Attachment Interview (AAI) and employing a dimensional approach to obtain continuous measures. Mediation models were performed with the affective temperaments as predictor, depressive symptoms as the criterion variable, and attachment dimensions as mediators.

RESULTS

Findings showed significant direct effects between all the affective temperaments and depressive symptoms. Only the cyclothymic (β = 0.22; SE = 0.1; 95% IC = 0.05, 0.42) and irritable (β = 0.21; SE = 0.09; 95% IC = 0.04, 0.4) temperaments showed an indirect effect on depressive symptoms through secure-insecure attachment. Dismissing attachment did not predict either the affective temperaments nor depressive symptoms. Preoccupied attachment significantly predicts depressive symptoms and, when controlling for it, the hyperthymic temperament no longer directly associates with depressive symptoms.

LIMITATIONS

The cross-sectional study design limit conclusion about causation and directionality.

CONCLUSIONS

Secure attachment could be a protective factor for depressive symptoms for individuals with a cyclothymic or irritable temperament. Differently, the hyperthymic temperament loses its protective role toward depressive symptoms when accounting for preoccupied attachment.

Genome-wide mapping of brain phenotypes in extended pedigrees with strong genetic loading for bipolar disorder

Bipolar disorder is a highly heritable illness, associated with alterations of brain structure. As such, identification of genes influencing inter-individual differences in brain morphology may help elucidate the underlying pathophysiology of bipolar disorder (BP). To identify quantitative trait loci (QTL) that contribute to phenotypic variance of brain structure, structural neuroimages were acquired from family members (n = 527) of extended pedigrees heavily loaded for bipolar disorder ascertained from genetically isolated populations in Latin America. Genome-wide linkage and association analysis were conducted on the subset of heritable brain traits that showed significant evidence of association with bipolar disorder (n = 24) to map QTL influencing regional measures of brain volume and cortical thickness. Two chromosomal regions showed significant evidence of linkage; a QTL on chromosome 1p influencing corpus callosum volume and a region on chromosome 7p linked to cortical volume. Association analysis within the two QTLs identified three SNPs correlated with the brain measures.

Genetic underpinnings of affective temperaments: a pilot GWAS investigation identifies a new genome-wide significant SNP for anxious temperament in ADGRB3 gene

Although recently a large-sample GWASs identified significant loci in the background of depression, the heterogeneity of the depressive phenotype and the lack of accurate phenotyping hinders applicability of findings. We carried out a pilot GWAS with in-depth phenotyping of affective temperaments, considered as subclinical manifestations and high-risk states for affective disorders, in a general population sample of European origin. Affective temperaments were measured by TEMPS-A. SNP-level association was assessed by linear regression models, assuming an additive genetic effect, using PLINK1.9. Gender, age, the first ten principal components (PCs) and the other four temperaments were included in the regression models as covariates. SNP-level relevances (p-values) were aggregated to gene level using the PEGASUS method¹. In SNP-based tests, a Bonferroni-corrected significance threshold of p ≤ 5.0 × 10^-8 and a suggestive significance threshold of p ≤ 1.0 × 10^-5, whereas in gene-based tests a Bonferroni-corrected significance of 2.0 × 10^-6 and a suggestive significance of p ≤ 4.0 × 10^-4 was established. To explore known functional effects of the most significant SNPs, FUMA v1.3.5 was used. We identified 1 significant and 21 suggestively significant SNPs in ADGRB3, expressed in the brain, for anxious temperament. Several other brain-relevant SNPs and genes emerged at suggestive significance for the other temperaments. Functional analyses reflecting effect on gene expression and participation in chromatin interactions also pointed to several genes expressed in the brain with potentially relevant phenotypes regulated by our top SNPs. Our findings need to be tested in larger GWA studies and candidate gene analyses in well-phenotyped samples in relation to affective disorders and related phenotypes.

Psychological symptoms during and after Austrian first lockdown in individuals with bipolar disorder? A follow-up control-group investigation

BACKGROUND

The coronavirus disease (COVID-19) pandemic, a global health crisis, has resulted in widespread socioeconomic restrictions including lockdown, social distancing, and self-isolation. To date, little is known about the psychological impact of the COVID-19 pandemic and lockdown on patients with bipolar disorder as a particularly vulnerable group.

METHODS

An online survey was conducted in Austria at two points of measurement (T1 April 2020 during the first lockdown vs. T2 May 2020 at post-lockdown). The sample comprises 20 patients with bipolar disorder (mean age = 49.4 ± 15.6 years) and 20 healthy controls (mean age = 32.7 ± 9.6 years). A 2 × 2 factorial design to compare two time points (T1 vs. T2) and two groups (patients vs. healthy controls) was used. Main outcome measures included the Brief Symptom Inventory-18 (BSI-18) and a (non-validated and non-standardized) assessment to determine COVID-19 fears and emotional distress due to social distancing. Multiple linear regression analyses were used to assess the longitudinal association of COVID-19 fears/emotional distress due to social distancing during lockdown (T1) and psychological symptoms after lockdown (T2).

RESULTS

At T1, results demonstrated higher scores in BSI-18 subscales depression, anxiety and global severity index as well as emotional distress due to social distancing in bipolar patients compared to controls. There was a significant time x group interaction in the BSI-18 subscale somatization showing a decreasing trend in patients with BD compared to controls. No time effects in BSI-18 subscales or COVID-19 fears/emotional distress due to social distancing were observed. Regression analyses showed that COVID-19 fears during lockdown predicted somatization, only in patients.

CONCLUSIONS

There was a connection between the lockdown measures and somatization symptoms observed in patients. When the first steps of easing the social restrictions in May 2020 took place, somatization decreased only in the bipolar compared to the control group. Higher COVID-19 fears during lockdown predicted later symptoms at post-lockdown. Long-term impacts of the COVID-19 pandemic need further investigations to improve current therapeutic approaches and prevent fears and distress during lockdown in individuals with bipolar disorder in times of crisis.

Quantitative Proteomic Approach for Discriminating Major Depressive Disorder and Bipolar Disorder by Multiple Reaction Monitoring-Mass Spectrometry

Because major depressive disorder (MDD) and bipolar disorder (BD) manifest with similar symptoms, misdiagnosis is a persistent issue, necessitating their differentiation through objective methods. This study was aimed to differentiate between these disorders using a targeted proteomic approach. Multiple reaction monitoring-mass spectrometry (MRM-MS) analysis was performed to quantify protein targets regarding the two disorders in plasma samples of 270 individuals (90 MDD, 90 BD, and 90 healthy controls (HCs)). In the training set (72 MDD and 72 BD), a generalizable model comprising nine proteins was developed. The model was evaluated in the test set (18 MDD and 18 BD). The model demonstrated a good performance (area under the curve (AUC) >0.8) in discriminating MDD from BD in the training (AUC = 0.84) and test sets (AUC = 0.81) and in distinguishing MDD from BD without current hypomanic/manic/mixed symptoms (90 MDD and 75 BD) (AUC = 0.83). Subsequently, the model demonstrated excellent performance for drug-free MDD versus BD (11 MDD and 10 BD) (AUC = 0.96) and good performance for MDD versus HC (AUC = 0.87) and BD versus HC (AUC = 0.86). Furthermore, the nine proteins were associated with neuro, oxidative/nitrosative stress, and immunity/inflammation-related biological functions. This proof-of-concept study introduces a potential model for distinguishing between the two disorders.

Neuronal Glycoprotein M6a: An Emerging Molecule in Chemical Synapse Formation and Dysfunction

The cellular and molecular mechanisms underlying neuropsychiatric and neurodevelopmental disorders show that most of them can be categorized as synaptopathies-or damage of synaptic function and plasticity. Synaptic formation and maintenance are orchestrated by protein complexes that are in turn regulated in space and time during neuronal development allowing synaptic plasticity. However, the exact mechanisms by which these processes are managed remain unknown. Large-scale genomic and proteomic projects led to the discovery of new molecules and their associated variants as disease risk factors. Neuronal glycoprotein M6a, encoded by the GPM6A gene is emerging as one of these molecules. M6a has been involved in neuron development and synapse formation and plasticity, and was also recently proposed as a gene-target in various neuropsychiatric disorders where it could also be used as a biomarker. In this review, we provide an overview of the structure and molecular mechanisms by which glycoprotein M6a participates in synapse formation and maintenance. We also review evidence collected from patients carrying mutations in the GPM6A gene; animal models, and in vitro studies that together emphasize the relevance of M6a, particularly in synapses and in neurological conditions.

Identification by proximity labeling of novel lipidic and proteinaceous potential partners of the dopamine transporter

Dopamine (DA) transporters (DATs) are regulated by trafficking and modulatory processes that probably rely on stable and transient interactions with neighboring proteins and lipids. Using proximity-dependent biotin identification (BioID), we found novel potential partners for DAT, including several membrane proteins, such as the transmembrane chaperone 4F2hc, the proteolipid M6a and a potential membrane receptor for progesterone (PGRMC2). We also detected two cytoplasmic proteins: a component of the Cullin1-dependent ubiquitination machinery termed F-box/LRR-repeat protein 2 (FBXL2), and the enzyme inositol 5-phosphatase 2 (SHIP2). Immunoprecipitation (IP) and immunofluorescence studies confirmed either a physical association or a close spatial proximity between these proteins and DAT. M6a, SHIP2 and the Cullin1 system were shown to increase DAT activity in coexpression experiments, suggesting a functional role for their association. Deeper analysis revealed that M6a, which is enriched in neuronal protrusions (filopodia or dendritic spines), colocalized with DAT in these structures. In addition, the product of SHIP2 enzymatic activity (phosphatidylinositol 3,4-bisphosphate [PI(3,4)P₂]) was tightly associated with DAT, as shown by co-IP and by colocalization of mCherry-DAT with a specific biosensor for this phospholipid. PI(3,4)P₂ strongly stimulated transport activity in electrophysiological recordings, and conversely, inhibition of SHIP2 reduced DA uptake in several experimental systems including striatal synaptosomes and the dopaminergic cell line SH-SY5Y. In summary, here we report several potential new partners for DAT and a novel regulatory lipid, which may represent new pharmacological targets for DAT, a pivotal protein in dopaminergic function of the brain.

Affective temperaments (TEMPS-A) in panic disorder and healthy probands: Genetic modulation by 5-HTT variation

OBJECTIVES

Temperamental traits as ascertained by the Temperament Evaluation of Memphis, Pisa, Paris and San Diego Auto-Questionnaire (TEMPS-A) have been suggested as promising intermediate phenotypes of mental disorders. In anxiety disorders, however, TEMPS scales and their genetic underpinnings are still understudied.

METHODS

TEMPS-A scores in 109 patients with panic disorder (PD) were compared to a sample of 536 healthy probands. All participants were genotyped for serotonin transporter gene variation (5-HTTLPR/rs25531).

RESULTS

PD patients displayed significantly increased scores on the dysthymic, cyclothymic, irritable and anxious subscales, and lower scores on the hyperthymic subscale, respectively (all ps < 0.001) compared to healthy probands. In the total sample, the less active 5-HTTLPR/rs25531 S/L_G alleles were associated with higher scores on the dysthymic, cyclothymic, irritable and anxious temperaments (all ps < 0.01), but not the hyperthymic subscale. Mediation analyses revealed anxious temperament in particular to mediate the relationship between 5-HTT genotype and PD.

CONCLUSIONS

Dysthymic, cyclothymic, irritable and notably anxious temperament could serve as valuable intermediate phenotypes in efforts to unravel neurobiological, particularly serotonin system related genetic pathomechanisms associated with PD and potentially contribute to a panel of vulnerability markers guiding early targeted preventive interventions.

Identification of Potential Interacting Proteins With the Extracellular Loops of the Neuronal Glycoprotein M6a by TMT/MS

Nowadays, great efforts are made to gain insight into the molecular mechanisms that underlie structural neuronal plasticity. Moreover, the identification of signaling pathways involved in the development of psychiatric disorders aids the screening of possible therapeutic targets. Genetic variations or alterations in GPM6A expression are linked to neurological disorders such as schizophrenia, depression, and Alzheimer's disease. GPM6A encodes the neuronal surface glycoprotein M6a that promotes filopodia/spine, dendrite, and synapse formation by unknown mechanisms. A substantial body of evidence suggests that the extracellular loops of M6a command its function. However, the proteins that associate with them and that modulate neuronal plasticity have not been determined yet. To address this question, we generated a chimera protein that only contains the extracellular loops of M6a and performed a co-immunoprecipitation with rat hippocampus samples followed by TMT/MS. Here, we report 72 proteins, which are good candidates to interact with M6a's extracellular loops and modify its function. Gene ontology (GO) analysis showed that 63% of the potential M6a's interactor proteins belong to the category "synapse," at both sides of the synaptic cleft, "neuron projections" (51%) and "presynapse" (49%). In this sense, we showed that endogenous M6a interacts with piccolo, synaptic vesicle protein 2B, and synapsin 1 in mature cultured hippocampal neurons. Interestingly, about 28% of the proteins left were related to the "myelin sheath" annotation, suggesting that M6a could interact with proteins at the surface of oligodendrocytes. Indeed, we demonstrated the (cis and trans) interaction between M6a and proteolipid protein (PLP) in neuroblastoma N2a cells. Finally, the 72 proteins were subjected to disease-associated genes and variants screening by DisGeNET. Apart from the diseases that have already been associated with M6a, most of the proteins are also involved in "autistic disorder," "epilepsy," and "seizures" increasing the spectrum of disorders in which M6a could play a role. Data are available via ProteomeXchange with identifier PXD017347.

Nature and Nurture: Effects of Affective Temperaments on Depressive Symptoms Are Markedly Modified by Stress Exposure

BACKGROUND

Lack of proper consideration of the interaction between biological and environmental factors limits our understanding of the development of depression. Our cross-sectional study investigated whether recent stress influences the effect of affective temperaments on depressive symptoms.

METHODS

1015 general population participants completed the Brief Symptom Inventory to capture depressive symptoms, the List of Threatening Experiences Questionnaire to assess recent stressors, and the Temperament Evaluation of Memphis Pisa, Paris, and San Diego Autoquestionnaire to evaluate affective temperaments (TEMPS-A). Linear regression models were built to investigate the effect of temperament and stress on depression, temperament on stress, and the effect of temperament on depressive symptoms in different stress exposure groups.

RESULTS

Recent life events and anxious, depressive, cyclothymic, and hyperthymic temperaments significantly predicted depressive symptoms, and cyclothymic, and hyperthymic temperaments significantly predicted recent life event exposure. While in case of mild stress all affective temperaments except irritable predicted depression, in case of moderate exposure only the effect of depressive, cyclothymic, and hyperthymic temperament, while in the high exposure group only the effect of anxious temperament was significant.

LIMITATIONS

All measures were based on self-report, and subjective impact of life events was not considered. This was a cross-sectional study with a correlational nature which does not allow for causative conclusions.

CONCLUSIONS

The contribution of affective temperaments to depression is much higher compared to stress, and severity of exposure to life events influences the impact of affective temperaments on depressive symptoms, pointing to divergent pathways of emotional reactivity mediating the effects of stress on depression which can be exploited for prevention and treatment.

Personality Structure and Attachment in Bipolar Disorder

BACKGROUND

An impairment of self and interpersonal functioning has an impact on coping strategies, regulation of affect and stress. Little is known so far about the impairment of personality functioning in patients with bipolar disorder (BD). The aim of this study is to assess the effects of personality structure and attachment in BD patients on the symptom burden.

METHODS

Forty-six patients with the diagnosis of BD were assessed by the 12-item Operationalized Psychodynamic Diagnosis Structure Questionnaire (OPD-SQS), the short version of Experience in Close Relationship-revised (ECR-R-D), and the Brief Symptom Inventory-18 (BSI 18) to determine the level of personality functioning, attachment patterns, and symptom load.

RESULTS

We observed positive correlations between personality difficulties, insecure attachment, and symptom load in patients with BD. A low level of structural integration and an insecure attachment style in patients with BD were accompanied by a significantly higher symptom load (r = 0.66, p ≤ 0.01). Interestingly, there were no significant differences in the structural integration (T(1.44) = -0.93, p = 0.357) and in the attachment style attachment related avoidance: (T(1,44) = 1.50, p = 0.140); attachment related anxiety (T(1,44) = -0.781, p = 0.439) of study participants with BD when compared to the normative value of the general population.

LIMITATIONS

Our limitations are the small sample size of our group and the lack of a control group.

CONCLUSION

In general, our results suggest that there is a link between personality structure and affective dynamics including depressive, anxiety, and somatization symptoms in BD. These findings underline the increasing importance of assessing personality structure and attachment for diagnosis and treatment planning of BD.

A comprehensive study on identifying the structural and functional SNPs of human neuronal membrane glycoprotein M6A (GPM6A)

Glycoprotein M6A, a stress related gene, plays an important role in synapse and filopodia formation. Filopodia formation is vital for development, immunity, angiogenesis, wound healing and metastasis. In this study, structural and functional analysis of high-risk SNPs associated with Glycoprotein M6-A were evaluated using six different bioinformatics tools. Results classified T210I, T134I, Y153H, I215T, F156L, T160I, I226T, R247W, R178C, W159R, N157S and P151L as deleterious mutants that are crucial for the structure and function of the protein causing malfunction of M6-a and ultimately leads to disease development. The three-dimensional structure of wild-type M6-a and mutant M6-a were also predicted. Furthermore, the effects of high risk substitutions were also analyzed with interaction with valproic acid. Based on structural models obtained, the binding pocket of ligand bound glycoprotein M6-A structure showed few core interacting residues which are different in the mutant models. Among all substitutions, F156L showed complete loss of binding pocket when interacting with valproic acid as compared to the wild type model. Up to the best of our knowledge this is the first comprehensive study where GPM6A mutations were analyzed. The mechanism of action of GPM6A is still not fully defined which limits the understanding of functional details encoding M6-A. Our results may help enlighten some molecular aspects underlying glycoprotein M6-A. Communicated by Ramaswamy H. Sarma.

Genetic Intersections of Language and Neuropsychiatric Conditions

PURPOSE OF REVIEW

To better understand the shared basis of language and mental health, this review examines the behavioral and neurobiological features of aberrant language in five major neuropsychiatric conditions. Special attention is paid to genes implicated in both language and neuropsychiatric disorders, as they reveal biological domains likely to underpin the processes controlling both.

RECENT FINDINGS

Abnormal language and communication are common manifestations of neuropsychiatric conditions, and children with impaired language are more likely to develop psychiatric disorders than their peers. Major themes in the genetics of both language and psychiatry include master transcriptional regulators, like FOXP2; key developmental regulators, like AUTS2; and mediators of neurotransmission, like GRIN2A and CACNA1C.

Genetic dissection of complex behaviour traits in German Shepherd dogs

A favourable genetic structure and diversity of behavioural features highlights the potential of dogs for studying the genetic architecture of behaviour traits. However, behaviours are complex traits, which have been shown to be influenced by numerous genetic and non-genetic factors, complicating their analysis. In this study, the genetic contribution to behaviour variation in German Shepherd dogs (GSDs) was analysed using genomic approaches. GSDs were phenotyped for behaviour traits using the established Canine Behavioural Assessment and Research Questionnaire (C-BARQ). Genome-wide association study (GWAS) and regional heritability mapping (RHM) approaches were employed to identify associations between behaviour traits and genetic variants, while accounting for relevant non-genetic factors. By combining these complementary methods we endeavoured to increase the power to detect loci with small effects. Several behavioural traits exhibited moderate heritabilities, with the highest identified for Human-directed playfulness, a trait characterised by positive interactions with humans. We identified several genomic regions associated with one or more of the analysed behaviour traits. Some candidate genes located in these regions were previously linked to behavioural disorders in humans, suggesting a new context for their influence on behaviour characteristics. Overall, the results support dogs as a valuable resource to dissect the genetic architecture of behaviour traits and also highlight the value of focusing on a single breed in order to control for background genetic effects and thus avoid limitations of between-breed analyses.

Vulnerability to bipolar disorder is linked to sleep and sleepiness

Sleep impairments are a hallmark of acute bipolar disorder (BD) episodes and are present even in the euthymic state. Studying healthy subjects who are vulnerable to BD can improve our understanding of whether sleep impairment is a predisposing factor. Therefore, we investigated whether vulnerability to BD, dimensionally assessed by the hypomanic personality scale (HPS), is associated with sleep disturbances in healthy subjects. We analyzed participants from a population-based cohort who had completed the HPS and had either a 7-day actigraphy recording or a Pittsburgh sleep quality index (PSQI) assessment. In addition, subjects had to be free of confounding diseases or medications. This resulted in 771 subjects for actigraphy and 1766 for PSQI analyses. We found strong evidence that higher HPS scores are associated with greater intraindividual sleep variability, more disturbed sleep and more daytime sleepiness. In addition, factor analyses revealed that core hypomanic features were especially associated with self-reported sleep impairments. Results support the assumption of disturbed sleep as a possibly predisposing factor for BD and suggest sleep improvement as a potential early prevention target.

NGL-1/LRRC4C-Mutant Mice Display Hyperactivity and Anxiolytic-Like Behavior Associated With Widespread Suppression of Neuronal Activity

Netrin-G ligand-1 (NGL-1), encoded by Lrrc4c, is a post-synaptic adhesion molecule implicated in various brain disorders, including bipolar disorder, autism spectrum disorder, and developmental delay. Although previous studies have explored the roles of NGL-1 in the regulation of synapse development and function, the importance of NGL-1 for specific behaviors and the nature of related neural circuits in mice remain unclear. Here, we report that mice lacking NGL-1 (Lrrc4c^–/–) show strong hyperactivity and anxiolytic-like behavior. They also display impaired spatial and working memory, but normal object-recognition memory and social interaction. c-Fos staining under baseline and anxiety-inducing conditions revealed suppressed baseline neuronal activity as well as limited neuronal activation in widespread brain regions, including the anterior cingulate cortex (ACC), motor cortex, endopiriform nucleus, bed nuclei of the stria terminalis, and dentate gyrus. Neurons in the ACC, motor cortex, and dentate gyrus exhibit distinct alterations in excitatory synaptic transmission and intrinsic neuronal excitability. These results suggest that NGL-1 is important for normal locomotor activity, anxiety-like behavior, and learning and memory, as well as synapse properties and excitability of neurons in widespread brain regions under baseline and anxiety-inducing conditions.

Unravelling the genetic basis of schizophrenia and bipolar disorder with GWAS: A systematic review

OBJECTIVES

To systematically review findings of GWAS in schizophrenia (SZ) and in bipolar disorder (BD); and to interpret findings, with a focus on identifying independent replications.

METHOD

PubMed search, selection and review of all independent GWAS in SZ or BD, published since March 2011, i.e. studies using non-overlapping samples within each article, between articles, and with those of the previous review (Li et al., 2012).

RESULTS

From the 22 GWAS included in this review, the genetic associations surviving standard GWAS-significance were for genetic markers in the regions of ACSL3/KCNE4, ADCY2, AMBRA1, ANK3, BRP44, DTL, FBLN1, HHAT, INTS7, LOC392301, LOC645434/NMBR, LOC729457, LRRFIP1, LSM1, MDM1, MHC, MIR2113/POU3F2, NDST3, NKAPL, ODZ4, PGBD1, RENBP, TRANK1, TSPAN18, TWIST2, UGT1A1/HJURP, WHSC1L1/FGFR1 and ZKSCAN4. All genes implicated across both reviews are discussed in terms of their function and implication in neuropsychiatry.

CONCLUSION

Taking all GWAS to date into account, AMBRA1, ANK3, ARNTL, CDH13, EFHD1 (albeit with different alleles), MHC, PLXNA2 and UGT1A1 have been implicated in either disorder in at least two reportedly non-overlapping samples. Additionally, evidence for a SZ/BD common genetic basis is most strongly supported by the implication of ANK3, NDST3, and PLXNA2.

NGL-1/LRRC4C Deletion Moderately Suppresses Hippocampal Excitatory Synapse Development and Function in an Input-Independent Manner

Netrin-G ligand-1 (NGL-1), also known as LRRC4C, is a postsynaptic densities (PSDs)-95-interacting postsynaptic adhesion molecule that interacts trans-synaptically with presynaptic netrin-G1. NGL-1 and its family member protein NGL-2 are thought to promote excitatory synapse development through largely non-overlapping neuronal pathways. While NGL-2 is critical for excitatory synapse development in specific dendritic segments of neurons in an input-specific manner, whether NGL-1 has similar functions is unclear. Here, we show that Lrrc4c deletion in male mice moderately suppresses excitatory synapse development and function, but surprisingly, does so in an input-independent manner. While NGL-1 is mainly detected in the stratum lacunosum moleculare (SLM) layer of the hippocampus relative to the stratum radiatum (SR) layer, NGL-1 deletion leads to decreases in the number of PSDs in both SLM and SR layers in the ventral hippocampus. In addition, both SLM and SR excitatory synapses display suppressed short-term synaptic plasticity in the ventral hippocampus. These morphological and functional changes are either absent or modest in the dorsal hippocampus. The input-independent synaptic changes induced by Lrrc4c deletion involve abnormal translocation of NGL-2 from the SR to SLM layer. These results suggest that Lrrc4c deletion moderately suppresses hippocampal excitatory synapse development and function in an input-independent manner.

Possible Association of the Ubiquitin-Specific Peptidase 46 Gene (USP46) with Affective Temperamental Traits in Healthy Korean Volunteers

OBJECTIVE

Ubiquitin-specific peptidase 46 gene (USP46) polymorphisms is part of ubiquitin-proteasome system, which is responsible for dynamic cellular processes such as the regulation of cell cycle. USP46 has been reported to be associated with major depressive disorder. The objective of the present study was to investigate the association of USP46 polymorphisms with affective temperamental traits in healthy subjects.

METHODS

A total of 557 Korean healthy volunteers were recruited, and 545 subjects (328 male, 217 female) were included in the final analysis. The DNA of the subjects was isolated from saliva samples. Two single-nucleotide polymorphisms (SNPs) rs346005, rs2244291 in USP46 were genotyped. Affective temperaments were assessed using the Korean version of Temperament Evaluation of the Memphis, Pisa, Paris, and San Diego Autoquestionnaire (TEMPS-A).

RESULTS

A significant association was found between rs346005 genotypes and TEMPS-A only in male subjects. In particular, subjects with the CC genotype of rs346005 showed a more depressive temperament than subjects with AA or CA genotypes in males. For rs2244291, there were no associations between the rs2244291 genotypes and TEMPS-A scores.

CONCLUSION

Some affective temperaments may serve as a genetic predisposing factors for affective disorders, such as depressive disorder, via vulnerability genes related to the ubiquitin-proteasome system.

Affective temperament in inflammatory bowel diseases: Another brick in the wall of differentiation

Psychiatric disorders are significantly common complications among patients suffering from inflammatory bowel diseases (IBD). Affective temperament is a concept of core personality traits, which can decribe the vulnerability to mood disorders, therefore its evaluation might convey useful information about patients' mental status in autoimmune disorders. The aim of the study was to evaluate the affective temperament in patients with Crohn's disease (CD) and ulcerative colitis (UC) as characteristic features of these diseases, but also in the clinical course and the severity of anxiety and depression.Due to our knowledge this is the first study of this kind. The study enrolled 130 patients with IBD, including 68 with CD and 62 with UC. We used TEMPS-A to evaluate affective temperament and HADS scales to assess the intensity of depressive and anxiety symptoms. Harvey Bradshaw scale, Crohn’s Disease Activity Index (CDAI) and Mayo Score were used to evaluate clinical severity of the diseases. We observed significantly higher prevalence of depressive, cyclothymic and anxiety temperaments in CD patients compared to the control group. Harvey Bradshaw scale, CDAI and Mayo Self Report showed statistically significant outcomes, including significant positive correlations with depressive, cyclothymic and anxiety subscales of TEMPS-A, and negative correlation with the hyperthymic temperament in CD subjects. Our findings indicate significant differences between CD and UC due to temperament traits, and suggest distinct pathogenesis of mood disorders in IBD.

A Population-Based Twin Study of Childhood Irritability and Internalizing Syndromes

Childhood irritability exhibits significant theoretical and empirical associations with depression and anxiety syndromes. The current study used the twin design to parse genetic and environmental contributions to these relationships. Children ages 9-14 from 374 twin pairs were assessed for irritability and symptoms of depression, generalized anxiety, panic, social phobia, and separation anxiety using dimensional self-report instruments. Multivariate structural equation modeling decomposed the correlations between these syndromes into genetic and environmental components to examine shared and specific risk domains. Irritability had significant associations with each internalizing symptom domain. Genetic contributions to irritability are moderately correlated with genetic risk for symptoms of depression, generalized anxiety, and separation anxiety with weaker overlap with the other anxiety syndromes. Familial and specific environmental risk factors explained covariation among syndromes and indicated potential syndrome-specific risk. There is substantial overlap among the genetic and environmental factors that influence individual differences in irritability and those that increase liability for depression and anxiety symptoms in children. These findings deepen the current understanding of childhood internalizing risk factors and provide important implications for syndrome prediction and susceptibility gene discovery efforts.

Alanine Scanning Mutagenesis of the C-Terminal Cytosolic End of Gpm6a Identifies Key Residues Essential for the Formation of Filopodia

Neuronal membrane glycoprotein M6a (Gpm6a) is a protein with four transmembrane regions and the N- and the C-ends facing the cytosol. It functions in processes of neuronal development, outgrowth of neurites, and formation of filopodia, spines, and synapsis. Molecular mechanisms by which Gpm6a acts in these processes are not fully comprehended. Structural similarities of Gpm6a with tetraspanins led us to hypothesize that, similarly to tetraspanins, the cytoplasmic tails function as connections with cytoskeletal and/or signaling proteins. Here, we demonstrate that the C- but not the N-terminal cytosolic end of Gpm6a is required for the formation of filopodia by Gpm6a in cultured neurons from rat hippocampus and in neuroblastoma cells N2a. Further immunofluorescence microcopy and flow cytometry analysis show that deletion of neither the N- nor the C-terminal intracellular domains interferes with the recognition of Gpm6a by the function-blocking antibody directed against the extracellular part of Gpm6a. Expression levels of both truncation mutants were not affected but we observed decrease in the amount of both truncated proteins on cell surface suggesting that the incapacity of the Gpm6a lacking C-terminus to induce filopodium formation is not due to the lower amount of Gpm6a on cell surface. Following colocalization assays shows that deletion of the C- but not the N-terminus diminishes the association of Gpm6a with clathrin implying involvement of clathrin-mediated trafficking events. Next, using comprehensive alanine scanning mutagenesis of the C-terminus we identify K250, K255, and E258 as the key residues for the formation of filopodia by Gpm6a. Substitution of these charged residues with alanine also diminishes the amount of Gpm6a on cell surface and in case of K255 and E258 leads to the lower amount of total expressed protein. Subsequent bioinformatic analysis of Gpm6a amino acid sequence reveals that highly conserved and functional residues cluster preferentially within the C- and not within the N-terminus and that K250, K255, and E258 are predicted as part of sorting signals of transmembrane proteins. Altogether, our results provide evidence that filopodium outgrowth induced by Gpm6a requires functionally critical residues within the C-terminal cytoplasmic tail.

In Vivo and In Vitro Neuronal Plasticity Modulation by Epigenetic Regulators

Prenatal stress (PS) induces molecular changes that alter neural connectivity, increasing the risk for neuropsychiatric disorders. Here we analyzed -in the hippocampus of adult rats exposed to PS- the epigenetic signature mediating the PS-induced neuroplasticity changes. Furthermore, using cultured hippocampal neurons, we investigated the effects on neuroplasticity of an epigenetic modulator. PS induced significant modifications in the mRNA levels of stress-related transcription factor MEF2A, SUV39H1 histone methyltransferase, and TET1 hydroxylase, indicating that PS modifies gene expression through chromatin remodeling. In in vitro analysis, histone acetylation inhibition with apicidin increased filopodium density, suggesting that the external regulation of acetylation levels might modulate neuronal morphology. These results offer a way to enhance neural connectivity that could be considered to revert PS effects.

The impact of affective temperaments on clinical and functional outcome of Bipolar I patients that initiated or changed pharmacological treatment for mania

BACKGROUND

Affective temperaments have been shown to impact on the clinical manifestations and the course of bipolar disorder. We investigated their influence on clinical features and functional outcome of manic episode.

METHOD

In a naturalistic, multicenter, national study, a sample of 194 BD I patients that initated or changed pharmacological treatment for DSM-IV-TR manic episode underwent a comprehensive evaluation including briefTEMPS-M, CTQ, YMRS, MADRS, FAST, and CGI-BP. Factorial, correlation and comparative analyses were conducted on different temperamental subtypes.

RESULTS

Depressive, cyclothymic, irritable and anxious temperaments resulted significantly correlated with each other. On the contrary, hyperthymic temperament scores were not correlated with the other temperamental dimensions. The factorial analysis of the briefTEMPS-M sub-scales total scores allowed the extraction of two factors: the Cyclothymic-Depressive-Anxious (Cyclo-Dep-Anx) and the Hyperthymic. At final evaluation Dominant Cyclo-Dep-Anx patients reported higer scores in MADRS and in CTQ emotional neglect and abuse subscale scores than Dominant Hyperthymic patients. The latter showed a greater functional outcome than Cyclo-Dep-Anx patients.

CONCLUSIONS

Affective temperaments seem to influence the course of mania. Childhood emotional abuse and neglect were related to the cyclothymic disposition. Cyclothymic subjects showed more residual depressive symptoms and Hyperthymic temperament is associated with a better short-term functional outcome.

The Membrane Glycoprotein M6a Endocytic/Recycling Pathway Involves Clathrin-Mediated Endocytosis and Affects Neuronal Synapses

Single point mutations or variations in the expression of the gene encoding the neuronal glycoprotein M6a have been associated with psychiatric disorders such as Alzheimer’s disease, depression and schizophrenia. In cultured neurons, M6a positively contributes to neurite extension, axon guidance, filopodia/spine outgrowth, and synapse formation. The endocytic processes of neuronal membrane proteins are linked to the differentiation, growth, signaling and plasticity of neurons. However, the roles of M6a and the precise mechanisms through which M6a internalizes and recycles back to the neuronal membrane are unknown. Here, by using a controlled in vitro assay, we showed that if 30–40% of M6a is endocytosed, the number of synapses in hippocampal neurons decreases. When re-establishing the levels of M6a at the cell surface, the number of synapses returned to normal values. M6a internalization involves clathrin-coated pits, probably by association between the adaptor protein 2 and the 251YEDI254 “tyrosine-based” motif located within the C-tail of M6a. Upon endocytosis, M6a is sorted to early endosome antigen 1- and Rab5-positive endosomes and then sorted back to the cell surface via Rab11-positive endosomes or to degradation via Rab7 and, finally LAMP-1-positive endosomes. Our results demonstrated that the levels of M6a at the cell surface modified the formation/maintenance of synapses, without altering the protein levels of synaptophysin or N-methyl-D-aspartate receptor type-1. This novel mechanism might be relevant during neuronal development, pruning and/or many of the neurological disorders in which the number of synapses is affected.

Neural glycoprotein M6a is released in extracellular vesicles and modulated by chronic stressors in blood

Membrane neuronal glycoprotein M6a is highly expressed in the brain and contributes to neural plasticity promoting neurite growth and spine and synapse formation. We have previously showed that chronic stressors alter hippocampal M6a mRNA levels in rodents and tree shrews. We now show that M6a glycoprotein can be detected in mouse blood. M6a is a transmembrane glycoprotein and, as such, unlikely to be free in blood. Here we demonstrate that, in blood, M6a is transported in extracellular vesicles (EVs). It is also shown that M6a-containing EVs are delivered from cultured primary neurons as well as from M6a-transfected COS-7 cells. Released EVs containing M6a can be incorporated into COS-7 cells changing its phenotype through formation of membrane protrusions. Thus, M6a-containing EVs might contribute to maintain cellular plasticity. M6a presence in blood was used to monitor stress effects. Chronic restraint stress modulated M6a protein level in a sex dependent manner. Analysis of individual animals indicated that M6a level variations depend on the stressor applied. The response to stressors in blood makes M6a amenable to further studies in the stress disorder field.

Measuring affective temperaments: a systematic review of validation studies of the Temperament Evaluation in Memphis Pisa and San Diego (TEMPS) instruments

BACKGROUND

The assessment of affective temperaments has provided useful insights for the psychopathological understanding of affective disorders and for the conceptualization of bipolar spectrum disorders. The Temperament in Memphis Pisa and San Diego (TEMPS) instrument has been widely used in research, yet its psychometric properties and optimal factor structure are unclear.

METHODS

The PubMed/MEDLINE, PsycINFO, and EMBASE electronic databases were searched from inception until March 15th, 2016. Validation peer-reviewed studies of different versions of the TEMPS performed in adult samples were considered for inclusion.

RESULTS

Twenty-seven studies (N=20,787) met inclusion criteria. Several versions of the TEMPS have been validated in 14 languages across 15 countries. The 110-item self-reported version of the TEMPS has been the most studied version. Most studies (50%) supported a five factor solution although few studies performed confirmatory factor analyses. A five-factor solution has consistently been reported for the 39-item version of the TEMPS-A. Overall, evidence indicates that different versions of the TEMPS have adequate internal consistency reliability, while the TEMPS-A-110 version has acceptable test-retest reliability. The methodological quality of included studies varied.

LIMITATIONS

A meta-analysis could not be performed due to the heterogeneity of settings and versions of the TEMPS utilized.

CONCLUSIONS

Different versions of the TEMPS have been validated across different cultures. The short 39-item version of the TEMPS-A holds promise and merits further investigation. Culture-bound factors may influence the expression and/or assessment of affective temperaments with the TEMPS.

Genome-wide analyses for personality traits identify six genomic loci and show correlations with psychiatric disorders

Personality is influenced by genetic and environmental factors and associated with mental health. However, the underlying genetic determinants are largely unknown. We identified six genetic loci, including five novel loci, significantly associated with personality traits in a meta-analysis of genome-wide association studies (N = 123,132-260,861). Of these genome-wide significant loci, extraversion was associated with variants in WSCD2 and near PCDH15, and neuroticism with variants on chromosome 8p23.1 and in L3MBTL2. We performed a principal component analysis to extract major dimensions underlying genetic variations among five personality traits and six psychiatric disorders (N = 5,422-18,759). The first genetic dimension separated personality traits and psychiatric disorders, except that neuroticism and openness to experience were clustered with the disorders. High genetic correlations were found between extraversion and attention-deficit-hyperactivity disorder (ADHD) and between openness and schizophrenia and bipolar disorder. The second genetic dimension was closely aligned with extraversion-introversion and grouped neuroticism with internalizing psychopathology (e.g., depression or anxiety).

Factor analysis of temperament and personality traits in bipolar patients: Correlates with comorbidity and disorder severity

BACKGROUND

Temperament and personality traits have been suggested as endophenotypes for bipolar disorder based on several lines of evidence, including heritability. Previous work suggested an anxious-reactive factor identified across temperament and personality inventories that produced significant group discrimination and could potentially be useful in genetic analyses. We have attempted to further characterize this factor structure in a sample of bipolar patients.

METHODS

A sample of 1195 subjects with bipolar I disorder was evaluated, all with complete data available. Dimension reduction across two inventories identified 18 factors explaining 39% of the variance.

RESULTS

The two largest factors reflected affective instability and general anxiety/worry, respectively. Subsequent analyses of the clinical features associated with bipolar disorder revealed specificity for the factors in a predictable pattern. Cluster analysis of the factors identified a subgroup defined by a strong lack of general anxiety and low affective instability represented by the first two factors. The remaining subjects could be distinguished into two clusters by the presence of either more positive characteristics, including persistence/drive, spirituality, expressivity, and humor, or more negative characteristics of depression and anxiety.

LIMITATIONS

These analyses involved bipolar I subjects only and must be extended to other bipolar spectrum diagnoses, unaffected relatives, and individuals at risk.

CONCLUSIONS

These results suggest that temperament and personality measures access latent traits associated with important clinical features of bipolar disorder. By translating clinical variables into quantitative traits, we may identify subgroups of bipolar patients with distinct clinical profiles, thereby facilitating both individual treatment strategies and genetic analyses.

KAT2B polymorphism identified for drug abuse in African Americans with regulatory links to drug abuse pathways in human prefrontal cortex

Drug abuse is a common and heritable set of disorders, but the underlying genetic factors are largely unknown. We conducted genome-wide association studies of drug abuse using 7 million imputed single nucleotide polymorphisms (SNPs) and insertions/deletions in African Americans (AAs; n = 3742) and European Americans (EAs; n = 6845). Cases were drawn from the Urban Health Study of street-recruited people, who injected drugs and reported abusing opioids, cocaine, marijuana, stimulants and/or other drugs 10 or more times in the past 30 days, and were compared with population controls. Independent replication testing was conducted in 755 AAs and 1131 EAs from the Genetic Association Information Network. An intronic SNP (rs9829896) in the K(lysine) acetyltransferase 2B (KAT2B) gene was significantly associated with drug abuse in AAs (P = 4.63 × 10-8 ) and independently replicated in AAs (P = 0.0019). The rs9829896-C allele (frequency = 12%) had odds ratios of 0.68 and 0.53 across the AA cohorts: meta-analysis P = 3.93 × 10-10 . Rs9829896-C was not associated with drug abuse across the EA cohorts: frequency = 36% and meta-analysis P = 0.12. Using dorsolateral prefrontal cortex data from the BrainCloud cohort, we found that rs9829896-C was associated with reduced KAT2B expression in AAs (n = 113, P = 0.050) but not EAs (n = 110, P = 0.39). KAT2B encodes a transcriptional regulator in the cyclic adenosine monophosphate and dopamine signaling pathways, and rs9829896-C was associated with expression of genes in these pathways: reduced CREBBP expression (P = 0.011) and increased OPRM1 expression (P = 0.016), both in AAs only. Our study identified the KAT2B SNP rs9829896 as having novel and biologically plausible associations with drug abuse and gene expression in AAs but not EAs, suggesting ancestry-specific effects.

A comparative meta-analysis of TEMPS scores across mood disorder patients, their first-degree relatives, healthy controls, and other psychiatric disorders

BACKGROUND

The Temperament Evaluation Memphis, Pisa, Paris and San Diego Auto-questionnaire (TEMPS) is validated to assess temperament in clinical and non-clinical samples. Scores vary across bipolar disorder (BD), major depressive disorder (MDD), attention-deficit/hyperactivity disorder (ADHD), borderline personality disorder (BPD) and healthy controls (HCs), but a meta-analysis is missing.

METHODS

Meta-analysis of studies comparing TEMPS scores in patients with mood disorders or their first-degree relatives to each other, or to a psychiatric control group or HCs.

RESULTS

Twenty-six studies were meta-analyzed with patients with BD (n= 2025), MDD (n=1283), ADHD (n=56) and BPD (n=43), relatives of BD (n=436), and HCs (n=1757). Cyclothymic (p<0.001) and irritable TEMPS scores (p<0.001) were higher in BD than MDD (studies=12), and in MDD vs HCs (studies=8). Cyclothymic (p<0.001), irritable (p<0.001) and anxious (p=0.03) scores were higher in BD than their relatives, who, had higher scores than HCs. No significant differences emerged between ADHD and BD (studies=3);

CONCLUSION

Affective temperaments are on a continuum, with increasing scores ranging from HCs through MDD to BD regarding cyclothymic and irritable temperament, from MDD through BD to HC regarding hyperthymic temperament, and from HC through BD relatives to BD regarding cyclothymic, irritable and anxious temperament. Depressive and anxious temperaments did not differ between BD and MDD, being nonetheless the lowest in HCs. BD did not differ from ADHD in any investigated TEMPS domain.

LIMITATIONS

Different TEMPS versions, few studies comparing BD with ADHD or BPD, no correlation with other questionnaires.

Neuronal filopodium formation induced by the membrane glycoprotein M6a (Gpm6a) is facilitated by coronin-1a, Rac1, and p21-activated kinase 1 (Pak1)

Stress-responsive neuronal membrane glycoprotein M6a (Gpm6a) functions in neurite extension, filopodium and spine formation and synaptogenesis. The mechanisms of Gpm6a action in these processes are incompletely understood. Previously, we identified the actin regulator coronin-1a (Coro1a) as a putative Gpm6a interacting partner. Here, we used co-immunoprecipitation assays with the anti-Coro1a antibody to show that Coro1a associates with Gpm6a in rat hippocampal neurons. By immunofluorescence microscopy, we demonstrated that in hippocampal neurons Coro1a localizes in F-actin-enriched regions and some of Coro1a spots co-localize with Gpm6a labeling. Notably, the over-expression of a dominant-negative form of Coro1a as well as its down-regulation by siRNA interfered with Gpm6a-induced filopodium formation. Coro1a is known to regulate the plasma membrane translocation and activation of small GTPase Rac1. We show that Coro1a co-immunoprecipitates with Rac1 together with Gpm6a. Pharmacological inhibition of Rac1 resulted in a significant decrease in filopodium formation by Gpm6a. The same was observed upon the co-expression of Gpm6a with the inactive GDP-bound form of Rac1. In this case, the elevated membrane recruitment of GDP-bound Rac1 was detected as well. Moreover, the kinase activity of the p21-activated kinase 1 (Pak1), a main downstream effector of Rac1 that acts downstream of Coro1a, was required for Gpm6a-induced filopodium formation. Taken together, our results provide evidence that a signaling pathway including Coro1a, Rac1, and Pak1 facilitates Gpm6a-induced filopodium formation. Formation of filopodia by membrane glycoprotein M6a (Gpm6a) requires actin regulator coronin-1a (Coro1a), known to regulate plasma membrane localization and activation of Rac1 and its downstream effector Pak1. Coro1a associates with Gpm6a. Blockage of Coro1a, Rac1, or Pak1 interferes with Gpm6a-induced filopodium formation. Moreover, Gpm6a facilitates Rac1 membrane recruitment. Altogether, a mechanistic insight into the process of Gpm6a-induced neuronal filopodium formation is provided.

Genetics of emotional reactivity in bipolar disorders

BACKGROUND

Emotional reactivity has been proposed as a relevant intermediate phenotype of bipolar disorder (BD). Our goal was to identify genetic factors underlying emotional reactivity in a sample of bipolar patients.

METHODS

Affect intensity (a proxy measure of emotional reactivity) was measured in a sample of 281 euthymic patients meeting DSM-IV criteria for BD. We use a validated dimensional tool, the 40-item self-report Affect Intensity Measure scale developed by Larsen and Diener. Patients with BD were genotyped for 475. 740 SNPs (using Illumina HumanHap550 Beadchips or HumanHap610 Quad chip). Association was investigated with a general mixed regression model of the continuous trait against genotypes, including gender as covariate.

RESULTS

Four regions (1p31.3, 3q13.11, 11p15.1 and 11q14.4) with a p-value lower or equal to 5×10(-6) were identified. In these regions, the joint effect of the four variants accounted for 24.5% of the variance of AIM score. Epistasis analysis did not detect interaction between these variants. In the 11p15.1 region, the rs10766743 located in the intron of the NELL1 gene remained significant after correction for multiple testing (p=2×10(-7)).

CONCLUSIONS

These findings illustrate that focusing on quantitative intermediate phenotypes can facilitate the identification of genetic susceptibility variants in BD.

The genetics of early-onset bipolar disorder: A systematic review

BACKGROUND

Early-onset bipolar disorder has been associated with a significantly worse prognosis than late-onset BD and has been hypothesized to be a genetically homogenous subset of BD. A sizeable number of studies have investigated early-onset BD through linkage-analyses, candidate-gene association studies, genome-wide association studies (GWAS), and analyses of copy number variants (CNVs), but this literature has not yet been reviewed.

METHODS

A systematic review was conducted using the PubMed database on articles published online before January 15, 2015 and after 1990. Separate searches were made for linkage studies, candidate gene-association studies, GWAS, and studies on CNVs.

RESULTS

Seventy-three studies were included in our review. There is a lack of robust positive findings on the genetics of early-onset BD in any major molecular genetics method.

LIMITATIONS

Early-onset populations were quite small in some studies. Variance in study methods hindered efforts to interpret results or conduct meta-analysis.

CONCLUSIONS

The field is still at an early phase for research on early-onset BD. The largely null findings mirror the results of most genetics research on BD. Although most studies were underpowered, the null findings could mean that early-onset BD may not be as genetically homogenous as has been hypothesized or even that early-onset BD does not differ genetically from adult-onset BD. Nevertheless, clinically the probabilistic developmental risk trajectories associated with early-onset that may not be primarily genetically determined continued to warrant scrutiny. Future research should dramatically expand sample sizes, use atheoretical research methods like GWAS, and standardize methods.

Validation of the "rule of three", the "red sign" and temperament as behavioral markers of bipolar spectrum disorders in a large sample

BACKGROUND

Akiskal proposed the "rule of three" for behavioral indicators with high specificity for bipolarity in patients with major depression episodes. We evaluated these distinctive behaviors in controls and subjects with major depression or bipolar disorder.

METHODS

data was collected in the BRAINSTEP project with questions on general behaviors, style and talents. Univariate analysis was first conducted in 36,742 subjects and confirmatory multivariate analysis in further 34,505 subjects (22% with a mood disorder). Odds ratios were calculated adjusting for age.

RESULTS

Univariate analysis showed that 29 behavioral markers differentiated bipolar subjects from those with unipolar depression. The most robust differences in those with bipolarity (ORs >4) were ≥3 religion changes, ≥3 marriages, cheating the partner regularly, having ≥60 lifetime sexual partners, pathological love, heavy cursing, speaking ≥3 foreign languages, having ≥2 apparent tattoos, circadian dysregulation and high debts. Most behaviors were expressed in a minority of patients (usually around 5-30%) and usually the "rule of three" was the best numerical marker to distinguish those with bipolarity. However, multivariate analysis confirmed 11 of these markers for differentiating bipolar disorder from unipolar depression (reversed circadian rhythm and high debts for both genders, ≥3 provoked car accidents and talent for poetry in men, and frequent book reading, ≥3 religion changes, ≥60 sexual partners, pathological love ≥2 times, heavy cursing and extravagant dressing style in women).

LIMITATIONS

Self-report data collection only.

CONCLUSIONS

These behavioral markers should alert the clinician to perform a thorough investigation of bipolarity in patients presenting with a depressive episode.

A tale of two diatheses: Temperament, BIS, and BAS as risk factors for mood disorder

OBJECTIVE

Learning more about how biological traits, like temperament and sensitivity in the behavioral inhibition (BIS) and behavioral activation (BAS) systems, relate to mood pathology is consistent with the Research Domain Criteria initiative׳s goal of investigating mechanisms of risk.

METHOD

Korean young adults (n=128) and American young adults (n=630, of whom 23 has recent treatment for bipolar disorder, and 21for depression) completed self-report questionnaires, including the TEMPS-A, the BIS/BAS scales, Beck Depression Inventory (BDI), and Hypomanic Checklist (HCL-32). Linear regression quantified relations between mood symptoms, sample characteristics, temperament, and BIS/BAS.

RESULTS

Temperament styles explained 49% of the variance in BDI scores. BIS explained an additional 1% of the variance in BDI scores. BAS Fun and Reward (p<.01), in addition to cyclothymic and hyperthymic temperaments (p<.001) explained 21% of the variance in HCL-32 scores. Sample characteristics were not significant predictors in the full model.

LIMITATIONS

Differences in sample size, the cross-sectional study design, and lack of collateral report or behavioral measures of constructs are limitations.

CONCLUSIONS

Affective temperament and BIS/BAS are complementary but distinct constructs. Affective temperament, particularly cyclothymic, may represent a stronger diathesis for mood pathology, and seems potent irrespective of culture or diagnosis. Assessing temperament may help overcome some challenges in diagnosing mood disorders.

Chronology of illness in dual diagnosis heroin addicts: The role of mood disorders

BACKGROUND

Recent celebrity deaths have been widely reported in the media and turned the public attention to the coexistence of mood, psychiatric and substance-abuse disorders. These tragic and untimely deaths motivated us to examine the scientific and clinical data, including our own work in this area. The self-medication hypothesis states that individuals with psychiatric illness tend to use heroin to alleviate their symptoms. This study examined the correlations between heroin use, mood and psychiatric disorders, and their chronology in the context of dual diagnosis.

METHODS

Out of 506 dual diagnosed heroin addicts, 362 patients were implicated in heroin abuse with an onset of at least one year prior to the associated mental disorder (HER-PR), and 144 patients were diagnosed of mental illness at least one year prior to the associated onset of heroin use disorder (MI-PR). The retrospective cross-sectional analysis of the two groups compared their demographic, clinical and diagnostic characteristics at univariate and multivariate levels.

RESULTS

Dual diagnosis heroin addicts whose heroin dependences existed one year prior to their diagnoses (HER-PR) reported more frequent somatic comorbidity (p≤0.001), less major problems at work (p=0.003), more legal problems (p=0.004) and more failed treatment for their heroin dependence (p<0.001) in the past. More than 2/3 reached the third stage of heroin addiction (p=<0.001). Their length of dependence was longer (p=0.004). HER-PR patients were diagnosed more frequently as affected by mood disorders and less frequently as affected by psychosis (p=0.004). At the multivariate level, HER-PR patients were characterized by having reached stage 3 of heroin dependence (OR=2.45), diagnosis of mood disorder (OR=2.25), unsuccessful treatment (OR=2.07) and low education (OR=1.79).

LIMITATIONS

The main limitation is its retrospective nature. Nonetheless, it does shed light on what needs to be done from a clinical and public health perspective and especially prevention.

CONCLUSIONS

The data emerging from this study, does not allow us to determine a causal relation between heroin use and mental illness onset. However, this data, even if requiring longitudinal studies, suggest that self-medication theory, in these patients, can be applied only for chronic psychoses, but should not be applied to patients with mood disorders using heroin.